JP2009028805A - Polishing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing device capable of finding abnormality of the device earlier. <P>SOLUTION: The polishing device comprises a rotary driving device for rotating and driving a polishing member including a servomotor 31, a motor current sensor substrate 36 for detecting the amount of a current supplied to the servomotor 31, a signal processing substrate 37 for calculating the amount of torque of the servomotor 31 based on the amount of the current detected in the motor current sensor substrate 36, and a torque monitor 38 for determining whether or not an abnormality exists in the device based on change in the torque of the servomotor 31 calculated by the signal processing substrate 37. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polishing apparatus for polishing an object to be polished such as a semiconductor wafer.

  Conventionally, as a polishing apparatus for flattening the surface of an object to be polished such as a semiconductor wafer, a wafer holding apparatus that holds the wafer in a state where the polished surface is exposed, and a surface to be polished of the wafer held by the wafer holding apparatus And a polishing head for holding a polishing member to which a polishing pad opposite to the substrate is attached. With both of them rotated, the polishing pad is pressed against the surface to be polished of the wafer, and the polishing member is in the contact surface inward direction. There is known a configuration in which a wafer is polished by swinging it (see, for example, Patent Document 1). Further, in addition to such mechanical polishing, chemical mechanical polishing (Chemical Mechanical Polishing) that supplies the polishing agent (slurry) to the contact surface between the polishing pad and the wafer and promotes the polishing by the chemical action of the polishing agent. CMP apparatus for performing CMP) is also known.

The polishing process of the wafer using the polishing apparatus having such a configuration is performed by bringing the polishing pad into contact with the surface to be polished held by the wafer holding apparatus while rotating the polishing pad together with the polishing head. The pad reciprocates horizontally with respect to the wafer while rotating, so that the entire surface of the wafer is uniformly polished.
Japanese Patent No. 2968784

  By the way, in the conventional polishing apparatus as described above, in order to prevent a sudden failure of the apparatus, there has been a demand for a measure for detecting an abnormality of the apparatus as soon as possible.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a polishing apparatus capable of finding an abnormality of the apparatus earlier.

  To achieve such an object, a polishing apparatus according to the present invention includes a holding device that holds an object to be polished, a polishing member that can polish the object to be polished held by the holding device, and an object to be polished. A polishing device configured to move the polishing member relative to the object to be polished and move the polishing member relative to the object to be polished while the polishing member is in contact with the object to be polished. In the apparatus, the driving device is configured to include an electric motor that generates torque for moving the polishing member relative to the polishing member, and the magnitude of the current supplied to the electric motor to generate the torque is determined. A current detector to be detected; a torque calculation unit for calculating the magnitude of the torque based on the magnitude of the current detected by the current detector; and a change in the torque calculated by the torque calculation unit. Based on, and a determination unit that determines presence or absence of abnormality of the apparatus.

  In the above-described invention, it is preferable to include a display unit that displays the magnitude of the torque calculated by the torque calculation unit.

  Further, in the above-described invention, a position measuring device that measures a relative position of the polishing member with respect to the object to be polished is provided, and the display unit includes the relative position of the polishing member measured by the position measuring device. It is preferable to display the magnitude of the torque when the polishing member is located at the relative position.

  In the above-described invention, it is preferable that the driving device is configured to rotationally drive the polishing member by the electric motor.

  Moreover, in the above-mentioned invention, it is preferable that the electric motor is a servo motor.

  According to the present invention, it is possible to detect an abnormality of a device earlier.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. A part of a CMP apparatus (chemical mechanical polishing apparatus) which is a typical example of the polishing apparatus according to the present invention is shown in FIG. The CMP apparatus C includes a cassette index unit, a wafer cleaning unit, and a polishing unit according to the polishing process. The polishing unit includes three polishing chambers and one polishing chamber provided in each section of the index table divided into four. In this embodiment, only one polishing chamber will be described.

  In the polishing chamber 1 into which the semiconductor wafer W is transferred from the transfer chamber, an index table 2, which is divided into four parts and rotated and fed every 90 degrees by the operation of a stepping motor, a polishing arm 3, a dressing device 4, A pad exchanging table 5 and a surface shape measuring device 6 are arranged. Each section of the index table 2 is provided with a wafer holding device 10 that sucks and holds a wafer W as an object to be polished from the back surface, and moves the wafer W to the polishing chamber 1 by suction. The wafer holding device 10 is supported by the index table 2 so as to be rotatable in a horizontal plane, and is rotated at a high speed by driving means such as an electric motor or an air motor (not shown) disposed inside the index table 2.

  The polishing arm 3 is configured to be turnable in the horizontal direction with respect to the index table 2 and to be vertically movable in the vertical direction. A polishing head 20 is rotatably attached to the oscillating end of the polishing arm 3. The polishing head 20 has a polishing member 21 having a polishing pad 22 attached to the lower surface side as shown in FIG. Is detachably held. A polishing surface 23 is formed on the surface (lower surface) of the polishing pad 22 to be in contact with the surface (surface to be polished) of the wafer W for polishing.

  Such a polishing head 20 is rotationally driven by a rotation driving device 30 disposed in the polishing arm 3 and is configured to be rotatable at high speed in a horizontal plane. Further, the polishing head 20 is rotationally driven in a direction opposite to the rotation direction of the wafer holding device 10 described above, and is rotated relative to the wafer W at high speed while the polishing surface 23 of the polishing pad 22 is in contact with the wafer W. The surface (surface to be polished) is polished flat. Further, as shown in FIG. 1, the polishing head 20 can move above the wafer holding device 10, the dressing device 4, the pad changer 5, and the surface shape measuring device 6 by the rotation of the polishing arm 3. It can be done.

  The dressing device 4 shown in FIG. 1 is a device that corrects clogging and unevenness of the polishing pad 22 caused by polishing the wafer W (dressing, sharpening), and detailed illustration is omitted. And a disk having diamond abrasive grains or the like fixed on its surface and a rotatable disk, and a cleaning nozzle for cleaning the polishing pad with pure water by spraying pure water onto the surface of the dressed polishing pad. The pad changer 5 is a device for replacing the used polishing pad 22 with a new one, and the surface shape measuring device 6 is a device for measuring the surface shape of the polishing pad 22.

  As shown in FIG. 3, the rotation driving device 30 includes a servo motor 31 that generates torque for rotating the polishing head 20 (and the polishing member 21). The servo motor 31 is electrically connected to the servo amplifier 34 and is operated by a drive current supplied from the servo amplifier 34 via the motor power cable 32. The servo motor 31 has a built-in motor encoder (not shown) for detecting the rotational displacement of the motor shaft, and the rotational displacement signal of the motor shaft detected by the motor encoder is servoed via the motor encoder cable 33. The signal is input to the amplifier 34.

  The servo amplifier 34 is electrically connected to the host controller 35 and drives the servo motor 31 calculated according to the rotation control signal input from the host controller 35 and the rotation displacement signal of the motor shaft input from the motor encoder. The current is output and supplied to the servo motor 31 via the motor power cable 32. A motor current sensor board 36 is disposed on the motor power cable 32, and the motor current sensor board 36 detects the magnitude of the drive current of the servo motor 31 flowing through the motor power cable 32 and outputs it to the signal processing board 37. To do.

  The signal processing board 37 is electrically connected to the motor current sensor board 36 and the torque monitor 38, and the magnitude of the torque generated in the servo motor 31 based on the magnitude of the driving current input from the motor power cable 32. Is calculated and output to the torque monitor 38. The magnitude of the torque is calculated using the correlation between the torque of the servo motor 31 and the drive current.

  The torque monitor 38 is electrically connected to an encoder 39 (see also FIG. 1) disposed on a rocking shaft (not shown) at the base end of the polishing arm 3, and the encoder 39 is connected to the polishing arm 3. , That is, the horizontal relative position of the polishing member 21 with respect to the wafer W is measured and output to the torque monitor 38. Then, the torque monitor 38 performs polishing along with the relative position of the polishing member 21 based on the magnitude of the torque of the servo motor 31 input from the signal processing board 37 and the relative position of the polishing member 21 input from the encoder 39. The magnitude of torque of the servo motor 31 when the member 21 is located at the relative position is displayed.

  In the polishing process of the wafer W using the CMP apparatus C having such a configuration, the polishing surface 22 of the polishing pad 22 is rotated and held on the wafer holding apparatus 10 while rotating the polishing pad 22 (polishing member 21) together with the polishing head 20. In this case, the polishing pad 22 reciprocates (oscillates) in the horizontal direction with respect to the wafer W while rotating. The entire surface is polished flat. At this time, an abrasive (slurry) is supplied between the polishing pad 22 and the wafer W.

  When the polishing of the wafer W is completed a predetermined number of times, the polishing arm 20 is moved from above the wafer holding device 10 to above the dressing device 4 by the operation of the polishing arm 3, where the polishing pad 22 is dressed. After the dressing is completed, the polishing head 20 is moved from above the dressing device 4 to above the surface shape measuring device 6 by the operation of the polishing arm 3, and the surface shape (groove depth, pad thickness, etc.) of the polishing pad 22 is measured there. Is done.

  If the pad thickness or groove depth is less than the prescribed value, the polishing head 20 is moved above the pad changer 5 to replace the polishing pad 22 (polishing member 21), and further the polishing head 20 Is moved above the wafer holding apparatus 10 to newly polish the wafer W. On the other hand, if the pad thickness or groove depth is equal to or greater than the prescribed value, the polishing head 20 is returned to above the wafer holding device 10 and polishing of a new wafer W is started.

  When performing such polishing processing of the wafer W, the motor current sensor substrate 36 detects the magnitude of the drive current of the servo motor 31 flowing through the motor power cable 32 and outputs it to the signal processing substrate 37. The signal processing board 37 calculates the magnitude of the torque generated in the servo motor 31 based on the magnitude of the drive current input from the motor power cable 32 and outputs it to the torque monitor 38. At this time, the encoder 39 measures the oscillation displacement of the polishing arm 3, that is, the horizontal relative position of the polishing member 21 with respect to the wafer W, and outputs it to the torque monitor 38.

  Based on the magnitude of the torque of the servo motor 31 input from the signal processing board 37 and the relative position of the polishing member 21 input from the encoder 39, the torque monitor 38 has the polishing member 21 together with the relative position of the polishing member 21. Indicates the magnitude of the torque of the servo motor 31 when is positioned at the relative position. Thereby, the magnitude of the torque of the servo motor 31 and the relative position of the polishing member 21 with respect to the wafer W can be constantly monitored. The torque monitor 38 determines whether or not there is an abnormality in the apparatus based on a change in torque input from the signal processing board 37. By doing so, the abnormality in the apparatus can be detected earlier (failure). Before you can discover).

  By the way, since the magnitude of the torque of the servo motor 31 cannot be directly monitored, it is usually considered to monitor the voltage of the analog monitor output from the servo amplifier 34. However, the analog monitor output from the servo amplifier 34 has a low resolution because the voltage of 8V in full scale is normalized with 256 gradations. On the other hand, since the drive current flowing through the servo motor 31 is considered to have a correlation with the torque generated by the servo motor 31, the drive current flowing through the servo motor 31 is measured and the magnitude of the torque of the servo motor 31 is monitored. As a result, the drive current of the servo motor 31 is increased or decreased according to the magnitude of the torque, so that the resolution is increased and a smaller amount of torque change can be monitored.

  FIG. 4 shows an example of the transition of the polishing torque generated by the servo motor 31. Region A in FIG. 4 is a transition of polishing torque when polishing is performed, and regions other than region A (polishing torque is low) are polished when the wafer W is not polished due to replacement of the wafer W or the like. It is the transition of torque. When polishing a wafer W larger than the polishing pad 22, the contact area of the polishing pad 22 with the wafer W changes by rocking polishing. When the contact area changes, the magnitude of the torque of the servo motor 31 also changes in proportion to the contact area, as indicated by region A in FIG. As described above, in order to find an abnormality in the apparatus, it is necessary to distinguish between a torque fluctuation due to rocking polishing and a torque fluctuation due to the apparatus abnormality.

  Therefore, as described above, by constantly monitoring the relative position of the polishing member 21 to which the polishing pad 22 is attached, the torque monitor 38 can detect, for example, the relative position of the polishing member 21 and the torque of the servo motor 31 during normal operation. Is stored in a data table (not shown), and the torque fluctuation of the servo motor 31 corresponding to the relative movement of the polishing member 21 is compared with the data table to determine whether there is an abnormality in the apparatus. It becomes possible to determine, and it is possible to specify the location (or content) of the abnormality. The host controller 35 that controls the servo motor commands the movement distance, rotational speed, etc. of the polishing member 21, but the actual control is performed by a servo amplifier, and the relative position of the polishing member 21 is transferred to the host controller 35. I do n’t know.

  In general, the relationship between the relative position of the polishing member 21 and the magnitude of the torque of the servo motor 31 indicates that the torque of the servo motor 31 increases as the polishing member 21 (polishing pad 22) moves toward the center of the wafer W, and the wafer W The torque decreases as it moves outward. Therefore, for example, when the torque increases during the movement of the polishing member 21 to the outside of the wafer W, an abnormality such as a so-called catch due to an abnormality of the polishing pad 22 or the abrasive (slurry) can be considered. Conversely, when the torque suddenly decreases, an abnormality such as breakage (idling) of the motor shaft may be considered. As described above, when an abnormality occurs in the apparatus, it is possible to identify the occurrence location.

  Further, systematic maintenance of the apparatus can be realized by detecting a response delay in which the rising of the torque is delayed when the polishing pad 22 is in contact with the wafer W and a state in which the fluctuation of the torque is larger than the normal state (abnormality determination). It becomes possible, and sudden failure of the apparatus can be prevented.

  As described above, according to the CMP apparatus C configured as described above, it is possible to detect an abnormality of the apparatus earlier. In particular, a high effect can be obtained by applying the present invention to the rotational drive device 30 of the polishing member 21 having the servo motor 31.

  In the above-described embodiment, the polishing apparatus in which the wafer W is sucked and held by the wafer holding apparatus 10 below the polishing member 21 has been described. However, the present invention is not limited to this, and the present invention is arranged above the polishing member. It can also be used in a polishing apparatus having a configuration in which a wafer is sucked and held by a holding device.

  Further, in the above-described embodiment, the disk-shaped semiconductor wafer W is used as the object to be polished, but the present invention is not limited to this, and it may be formed in a rectangular plate shape like a glass substrate.

  In the above-described embodiment, the present invention is applied to the rotational drive device 30 of the polishing member 21 having the servo motor 31. However, the present invention is not limited to this. For example, an electric motor that swings the polishing arm 3 is used. In addition, the present invention is applicable to any driving device that moves the polishing member 21 relative to the wafer W, such as an electric motor that rotates the wafer holding device 10.

  In the above-described embodiment, one motor current sensor board 36 is disposed in the motor power cable 32. However, the present invention is not limited to this. For example, three motor current sensor boards are provided in parallel, These detection currents may be added together. In this way, even when a high load is applied to the servo motor 31 and a drive current of 300% of the rated current flows, the magnitude of the drive current of the servo motor 31 can be accurately detected.

1 is a plan view of a CMP apparatus which is an example of a polishing apparatus according to the present invention. It is a side view of a polishing head. It is a circuit block diagram around a servo motor. It is a graph which shows transition of grinding torque which arises with a servomotor.

Explanation of symbols

C CMP equipment (polishing equipment) W Wafer (object to be polished)
DESCRIPTION OF SYMBOLS 10 Wafer holding device 20 Polishing head 21 Polishing member 22 Polishing pad 23 Polishing surface 30 Rotation drive device 31 Servo motor 36 Motor current sensor board (current detector)
37 Signal processing board (torque calculator)
38 Torque monitor (judgment section and display section)
39 Encoder (position measuring device)

Claims (5)

A holding device for holding an object to be polished, a polishing member capable of polishing the object to be polished held by the holding device, and a drive device for moving the polishing member relative to the object to be polished, In a polishing apparatus configured to perform polishing of the object to be polished by moving the polishing member relative to the object to be polished while abutting the object to be polished,
The driving device is configured to include an electric motor that generates torque for moving the polishing member relative to each other.
A current detector for detecting a magnitude of a current supplied to the electric motor to generate the torque;
A torque calculator that calculates the magnitude of the torque based on the magnitude of the current detected by the current detector;
A polishing apparatus comprising: a determination unit that determines whether there is an abnormality in the apparatus based on a change in the torque calculated by the torque calculation unit.   The polishing apparatus according to claim 1, further comprising a display unit that displays the magnitude of the torque calculated by the torque calculation unit. A position measuring device for measuring a relative position of the polishing member with respect to the object to be polished;
The said display part displays the magnitude | size of the said torque when the said polishing member is located in the said relative position with the said relative position of the said polishing member measured by the said position measuring device. The polishing apparatus according to 1.   4. The polishing apparatus according to claim 1, wherein the driving device is configured to rotationally drive the polishing member by the electric motor. 5.   The polishing apparatus according to any one of claims 1 to 4, wherein the electric motor is a servo motor.

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