CN1168127C - Abnormal detector for chemical mechanical polishing - Google Patents

Abstract

A chemical mechanical polishing abnormality detection device includes: a motor; an inverter; a control circuit, which controls the AC current output by the inverter and whether it works; a speed sensor, which converts the speed of the motor into a speed signal and outputs it to the control circuit; a current detector, which detects the AC current of the motor and outputs the current signal to a relay controller, and the relay controller outputs a drive signal to the mechanical polishing controller, and the mechanical polishing controller outputs a stop signal to the control circuit. This allows timely detection of scratches or cracks on the wafer during the polishing process, so as to reduce the number of wafers damaged by polishing.

Description

Chemical mechanical polishing anomaly detection device

The invention relates to a detector for detecting the situation of the wafer in the chemical mechanical polishing process, and in particular to a detector for detecting the scratch or crack of the polished wafer during the chemical mechanical polishing process.

Chemical-Mechanical Polishing (CMP) is a technology that provides "Global Planarization" (Global Planarization) of VLSI (Very Large Scale Integration) or ULSI (Ultra Large Scale Integration) process. The mechanical grinding principle of "abrasive tool", combined with appropriate chemical additives (Reagent), is a planarization technology that grinds the uneven contours of the wafer surface.

FIG. 1 shows a schematic diagram of equipment for a chemical mechanical polishing planarization process. In FIG. 1 , a grinding table 10 for grinding a wafer 14 and a holder 16 for grasping the wafer 14 to be ground are formed. Wherein, the handle 16 grasps the back side of the wafer 14, and then, the front side of the wafer 14 is pressed on the grinding table 10 covered with a layer of polishing pad (Polishing Pad) 12, to carry out so-called chemical mechanical polishing.

When the chemical mechanical grinding is in progress, the grinding table 10 and the handle 16 rotate in a certain direction, and when grinding, the chemical auxiliary agent (not shown) used to help the chemical mechanical grinding is continuously supplied to the Grinding table 10. That is, the protruding deposition layer on the wafer 14 is removed step by step by using the chemical reaction provided by the chemical additives and the mechanical grinding of the wafer 14 on the grinding table 10 .

When the wafer is undergoing a CMP planarization process, sometimes the grinding contaminants on the grinding table will cause severe scratches or cracks to the polished wafer. Moreover, when serious scratches or cracks occur on the wafer, the polishing table cannot monitor and send a warning signal in time to stop the chemical mechanical polishing and planarization process of the wafer and remove the grinding pollutants that cause problems in time. Due to the continuous progress of the modern process, when serious scratches or cracks are found on the wafers in the later stage of the process, many batches of wafers have been scratched or cracked due to the grinding pollutants on the grinding table, and then we start to move forward. Finding damaged wafers often results in the scrapping of a large number of wafers.

Therefore, the present invention provides a chemical mechanical polishing abnormality detection device, which can detect in time whether the wafer is seriously scratched or broken due to the influence of grinding pollutants on the grinding table during the grinding process, so as to avoid causing a large number of chips are scrapped.

The invention provides a chemical mechanical grinding abnormal detection device, which includes: an electric motor; an inverter, which converts DC power into AC power, and supplies the AC power to the motor; a control circuit, which controls the AC power outputted by the inverter. The magnitude of the current and whether it is working or not; a sensor that converts the speed of the motor into a speed signal and outputs the speed signal to the control circuit; and a detector that detects the magnitude of the AC current output from the inverter to the motor to output a shutdown signal to the control circuit.

The invention provides a chemical mechanical grinding abnormal detection device, which includes: an electric motor; an inverter, which converts DC power into AC power, and supplies the AC power to the motor; a control circuit, which controls the AC power outputted by the inverter. The size of the current and whether it is working or not; a speed sensor converts the speed of the motor into a speed signal, and outputs the speed signal to the control circuit; a current detector detects the magnitude of the AC current of the motor, and outputs a current signal. A relay controller receives a current signal from the current detector and outputs a driving signal; and a mechanical grinding controller receives a driving signal from the relay controller to output a shutdown signal to the control circuit.

The invention provides a chemical mechanical grinding abnormal detection device. When the wafer is severely scratched or broken during the grinding process, there will be abnormal stress in the mechanical grinding, and the electrical system will also have abnormal current. If the current changes, it can be detected in time whether the wafer is scratched or broken during the grinding process.

In order to make the above-mentioned purposes, features, and advantages of the present invention more comprehensible, preferred embodiments are introduced below, together with the accompanying drawings, as follows:

Fig. 1 shows the schematic diagram of the equipment of chemical mechanical polishing planarization process;

Fig. 2 represents chemical mechanical grinding circuit block diagram of the present invention;

Fig. 3 represents the chemical mechanical polishing circuit block diagram of preferred embodiment of the present invention; And

Fig. 4A, Fig. 4B, Fig. 4C show the waveforms of the phase currents of the three-phase AC induction motor measured by the current transformer.

Label description:

10: Grinding table

12: Grinding pad

14: Wafer

16: handle

20, 36: DC power supply

22: Inverter

24: Motor

26: Sensor

28: Detector

30, 38: Control circuit

32: Three-phase AC induction motor

34: Three phase inverter (three phase inverter)

40: Speed sensor

42: Current transformer

44: relay controller

46: Mechanical Grinding Controller

48: Transistor

50: diode

Fig. 2 shows a block diagram of the chemical mechanical polishing circuit of the present invention. In Fig. 2, the grinding table is rotated by a motor 24, and the motor 24 can be a three-phase AC induction motor, and the power supply of the motor 24 is provided by an inverter 22, and the inverter mainly converts the DC power supply 20 Convert the three-phase AC power supply, and then output the three-phase AC power supply to the motor 24 .

In FIG. 2 , the control circuit 30 controls the magnitude of the AC power output by the inverter 22 and controls whether the inverter 22 works. The control circuit 30 receives the signal of the sensor 26 and the signal of the detector 28 at the same time. The signal output by the sensor 26 represents the rotation speed of the motor 24. When the control circuit 30 receives the signal output by the sensor 26, the control circuit 30 will control the inverter The output power of the device 22 keeps the motor 24 at a certain speed. The signal output by the detector 28 represents the working current of the motor 24. When the control circuit 30 receives the signal output by the detector 28, the control circuit 30 will control the operation of the inverter 22 to make the motor 24 rotate or stop.

FIG. 3 shows a block diagram of a chemical mechanical polishing circuit in a preferred embodiment of the present invention. In FIG. 3 , a three-phase AC induction motor 32 is taken as an example to generate rotational power for the grinding table. The three-phase inverter 34 converts the DC power supply Ed 36 into a three-phase AC power supply to the three-phase AC induction motor 32, and the three-phase inverter 34 is composed of six transistors 48 to form a three-phase circuit, each of which is controlled by a control circuit 38 The conduction time of the transistor 48, each transistor 48 is connected in parallel with a diode 50 to generate a freewheeling effect (Flywheel Effect).

In FIG. 3 , the rotational speed sensor 40 detects the rotational speed of the three-phase AC induction motor 32 , and the rotational speed sensor 40 outputs a rotational speed signal to the control circuit 38 . When the control circuit 38 receives the rotational speed signal of the rotational speed sensor 40, the control circuit 38 controls the conduction time of the transistor 48 in the three-phase inverter 34, so as to control the three-phase power outputted by the three-phase inverter 34, so that the three-phase The AC induction motor 32 maintains a constant rotation speed.

In Fig. 3, a current detector such as a current transformer 42 is added between the three-phase inverter 34 and the three-phase AC induction motor 32, and the current transformer 42 measures the voltage supplied to the three-phase The phase current _ia of the AC induction motor 32 and outputs the current signal to the input terminal of the I/O (input/output) of the relay controller 44 . The relay controller 44 compares the current of the built-in database of the relay controller 44 according to the size of the current signal received at the I/O input terminal. When the received current signal has a large change, such as wafer grinding In case of scratches or cracks, the relay controller 44 sends an I/O drive signal to the I/O input of the mechanical grinding controller 46 . When the mechanical grinding controller 46 receives the I/O driving signal from the relay controller 44 , the mechanical grinding controller 46 sends a shutdown signal to the control circuit 38 . After receiving the shutdown signal, the control circuit 38 controls the three-phase inverter 34 to output the three-phase AC power to be zero, so that the three-phase AC induction motor 32 stops rotating. At this time, the grinding table will send a warning signal to the on-site personnel to eliminate the problem of grinding table shutdown.

In FIG. 3 , the rotational torque of the three-phase AC induction motor 32 is T=PΦ _a × _ia . Wherein, P is the number of magnetic poles of the three-phase AC induction motor 32 , Φ _a is the magnetic flux of the three-phase AC induction motor 32 magnetic poles, and _ia is the phase current of the three-phase AC induction motor 32 . The number of poles of the 32 magnetic poles of the three-phase AC induction motor is fixed, and the magnetic flux of the 32 magnetic poles of the three-phase AC induction motor is related to the temperature and magnetic saturation of the permanent magnets, so the magnetic flux of the 32 magnetic poles of the three-phase AC induction motor will not change greatly. Therefore, the rotational torque of the three-phase AC induction motor 32 is related to the phase current of the three-phase AC induction motor 32, that is, the relationship between the rotational torque of the three-phase AC induction motor 32 and the phase current of the three-phase AC induction motor 32 is change proportionally.

When the rotational speed of the three-phase AC induction motor 32 is stable, if the grinding table is scratched or broken when grinding wafers, the friction force of the grinding table will increase. In this way, the rotational torque of the three-phase AC induction motor 32 will be There will be changes, and the phase current of the three-phase AC induction motor 32 will also change.

At this time, the current transformer 42 will detect the change of the phase current i _a supplied to the three-phase AC induction motor 32 by the three-phase inverter 34, as shown in Fig. 4A, Fig. 4B, and Fig. 4C. The waveform of the phase current of an AC induction motor is shown. In FIG. 4A , when the wafer is not scratched or broken by the grinding table, the waveform of the phase current detected by the current transformer 42 does not change much. In FIG. 4B , when the wafer is scratched on the grinding table, the waveform of the phase current sensed by the current transformer 42 has a large change. In FIG. 4C , when the grinding table is cracked while grinding the wafer, the waveform of the phase current detected by the current transformer 42 is smaller than the normal waveform of the phase current.

Therefore, the current transformer 42 converts the measured phase current ia of the three-phase AC induction motor 32 into a current signal and outputs it to the input terminal of the I/O of the relay controller 44, and the relay controller 44 according to the The magnitude of the current signal received by the input end of the relay controller 44 is compared with the current of the built-in database of the relay controller. When the received current signal has a large change, for example, the grinding of the wafer produces scratches or cracks. The follower controller 44 sends an I/O drive signal to the I/O input of the mechanical grinding controller 46 . When the mechanical grinding controller 46 receives the I/O driving signal from the relay controller 44 , the mechanical grinding controller 46 sends a shutdown signal to the control circuit 38 . After the control circuit 38 receives the stop signal, it controls the three-phase inverter 34 so that the three-phase AC induction motor 32 stops rotating. At the same time, the grinding table will send a warning signal to the on-site personnel to eliminate the problem of grinding machine shutdown.

Therefore, the advantage of the present invention is that when the wafer is severely scratched or broken during the grinding process, the mechanical grinding will have abnormal stress, and the electrical system will also have abnormal current. The current transformer is used to detect the current change of the electrical system. Compared with the current of the built-in database, it can detect in time whether the chip is scratched or broken during the grinding process, so as to reduce the number of chips damaged by grinding.

In summary, although the present invention has been described above with preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make various modifications without departing from the spirit and scope of the present invention. Actions and improvements, so the scope of protection of the present invention is based on the scope defined by the appended claims.

Claims (6)

1. A chemical mechanical grinding anomaly detection device, comprising: An electric motor for generating power for chemical mechanical grinding; an inverter, connected to the motor, converts a DC power to an AC power, and supplies the AC power to the motor; A control circuit, connected to the inverter, controls the magnitude of the alternating current output by the inverter and whether it works; a sensor, connected between the motor and the control circuit, converts the speed of the motor into a speed signal, and outputs the speed signal to the control circuit; and A detector, connected to the control circuit, detects the magnitude of the AC current output from the inverter to the motor, so as to output a shutdown signal to the control circuit. 2. The chemical mechanical polishing abnormality detecting device as claimed in claim 1, wherein the motor is a three-phase AC induction motor. 3. The chemical mechanical polishing anomaly detection device as claimed in claim 1, wherein the inverter converts the DC power into a three-phase AC power. 4. The chemical mechanical polishing abnormality detection device according to claim 1, wherein the sensor is a rotational speed sensor. 5. The chemical mechanical polishing abnormality detecting device as claimed in claim 1, wherein the detector comprises a current detector, a relay controller and a mechanical polishing controller. 6. The chemical mechanical polishing abnormality detecting device as claimed in claim 5, wherein the current detector is a current transformer.

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