JP6055537B2 - Plasma processing method - Google Patents

Description

  The present invention relates to a technique for performing plasma processing on a substrate to be processed, and more particularly to a power-coupled capacitively coupled plasma processing method that modulates high-frequency power supplied into a processing vessel into pulses.

  In the capacitively coupled plasma processing method, an upper electrode and a lower electrode are arranged in parallel in a processing vessel, a substrate to be processed (semiconductor wafer, glass substrate, etc.) is placed on the lower electrode, and the upper electrode or the lower electrode is placed. A high frequency having a frequency suitable for plasma generation (usually 13.56 MHz or more) is applied to the electrode. Electrons are accelerated by a high-frequency electric field generated between the electrodes facing each other by the application of the high frequency, and plasma is generated by impact ionization between the electrons and the processing gas. A thin film is deposited on the substrate or a material or thin film on the substrate surface is shaved by a gas phase reaction or surface reaction of radicals and ions contained in the plasma.

  In recent years, the design rules in the manufacturing process of semiconductor devices and the like have become increasingly finer, and in plasma etching, in particular, higher dimensional accuracy is required, and the selectivity to the mask or base in etching and the in-plane uniformity are increased. Is also sought. Therefore, low pressure and low ion energy in the process region in the chamber are aimed at, and high frequencies with a high frequency of 40 MHz or more are being used.

  However, due to the progress of lower pressure and lower ion energy in this way, the influence of charging damage, which has not been a problem in the past, cannot be ignored. In other words, even if the plasma potential varies in the plane in the conventional plasma processing apparatus having a high ion energy, no major problem occurs, but when the ion energy is lowered at a lower pressure, the in-plane plasma potential is not uniform in the gate oxide film. There is a problem that charging damage is likely to occur.

  In order to solve this problem, a method of modulating high-frequency power used for plasma generation into on / off (or H level / L level) pulses whose duty ratio can be controlled (hereinafter referred to as “first power modulation method”). )) Is effective (Patent Document 1). According to the first power modulation method, the plasma generation state of the processing gas and the non-plasma generation state (the state where no plasma is generated) are alternately repeated at a predetermined cycle during the plasma etching, so that the plasma processing is started. Compared with the normal plasma processing in which plasma is continuously generated from the end to the end, the time during which plasma is continuously generated is shortened. This reduces the amount of charge that flows from the plasma into the substrate to be processed at a time or the amount of accumulated charge on the surface of the substrate to be processed, so that charging damage is less likely to occur and stable plasma. Realization of processing and reliability of plasma process are improved.

  Conventionally, in a capacitively coupled plasma processing method, a high frequency of a low frequency (usually 13.56 MHz or less) is applied to a lower electrode on which a substrate is placed, and a negative bias voltage or sheath generated on the lower electrode is applied. An RF bias method is often used in which ions in plasma are accelerated by voltage and drawn into a substrate. By accelerating ions from the plasma and colliding with the substrate surface in this way, surface reaction, anisotropic etching, film modification, or the like can be promoted.

  However, when etching via holes, contact holes, etc. using the capacitively coupled plasma etching method, there is a problem that the etching rate varies depending on the size of the hole, so-called microloading effect occurs, and the etching depth can be controlled. There is a problem that it is difficult. In particular, in a large area such as a guard ring (GR), etching is often fast, and in small vias where CF-based radicals are difficult to enter, the etching rate is often slow.

  In order to solve this problem, a method of modulating the duty ratio of high-frequency power used for ion attraction into a controllable first level / second level (or on / off) pulse (hereinafter referred to as “second power modulation method”). ") Is effective. According to the second power modulation method, a period for maintaining a relatively high first level (H level) power suitable for progressing etching of a predetermined film of the substrate to be processed and a high frequency for ion attraction. Is maintained at a predetermined period alternately with a period of maintaining a relatively low second level (L level) power suitable for depositing a polymer on a predetermined film on the substrate to be processed. An appropriate polymer layer is deposited on a predetermined film at a higher deposition rate in a larger (wider) place, and the progress of etching is suppressed. This reduces undesirable microloading effects and enables high selectivity and high etch rate etching.

JP 2009-71292 A JP 2009-33080 A JP 2010-238881 A

  In the first power modulation method or the second power modulation method as described above, the matching operation of the matching unit provided on the high-frequency power supply line for transmitting the high frequency from the high-frequency power source to the plasma in the processing container is a problem. Become. That is, the matching unit matches the impedance on the load side including the matching circuit to the impedance on the high frequency power source side so that the high frequency power output from the high frequency power source is most efficiently transmitted to the plasma in the processing container. Operate. However, when high-frequency power is subjected to pulse-like modulation by the first or second pulse modulation method as described above, the impedance of the plasma load fluctuates periodically in synchronization with the pulse, and the matching operation is performed. It becomes difficult to follow.

  Particularly troublesome is that the reflected wave returning from the plasma to the high-frequency power source in the reverse direction on the high-frequency power supply line is not only a fundamental wave reflected wave corresponding to the high frequency but also a modulated wave and a harmonic wave corresponding to the frequency of the power modulation. It also includes different frequency reflected waves such as wave distortion. The challenge is to perform high-speed and accurate matching operation so that the power of the fundamental wave reflected wave is made as small as possible by responding only to the fundamental wave reflected wave without being affected by such a different frequency reflected wave. It has become.

  In this regard, initially, the matching operation is stopped and the high-frequency power is turned on (or during the period in which the high-frequency power to be subjected to power modulation is turned off (or L level) in one cycle of power modulation. The matching operation is performed during the period of (H level) (Patent Document 2). However, in each cycle of power modulation, the plasma state varies greatly at the start and end of the on (or H level) period. When the matching operation is performed following the fluctuation of the plasma transient state, a reactance element (for example, a capacitor) that can be controlled in the matching unit repeats fine movement, thereby inhibiting plasma stabilization and plasma processing. Becomes unstable, and the reactance element shortens its lifetime. Therefore, in each cycle of power modulation, not only during the off (or L level) period, but also during the on (or H level) period, control is performed to stop the matching operation for a predetermined time (transient time) from the start. (Patent Document 3).

  However, in recent plasma processing methods, regardless of which of the first and second power modulation methods is used, in order to improve or expand the technical effect based on the method and thus to improve the process performance, or to widen the process margin. As for the duty ratio, a wider range (for example, 10 to 90%) than the conventional (25 to 80%) is required, and for the pulse frequency of power modulation, a range higher than the conventional (0.25 to 100 Hz) (for example, 100 Hz to 100 kHz). Is required. Therefore, for example, a condition in which the duty ratio is 10% and the power modulation pulse frequency is 90 kHz may be selected. The technique of intermittently stopping the matching operation of the matching unit in each cycle of power modulation as in the above-described prior art is such that when the pulse frequency of the power modulation is on the order of kHz or 10 kHz, the load (plasma) impedance varies. In addition to being unable to follow, there is a risk of failure of movable parts in the matching unit and shortening of the service life. For this reason, it cannot be adapted to a power modulation method having a high pulse frequency.

  Further, conventionally, no special control is applied to the matching unit provided on the high-frequency power supply line for the high frequency on the side where power modulation is not performed. Therefore, the matching unit is not synchronized with the power modulation applied to the other high frequency, as if the high frequency without power modulation on the high frequency power supply line is applied to the plasma in the processing container alone, A normal matching operation that responds instantaneously (continuously) to fluctuations in load (plasma) impedance is performed. However, in such a normal alignment operation, it has been difficult to establish a complete alignment state or a semi-alignment state stably and reliably. In addition, when the frequency of power modulation is on the order of kHz or 10 kHz as described above, the matching problem on the high frequency side where power modulation is not applied becomes significant.

  The present invention has been made in view of the above-described problems of the prior art, and has high reproducibility in the first or second power modulation system that modulates high-frequency power supplied into a processing vessel into pulses. Provided is a capacitively coupled plasma processing method capable of performing a stable and accurate alignment operation.

A plasma processing method according to a first aspect of the present invention includes a first electrode on which a substrate to be processed is placed and a second electrode facing the first electrode, and plasma is generated between the electrodes by high-frequency discharge of a processing gas. A generated processing container capable of being evacuated; a first high-frequency power source that outputs a first high-frequency power having a frequency suitable for drawing ions from the plasma into the substrate to be processed on the first electrode; A first high-frequency power supply line for transmitting the first high-frequency wave output from the first high-frequency power source to the first electrode; an impedance on the first high-frequency power source side; and an impedance on a load side thereof A first matching unit including a variable reactance element for matching, a second high frequency power source for outputting a second high frequency having a frequency suitable for generating the plasma, and the second high frequency A second high-frequency power supply line for transmitting the second high-frequency wave output from the wave power source to either the first electrode or the second electrode, and the second high-frequency power supply line on the second high-frequency power supply line A second matching unit for matching the impedance on the second high frequency power supply side with the impedance on the load side; and a first period in which the second high frequency power is on or at a first level and off A plasma having a high-frequency power modulation unit for controlling the second high-frequency power supply so as to alternately repeat a state or a second period of a second level lower than the first level at a constant pulse frequency A plasma processing method for performing desired plasma processing on the substrate to be processed in a processing apparatus, wherein the plasma processing method is provided in both of the first and second periods within one cycle of the pulse frequency. During the first monitoring time, the voltage detection signal and the current detection signal corresponding to the first high frequency obtained on the first high frequency power supply line are sampled at a predetermined sampling frequency, and the average of those signals is obtained. a sampling average value calculation step of calculating a value based on the average value of each cycle which is more give to the sampling average value calculation step, the frequency of the 1 / m times the pulse frequency (m is an integer of 2 or more) movement of the moving average value calculating step and the voltage detection signal more obtained the moving average value calculation process and the current detection signal in the cycle of the sampling clock calculating the moving average value of the voltage detection signal and the current sense signal with Load impedance measurement value calculation for calculating a measurement value of the load-side impedance for the first high-frequency power source based on an average value And process, as the measured value of the load impedance more obtained the load impedance measured value calculating step is equal or close to a predetermined matching points corresponding to the impedance of the first RF power supply side, the variable reactance element A reactance control step for controlling the reactance of

A plasma processing method according to a second aspect of the present invention includes a first electrode on which a substrate to be processed is placed and a second electrode facing the first electrode, and plasma is generated between the electrodes by high-frequency discharge of a processing gas. A generated processing container capable of being evacuated; a first high-frequency power source that outputs a first high-frequency power having a frequency suitable for drawing ions from the plasma into the substrate to be processed on the first electrode; A first high-frequency power supply line for transmitting the first high-frequency power output from the first high-frequency power supply to the first electrode; and the first high-frequency power supply side on the first high-frequency power supply line A first matching section including a variable reactance element for matching the impedance of the first load and the impedance of the load side, and a second high frequency having a frequency suitable for generating the plasma A second high-frequency power supply line for transmitting the second high-frequency power output from the second high-frequency power supply to either the first electrode or the second electrode; A second matching section for matching the impedance on the second high-frequency power supply side and the impedance on the load side on the second high-frequency power supply line; and the second high-frequency power is in the on state or the first The second high-frequency power supply is controlled so as to alternately repeat a first period of level and a second period of off state or a second level lower than the first level at a constant pulse frequency. A plasma processing method for performing desired plasma processing on the substrate to be processed in a plasma processing apparatus having a high-frequency power modulation unit that performs the first processing within one cycle of the pulse frequency. During the first monitoring time set for both the first period and the second period, the measured values of the load-side impedance obtained on the first high-frequency power supply line are sampled at a predetermined sampling frequency and measured. a sampling average value calculation step of calculating an average value of values, based on the average value of each cycle which is more give to the sampling average value calculating step, 1 / m times the pulse frequency (m is an integer of 2 or more) a moving average value calculation step of calculating the moving average of the periods in the load impedance measurement value of the sampling clock having a frequency of, the moving average value of the load impedance measurements more obtained the moving average value calculation step wherein The variable reactance element is matched or approximated to a predetermined matching point corresponding to the impedance on the first high frequency power supply side. A reactance control step for controlling the reactance of the child.

A plasma processing method according to a third aspect of the present invention includes a first electrode on which a substrate to be processed is placed and a second electrode facing the first electrode, and plasma is generated between the electrodes by high-frequency discharge of a processing gas. A processing container that can be evacuated, a first high-frequency power source that outputs a first high-frequency wave having a frequency suitable for generating the plasma, and the first high-frequency power source that is output from the first high-frequency power source. And a first high-frequency power supply line for transmitting the high-frequency power to either the first electrode or the second electrode, and an impedance on the first high-frequency power supply side on the first high-frequency power supply line, A first matching unit including a variable reactance element for matching the impedance on the load side, and a frequency suitable for drawing ions from the plasma into the substrate to be processed on the first electrode. A second high-frequency power supply that outputs a second high-frequency power having a second high-frequency power supply line for transmitting the second high-frequency power output from the second high-frequency power supply to the first electrode; A second matching unit configured to match the impedance on the second high-frequency power supply side and the impedance on the load side on the second high-frequency power supply line; The second high-frequency power supply is configured to alternately repeat a first period of the second level and an off state or a second period of the second level lower than the first level at a constant pulse frequency. A plasma processing method for performing desired plasma processing on the substrate to be processed in a plasma processing apparatus having a high-frequency power modulation unit to control, wherein the first processing is performed within one cycle of the pulse frequency. And a predetermined sampling of the voltage detection signal and the current detection signal corresponding to the first high frequency obtained on the first high frequency power supply line during the first monitoring time set in both the first period and the second period. a sampling average value calculation step of calculating an average value of the signal by sampling at a frequency based on the average value of each cycle which is more give to the sampling average value calculating step, 1 / m times the pulse frequency ( m is an integer of 2 or more) of the moving average value calculation step in the cycle of the sampling clock calculating the moving average value of the voltage detection signal and the current sense signal having a frequency, said which is more give to the moving average value calculating step Based on the moving average value of the voltage detection signal and the current detection signal, the measured value of the load side impedance for the first high frequency power supply is calculated. That the load impedance measured value calculating step, so that the measured value of the load impedance more obtained the load impedance measured value calculating step is equal or close to a predetermined matching points corresponding to the impedance of the first high frequency power supply side And a reactance control step for controlling the reactance of the variable reactance element.

A plasma processing method according to a fourth aspect of the present invention includes a first electrode on which a substrate to be processed is placed and a second electrode facing the first electrode, and plasma is generated between the electrodes by high-frequency discharge of a processing gas. A processing container that can be evacuated, a first high-frequency power source that outputs a first high-frequency wave having a frequency suitable for generating the plasma, and the first high-frequency power source that is output from the first high-frequency power source. And a first high-frequency power supply line for transmitting the high-frequency power to either the first electrode or the second electrode, and an impedance on the first high-frequency power supply side on the first high-frequency power supply line, A first matching unit including a variable reactance element for matching the impedance on the load side, and a frequency suitable for drawing ions from the plasma into the substrate to be processed on the first electrode. A second high-frequency power supply that outputs a second high-frequency power having a second high-frequency power supply line for transmitting the second high-frequency power output from the second high-frequency power supply to the first electrode; A second matching unit configured to match the impedance on the second high-frequency power supply side and the impedance on the load side on the second high-frequency power supply line; The second high-frequency power supply is configured to alternately repeat a first period of the second level and an off state or a second period of the second level lower than the first level at a constant pulse frequency. A plasma processing method for performing desired plasma processing on the substrate to be processed in a plasma processing apparatus having a high-frequency power modulation unit to control, wherein the first processing is performed within one cycle of the pulse frequency. During the first monitoring time set for both the first period and the second period, the measured values of the load-side impedance obtained on the first high-frequency power supply line are sampled at a predetermined sampling frequency and measured. a sampling average value calculation step of calculating an average value of values, based on the average value of each cycle which is more give to the sampling average value calculating step, 1 / m times the pulse frequency (m is an integer of 2 or more) a moving average value calculation step of calculating the moving average of the periods in the load impedance measurement value of the sampling clock having a frequency of, the moving average value of the load impedance measurements more obtained the moving average value calculation step wherein The variable reactance element is matched or approximated to a predetermined matching point corresponding to the impedance on the first high frequency power supply side. A reactance control step for controlling the reactance of the child.

A plasma processing method according to a fifth aspect of the present invention includes a first electrode on which a substrate to be processed is placed and a second electrode facing the first electrode, and plasma is generated between the electrodes by high-frequency discharge of a processing gas. A generated processing container capable of being evacuated, a high-frequency power source, and a high-frequency power supply line for transmitting the high-frequency power output from the high-frequency power source to either the first electrode or the second electrode; A matching unit including a variable reactance element for matching the impedance on the high-frequency power supply side and the load-side impedance on the high-frequency power supply line, and a first period in which the high-frequency power is turned on and an off state. A plasma processing apparatus having a high-frequency power modulation unit for controlling the high-frequency power supply so that the second period is alternately repeated at a constant pulse frequency. A plasma processing method for performing a desired plasma processing on the substrate to be processed, wherein the high frequency obtained from the high frequency power supply line during the monitoring time set in the first period within one cycle of the pulse frequency. corresponding voltage detection signal and current sampling average value calculation step of calculating an average value of the signal detection signal by sampling at a predetermined sampling frequency, the sampling average value greater mean values obtained for each cycle calculating step A moving average value calculating step for obtaining a moving average value of the voltage detection signal and the current detection signal at a period of a sampling clock having a frequency of 1 / m times the pulse frequency (m is an integer of 2 or more), , based on the moving average value of the voltage detection signal and the current sense signal more obtained the moving average value calculating step The a load impedance measurement value calculation step of calculating the measured value of the load impedance for the high frequency power source, the impedance measurements of the high frequency power supply side of the front Symbol load impedance more obtained the load impedance measured value calculating step A reactance control step of controlling a reactance of the variable reactance element so as to match or approximate a corresponding predetermined matching point.

A plasma processing method according to a sixth aspect of the present invention includes a first electrode on which a substrate to be processed is placed and a second electrode facing the first electrode, and plasma is generated between the electrodes by high-frequency discharge of a processing gas. A generated processing container capable of being evacuated, a high-frequency power source, and a high-frequency power supply line for transmitting the high-frequency power output from the high-frequency power source to either the first electrode or the second electrode; A matching unit including a variable reactance element for matching the impedance on the high-frequency power supply side and the load-side impedance on the high-frequency power supply line, and a first period in which the high-frequency power is turned on and an off state. A plasma processing apparatus having a high-frequency power modulation unit for controlling the high-frequency power supply so that the second period is alternately repeated at a constant pulse frequency. A plasma processing method for performing desired plasma processing on the substrate to be processed, the load side obtained from the high-frequency power supply line during a monitoring time set in the first period within one cycle of the pulse frequency a sampling average value calculation step of calculating an average value of the measured values of the measurement values of the impedance is sampled at a predetermined sampling frequency, based on the average value of each cycle which is more give to the sampling average value calculation step, A moving average value calculating step for obtaining a moving average value of the load side impedance measurement value at a sampling clock cycle having a frequency of 1 / m times the pulse frequency (m is an integer of 2 or more), and the moving average value calculating step corresponding to the impedance of the high frequency power supply side moving average value of the load impedance measurements more obtained Predetermined to match or approximate the consistency point that has a reactance control step of controlling the reactance of the variable reactance element.

  According to the plasma processing method of the present invention, with the configuration and operation as described above, stable and highly reproducible in the first or second power modulation system that modulates the high-frequency power supplied into the processing container into pulses. Accurate alignment operation can be performed.

It is sectional drawing which shows the structure of the capacitive coupling type plasma processing apparatus suitable for enforcing the plasma processing method in one Embodiment of this invention. It is a high-frequency waveform diagram showing an example of power modulation in the plasma processing apparatus. It is a high-frequency waveform diagram showing another example of power modulation in the plasma processing apparatus. It is a figure which shows the spectrum of the high frequency and the sideband (modulation part) by which the power modulation is performed. It is a figure which shows the spectrum of the reflected wave in case matching is taken. It is a figure which shows the spectrum of the high frequency and the sideband (modulation part) of the side which cannot apply power modulation. It is a figure which shows the spectrum of the reflected wave in case matching is taken. It is a block diagram which shows the structure of the high frequency power supply for plasma production, and a matching device. It is a block diagram which shows the structure in the matching device of FIG. It is a block diagram which shows the structure of the high frequency power supply for ion attraction, and a matching device. It is a block diagram which shows the structure in the matching device of FIG. It is a wave form diagram of each part for demonstrating the effect | action of the matching device in embodiment. It is a figure for demonstrating the effect | action of the moving average value calculation in embodiment. It is a figure for demonstrating the effect | action of the moving average value calculation in embodiment. It is a figure which shows distribution (an example) of the alignment operation | movement point on the Smith chart in embodiment. It is a block diagram which shows the structure of the impedance sensor in one modification. It is a block diagram which shows the structure of the impedance sensor in one modification.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[Configuration of plasma processing apparatus]

  FIG. 1 shows a configuration of a plasma processing apparatus suitable for carrying out a plasma processing method according to an embodiment of the present invention. This plasma processing apparatus is configured as a capacitive coupling type (parallel plate type) plasma etching apparatus of a lower two high-frequency superimposition application method, for example, a cylindrical vacuum chamber made of aluminum whose surface is anodized (anodized). (Processing container) 10 is provided. The chamber 10 is grounded.

  A cylindrical susceptor support 14 is disposed at the bottom of the chamber 10 via an insulating plate 12 such as ceramic, and a susceptor 16 made of, for example, aluminum is provided on the susceptor support 14. The susceptor 16 constitutes a lower electrode, on which, for example, a semiconductor wafer W is placed as a substrate to be processed.

  An electrostatic chuck 18 for holding the semiconductor wafer W is provided on the upper surface of the susceptor 16. This electrostatic chuck 18 is obtained by sandwiching an electrode 20 made of a conductive film between a pair of insulating layers or insulating sheets, and a DC power supply 24 is electrically connected to the electrode 20 via a switch 22. The semiconductor wafer W can be held on the electrostatic chuck 18 by an electrostatic attraction force by a DC voltage from the DC power source 24. A focus ring 26 made of, for example, silicon is disposed on the upper surface of the susceptor 16 around the electrostatic chuck 18 to improve etching uniformity. A cylindrical inner wall member 28 made of, for example, quartz is attached to the side surfaces of the susceptor 16 and the susceptor support base 14.

  Inside the susceptor support 14, for example, a refrigerant chamber 30 extending in the circumferential direction is provided. A refrigerant of a predetermined temperature, for example, cooling water, is circulated and supplied to the refrigerant chamber 30 through piping 32a and 32b from an external chiller unit (not shown). The processing temperature of the semiconductor wafer W on the susceptor 16 can be controlled by the temperature of the refrigerant. Further, a heat transfer gas such as He gas from a heat transfer gas supply mechanism (not shown) is supplied between the upper surface of the electrostatic chuck 18 and the back surface of the semiconductor wafer W via the gas supply line 34.

High frequency power sources 36 and 38 are electrically connected to the susceptor 16 through matching units 40 and 42 and a common power supply conductor (for example, power supply rod) 44, respectively. One high frequency power source 36 outputs a high frequency RF1 having a constant frequency f _RF1 (for example, 100 MHz) suitable for plasma generation. The other high-frequency power source 38 outputs a high-frequency RF 2 having a constant frequency f _RF2 (for example, 13.56 MHz) suitable for drawing ions from the plasma into the semiconductor wafer W on the susceptor 16.

  As described above, the matching unit 40 and the power supply rod 44 constitute a part of a high frequency power supply line (high frequency transmission path) 43 that transmits the high frequency RF 1 for plasma generation from the high frequency power source 36 to the susceptor 16. On the other hand, the matching unit 42 and the power supply rod 44 constitute a part of a high frequency power supply line (high frequency transmission path) 45 that transmits the high frequency RF 2 for ion attraction from the high frequency power supply 38 to the susceptor 16.

  An upper electrode 46 having a ground potential is provided on the ceiling of the chamber 10 so as to face the susceptor 16 in parallel. The upper electrode 46 includes an electrode plate 48 made of a silicon-containing material such as Si or SiC having a large number of gas ejection holes 48a, and a conductive material that detachably supports the electrode plate 48, such as aluminum whose surface is anodized. The electrode support body 50 which consists of is comprised. A plasma generation space or a processing space PS is formed between the upper electrode 46 and the susceptor 16.

  The electrode support 50 has a gas buffer chamber 52 therein, and a plurality of gas vent holes 50a communicating from the gas buffer chamber 52 to the gas ejection holes 48a of the electrode plate 48 on the lower surface thereof. A processing gas supply source 56 is connected to the gas buffer chamber 52 via a gas supply pipe 54. The processing gas supply source 56 is provided with a mass flow controller (MFC) 58 and an opening / closing valve 60. When a predetermined processing gas (etching gas) is introduced from the processing gas supply source 56 into the gas buffer chamber 52, the processing gas enters the processing space PS from the gas ejection hole 48 a of the electrode plate 48 toward the semiconductor wafer W on the susceptor 16. Is ejected like a shower. Thus, the upper electrode 46 also serves as a shower head for supplying the processing gas to the processing space PS.

  In addition, a passage (not shown) through which a coolant such as cooling water flows is provided inside the electrode support 50, and the entire upper electrode 46, in particular, the electrode plate 48 is kept at a predetermined temperature via the coolant by an external chiller unit. It is supposed to adjust the temperature. Further, in order to further stabilize the temperature control for the upper electrode 46, a configuration in which a heater (not shown) made of a resistance heating element is attached to the inside or the upper surface of the electrode support 50 is also possible.

  An annular space formed between the susceptor 16 and the susceptor support 14 and the side wall of the chamber 10 is an exhaust space, and an exhaust port 62 of the chamber 10 is provided at the bottom of the exhaust space. An exhaust device 66 is connected to the exhaust port 62 via an exhaust pipe 64. The exhaust device 66 has a vacuum pump such as a turbo molecular pump, and can depressurize the interior of the chamber 10, particularly the processing space PS, to a desired degree of vacuum. A gate valve 70 that opens and closes the loading / unloading port 68 for the semiconductor wafer W is attached to the side wall of the chamber 10.

  The main control unit 72 includes one or a plurality of microcomputers, and in accordance with software (program) and recipe information stored in an external memory or internal memory, each unit in the apparatus, in particular, the high frequency power supplies 36 and 38, the matching unit 40, and the like. , 42, MFC 58, opening / closing valve 60, exhaust device 66, and the like and the overall operation (sequence) of the device.

  The main control unit 72 stores an operation panel (not shown) for a man-machine interface including an input device such as a keyboard and a display device such as a liquid crystal display, and various data such as various programs, recipes, and setting values. Alternatively, it is also connected to an external storage device (not shown) that accumulates. In this embodiment, the main control unit 72 is shown as one control unit. However, a plurality of control units may share the functions of the main control unit 72 in parallel or hierarchically.

  The basic operation of single wafer dry etching in this capacitively coupled plasma etching apparatus is performed as follows. First, the gate valve 70 is opened and the semiconductor wafer W to be processed is loaded into the chamber 10 and placed on the electrostatic chuck 18. Then, a processing gas, that is, an etching gas (generally a mixed gas) is introduced into the chamber 10 from the processing gas supply source 56 at a predetermined flow rate and flow rate ratio, and the pressure in the chamber 10 is set to a set value by vacuum evacuation by the exhaust device 66. . Further, a high frequency RF 1 (100 MHz) for plasma generation and a high frequency RF 2 (13.56 MHz) for ion attraction are superimposed and applied to the susceptor 16 from the high frequency power sources 36 and 38, respectively, with a predetermined power. Further, a DC voltage is applied from the DC power source 24 to the electrode 20 of the electrostatic chuck 18 to fix the semiconductor wafer W on the electrostatic chuck 18. The etching gas discharged from the shower head of the upper electrode 46 is discharged under a high-frequency electric field between the electrodes 46 and 16, and plasma is generated in the processing space PS. The film to be processed on the main surface of the semiconductor wafer W is etched by radicals and ions contained in the plasma.

  In this capacitively coupled plasma etching apparatus, for example, as a countermeasure against charging damage as described above, the power of the high frequency RF1 for plasma generation output from the high frequency power source 36 is controlled within a range of, for example, 10 to 90%. Preferably, a first power modulation scheme that modulates on / off (or H level / L level) pulses at a pulse frequency of, for example, 1 kHz to 100 kHz can be used for a given etching process. For example, as a countermeasure against the microloading effect as described above, the duty ratio can be controlled within the range of, for example, 10 to 90% of the power of the high frequency RF2 for ion attraction output from the high frequency power supply 38, for example, 100 Hz. It is also possible to use a second power modulation scheme for a given etching process that modulates on / off (or H / L level) pulses at a pulse frequency of ˜50 kHz.

For example, when dry etching as described above is performed by the first power modulation method, the modulation control pulse signal PS defining the pulse frequency f _S and the duty ratio D _S set for power modulation by the main controller 72 is generated. A high frequency power source 36 is provided. The high frequency power supply 36 turns on / off the output of the plasma generating high frequency RF1 in synchronization with the modulation control pulse signal PS. Here, assuming that the period, on period (first period), and off period (second period) of the modulation control pulse signal PS are T _C , T _on , and T _off , respectively, T _C = 1 / f _S , T The relational expression of _C = T _on + T _off and D _S = T _on / (T _on + T _off ) holds.

On the other hand, in the first power modulation method, the high frequency power supply 38 continuously outputs the high frequency RF 2 for ion attraction without being turned on / off. However, since the impedance of the plasma moves between two values in the chamber 10 by turning on and off the high frequency RF1, the matching operation or matching degree on the high frequency power supply line 45 is synchronized with the on and off of the high frequency RF1. Go back and forth between the two states. More specifically, as will be described later, the degree of matching differs between the on period _Ton and the off period _Toff constituting one cycle of the pulse frequency f _S according to the length of the duration, and the relative The longer period is closer to the perfect matching state than the shorter period, and accordingly, the power of the high-frequency RF 2 on the high-frequency feed line 45 is also different.

That is, as shown in FIG. 2A, when the on period T _on is sufficiently longer than the off period T _off (when the duty ratio D _S is sufficiently large), when people when the on-period T _on is off period T _off to approach complete alignment than the power of the high frequency RF2 when the on-period T _on is higher than the off period T _off.

Conversely, as shown in FIG. 2B, the off period T _off if sufficiently longer than the on-period T _on (when the duty ratio D _S is sufficiently small), the direction of the off period T _off is the on-period T _on to approach complete alignment than when the power of the high frequency RF2 is higher than when the off period T _off is the on-period T _on.

As described above, when the high frequency RF 1 for plasma generation is subjected to power modulation by the first power modulation method, the original high frequency is included in the traveling wave from the high frequency power supply 36 toward the susceptor 16 in the chamber 10 on the high frequency power supply line 43. In addition to RF1, as shown in FIG. 3A, sideband frequency components (pulse frequency modulation) corresponding to the pulse frequency f _S are generated around the high frequency RF1 (on both sides) on the frequency axis. In this case, when the matching operation of the matching unit 40 is effective and good matching is achieved, the power of the high frequency RF1 is absorbed most efficiently by the plasma. Therefore, in the reflected wave propagating from the plasma in the chamber 10 in the reverse direction on the high-frequency feed line 43, the power of the fundamental reflected wave having the same frequency _fRF1 as the high-frequency RF1 is conspicuous as shown in FIG. 3B. Become lower.

On the other hand, even in the power supply system on the high frequency RF2 side where power modulation is not performed, the power of the high frequency RF2 goes back and forth (fluctuates) between two values in synchronization with the on / off of the high frequency RF1 as described above. As shown in 4A, in the traveling wave and the reflected wave, not only the original high frequency RF2 and the fundamental reflected wave, but also a sideband frequency component corresponding to the modulation frequency f _S (pulse frequency modulation) is generated. Therefore, when the matching operation of the matching unit 42 is effective and good matching is achieved, the power of the high-frequency RF 2 is absorbed most efficiently by the plasma. In this case, in the reflected wave propagating from the plasma in the chamber 10 in the reverse direction on the high-frequency power supply line 45, as shown in FIG. 4B, the power of the fundamental wave reflected wave having the same frequency _fRF2 as the high-frequency RF2 is obtained. Remarkably lower.

Even when power modulation is applied to the power of the high frequency RF2 for ion attraction by the second power modulation method, the sidebands associated with the power modulation similar to the above are merely obtained by reversing the positions of the high frequency RF1 and the high frequency RF2. The required performance similar to that described above is imposed on the matching operation of the matching devices 40 and 42.

[Configuration of high frequency power supply and matching unit]

  FIG. 5 shows the configuration of the high-frequency power source 36 and matching unit 40 of the plasma generation system in this embodiment.

  The high frequency power source 36 includes an oscillator 80A that generates a sine wave having a constant frequency (for example, 100 MHz) for plasma generation, and a power amplifier that amplifies the gain of the sine wave output from the oscillator 80A with a gain or an amplification factor. 82A and a power control unit 84A that directly controls the oscillator 80A and the power amplifier 82A in accordance with a control signal from the main control unit 72. The main control unit 72 to the power control unit 84A are supplied with not only the modulation control pulse signal PS but also control signals such as normal power on / off and power interlock, and data such as power setting values. The main control unit 72 and the power supply control unit 84A constitute a high frequency RF1 power modulation unit.

  In the unit of the high frequency power source 36, an RF power monitor 86A is also provided. The RF power monitor 86A includes a directional coupler, a traveling wave power monitor unit, and a reflected wave power monitor unit (not shown). Here, the directional coupler extracts signals corresponding to the RF power (traveling wave) propagating in the forward direction on the high-frequency power supply line 43 and the RF power (reflecting wave) propagating in the reverse direction. The traveling wave power monitor generates a signal representing the power of the fundamental traveling wave (100 MHz) included in the traveling wave on the high-frequency power supply line 43 based on the traveling wave power detection signal extracted by the directional coupler. . This signal, that is, the fundamental traveling wave power measurement value signal, is supplied to the power control unit 84A in the high frequency power source 36 for power feedback control and also to the main control unit 72 for monitor display. The reflected wave power monitor unit measures the power of the reflected fundamental wave (100 MHz) included in the reflected wave returned from the plasma in the chamber 10 to the high frequency power source 36 and returns to the high frequency power source 36 from the plasma in the chamber 10. The total power of all reflected wave spectra included in the incoming reflected wave is measured. The fundamental reflected wave power measurement value obtained by the reflected wave power monitor unit is given to the main control unit 72 for monitor display, and the total reflected wave power measurement value is used as a monitor value for power amplifier protection to control the power supply in the high frequency power source 36. Part 84A.

The matching unit 40 includes a matching circuit 88A including a plurality of, for example, two controllable reactance elements (for example, capacitors or inductors) X _H1 and X _H2 , and reactances of the reactance elements X _H1 and X _H2 by an actuator such as a motor (M) 90A, A matching controller 94A that is controlled via 92A and an impedance sensor 96A that measures the impedance on the load side including the impedance of the matching circuit 88A on the high-frequency power supply line 43 are provided.

The matching controller 94A operates under the control of the main controller 72, and uses the load side impedance measurement value given from the impedance sensor 96A as a feedback signal, and the load side impedance measurement value corresponds to the impedance on the high frequency power source 36 side. The reactances of the reactance elements X _H1 and X _H2 are controlled through drive control of the motors 90A and 92A so as to match or approximate (usually 50Ω).

  FIG. 6 shows the configuration inside the impedance sensor 96A. The impedance sensor 96A includes a voltage sensor system RF voltage detector 100A, a voltage detection signal generation circuit 102A, a sampling average value calculation circuit 104A and a moving average value calculation circuit 106A, a current sensor system RF current detector 108A, and current detection. It has a signal generation circuit 110A, a sampling average value calculation circuit 112A, a moving average value calculation circuit 114A, and a load impedance calculation circuit 116A.

  In the voltage sensor system, the RF voltage detector 100 </ b> A detects a high frequency voltage on the high frequency power supply line 43. The voltage detection signal generation circuit 102A has a superheterodyne filter circuit, for example, and applies a high-frequency voltage detection signal from the RF voltage detector 100A to an analog filtering process to generate a voltage detection signal corresponding to the high-frequency RF1.

Sampling average value calculating circuit 104A operates in synchronization with the power modulation, a voltage detection signal from the voltage detection signal generation circuit 102A during a predetermined monitoring time T _H of one cycle of the pulse frequency f _S at a predetermined frequency Sampling and calculating the average value. In this configuration example, the analog voltage detection signal from the voltage detection signal generation circuit 102A is converted into a digital signal by the sampling average value calculation circuit 104A. The main control unit 72 includes a clock ACK ₁ for sampling, give the RF1 monitor signal AS to instruct the monitoring time T _H of the high-frequency RF1 based on the sampling average value calculating circuit 104A. Since the sampling average value calculation circuit 104A is required to perform high-speed and large-volume signal processing in synchronization with a sampling clock ACK ₁ of several tens of MHz or more, an FPGA (Field Programmable Gate Array) can be preferably used.

The moving average value calculation circuit 106A calculates a moving average value of the voltage detection signal based on the average value of each cycle obtained from the sampling average value calculation circuit 104A. That is, the average value of the N consecutive voltage detection signals obtained from the sampling average value calculation circuit 104A is sampled at a constant period, the moving average value is obtained for these N average values, and sampling is performed on the time axis. The above-mentioned moving average value calculation is repeated by moving the range at a desired moving pitch. The value of the moving pitch can be set arbitrarily. The main control unit 72 provides the sampling clock ACK ₂ to the moving average value calculation circuit 106A. Since the moving average value calculation circuit 106A does not require particularly high-speed signal processing, a normal CPU can be preferably used.

In the current sensor system, the RF current detector 108 </ b> A detects a high-frequency current on the high-frequency power supply line 43. The current detection signal generation circuit 110A has the same configuration and function as the voltage detection signal generation circuit 102A described above, and generates a current detection signal corresponding to the high frequency RF1. The sampling average value calculation circuit 112A has the same configuration and function as the above-described sampling average value calculation circuit 104A, and from the current detection signal generation circuit 110A during a predetermined monitoring time T _H within one cycle of the pulse frequency f _S. The current detection signal is sampled at a predetermined frequency, and the average value is calculated. The moving average value calculation circuit 114A has the same configuration and function as the above-described moving average value calculation circuit 106A, and the moving average of the current detection signal based on the average value of each cycle obtained from the sampling average value calculation circuit 112A. Find the value.

The load impedance calculation circuit 116A is based on the moving average value of the voltage detection signal from the moving average value calculation circuit 106A and the moving average value of the current detection signal from the moving average value calculation circuit 114A. Calculate the measured value. Measurement of the load impedance outputted from the load impedance computing circuit 116A is updated in synchronization with the sampling clock ACK _2. The main control unit 72 gives the required clock ACK ₃ to the load impedance calculation circuit 116A. Usually, the measured value of the load side impedance output from the load impedance calculation circuit 116A includes the absolute value of the load side impedance and the measured value of the phase.

The matching controller 94A in the matching unit 40 is responsive to the load side impedance measurement value given from the impedance sensor 96A, and the motor 90A, 90A, 90B, and the phase of the load side impedance measurement value are zero (0) and the absolute value is 50Ω. The reactance of the reactance elements X _H1 and X _H2 in the matching circuit 88A is controlled by driving the 92A.

The load-side impedance measurement value supplied from the impedance sensor 96A to the matching controller 94A is updated in synchronization with the power modulation (more precisely, in the period of the moving average value calculation). The matching controller 94A does not stop the matching operation, that is, the reactance control of the reactance elements X _H1 and X _H2 during this update, so that the load side impedance measurement value immediately before the update matches or approximates the matching point. The motors 90A and 92A are continuously driven and controlled.

In this embodiment, as described above, the sampling average value calculation circuits 104A and 112A and the moving average value calculation circuits 106A and 114A apply the double sampling averaging process to the measured values of the RF voltage and current, thereby the impedance sensor 96A. The speed of updating the load-side impedance measurement value output from the output and the speed of drive control of the motors 90A and 92A (that is, reactance control of the reactance elements X _H1 and X _H2 ) in the matching controller 94A can be well matched. . As a result, even if the power modulation pulse frequency is set to the order of several tens of kHz or more, in the matching operation of the matching unit 40, the failure of movable parts (particularly the reactance elements X _H1 and X _H2 ) has been shortened. In addition, it is possible to accurately follow fluctuations in load (plasma) impedance.

Further, in this embodiment, as described above, the measured value of the load side impedance obtained based on the voltage detection signal and the current detection signal corresponding to the high frequency RF1 obtained on the high frequency power supply line 43 matches or approximates the matching point. Therefore, even if there is a sideband frequency component (modulation of the pulse frequency f _S ) corresponding to the modulation frequency around the high frequency RF1 (on both sides) on the frequency axis, the matching unit 40 The matching operation is selectively effective for the high frequency RF1. Therefore, in the reflected wave power monitor unit in the RF power monitor 86A, it is possible to obtain a monitor result in which the power of the fundamental wave reflected wave (f _RF1 ) is remarkably lowered as shown in FIG. 3B.

  FIG. 7 shows the configuration of the high frequency power supply 38 for ion attraction and the matching unit 42 in this embodiment.

  The high frequency power supply 38 controls an oscillator 80B that generates a sine wave having a constant frequency (for example, 13.56 MHz) for ion attraction, and a power of the sine wave output from the oscillator 80B, and amplifies the sine wave with the gain or amplification factor. A power amplifier 82B, a power controller 84B that directly controls the oscillator 80B and the power amplifier 82B in accordance with a control signal from the main controller 72, and an RF power monitor 86B are provided. Except for the point that the frequency (13.56 MHz) of the oscillator 80B is different from the frequency (100 MHz) of the oscillator 80A, the units 80B to 86B in the high frequency power supply 38 are the same as the units 80A to 86A in the high frequency power supply 36 for plasma generation, respectively. It has the structure and function. The main control unit 72 and the power supply control unit 84B constitute a high frequency RF2 power modulation unit.

The matching unit 42 includes a matching circuit 88B including a plurality of, for example, two controllable reactance elements (for example, capacitors or inductors) X _L1 and X _L2 , and reactance of the reactance elements X _L1 and X _L2 by an actuator such as a motor (M) 90B. , 92B and an impedance sensor 96B for measuring the load-side impedance including the impedance of the matching circuit 88B on the high-frequency power supply line 45.

The matching controller 94B operates under the control of the main control unit 72, and the load side impedance measurement value given from the impedance sensor 96B is used as a feedback signal, and the load side impedance measurement value corresponds to the impedance on the high frequency power supply 38 side. The reactances of the reactance elements X _L1 and X _L2 are controlled by driving the motors 90B and 92B so as to coincide with or approximate (usually 50Ω).

  FIG. 8 shows a configuration in the impedance sensor 96B. The impedance sensor 96B includes a voltage sensor RF voltage detector 100B, a voltage detection signal generation circuit 102B, a sampling average value calculation circuit 104B and a moving average value calculation circuit 106B, a current sensor RF current detector 108B, and current detection. It has a signal generation circuit 110B, a sampling average value calculation circuit 112B, a moving average value calculation circuit 114B, and a load impedance calculation circuit 116B.

  In the voltage sensor system, the RF voltage detector 100 </ b> B detects a high frequency voltage on the high frequency power supply line 45. The voltage detection signal generation circuit 102B has, for example, a superheterodyne filter circuit, and applies a high frequency voltage detection signal from the RF voltage detector 100B to an analog filtering process to generate a voltage detection signal corresponding to the high frequency RF1.

The sampling average value calculation circuit 104B operates in synchronization with the power modulation, and outputs the current detection signal from the current detection signal generation circuit 102B at a predetermined frequency during a predetermined monitoring time T _L within one cycle of the pulse frequency f _S. Sampling and calculating the average value. In this configuration example, the analog current detection signal from the current detection signal generation circuit 102B is converted into a digital signal by the sampling average value calculation circuit 104B. The main control unit 72 supplies the sampling clock BCK ₁ and the RF2 monitor signal BS defining the high frequency RF2 system monitoring time _TL to the sampling average value calculation circuit 104B.

  The moving average value calculation circuit 106B obtains the moving average value of the current detection signal based on the average value of each cycle obtained from the sampling average value calculation circuit 104B. That is, the average value of the N consecutive current detection signals obtained from the sampling average value calculation circuit 104B is sampled at a constant period, the moving average value is obtained for these N average values, and sampling is performed on the time axis. The above-mentioned moving average value calculation is repeated by moving the range at a desired moving pitch. The value of the moving pitch can be set arbitrarily.

In the current sensor system, the RF current detector 108 </ b> B detects a high-frequency current on the high-frequency power supply line 45. The current detection signal generation circuit 110B has the same configuration and function as the above-described current detection signal generation circuit 102B, and generates a current detection signal corresponding to the high frequency RF2. The sampling average value calculation circuit 112B has the same configuration and function as the above-described sampling average value calculation circuit 104B, and from the current detection signal generation circuit 110B during a predetermined monitoring period T _RF2 within one cycle of the pulse frequency f _S. The current detection signal is sampled at a predetermined frequency, and the average value is calculated. The moving average value calculation circuit 114B has the same configuration and function as the above-described moving average value calculation circuit 106B, and the moving average of the current detection signal based on the average value of each cycle obtained from the sampling average value calculation circuit 112B. Find the value.

The load impedance calculation circuit 116B is based on the moving average value of the voltage detection signal from the moving average value calculation circuit 106B and the moving average value of the current detection signal from the moving average value calculation circuit 114B. Calculate the measured value. The measured value of the load-side impedance output from the load impedance calculation circuit 116B is updated in synchronization with the sampling clock BCK ₂ for moving average value calculation. The main controller 72 gives the required clock BCK ₃ to the load impedance calculation circuit 116B. Usually, the measured value of the load side impedance output from the load impedance calculation circuit 116B includes the absolute value of the load side impedance and the measured value of the phase.

The matching controller 94B in the matching unit 42 responds to the load side impedance measurement value given from the impedance sensor 96B, and the motor 90B, the phase of the load side impedance measurement value is zero (0) and the absolute value is 50Ω. The reactance of the reactance elements X _L1 and X _L2 in the matching circuit 88B is controlled by driving the 92B.

The load-side impedance measurement value given from the impedance sensor 96B to the matching controller 94B is updated in synchronization with the power modulation (more accurately, in the period of the moving average value calculation). The matching controller 94B does not stop the matching operation, that is, reactance control of the reactance elements X _L1 and X _L2 during the update, so that the load side impedance measurement value immediately before the update matches or approximates the matching point. The motors 90B and 92B are driven and controlled.

In this embodiment, as described above, the sampling average value calculation circuits 104B and 112B and the moving average value calculation circuits 106B and 114B apply the double sampling averaging process to the RF voltage and current measurement values, thereby allowing the impedance sensor 96B to The update speed of the output load side impedance measurement value and the speed of the drive control of the motors 90B and 92B (that is, the reactance control of the reactance elements X _L1 and X _L2 ) in the matching controller 94B can be well matched. As a result, even if the power modulation frequency is set to the order of several tens of kHz or more, the matching unit 42 is in a matching operation, resulting in failure of movable parts (particularly reactance elements X _L1 and X _L2 ) and a shortened life. In addition, it is possible to accurately follow fluctuations in load (plasma) impedance.

Further, in this embodiment, as described above, the measured value of the load side impedance obtained based on the voltage detection signal and the current detection signal corresponding to the high frequency RF2 obtained on the high frequency power supply line 45 matches or approximates the matching point. Auto-matching is performed. That is, the matching operation of the matching unit 42 is performed on the high-frequency RF 2 even when there is a frequency component (pulse frequency modulation) corresponding to the modulation frequency f _S around the high-frequency RF 2 on the frequency axis (on both sides). It is designed to work selectively. Therefore, in the reflected wave power monitor unit in the RF power monitor 86B, it is possible to obtain a monitor result in which the power of the fundamental wave reflected wave (f _RF2 ) is remarkably lowered as shown in FIG. 4B.

[Action of matching device]

  Next, the operation of the matching units 40 and 42 in the first power modulation method will be described in detail with reference to FIG. 9 as an example.

  When a given dry etching is performed by the first power modulation method, a modulation control pulse signal PS is given from the main control unit 72 to the high frequency power supply 36 for plasma generation. As shown in FIG. 9, the high frequency power supply 36 turns on or off the output or power of the high frequency RF1 in synchronization with the modulation control pulse signal PS.

In this case, the RF1 monitor signal AS by the sampling average value calculating circuit 104A in the matching unit 40 of the radio frequency RF1 system, the monitoring time T _H of the sampling averaging process indicated in the 112A from the main control unit 72, the pulse frequency f _S It is set within one cycle of the on-period T _on of. Preferably, as shown in FIG. 9, high frequency power supply line 43 on at RF1 system power of the reflected wave of excluding immediately after the start of the on-period T _on for sudden increases and end just before the transient time T _A1, T _A2 A monitoring time _TH is set in the section. Even if the high frequency RF1 is turned on / off at the pulse frequency f _s , the monitor time _TH is set only in the on period T _on and not in the off period T _off . Therefore, the matching unit 40 functions only when the high frequency RF1 is in an on state.

Sampling average value calculating circuit 104A, 112A samples the voltage detection signal and current detection signal in synchronization during the monitoring time T _H in the sampling clock ACK _1, computed their average value, respectively.

For example, the pulse frequency f _S is 10 kHz, the duty ratio D _S is 80%, a frequency is 40MHz sampling clock ACK _1, the length of the monitoring time T _H is a half of the on-period T _on (50%) To do. In this case, for each cycle of the pulse frequency f _S , sampling is performed 1600 times during the monitoring time T _H within the on-period T _on , and one average value data a representing the average value for 1600 is obtained. It is done.

The moving average value calculation circuit 106A of the voltage sensor system in the matching unit 40 takes in the average value data a output from the sampling average value calculation circuit 104A for each cycle of the pulse frequency f _S as shown in FIG. The average value a of the N consecutive voltage detection signals is sampled at the period T _A of the sampling clock ACK ₂ , the moving average value is obtained for the N average value data a, and the sampling range is sampled on the time axis It is moved in the moving pitch according to the clock ACK ₂ period T _a to repeat the moving average value computation above.

For example, when the pulse frequency f _S is 10 kHz and the period T _A of the sampling clock ACK ₂ is 200 μsec (5 kHz in frequency), as shown in FIG. 10, the moving pitch (average value data on the head side on the time axis) The number of “a” and the rearmost average value data “a” are replaced by one moving average value calculation) is “2”. Thus, when the value of the moving pitch is set to an arbitrary “m” (m is an integer of 2 or more), the frequency of the sampling clock signal ACK ₂ may be selected to be 1 / m times the pulse frequency f _S. .

  The moving average value calculation circuit 114A of the current sensor system in the matching unit 40 also operates at the same timing as the moving average value calculation circuit 106A of the voltage sensor system, and performs the same signal processing on the average value of the voltage detection signal.

Thus, when using the first power modulation process, in matching device 40 of the plasma generating high frequency RF1 systems, pulse frequency f each cycle of the on-period T in _on the _S (preferably more transient time of the reflected wave power The sampling average value calculation circuits 104A and 112A perform high-speed and precise sampling average signal processing during the monitoring time T _H set in the interval excluding the above), and the moving average value calculation circuits 106A and 114A have many cycles. The signal processing of the moving average over the range is performed. The matching controller 94A continuously performs reactance control of the reactance elements X _H1 and X _H2 according to the load side impedance measurement value from the load impedance measurement value calculation circuit 116A updated in synchronization with the moving average sampling clock. Do. As a result, even if the power modulation pulse frequency is set to the order of several tens of kHz or more, and the duty ratio D _s is set to an arbitrary magnitude, in the matching operation of the matching unit 40, movable parts (particularly reactance elements) are used. X _H1 , X _H2 ) can follow the fluctuation of the load (plasma) impedance accurately without causing failure or shortening of the service life.

  On the other hand, in the first power modulation method, the modulation control pulse signal PS is not supplied to the high frequency power supply 38 for ion attraction. Therefore, the high frequency power supply 38 continuously outputs the high frequency wave RF2 with the set value power.

In this case, the monitoring time T _L of the sampling averaging process instructed to the sampling average value calculation circuits 104B and 112B in the matching unit 42 of the high frequency RF2 system by the RF2 monitor signal BS from the main control unit 72 is the pulse frequency f _{S Are} set to an on period _Ton and an on period _Toff of one cycle. Preferably, as shown in FIG. 9, in the on-period T _on, the immediately after the start of high frequency power supply line 45 on at RF2 system power of the reflected wave is suddenly increased and end just before the transient time T _B1, T _B2 One monitoring time T _L1 is set in the excluded section. On the other hand, in the off period T _off , another monitor time T _L2 is set over the entire section.

The sampling average value calculation circuits 104B and 112B sample the voltage detection signal and the current detection signal in synchronization with the sampling clock BCK ₁ during the front monitoring time T _L1 every cycle of the pulse frequency f _S , The average value b is calculated, and the voltage detection signal and the current detection signal are sampled in synchronization with the sampling clock BCK ₁ during the rear monitoring time T _L2 , and the average value c is calculated.

For example, the pulse frequency f _S is 10 kHz, the duty ratio D _S is 80%, a frequency is 40MHz sampling clock BCK _1, the length of the front of the monitor time T _L1 is on-period T _on the half (50%) _Therefore , it is assumed that the length of the rear monitoring time T _L2 is the entire on-period T _off . In this case, within one cycle of the pulse frequency f _S , sampling is performed 1600 times during the front monitoring time T _L1 , and one average value data b representing the average value for 1600 is obtained. During the rear monitoring time T _L2 , sampling is performed 800 times, and one piece of average value data c representing the average value for 800 pieces is obtained.

As shown in FIG. 11, the moving average value calculation circuit 106B of the voltage sensor system in the matching unit 42 receives the average value data b and c output from the sampling average value calculation circuit 104B for each cycle of the pulse frequency f _S. incorporating together, the average value of consecutive N sets of the voltage detection signal [b, c] a sampling with a period T _B of the sampling clock BCK _2, the moving average for their N sets of average value data [b, c] calculated values, is moved by movement pitch corresponding sampling range to the period T _B of the sampling clock BCK ₂ on the time axis keeps moving average value computation above.

For example, if the pulse frequency f _S is 10 kHz, when the (5 kHz in frequency) the period T _B of the sampling clock BCK ₂ 200 .mu.sec, as shown in FIG. 11, the average value data of the head side of the movement pitch (time axis The number of pairs in which [b, c] and the last-side average value data [b, c] are exchanged by one moving average value calculation) is “2”. Thus, when the value of the moving pitch is set to an arbitrary “m” (m is an integer of 2 or more), the frequency of the sampling clock signal BCK ₂ may be selected to be 1 / m times the pulse frequency f _S. .

  The moving average value calculation circuit 112B of the current sensor system in the matching unit 42 also operates at the same timing as the moving average value calculation circuit 106B of the voltage sensor system, and performs similar signal processing on the average value of the current detection signal.

Thus, in this embodiment, the front part set in the ON period _Ton (preferably the period excluding the transient time with high reflected wave power) and the OFF period _Toff in each cycle of the pulse frequency f _S and In the rear monitoring times T _L1 and T _L2 , the sampling average value calculation circuits 104B and 112B perform high-speed and precise sampling average signal processing, and the moving average value calculation circuits 106B and 112B perform moving average calculation over many cycles. Perform signal processing. The matching controller 94B continuously performs reactance control of the reactance elements X _L1 and X _L2 in accordance with the load side impedance measurement value from the load impedance measurement value calculation circuit 116B updated in synchronization with the moving average sampling clock. Do. As a result, even if the power modulation pulse frequency is set to an order of several tens of kHz or more, and the duty ratio D _s is set to an arbitrary magnitude, in the matching operation of the matching unit 42, movable parts (particularly reactance elements) are used. X _L1 , X _L2 ) can follow the fluctuations in the load (plasma) impedance accurately without causing failure or shortening of the service life.

However, the matching device 40 of the radio frequency RF1 system, since the plasma impedance during the on-time T _on may take the matching as described above, the matching point matching operation point A as shown on the Smith chart of FIG. 12 ( 50Ω) or as close as possible.

On the other hand, the high-frequency RF2-based matching unit 42 matches both the plasma impedance during the on-period T _on and the plasma impedance during the off-period T _off , so that it is quasi-matched rather than a perfect matching state. Operates to establish state. Here, the matching unit 42 performs the double sampling averaging process as described above, so that the monitoring time (sampling period) T _L1 , T _L between the on period T _on and the off period T _off. The degree of matching differs in proportion to the length of _L2 , and the relatively longer period is closer to the perfectly aligned state than the shorter period. Therefore, when the duty ratio D _S is sufficiently large as shown in FIG. 9, than matching point C when matching point B is off period T _off when the on-period T _on, as shown on the Smith chart of FIG. 12 Close to the alignment point. Further, the RF2 reflected wave power during the monitoring time (sampling period) T _L1 and T _L2 is inversely proportional to the length of the monitoring period, and as shown in FIG. 9, the off period T _off is the ON period T _on . Be bigger than time.

In the present invention, the matching state, aim without another without matching point (50 [Omega) as far as the matching operation point ON period T _on or off period T _off, and fall within the proximity range constant (first) It is in a state. In contrast, the quasi-alignment, the aligning operation point based on the difference in the load impedance at the time of the OFF period T _off when the on-period T _on is moved around the alignment point (50 [Omega), still first Is in a certain (second) proximity range that is larger than the proximity range.

Even when power modulation is performed on the power of the high-frequency RF 2 for ion attraction by the second power modulation method, both the matching units 40 are merely reversed in the positions of the high-frequency RF 1 (matching unit 40) and the high-frequency RF 2 (matching unit 42). , 42 has the same effect as described above, and the same effect as described above can be obtained.

[Other Embodiments or Modifications]

  Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the technical idea.

  For example, as shown in FIG. 13, the impedance sensor 96A in the matching unit 40 is replaced with an RF voltage detector 100A, an RF current detector 108A, a load impedance calculation circuit 120A, a sampling average value calculation circuit 122A, and a moving average value calculation circuit 124A. It is also possible to configure.

  Here, the load impedance calculation circuit 120A calculates the measurement value of the load side impedance on the high frequency power supply line 43 based on the RF voltage detection signal and the RF current detection signal obtained from the RF voltage detector 100A and the RF current detector 108A. To do. The load impedance calculation circuit 120A can be an analog circuit, but is preferably constituted by a digital circuit.

  The sampling average value calculation circuit 122A and the moving average value calculation circuit 124A simply replace the signal to be processed with the load side impedance measurement value, and the sampling average value calculation circuits 104A and 112A and the moving average value calculation circuit 106A in the above embodiment. , 114A, the same sampling averaging process may be performed.

In this case, the matching controller 94A (FIG. 5) adjusts or approximates the moving average value of the load side impedance measurement value obtained from the moving average value calculation circuit 124A to the matching point corresponding to the impedance on the high frequency power source 36 side. The reactances of the reactance elements X _H1 and X _H2 are controlled through motors 90A and 92A.

  Similarly, as shown in FIG. 14, the impedance sensor 96B in the matching unit 42 is replaced with an RF voltage detector 100B, an RF current detector 108B, a load impedance calculation circuit 120B, a sampling average value calculation circuit 122B, and a moving average value calculation circuit. It is also possible to configure with 124A.

  Here, the load impedance calculation circuit 120B calculates the measurement value of the load side impedance on the high frequency power supply line 45 based on the RF voltage detection signal and the RF current detection signal obtained from the RF voltage detector 100B and the RF current detector 108B. To do. The load impedance calculation circuit 120B can be an analog circuit, but is preferably constituted by a digital circuit.

  The sampling average value calculation circuit 122B and the moving average value calculation circuit 124B simply replace the signal to be processed with the load side impedance measurement value, and the sampling average value calculation circuits 104B and 112B and the moving average value calculation circuit 106B in the above embodiment. , 114B, the same sampling averaging process may be performed.

In this case, the matching controller 94B (FIG. 7) adjusts or approximates the moving average value of the load side impedance measurement value obtained from the moving average value calculation circuit 124B to the matching point corresponding to the impedance on the high frequency power supply 38 side. The reactances of the reactance elements X _L1 and X _L2 are controlled through the motors 90B and 92B.

  In the present invention, as the first power modulation method, a first period in which the power of the high frequency RF1 is at the first level and a second period in which the second level is lower than the first level are constant. A form that alternately repeats at the pulse frequency is also possible. Similarly, as the second power modulation method, a first period in which the power of the high-frequency RF2 is at the first level and a second period in which the second level is lower than the first level are set to a constant pulse frequency. It is also possible to repeat the mode alternately.

  In the above embodiment (FIG. 1), the high frequency RF 1 for plasma generation is applied to the susceptor (lower electrode) 16. However, a configuration in which the high frequency RF 1 for plasma generation is applied to the upper electrode 46 is also possible.

  The present invention is not limited to the capacitively coupled plasma etching method, and can be applied to a capacitively coupled plasma processing method that performs any plasma process such as plasma CVD, plasma ALD, plasma oxidation, plasma nitridation, and sputtering. The substrate to be treated in the present invention is not limited to a semiconductor wafer, and a flat panel display, organic EL, various substrates for solar cells, a photomask, a CD substrate, a printed substrate, and the like are also possible.

10 chamber 16 susceptor (lower electrode)
36 (for plasma generation) high frequency power supply 38 (for ion attraction) high frequency power supply 40, 42 matching unit 43, 45 high frequency power supply line 46 upper electrode (shower head)
56 Processing gas supply source 72 Main controller 88A, 88B Matching circuit 94A, 94B Matching controller 96A, 96B Impedance sensor 100A, 100B RF voltage detector 102A, 102B Voltage detection signal generation circuit 104A, 104B, 112A, 112B Sampling average value calculation circuit
106A, 106B, 114A, 114B Moving average value calculation circuit
116A, 116B Load impedance measurement value calculation circuit 120A, 120B Load impedance measurement value calculation circuit 122A, 122B Sampling average value calculation circuit
124A, 124B moving average value calculation circuit

Claims (12)

A processing container capable of being evacuated and containing a first electrode on which a substrate to be processed is placed and a second electrode opposite to the first electrode, and generating plasma by high-frequency discharge of processing gas between both electrodes, and the plasma From a first high-frequency power source that outputs a first high-frequency power having a frequency suitable for drawing ions into the substrate to be processed on the first electrode, and the first high-frequency power source that is output from the first high-frequency power source. A first high-frequency power supply line for transmitting the high-frequency power to the first electrode, and a variable reactance element for matching the impedance on the first high-frequency power supply side and the impedance on the load side. A matching unit; a second high-frequency power source that outputs a second high-frequency wave having a frequency suitable for generating the plasma; and the second high-frequency power source that is output from the second high-frequency power source. A second high-frequency power supply line for transmitting to either the first electrode or the second electrode, and an impedance on the second high-frequency power supply side and an impedance on the load side on the second high-frequency power supply line A second matching unit for matching the first high-frequency power, a first period in which the second high-frequency power is in the on state or the first level, and a second level lower than the first state and the off state. Plasma for performing desired plasma processing on the substrate to be processed in a plasma processing apparatus having a high-frequency power modulation unit for controlling the second high-frequency power supply so that the second period is alternately repeated at a constant pulse frequency. A processing method,
Corresponding to the first high frequency obtained on the first high frequency power supply line during a first monitoring time set in both the first and second periods within one cycle of the pulse frequency. Sampling average value calculation step of sampling the voltage detection signal and the current detection signal at a predetermined sampling frequency and calculating the average value of those signals;
Based on the average value of each cycle which is more give to the sampling average value calculating step, 1 / m times the pulse frequency (m is an integer of 2 or more) the voltage sense signal and in a cycle of the sampling clock having a frequency of A moving average value calculating step for obtaining a moving average value of the current detection signal;
Wherein based on the moving average of the moving average value wherein the voltage sense signal more obtained in the calculation step and the current sense signal, said first calculates the measured value of the load impedance to the high frequency power load impedance measurement operation Process,
The so measured value of the load impedance more obtained load impedance measurement calculation process is equal or close to a predetermined matching points corresponding to the impedance of the first high frequency power supply side, the reactance of the variable reactance element And a reactance control step for controlling . A processing container capable of being evacuated and containing a first electrode on which a substrate to be processed is placed and a second electrode opposite to the first electrode, and generating plasma by high-frequency discharge of processing gas between both electrodes, and the plasma From a first high-frequency power source that outputs a first high-frequency power having a frequency suitable for drawing ions into the substrate to be processed on the first electrode, and the first high-frequency power source that is output from the first high-frequency power source. A first high-frequency power supply line for transmitting the high-frequency power to the first electrode, and matching the impedance on the first high-frequency power supply side and the impedance on the load side on the first high-frequency power supply line A first matching unit including the variable reactance element, a second high-frequency power source that outputs a second high-frequency wave having a frequency suitable for generating the plasma, and an output from the second high-frequency power source. A second high frequency power supply line for transmitting the second high frequency power to either the first electrode or the second electrode; and the second high frequency power supply on the second high frequency power supply line A second matching section for matching the impedance on the load side and the impedance on the load side, a first period in which the power of the second high frequency is in an on state or a first level, an off state, or the first A plasma processing apparatus having a high-frequency power modulation unit that controls the second high-frequency power supply so as to alternately repeat a second period that is a second level lower than the second level at a constant pulse frequency. A plasma processing method for performing desired plasma processing on a processing substrate,
The measured value of the load-side impedance obtained on the first high-frequency power supply line during the first monitoring time set for both the first and second periods within one cycle of the pulse frequency. Sampling average value calculation step of sampling at a predetermined sampling frequency and calculating the average value of those measured values;
Based on the average value of each cycle which is more give to the sampling average value calculating step, 1 / m times the pulse frequency (m is an integer of 2 or more) the load impedance measured by the cycle of the sampling clock having a frequency of A moving average value calculating step for obtaining a moving average value of the values ;
Wherein as the moving average of the moving average value the load impedance measurements more obtained in the calculation process is equal or close to a predetermined matching points corresponding to the impedance of the first high frequency power supply side, of the variable reactance element And a reactance control step for controlling the reactance . A processing container capable of being evacuated and containing a first electrode on which a substrate to be processed is placed and a second electrode opposite to the first electrode, and generating plasma by high-frequency discharge of processing gas between both electrodes, and the plasma A first high-frequency power source that outputs a first high-frequency power having a frequency suitable for generating the first high-frequency power source, and the first high-frequency power source that is output from the first high-frequency power source is the first electrode or the second A first high-frequency power supply line for transmitting to one of the electrodes, and a variable reactance for matching the impedance on the first high-frequency power supply side and the impedance on the load side on the first high-frequency power supply line A first matching unit including an element; and a second high-frequency electric power that outputs a second high-frequency having a frequency suitable for drawing ions from the plasma into the substrate to be processed on the first electrode. A second high frequency power supply line for transmitting the second high frequency output from the second high frequency power supply to the first electrode, and the second high frequency power supply line on the second high frequency power supply line A second matching section for matching the impedance on the power supply side and the impedance on the load side; a first period in which the second high-frequency power is on or at a first level; and an off state or the first A plasma processing apparatus having a high-frequency power modulation unit that controls the second high-frequency power supply so as to alternately repeat a second period that becomes a second level lower than the first level at a constant pulse frequency. A plasma processing method for performing desired plasma processing on a substrate to be processed,
Corresponding to the first high frequency obtained on the first high frequency power supply line during a first monitoring time set in both the first and second periods within one cycle of the pulse frequency. Sampling average value calculation step of sampling the voltage detection signal and the current detection signal at a predetermined sampling frequency and calculating the average value of those signals;
Based on the average value of each cycle which is more give to the sampling average value calculating step, 1 / m times the pulse frequency (m is an integer of 2 or more) the voltage sense signal and in a cycle of the sampling clock having a frequency of A moving average value calculating step for obtaining a moving average value of the current detection signal;
Wherein based on the moving average of the moving average value wherein the voltage sense signal more obtained in the calculation step and the current sense signal, said first calculates the measured value of the load impedance to the high frequency power load impedance measurement operation Process,
The so measured value of the load impedance more obtained load impedance measurement calculation process is equal or close to a predetermined matching points corresponding to the impedance of the first high frequency power supply side, the reactance of the variable reactance element And a reactance control step for controlling . A processing container capable of being evacuated and containing a first electrode on which a substrate to be processed is placed and a second electrode opposite to the first electrode, and generating plasma by high-frequency discharge of processing gas between both electrodes, and the plasma A first high-frequency power source that outputs a first high-frequency power having a frequency suitable for generating the first high-frequency power source, and the first high-frequency power source that is output from the first high-frequency power source is the first electrode or the second A first high-frequency power supply line for transmitting to one of the electrodes, and a variable reactance for matching the impedance on the first high-frequency power supply side and the impedance on the load side on the first high-frequency power supply line A first matching unit including an element; and a second high-frequency electric power that outputs a second high-frequency having a frequency suitable for drawing ions from the plasma into the substrate to be processed on the first electrode. A second high frequency power supply line for transmitting the second high frequency output from the second high frequency power supply to the first electrode, and the second high frequency power supply line on the second high frequency power supply line A second matching section for matching the impedance on the power supply side and the impedance on the load side; a first period in which the second high-frequency power is on or at a first level; and an off state or the first A plasma processing apparatus having a high-frequency power modulation unit that controls the second high-frequency power supply so as to alternately repeat a second period that becomes a second level lower than the first level at a constant pulse frequency. A plasma processing method for performing desired plasma processing on a substrate to be processed,
The measured value of the load-side impedance obtained on the first high-frequency power supply line during the first monitoring time set for both the first and second periods within one cycle of the pulse frequency. Sampling average value calculation step of sampling at a predetermined sampling frequency and calculating the average value of those measured values;
Based on the average value of each cycle which is more give to the sampling average value calculating step, 1 / m times the pulse frequency (m is an integer of 2 or more) the load impedance measured by the cycle of the sampling clock having a frequency of A moving average value calculating step for obtaining a moving average value of the values ;
Wherein as the moving average of the moving average value the load impedance measurements more obtained in the calculation process is equal or close to a predetermined matching points corresponding to the impedance of the first high frequency power supply side, of the variable reactance element And a reactance control step for controlling the reactance .   5. The plasma processing method according to claim 1, wherein the first monitoring time does not include a first transient time immediately after the start of the first period. 6.   The plasma processing method according to claim 1, wherein the first monitoring time does not include a second transition time immediately before the end of the first period. A processing container that accommodates a first electrode on which a substrate to be processed and a second electrode facing the first electrode are accommodated, and plasma is generated by high-frequency discharge of processing gas between both electrodes, and a high-frequency power source A high-frequency power supply line for transmitting the high-frequency output from the high-frequency power supply to either the first electrode or the second electrode, and an impedance on the high-frequency power supply side on the high-frequency power supply line A matching unit including a variable reactance element for matching the impedance on the load side, and a first period in which the high-frequency power is turned on and a second period in which the high-frequency power is turned off alternately at a constant pulse frequency In a plasma processing apparatus having a high-frequency power modulation unit for controlling the high-frequency power source, a process for performing desired plasma processing on the substrate to be processed is repeated. Be between processing method,
During the monitoring time set in the first period within one cycle of the pulse frequency, the voltage detection signal and the current detection signal corresponding to the high frequency obtained from the high frequency power supply line are sampled at a predetermined sampling frequency. A sampling average value calculating step for calculating the average value of these signals;
Based on the average value of each cycle which is more give to the sampling average value calculating step, 1 / m times the pulse frequency (m is an integer of 2 or more) the voltage sense signal and in a cycle of the sampling clock having a frequency of A moving average value calculating step for obtaining a moving average value of the current detection signal;
Wherein based on the moving average of the moving average value wherein the voltage sense signal more obtained in the calculation step and the current sense signal, and the load impedance measurement value calculation step of calculating the measured value of the load impedance to the high frequency power source,
As measured value before Symbol load impedance more obtained the load impedance measured value calculating step is equal or close to a predetermined matching points corresponding to the impedance of the high frequency power source side, to control the reactance of the variable reactance element And a reactance control step. A processing container that accommodates a first electrode on which a substrate to be processed and a second electrode facing the first electrode are accommodated, and plasma is generated by high-frequency discharge of processing gas between both electrodes, and a high-frequency power source A high-frequency power supply line for transmitting the high-frequency output from the high-frequency power supply to either the first electrode or the second electrode, and an impedance on the high-frequency power supply side on the high-frequency power supply line A matching unit including a variable reactance element for matching the impedance on the load side, and a first period in which the high-frequency power is turned on and a second period in which the high-frequency power is turned off alternately at a constant pulse frequency In a plasma processing apparatus having a high-frequency power modulation unit for controlling the high-frequency power source, a process for performing desired plasma processing on the substrate to be processed is repeated. Be between processing method,
During the monitoring time set in the first period within one cycle of the pulse frequency, the measured values of the load-side impedance obtained from the high-frequency power supply line are sampled at a predetermined sampling frequency, and the measured values are measured. A sampling average value calculating step for calculating an average value ;
Based on the average value of each cycle which is more give to the sampling average value calculating step, 1 / m times the pulse frequency (m is an integer of 2 or more) the load impedance measured by the cycle of the sampling clock having a frequency of A moving average value calculating step for obtaining a moving average value of the values ;
Wherein as the moving average of the moving average value the load impedance measurements more obtained in the calculation process is equal or close to a predetermined matching points corresponding to the impedance of the high frequency power supply side, it controls the reactance of the variable reactance element And a reactance control step.   The plasma processing method according to claim 7 or 8, wherein the monitoring time does not include a first transient time immediately after the start in the first period.   The plasma processing method according to any one of claims 7 to 9, wherein the monitoring time does not include a second transition time immediately before the end in the first period.   The plasma processing method according to claim 7, wherein the monitoring time is not set in the second period.   The high frequency power modulation unit sets at least one of the pulse frequency or the time of one cycle thereof and the ratio (duty ratio) of the first period in one cycle of the pulse frequency to an arbitrary value within a certain range. The plasma processing method as described in any one of Claims 1-11 which can be performed.

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