JP2008142892A - Polishing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing device which quickly takes a proper measure, by detecting separation of a polishing object from a polishing object holding mechanism in a short time. <P>SOLUTION: This polishing device has a polishing table 1 having a polishing surface and a top ring 4 holding a polishing object base board W, and polishes the polishing object base board W held by the top ring 4 by pressing to the polishing surface of the polishing table 1. Eddy current type sensors 8, 9 and 10 are arranged in one place or a plurality of places in the vicinity of the top ring 4. Separation of the polishing object base board W from the top ring 4 is detected by detecting a difference between a signal of a resistance component and the resistance component as a reference value measured in a state of holding the polishing object base board W by an under surface of the top ring 4, among the resistance component and a reactance component detected by the sensors 8, 9 and 10. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polishing apparatus that polishes an object to be polished such as a semiconductor wafer, and more particularly to a polishing apparatus that has a function of detecting separation / jumping of an object to be polished from the object holding mechanism during polishing.

  In recent years, miniaturization and high integration of semiconductor devices have progressed, and the distance between circuit wirings is becoming narrower. In particular, in the case of photolithography having a thickness of 0.5 μm or less, the depth of focus becomes shallow, so that the flatness of the imaging surface of the exposure apparatus is required. In order to realize this flatness, polishing by a polishing apparatus is widely adopted.

  This type of polishing equipment has a turntable and a top ring body with a polishing cloth affixed to the upper surface that rotates at an independent rotational speed, and presses the substrate to be polished held by the top ring body on the polishing surface of the turntable In addition, there is a polishing apparatus that polishes the surface of the substrate to be polished to a flat and mirror surface while supplying an abrasive liquid to the polishing surface. After the polishing, the substrate to be polished is detached from the top ring body, and the substrate to be polished is moved to the next process, for example, a cleaning process.

  In the polishing apparatus as described above, the substrate to be polished is broken during polishing, and debris may be scattered on the polishing cloth. In this way, when the polishing cloth in which the fragments of the substrate to be polished are scattered is reused, the surface of the substrate to be polished is damaged, so that the polishing cloth must be replaced every time it is cracked. Even if the substrate to be polished is not cracked, the substrate to be polished may jump out of the top ring body. At this time, if the substrate to be polished that protrudes is made of a brittle material such as a semiconductor silicon wafer, the outer surface of the substrate to be polished may be damaged due to collision with the wall surface of the casing that covers the turntable. is there. When the damaged substrate to be polished is polished again, it becomes easy to break even if a light force is applied in the vicinity of the damaged portion.

  In order to cope with the above problem, in Patent Document 1, an ultrasonic sensor is provided that is installed outside the top ring and measures the distance to the turntable surface, and the measurement distance to the turntable surface by the ultrasonic sensor is the turn distance. When the change is caused by the presence of the substrate to be polished on the table surface, this is detected as a polishing abnormality or a protrusion of the substrate to be polished. In addition, a capacitor in which the electrode plate is installed so as to sandwich both sides of the substrate to be polished held by the top ring or a capacitor in which the electrode plate is installed in a position to sandwich the substrate to be polished that protrudes outside the top ring is provided. A constant voltage is applied to the capacitor, and a current flowing from the capacitor is detected as abnormal polishing or popping out of the substrate to be polished. Further, a contact is brought into contact with the turntable on the lower surface of the top ring or around the top ring, and a current is passed between the contact and the surface of the turntable, and a change in the current is detected as a polishing abnormality or a protrusion of the substrate to be polished.

However, any of the above-described polishing anomalies or methods of detecting the pop-up of the substrate to be polished are susceptible to noise and the like, so there are many false detections, and there is a problem that reliability cannot be obtained. In addition, it takes time to detect and detect whether or not polishing abnormality or the substrate to be polished has popped out from the processed signal, and while taking appropriate measures such as stopping the top ring or turntable. For example, the substrate to be polished collides with the wall surface of the casing surrounding the turntable.
JP 2001-96455 A

  The present invention has been made in view of the above points, and provides a polishing apparatus that can detect the detachment of the object to be polished from the object holding mechanism in a short time and can take an appropriate action promptly. Objective.

  In order to solve the above-mentioned problem, the invention according to claim 1 is provided with a polishing table having a polishing surface and a workpiece holding mechanism for holding the workpiece, and the workpiece to be polished held by the workpiece holding mechanism. In a polishing apparatus that polishes an object to be polished by relative movement of the object to be polished held by the object holding mechanism and the polishing surface of the polishing table, the object holding mechanism An eddy current sensor is provided at one or a plurality of locations in the vicinity of the object holding part of the object, and among the resistance component and reactance component detected by the eddy current sensor, the resistance component signal and the object to be polished are held. By detecting a difference from a resistance component as a reference value measured while being held on the lower surface of the mechanism, the separation of the object to be polished from the object holding mechanism is detected.

  According to a second aspect of the present invention, in the polishing apparatus according to the first aspect, the eddy current type sensor is attached to a swinging arm that supports and swings the workpiece holding mechanism.

  According to a third aspect of the present invention, in the polishing apparatus according to the first or second aspect, the eddy current sensor includes one or a plurality of sensor electrodes having a substantially arc shape, and the sensor electrodes are held by an object to be polished. It is characterized by being arranged in the vicinity of the object holding part of the mechanism.

  According to the first aspect of the present invention, the eddy current sensor is provided at one or a plurality of locations in the vicinity of the workpiece holding portion of the workpiece holding mechanism, and the resistance component and reactance component detected by the eddy current sensor are detected. Among these, the object to be polished is detected by detecting the difference between the resistance component signal and the resistance component as a reference value measured in a state where the object to be polished is held on the lower surface of the object holding mechanism. By detecting the separation from the holding mechanism, it is possible to quickly detect (in a short time) the separation / jumping of the object to be polished from the object holding mechanism.

  According to the second aspect of the present invention, by attaching the eddy current sensor to the swing arm, it is possible to quickly detect the detachment of the workpiece even while the workpiece holding mechanism is swinging.

  According to the third aspect of the present invention, by providing an eddy current sensor including one or a plurality of sensor electrodes having a substantially arc shape in the vicinity of the object holding portion of the object holding mechanism. The removal of the polished object from a wide area can be detected quickly.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration example of a polishing apparatus according to the present invention, FIG. 1 (a) is a plan view showing the arrangement of a top ring and a polishing table, and FIG. 1 (b) is a side view of the polishing apparatus. In the figure, reference numeral 1 denotes a polishing table (turn table). A polishing cloth (polishing pad) 2 is attached to the upper surface of the polishing table 1 and is supported by a rotary shaft 3 so as to rotate in the direction of arrow A. Yes. Reference numeral 4 denotes a top ring (object to be polished holding mechanism) for holding a substrate W to be polished such as a semiconductor wafer on the lower surface. The top ring 4 is pivotally attached to the lower end of a top ring rotating shaft 5, and the top ring rotating shaft 5 Is supported by the top ring swinging arm 6 so as to be rotatable in the direction of arrow B. The top ring 4 together with the top ring rotating shaft 5 is lowered with respect to the polishing surface of the polishing table 1, that is, the polishing cloth 2 by the lifting means (not shown) to pressurize and raise the substrate W to be polished with a predetermined pressure. And can be separated.

  The top ring swing arm 6 is fixed to a swing shaft 7 and can be swung (turned) in the direction of arrow C by the swing shaft 7. Reference numerals 8, 9, and 10 denote sensors for detecting the separation and jump-out of the substrate to be polished W provided around the substrate holding portion of the top ring 4, and the sensors 8, 9, and 10 respectively swing the top ring. It is attached to the arm 6. Reference numeral 11 denotes an abrasive liquid supply nozzle for supplying an abrasive liquid 12 such as slurry to the upper surface of the polishing cloth 2 of the polishing table 1.

  In the polishing apparatus having the above configuration, the substrate to be polished W held on the lower end surface of the top ring 4 rotating around the top ring rotating shaft 5 is provided on the upper surface (polishing surface) of the polishing cloth 2 of the rotating polishing table 1. The substrate to be polished W is polished while pressing and supplying the abrasive liquid 12 from the abrasive liquid supply nozzle 11. If the substrate W to be polished is detached or jumps out from the top ring 4 during this polishing, it enters between the lower end of any one of the sensors 8, 9, 10 and the surface of the polishing pad 2. Or detect it.

  Here, since the sensors 8, 9, and 10 for detecting the substrate to be polished W are provided at three positions around the substrate holding portion of the top ring 4 respectively, the substrate W to be polished that has been detached or jumped out is provided. Although it can be detected by any of the sensors 8, 9, and 10 in any direction, the direction in which the substrate to be polished W separates and protrudes is, for example, the direction downstream from the top ring as viewed from the rotation direction of the polishing table. Therefore, sensors may be provided at one place or several places around the direction.

  As the sensors 8, 9, and 10, a capacitance type sensor, an eddy current type sensor, or a combination of the capacitance type sensor and the eddy current type sensor is used. FIG. 2 is a diagram for explaining a capacitance type sensor. FIG. 2A shows a state in which the substrate W to be polished is normally held on the lower surface of the top ring 4 and polished. ) Shows a state in which the substrate W to be polished is detached from or protruded from the lower surface of the top ring 4. As shown in FIG. 2A, when the substrate to be polished W is normally held on the lower surface of the top ring 4, the gap G1 between the lower surface of the sensor 8 and the surface of the polishing pad 2 and the thickness G2 of the polishing pad 2 are obtained. Is measured, and the value is defined as a reference value Cr. 2B, the bottom surface of the sensor 8 and the polishing cloth 2 when the substrate W is detached from and protruded from the bottom surface of the top ring 4 and enters the gap G1 between the bottom surface of the sensor 8 and the surface of the polishing cloth 2. When the combined capacitance formed by the gap G1 between the surfaces and the thickness G2 of the polishing pad 2 is Cc, the change in capacitance ΔC between the lower surface of the sensor 8 and the upper surface of the polishing table 1 is obtained as ΔC = Cc−Cr, The separation / jumping of the substrate W can be detected promptly (in a short time).

FIG. 3 is a diagram showing a schematic configuration of a capacitance measuring system using a capacitance type sensor. Here, if the corresponding area of the sensor 8 is A, the gap between the lower surface of the sensor 8 and the upper surface of the polishing table 1 is G1 + G2, and the dielectric constant of the substance existing between the lower surface of the sensor 8 and the upper surface of the polishing table 1 is ε, The gap G1 + G2 on the upper surface of the polishing table 1 and the capacitance between the lower surface of the sensor 8 and the polishing table 1 are:
C = (A × ε) / (G1 + G2)
It becomes. That is, since the capacitance C changes due to the presence of the substrate to be polished W having a different dielectric constant ε between the lower surface of the sensor 8 and the polishing table 1, the change in the capacitance C is performed by the control unit 13. By detecting this, separation of the substrate W to be polished can be detected.

  FIG. 4 is a diagram showing a circuit configuration example for detecting a change in capacitance using the capacitance type sensor 8. The detection unit 20 includes an oscillator (such as a crystal oscillator) 21, a resistor 22, an amplifier 23, a rectifier / smoothing device 24, an A / D converter 25, and a capacitance value converter 26. An oscillation signal (high frequency signal) from the oscillator 21 is supplied to the sensor 8, the signal from the polishing table 1 is amplified by the amplifier 23, converted into a DC signal by the rectifying / smoothing device 24, and a digital signal by the A / D converter 25. And the capacitance value converter 26 converts the voltage into an output voltage Vc corresponding to the capacitance value. When the capacitance C between the lower surface of the sensor 8 and the polishing table 1 changes, the signal current flowing from the sensor 8 to the polishing table 1 changes, and the output voltage Vc also changes. Can be detected from the top ring 4.

  FIG. 5 is a view for explaining the eddy current sensor. FIG. 5A shows a state in which the substrate W to be polished is normally held and polished on the lower surface of the top ring 4, and FIG. Indicates the state in which the substrate to be polished W is detached from the lower surface of the top ring 4. As shown in FIG. 5A, in the state where the substrate to be polished W is normally held on the lower surface of the top ring 4, the electrical resistance of the sensor 8 (electric resistance between the lower surface of the sensor and the polishing table) is measured, The measured value is set as a reference value Rr. Further, the electrical resistance of the sensor 8 is measured when the substrate W to be polished is detached from the lower surface of the top ring 4 and enters between the lower surface of the sensor 8 and the surface of the polishing pad 2 as shown in FIG. The value is Rs. By comparing the measured value Rs with the reference value Rr and capturing the difference ΔR = Rr−Rs, it is possible to quickly detect the removal of the substrate W to be polished.

  FIG. 6 is a diagram showing a circuit configuration example for detecting a resistance value between the lower surface of the sensor 8 and the surface of the polishing table using the eddy current type sensor 8. The sensor coil 41 of the sensor 8 is an air-core spiral coil, and the sensor coil 41 is disposed in the vicinity of the substrate W to be polished. The voltage detected at both ends of the sensor coil 41 passes through the band-pass filter 43, and the cos component and the sin component of the detection signal are taken out by the synchronous detection unit including the cos synchronous detector 45 and the sin synchronous detector 46. The oscillation signal from the oscillating unit 42 is formed into two signals of an in-phase component (0 °) and a quadrature component (90 °) of the signal source by the phase shift circuit 44, and a cos synchronous detector 45 and a sin synchronous detector 46, respectively. And the above synchronous detection is performed.

  From the synchronously detected signal, unnecessary high frequency components higher than the signal component are removed by the low-pass filters 47 and 48, and the resistance component (R) output which is the cos synchronous detection output and the reactance component (X which is the sin synchronous detection output) ) Outputs are taken out respectively. Since the resistance component (R) output and the reactance component (X) output change when the substrate to be polished W enters between the lower surface of the sensor 8 and the surface of the polishing table 1, the substrate W to be polished is detached from the top ring 4. It is possible to detect ejection.

  In the conventional eddy current sensor, when the substrate to be polished W is an insulator, for example, a silicon wafer, the presence / absence thereof cannot be detected. On the other hand, here, the electrical resistance of the eddy current type sensor 8 (the electrical resistance between the lower surface of the sensor and the polishing table 1) is measured, and the jump of the substrate to be polished is detected from the change. The removal / jump of the substrate W to be polished can be detected in a short time (within 1 msec), the rotation of the top ring 4 and / or the polishing table 1 is stopped, or the top ring is raised to separate the substrate W to be polished from the polishing surface. It is possible to perform such treatment.

  In the above example, the capacitance type or eddy current type sensors 8, 9, and 10 are arranged at a plurality of locations around the top ring 4 (three locations in FIG. 1). The electrode 17 may be arranged around the top ring 4 as shown in FIG. Accordingly, it is possible to quickly detect where the substrate to be polished W jumps out without using a plurality of capacitance type or eddy current type sensors.

  In an abnormality detection signal of a substrate to be polished such as a silicon wafer by a conventional current sensor or the like, the signal stability and reproducibility are not good unless signal averaging and moving average processing are performed. When these signals are averaged and the moving average process is performed, a time delay of about 3.6 seconds at maximum occurs, and when an abnormality is detected, the substrate W to be polished jumps out from the top ring 4 when the abnormality is detected. When an eddy current sensor is used as the sensor 8, it is detected by detecting which of the resistance component (R) output and the reactance component (X) output is higher than the normal level as described above. It becomes possible to detect separation / jumping of the substrate W from the top ring 4. The detection time at this time is within 10 msec.

  In the above-described embodiment, the turntable is described as an example of the polishing table. However, the polishing table is not limited to this, and a belt-like polishing pad 16 is provided with a driven roller 14 and a driving roller 15 as shown in FIG. The polishing table may be configured such that the polishing pad 16 is moved by the rotation of the driving roller 15. Further, the polishing table may be a scroll (translational circulation) motion table that revolves with a small radius without rotating, or a rotation / revolution table that can be controlled by independently controlling the rotation speed of each rotation / revolution.

  In the above-described embodiment, the sensor has been described as an example of a capacitive sensor, an eddy current sensor, or a combination thereof. However, for example, an ultrasonic sensor may be used as the sensor. Of course, sensors may be combined, or a sensor combining all of these may be used.

  In the above embodiment, the polishing pad is used as the polishing surface, but it may be a fixed abrasive (grinding stone or pad) in which the abrasive is hardened with a binder. In this case, a chemical liquid such as a surfactant may be used as the polishing liquid in order to supply water (pure water), the self-generated amount of abrasive grains, and the polishing rate to the polishing surface.

1A and 1B are diagrams showing a schematic configuration example of a polishing apparatus according to the present invention, in which FIG. 1A is a plan view showing the arrangement of a top ring and a polishing table, and FIG. 1B is a side view of the polishing apparatus. FIG. 2A is a diagram for explaining a capacitance type sensor of a polishing apparatus according to the present invention. FIG. 2A shows a state in which the substrate to be polished is normally held on the lower surface of the top ring and polished. b) is a diagram showing a state in which the substrate to be polished is detached from and protruded from the lower surface of the top ring. It is a figure which shows schematic structure of the electrostatic capacitance measurement system of the grinding | polishing apparatus which concerns on this invention. It is a figure which shows the example of a circuit structure for detecting the change of an electrostatic capacitance using an electrostatic capacitance type sensor. FIG. 5A is a diagram for explaining an eddy current sensor of the polishing apparatus according to the present invention. FIG. 5A shows a state in which the substrate to be polished is normally held on the lower surface of the top ring and polished. ) Is a view showing a state in which the substrate to be polished is detached from and protruded from the lower surface of the top ring. It is a figure which shows the circuit structural example for detecting the resistance value between a sensor lower surface and a grinding | polishing table surface using the eddy current type sensor 8. FIG. It is a figure which shows the arrangement configuration of the sensor electrode of the grinding | polishing apparatus which concerns on this invention. It is a figure which shows the schematic structural example of the grinding | polishing apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polishing table 2 Polishing cloth 3 Rotating shaft 4 Top ring 5 Top ring rotating shaft 6 Top ring oscillating arm 7 Oscillating shaft 8 Sensor 9 Sensor 10 Sensor 11 Abrasive fluid supply nozzle 12 Abrasive fluid 13 Controller 14 Driven roller 15 Drive roller DESCRIPTION OF SYMBOLS 16 Polishing pad 17 Electrode 20 Detection part 21 Oscillator 22 Resistor 23 Amplifier 24 Rectifier smoother 25 A / D converter 26 Capacitance value converter 41 Sensor coil 42 Oscillating part 43 Band pass filter 44 Phase shift circuit 45 cos synchronous detector 46 sin synchronous detector 47 Low-pass filter

Claims (3)

A polishing table having a polishing surface and an object holding mechanism for holding the object to be polished, the object to be polished held by the object holding mechanism pressed against the polishing surface of the polishing table, and the object to be polished In a polishing apparatus for polishing an object to be polished by relative movement of the object to be polished held by a holding mechanism and the polishing surface of the polishing table,
An eddy current sensor is provided at one or a plurality of locations in the vicinity of the workpiece holding portion of the workpiece holding mechanism, and among the resistance component and reactance component detected by the eddy current sensor, the signal of the resistance component and the object to be polished are provided. By detecting the difference from the resistance component as a reference value measured in a state where the polished object is held on the lower surface of the polished object holding mechanism, the separation of the polished object from the polished object holding mechanism is detected. A polishing apparatus characterized by: The polishing apparatus according to claim 1, wherein
A polishing apparatus, wherein the eddy current sensor is attached to a swinging arm that supports and swings the workpiece holding mechanism. The polishing apparatus according to claim 1 or 2,
The eddy current sensor includes one or a plurality of substantially arc-shaped sensor electrodes, and the sensor electrodes are arranged in the vicinity of the workpiece holding portion of the workpiece holding mechanism. apparatus.

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