JPH0461220A - Wafer holding device for x-ray aligner use - Google Patents

Abstract

PURPOSE:To enhance a yield and a productivity at an ultrafine processing operation by providing a control circuit which outputs an instruction signal instructing to start a next process when it confirms that a pressure, inside a suction tube at the inside of a hermetically sealed space, which is indicated by an output signal from a pressure sensor has become smaller than a prescribed value. CONSTITUTION:A pressure sensor 5 detects a differential pressure P between a pressure inside a suction tube 8 and an outside air pressure; it outputs a signal indicating said differential pressure P to a control circuit 10. The difference between a pressure, on the surface of a wafer, which is required to vacuumsuck and hold a wafer and a pressure on the rear, i.e., a prescribed differential pressure P0, is designated as a differential pressure PX1. When it is confirmed that the differential pressure P indicated by the output signal of the pressure sensor 5 has become larger than the prescribed differential pressure P0 (=PX1), an instruction signal instructing to start a next process, e.g. an instruction signal instructing to advance a wafer holding device for an X-ray aligner to an exposure position of the wafer, is output to a control circuit 10. Thereby, it is possible to vacuum-suck the wafer by using a suction force of a required minimum and in the evacuation time of a required minimum.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a wafer holding device for an X-ray exposure apparatus that uses synchrotron radiation as a light source and performs ultrafine processing on a wafer. [Prior Art] In semiconductor manufacturing equipment, as a wafer holding device when transferring a mask pattern onto a wafer, a vacuum suction type wafer holding device that holds the back side of the wafer by vacuum suction (for example, Patent Publication No. 1. 14703) is often used. FIGS. 5(A) and 5(CB) are diagrams each showing an example of a vacuum suction type wafer holding device. This vacuum suction type wafer holding device uses a holding table 40 that holds a wafer (not shown) by vacuum suction on the back side of the wafer holding device.
1, and an exhaust pump 4 for vacuum suctioning the wafer.
06, a pipe 404 connecting the exhaust pump 406 and a suction pipe 408 described later, and the exhaust pump 40 of the pipe '404.
6 and the holding table 401.
07, the pressure inside the pipe 404 and the introduction pipe 4 provided between the valve 407 of the pipe 404 and the holding table 401.
a pressure sensor 405 that detects the pressure difference between the pressure of outside air introduced from 11 (hereinafter referred to as 1, "external pressure"6);
When it is confirmed by the output signal of the pressure sensor 405 that the differential pressure indicated by the output signal has become larger than a predetermined value, an instruction signal is sent to proceed to the next process (for example, if the vacuum suction type wafer holding device is A control circuit 410 outputs an instruction signal for advancing the camera to the exposure position (c). Here, the holding table 401 has a suction surface 40 which is finished flat in order to maintain the flatness of the wafer that is vacuum suctioned.
2, one at the center of the suction surface 402, and one at the center of the suction surface 402.
Suction [] 403, each suction [-1403 and piping 4], are provided in two concentric circles shaped like 409409□ (Fig.
04 and a suction tube 408 to which it is connected. Also,
Valve 407i, closed; Piping 4 (]4
Piping 404 communicates between the inside and outside space, and in the open state
The interior of the exhaust pump 406 is communicated with the exhaust pump 406. In this vacuum suction type tube holding device, the vacuum-centered tube is conveyed by a known conveying hand (not shown) to a position where it contacts the suction surface 402 of the holding table 401. After that, the valve 407 is opened, and the transferred wafer and the suction surface 402 and the two engraved on the suction surface 402 are attached.
The gas in the space (hereinafter referred to as the "sealed space") formed by the concentric grooves 4 [191, 4092] of the book is
4 and is exhausted by the exhaust pump 406,
The back surface of the wafer is vacuum-adsorbed. At this time, the pressure sensor 405 detects a pressure difference between the pressure inside the pipe 404 and the outside air pressure, and outputs a signal indicating the pressure difference to the control circuit 410i. When the control circuit 410 confirms that the differential pressure indicated by the output signal of the pressure sensor 405 has become stronger than a predetermined value, it outputs the instruction signal. On the other hand, when the vacuum suction of the wafer is canceled -4, the valve 407 is closed and outside air is not sent into the pipe 404. [Problems to be Solved by the Invention] However, in the vacuum suction type wafer holding device described in "-", the pressure sensor 405 is installed at the valve 4 of the piping 404.
07 and the holding table 401, there is no problem with [I]I, which is as fine as that used in exposure equipment that uses far ultraviolet light as a light source, which is currently in practical use, but synchrotron radiation is used as a light source. X-ray exposure equipment (for example, λ, patent application 1986)
252991), new problems have arisen in which the yield and productivity are lowered for the following reasons. (1) The pressure inside the pipe 404 detected by the pressure sensor 405 differs from the B force inside the sealed space because the structures of the pipe 404 and the suction pipe 408 are actually complicated. (2) The differential pressure varies depending on the atmosphere of the space that this vacuum adsorption type wafer holding device cannot control and the condition of the back side of the wafer. Therefore, it is difficult to obtain the differential pressure with high accuracy. It is difficult to accurately estimate the pressure in the sealed space from the differential pressure detected by the pressure sensor 405.
It is not easy to accurately estimate the pressure in the closed space.
If the differential pressure detected in step 5 is not sufficiently small (-), the wafer must proceed to the next step, and the maximum adsorption force becomes excessive, causing severe distortion in the wafer being vacuum-adsorbed. However, when performing ultra-fine processing on the wafer, even the slightest distortion of the wafer causes a deterioration in pattern transfer accuracy, resulting in a decrease in yield.Furthermore, it takes extra time for the wafer suction operation. The purpose of the present invention is to adsorb 1... and then move σ to 1 culm with the minimum adsorption time and optimal adsorption force. , side J−
From this, ultra-fine machining] - yield r: j
It is an object of the present invention to provide a holding device for an X-ray exposure apparatus which has a high productivity and productivity. [Means for Solving the Problems J] The holding device for an X-ray exposure apparatus of the present invention includes an L1 kahinza that is provided in a holding table and detects the pressure in a closed space or in a suction pipe; When the output signal of the pressure sensor is supplied, and each time the force in the closed space or the suction indicated by the output signal becomes smaller than a predetermined value, the following occurs. It has a control circuit that outputs an instruction No. 3 to proceed to the process. Further, the holding table includes an introduction pipe through which outside air is introduced, and the pressure sensor detects a pressure difference between the pressure inside the closed space or the suction pipe and the outside air pressure, and the T good. Furthermore, the timer that determines the exhaust time is W ) When 1 becomes smaller than a predetermined value, the timer indicates 4. It is determined whether the exhaust time is longer than the predetermined exhaust time or not. Good. [Credit Co. 4 invention of X-ray exposure device J゛ha storage device τ'' is 11
'Install the Kasenza in the holding stand and place it in a closed space or (J
In order to detect the pressure inside the suction tube, this It is possible to detect the 1st force on the back side of I-Ha with high accuracy regardless of the relationship between the pressure sensor and the pressure inside the closed space or the suction pipe. By detecting the pressure (1) of the outside air introduced from the introduction (external pressure), the pressure in the closed space or in the suction pipe can be directly detected (4). Even if the outside air changes (5), the difference between the pressure on the front surface and the pressure on the back surface of the wafer can be accurately detected.Furthermore, it has a timer to measure the exhaust time g1,
Only when the pressure in the sealed space or in the suction pipe detected by the pressure distribution sensor becomes smaller than a predetermined value within a predetermined evacuation time, an instruction signal is sent to the control circuit to proceed to the next process. Since the difference between the pressure on the front surface of the wafer and the pressure on the back surface of the wafer can be set to an optimal value, the wafer can be held with the optimal adsorption force. The wafer can be vacuum-adsorbed, and the strain generated on the wafer can be minimized, and the time required to vacuum-adsorb the wafer can be minimized. The wafer can be vacuum-chucking within the suction time -C. [Example] Next, an example of the present invention will be described with reference to the drawings. FIGS. 1A and 1B are views showing a first embodiment of a wafer holding device for an X-ray exposure apparatus according to the present invention, respectively. The wafer holding device for an X-ray exposure apparatus according to this embodiment includes a holding table 1 for holding a wafer (not shown) each time the back side of the wafer is vacuum-suctioned, and an exhaust pump for vacuum-suctioning the wafer. 6 and the suction pipe 8 that comes with the throat air pump 6, which will be described later, and the exhaust pump 6 of the pipe 4 and the holding stand l.
and a valve 7 installed between the holding table 1 and the holding table 1.
However, in order to maintain the flatness of nTj after vacuum suction, there is a suction surface 2 with flat finishing grooves, one in the center of the suction surface 2, and one on the suction surface 2 (, - carved o). 4 each in the concentric grooves 91 and 92 of the book (Fig. 1 (A)
) and left and right), and a suction pipe 8 that connects each suction [ ] 3 to the piping 4, it is different from the vacuum suction type wafer holding device shown in FIG. It's the same. However, the pressure regulator 5 is installed inside the holding table 1.
An introduction pipe 1 that connects the pressure sensor 5 and the external space.
The pressure of outside air introduced from 1 (outside air f31) and the suction pipe 8
A timer 12 is provided to detect the differential pressure between the internal pressure and the internal pressure, and also to measure the evacuation time.Furthermore, the control circuit 10
When the pressure in the suction pipe 8 indicated by the output signal of the pressure sensor 5 is smaller than a predetermined value, the exhaust time indicated by the pressure sensor 12 is determined 4. Whether or not the exhaust time is greater than the predetermined exhaust time. It differs from the vacuum adsorption type wafer holding device shown in FIG. It communicates between the inside and outside space, and in the open state, communicates between the inside of the pipe 4 and the single air pump 6.Next, the operation of the vacuum holding device for the X-ray exposure apparatus of this embodiment will be explained. , will be explained using FIG. 2 and FIG. After that, the valve 7 is opened, and the space (sealed space) formed by the transferred wafer, the suction surface 2, and the two concentric grooves 91 and 92 cut in the suction surface 2 is opened. The gas in the sea urchin is discharged by the exhaust pump 6 through each suction port 3, the suction pipe 8, and the piping 4, so that the back side of the sea urchin is vacuum-adsorbed. The differential pressure P between the pressure and the outside air is detected, and a '1' signal indicating the differential pressure P is output to the control circuit 10. At this time, if there is no leakage t1 from the outside air in the sealed space (vacuum in J Exhaust time t from the start of adsorption and juice cassette>
The relationship between the H11 signal of +1'5 and the differential force P is as shown, for example, by the solid line in FIG. That is, before the sea urchin 78 is vacuum-adsorbed (exhaust time 1
-O), valve 7 is closed once.

[, 2'' (Since the inside of the pipe 4 and the outside space are communicated, the pressure inside the suction pipe 8 becomes equal to the outside air pressure, and the differential pressure P = 0 [T
It becomes orrl. Thereafter, when the vacuum suction of the wafer aij is started, the BE force in the suction tube 8 decreases as the evacuation progresses, so the differential pressure (K) increases, and the evacuation time t shown at point A ” At +, the differential pressure P
``Px+, exhaust time t', '=i shown at point C; 2, the differential pressure P=PX2 and the exhaust time t shown at point C
” j 3, the differential pressure P=PX3. Here, the difference between the pressure on the front surface of the wafer and the pressure on the back surface of the wafer (hereinafter referred to as "
"predetermined differential pressure". ) F). Then, the pressure difference between the pressure inside the suction pipe 8 detected by the pressure sensor 5 and the outside atmospheric pressure is equal to the pressure on the surface of the tube being vacuum-adsorbed. Pressure sensor 5 responds accurately to the difference in pressure on the back side.
The differential pressure P indicated by the output signal of is the predetermined differential pressure P o
(= P xt) (i.e.,
(The pressure inside the suction tube 8 has become smaller than a predetermined value)
When necessary, the control circuit 10 outputs an instruction signal to proceed to the next process (for example, an instruction signal to advance the wafer holding device for the X-ray exposure apparatus to the wafer exposure position). The wafer can be vacuum-adsorbed with the minimum suction force and with the minimum necessary evacuation time. In addition, in the above explanation, it is assumed that there is no leakage from the outside air into the sealed space, but in reality, distortion of the wafer, dust attached to the back side of the wafer, and the wafer when the wafer is placed on the suction surface 2 are caused. Due to the positional relationship between the suction surface 2 and the suction surface 2, leakage from outside air occurs in the closed space. In this case, the relationship between the evacuation time t from the start of vacuum suction and the differential pressure P indicated by the output signal of the pressure sensor 5 is, for example, as shown by the broken line in FIG. 2, and the differential pressure 1 at the same evacuation time t is , becomes smaller than when there is no leakage from the outside air into the sealed space. That is, at the exhaust time t shown at point B and t1, the differential pressure P=Pyi (Py+<p, l,) and point r), and at the exhaust time t'' t2, the differential pressure P
= PY2 (PY2<P-2). However, in the wafer holding device for the X-ray exposure apparatus of this embodiment, the differential pressure (■) indicated by the output signal of the pressure sensor Therefore, the differential pressure P is the predetermined differential pressure P. ("PX=)" (exhaust time t=t2 in FIG. 2), by causing the control circuit 10 to output the instruction signal, leakage from outside air into the sealed space is prevented. Even if this occurs, the wafer can be vacuum-adsorbed with the minimum necessary suction force and with the minimum necessary evacuation time. The relationship between the bleed time t and the differential pressure P is measured in advance, and the exhaust time 1. Figure 2 - In the case shown by the dotted chain line,
The exhaust time t=ts) shown at point F is determined, and the exhaust time t-ta is set as a predetermined exhaust time']. By setting the binding, the timer 12 measures the evacuation time t from the start of vacuum suction of the wafer to the predetermined evacuation time. (=t
2) Even if the differential pressure P indicated by the output signal of the pressure sensor 5 is greater than the predetermined differential pressure value). (=Px+)
If it does not become larger than , the control circuit 10 can be made to output an instruction signal to stop vacuum suction to the sea urchin or a signal to notify of an abnormality. Therefore, the control circuit 10 and the determining means 10□ are
By operating according to the flowchart shown in the figure, the yield is improved and the productivity is significantly improved. That is, when the vacuum layering of the wafer is started, the control circuit 10 sets the timer 1 to the force f5.
1; (step 71), and the determination stage 10. Here, the exhaust time 1 indicated by the output fiM of the timer 12 is the predetermined exhaust time T. In step 72), it is determined whether the previous a-JJi time i is greater than the predetermined exhaust time I'. If it is larger than , for example, a signal indicating an abnormality is output to the control circuit 10 (
Step 73). Horn, i? The evacuation time t is the predetermined evacuation time '1'. When it is smaller than (j, pressure cassette:), the fifth output of the world, the number Ko is shown.''<Differential pressure P is a predetermined differential pressure I]. Step 7
4), the differential pressure F) is the predetermined differential pressure (■). If it is smaller than , return to step 7]. Further, the differential pressure P is the predetermined differential pressure P. When you are more polite than (
”, the instruction signal is output from the control circuit ]0 (step 75). In addition, when releasing the vacuum suction of the wafer, please press valve 7.
℃ is closed, and outside air is sent into the pipe 4. A wafer holding device for an X-ray exposure apparatus according to this embodiment. A pressure sensor 5 is installed at the bottom of the holding table 1 (a suction tube 8 is installed).
By introducing the gas in the suction pipe 8 from a position close to the bottom of the wafer holding table, the pressure can be reduced even if cooling water piping is installed in the holding table 1 to cool the wafer during exposure. A place for installing the sensor 5 is secured. FIGS. 4A) and 4B are views showing a second embodiment of the wafer holding device for an X-ray exposure apparatus according to the present invention. The wafer holding device for an X-ray exposure apparatus of this embodiment is shown in FIG.
As shown in FIG. 4(A), a pressure sensor 35 provided in the holding table 31 is placed in the outer concentric groove 39□ provided on the suction surface 32 of the holding table 31, diagonally to the left in FIG. 4(A). The pressure in the closed space introduced via the second introduction pipe 45 from the introduction [ ] 46 provided at F, and the pressure of outside air introduced via the second introduction pipe 41 (outside pressure) It differs from the one shown in FIG. 1 in that it does not have a timer for detecting the differential pressure between the pump and the pump and measures the evacuation time, and that the control circuit 40 does not have the determination means 10 shown in FIG. . Therefore, in the wafer holding device for an X-ray exposure apparatus of this embodiment, since the pressure sensor 35 detects the differential pressure using the pressure in the sealed space, can be detected more accurately than that shown in FIG. Further, when the control circuit 40 confirms that the pressure in the sealed space indicated by the output signal of the pressure sensor j-35 has become smaller than a predetermined pressure, it sends an instruction signal to proceed to the next step [1]. It only has the function of outputting. Furthermore, in the wafer holding device for an X-ray exposure apparatus of this embodiment, a pressure sensor 35 is installed at the bottom of the holding table 31.
t. Each time the gas in the sealed space is introduced through the second introduction pipe 45, even if a cooling water pipe is provided in the holding table 31 to cool the wafer during exposure.
A place for installing the pressure sensor 35 is ensured. In this embodiment as well, the exhaust time is measured. Set the number -) 4 ■: Everyone j, 2, control the same 14 (monthly 1st figure 1: l i1ζ4-judgment: 1-stage 10, set (j Rugodo, place) j- From the opening of the mountain, the output of the juice cassette → f 3 E) 6: It is directly small, the child pressure is not higher than the predetermined differential pressure.2) That is,
When confirming that the pressure in the sealed space is less than 1 ㎡, the control circuit 40:
Proceed to the next step-J°
RJ for line exposure equipment), 1. ζ (, ζ - is also acceptable) to output the exposure position of FC (FC) when the sleeve retaining device is turned on. , and E (case two;) and the pressure sensor 35 shown in FIG.
The difference between 11 and 12 is 11 - something that detects force'a-2), but
It may be a device that directly detects the sweat inside the suction 2/3 or the closed space. In particular, there is no need to detect the pressure (when the energy E is controlled to be a - constant value (0)). 1.15.
In this place 6; 7i, the above? Tsunoni) Nikasen 4, 11.
．． 5.35ζ Since there is no need to introduce outside air, it is necessary to introduce 11 and the first introduction shield, 14],, i, J) lX
If you want to directly detect the 1L force in the sealed space, either the inside of the suction tube 8 or the inside of the suction tube (in case of directly detecting the 1L force in the sealed space, it consists of a rotary cell). 8 or (=, Moekita/It may be installed at a convenient place in a closed space.) A plurality of circular ↑"-shaped protrusions are provided on the opposite side of the back side of the vacuum suction roller of the stand.
It may be possible that it is based on the fya soku power formula. Effects of the Invention] The present invention has the following advantages. As mentioned above, the configuration is X\fr.
Next, the pressure inside the closed space or the suction pipe is detected by a pressure sensor, and when the detected Fl force is smaller than a predetermined value, the control circuit performs the following By outputting the ``-1'' signal to advance the woofer to the culm, it is possible to adsorb the woofer with the optimum adsorption force, minimizing the distortion caused by the 44H and -F on the culm. Since C1' and C1' can be vacuum-adsorbed with the minimum suction time, there is an effect that the yield during ultra-fine processing and the direction of aJi can be adjusted.

[Brief explanation of the drawing]

FIG. 1 (There is a diagram τ showing the first embodiment of the X-ray exposure apparatus wafer 4. 3) is a schematic diagram of the device;
Figure 2 shows the relationship between time and differential pressure, Figure 3 explains the operation of the control circuit and the judgment stages, Figure 4 shows the relationship between time and differential pressure. (A) is a diagram showing a second embodiment of the J-H holding device for a line exposure device, (A) is the soil surface of the holding stand, FB) is a schematic configuration diagram of the device, and FIG. shows an example of a vacuum suction type holding device; (A) is a top view of the holding table; (B) is a top view of the holding table;
, there is a schematic configuration diagram of the device. 1.:31... Holding stand, 2.32... Suction surface,
3.33... Suction [-1, 4, :34... Piping, 5
, 3Fi...j 王力廿anza, 6.36...Exhaust pump, 7.37...Valve, 8,38...Suction pipe, 9+
92.39+, 39z... Groove, 10.40... Control circuit, 10□... Judgment stage, 11... 41... 645... B P, l) x Introduction pipe, 12 ... timer, first introduction pipe, second introduction pipe, 46... introduction port, (], D
, F′ , F ・ ・ ・ U1, F′X
2 P X3. P v+, P Y2 Nine Forces, ■),... IJi constant differential pressure, 1,... 12.13...Exhaust time ゛]'.・・・i”j′i constant exhaust time. 1°

Claims (1)

[Scope of Claims] 1. A pressure sensor provided in a holding table to detect the pressure in a closed space or a suction pipe, and an output signal of the pressure sensor is supplied, and a pressure sensor in the closed space indicated by the output signal is provided. Alternatively, a wafer holding device for an X-ray exposure apparatus, comprising a control circuit that outputs an instruction signal to proceed to the next process when it is confirmed that the pressure in the suction tube has become smaller than a predetermined value. 2. A claim characterized in that the holding table has an introduction pipe for introducing outside air, and the pressure sensor detects a pressure difference between the pressure inside the closed space or the suction pipe and the outside air pressure. The wafer holding device for an X-ray exposure apparatus according to item 1. 3. It has a timer that measures the evacuation time, and the control circuit determines the evacuation time indicated by the timer when the pressure in the closed space or in the suction pipe indicated by the output signal of the pressure sensor becomes smaller than a predetermined value. 3. The wafer holding device for an X-ray exposure apparatus according to claim 1, further comprising determining means for determining whether the evacuation time is longer than a predetermined evacuation time.