JP2001138219A - Grinding apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grinding apparatus which is high in accuracy and efficient in operation without generating any surface burn or breakage of a workpiece or damaging the apparatus itself. SOLUTION: The workpiece W held by a chuck table 5 is positioned to a grinding means 7 of the grinding apparatus, and ground by a grinding part 8 while adjusting the feed speed of a spindle unit 12 by a spindle feed means 13. The grinding resistance generated by the grinding pressure during the grinding operation is detected by Kisler dynamometers A, B and C of an abrasive resistance detecting means 14, and the detected signal is inputted in a judging means 15 to judge whether or not the detected signal is within a predetermined threshold. When it is judged to be within the threshold, the command signal for maintaining the speed is inputted from a speed control device 16 into a CPU of the grinding apparatus to maintain the feed speed of the spindle unit 12 to be invariable. When it is judged that the detected signal exceeds the threshold, the feed speed of the spindle unit 12 is appropriately adjusted by the command for acceleration or deceleration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polishing apparatus for polishing a workpiece such as a semiconductor wafer.

[0002]

2. Description of the Related Art A polishing apparatus for polishing a workpiece such as a semiconductor wafer usually includes a chuck table for holding the workpiece and polishing means for polishing the surface of the workpiece held on the chuck table. It is at least configured to grind the surface of the workpiece to a desired thickness and a desired mirror surface.

[0003]

Conventionally, this type of polishing apparatus is of a type in which a grinding wheel is mounted and a workpiece is polished with fixed abrasive grains, and a polishing cloth is mounted in which a workpiece is polished with free abrasive grains. There are polishing types, and both types have the following problems. (1) Polishing is performed by pressing a grinding wheel or the like against the workpiece at a predetermined feed rate. However, when the polishing ability cannot follow the feed rate, the polishing pressure rises extremely and the workpiece becomes flat. It can burn, break, and sometimes even damage the entire device. (2) Conversely, if the polishing capacity exceeds the polishing feed rate or if the grinding wheel is significantly worn, the polishing cannot be performed efficiently. (3) The processing load (spindle load) may increase during the processing for preparing the processing surface for a certain time without polishing feed due to spark-out. If this state is continued, the workpiece may be burnt or damaged, and sometimes the apparatus itself may be damaged.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and has high accuracy and high efficiency without causing surface burn or breakage of a workpiece and without damaging the apparatus itself. An object of the present invention is to provide a polishing apparatus that can polish a workpiece.

[0005]

As technical means for achieving the above object, the present invention provides a chuck table for holding a workpiece, and polishing the surface of the workpiece held on the chuck table. A polishing unit configured to polish a workpiece, a mounter to which the polishing unit is mounted, a spindle supporting the mounter, and a rotatable support for the spindle. A spindle unit having a rotary drive source; and a spindle feed unit for feeding the spindle unit at a predetermined feed rate in a direction approaching or moving away from the workpiece, wherein the chuck table holds the workpiece. And a supporting portion for supporting the holding portion, wherein the polishing device has Polishing resistance value detecting means for detecting a polishing resistance value, determining means for receiving a resistance value signal from the polishing resistance value detecting means and determining whether or not the signal is within a predetermined threshold value, and this determining means The gist of the present invention is a polishing apparatus provided with a feed speed control unit for appropriately adjusting the feed speed of the spindle feed unit when it is determined that the predetermined threshold value is exceeded. Further, in this polishing apparatus, the polishing resistance value detecting means is a stress detector (Kistler dynamometer) for detecting a stress generated in a supporting portion of the chuck table.
Wherein the determining means determines whether or not the stress is within a predetermined threshold, and the polishing resistance detecting means determines a load current value (spindle current) of a current supplied to a drive source of the spindle unit. Is a current value detecting means that detects whether the load current value is within a predetermined threshold value. In the present invention, the feed speed (or feed amount) of the spindle unit is appropriately adjusted while constantly detecting the polishing resistance value as described above, and control is performed so that the polishing resistance value falls within a predetermined threshold value. Appropriate polishing can be performed without the amount of shaving into the object becoming excessive or excessive.

[0006]

Next, an embodiment of a polishing apparatus according to the present invention will be described with reference to the accompanying drawings. FIG. 1 shows an example of a polishing apparatus according to the present invention. First, a workpiece W such as a semiconductor wafer housed in a cassette 1 is unloaded by a loading / unloading means 2 and placed on a center alignment table 3. The center alignment of the workpiece W is performed by the plurality of alignment pieces 3a which are conveyed and move in the radial direction. Next, the workpiece W sucked by the first transporting means 4 having the turning arm is transported onto the chuck table 5 positioned at the receiving position Q and is suction-held, and the polishing means 7 is rotated by the rotation of the turntable 6. Moved to and positioned.

In the polishing means 7, a rough polishing means 7a for rough polishing the surface of the workpiece W and a finish polishing means 7b for finish polishing are arranged in parallel at a predetermined interval. , A mounter 9 on which the polisher 8 is mounted, a spindle 10 for supporting the mounter 9, a rotatable driving source 11 for rotatably supporting the spindle 10 And a spindle feeder 13 that feeds the spindle unit 12 at a predetermined feed speed in a direction approaching or moving away from the workpiece W.

The chuck table 5 has a holding portion 5a for holding the workpiece W and a supporting portion 5b for supporting the holding portion 5a, and a servo motor 5c for rotating the chuck table 5 is provided at a lower portion. And an encoder 5d, which are connected to the servo driver S. In addition, a plurality of stress detectors (in this case, three Kistler dynamometers A, B, and C) for detecting stress generated in the support portion 5b when the workpiece W is polished are provided below the support portion 5b.
Are arranged along the circumferential direction.

Each of the polishing means 7a and 7b includes a polishing resistance value detecting means 14 for detecting a polishing resistance value generated when polishing the workpiece W, and a resistance value signal from the polishing resistance value detecting means 14. A determining means 15 for receiving and determining whether or not the signal is within a predetermined threshold value; and when the determining means 15 determines that the signal exceeds the predetermined threshold value, the feed speed of the spindle feeding means 13 is appropriately adjusted. Speed control means 1 to adjust
6 are provided respectively.

The workpiece W held on the chuck table 5 is first positioned in the rough polishing means 7a and coarsely polished by the polishing unit 8. The polishing unit 8 is formed of, for example, a disc-shaped grindstone, and roughly polishes the surface of the workpiece W while rotating via the spindle 10 by the rotation drive source 11. The workpiece W is also rotated with the rotation of the chuck table 5 by the servomotor 5c.

In this rough polishing, the polishing section 8 applies a polishing pressure to the workpiece W in accordance with the feed of the spindle unit 12 by the spindle feed means 13. The polishing resistance value generated by the polishing pressure is detected by the Kistler dynamometers A, B, and C belonging to the polishing resistance value detection means 14, and the average value calculation unit 14a and the A / D conversion unit 1
4b, the determination means 15 via the timing adjustment unit 14c
Is input to

The resistance value signal input to the judgment means 15 is
It is determined whether or not the value is within a predetermined threshold, and is displayed on, for example, the monitor 15a. When it is determined that the value is within the threshold, a speed maintaining signal is input to the speed control means 16,
Further, the speed maintaining signal is input to the CPU of the polishing apparatus,
Spindle feeding means 1 via pulse motor driver P
3 is transmitted. Thereby, the spindle unit 12
Is maintained unchanged, and the polishing pressure of the polishing section 8 is maintained at an appropriate value.

On the other hand, when it is determined that the resistance value signal has exceeded the upper threshold line H, a deceleration signal is input from the determination means 15 to the speed control means 16, and the deceleration signal is input to the CPU of the polishing apparatus. It is transmitted to the spindle feed means 13 via the pulse motor driver P. This allows
The feed speed of the spindle unit 12 is reduced, and the polishing pressure of the polishing section 8 is reduced and corrected to an appropriate value.

When it is determined that the resistance value signal has exceeded the lower threshold line L, the determination means 15 sends the signal to the speed control means 1.
6 receives an acceleration signal, and the acceleration signal
It is input to the PU and transmitted to the spindle feed means 13 via the pulse motor driver P. As a result, the feed speed of the spindle unit 12 is accelerated, and the polishing pressure of the polishing section 8 is increased and corrected to an appropriate value. These correction results are fed back to the CPU.

In this way, the feed speed (or feed amount) of the spindle unit 12 is appropriately adjusted while constantly detecting the polishing resistance value during rough polishing, and the polishing resistance value is controlled so as to be within a predetermined threshold value. Therefore, it is possible to prevent a situation in which the workpiece W is burnt or damaged, or the apparatus itself is damaged.

After the rough polishing, the turntable 6 is rotated and the workpiece W is positioned on the finish polishing means 7b. While the workpiece W is being roughly polished, the next workpiece is unloaded from the cassette 1 and the center alignment table 3
, The workpiece is held on the chuck table at the receiving position Q, and the workpiece is positioned on the rough polishing means 7a at the same time that the first workpiece W is positioned on the finish polishing means 7b. Therefore, the finish polishing of the first workpiece W and the rough polishing of the next workpiece are performed simultaneously.

Also in the final polishing of the workpiece W, the polishing resistance value generated by the polishing pressure of the polishing section 8 is the same as that in the rough polishing, and the Kistler dynamometer A,
B and C, and the detection signal is sent to the judgment means 15
It is determined whether the value is within the threshold value. If the value is within the predetermined threshold value, a signal of a speed maintenance command is input from the speed control unit 16 to the CPU of the polishing apparatus.
If the threshold value is exceeded, a signal of a deceleration command or an acceleration command is input from the speed control means 16 to the CPU of the polishing apparatus. With these command signals, the spindle feed means 13 of the polishing apparatus can adjust the feed speed of the spindle unit 12 and appropriately adjust the polishing pressure of the polishing section 8. Thus, the workpiece W is not burned or damaged in the finish polishing step, or the apparatus itself is not damaged.

The finish polishing of the workpiece W and the rough polishing of the next workpiece are completed at the same time. Thereafter, the turntable 6 is rotated, and the workpiece W is moved to the transfer position R and the next workpiece is moved. Are positioned on the finish polishing means 7b, respectively.

The polished workpiece W positioned at the transfer position R is released from the suction holding of the chuck table 5, and is sucked by the second transfer means 17 having the turning arm shown in FIG. After being conveyed to the washing means 18 and subjected to spin cleaning and spin drying, it is accommodated in the cassette 1 or another cassette 1a placed at a position facing the cassette 1 by the carrying-in / out means 2. In this way, the workpiece W sequentially moves while taking the timing, and the polishing means 7
Returned after being polished.

In the above embodiment, the polishing resistance value detecting means 1
Although the Kistler dynamometers A, B, and C were used in 4, the current value detecting means (not shown) for detecting the load current value (spindle current) of the current supplied to the rotary drive source 11 of the spindle unit 12 may be used. It is possible. In this case, the judgment means 1
5 is configured to determine whether the load current value is within a predetermined threshold value.

The polishing resistance detecting means 14 includes a rotary driving source 11 for driving the spindle unit 12 (Z-axis driving).
The motor load current or load power from the motor and the motor control unit, or the servo motor 5c for driving the chuck table 5 and the motor load current or load power from the motor control unit, or the spindle unit 12 May be detected. It is also possible to combine these polishing resistance value detecting means arbitrarily.

Further, as a method of adjusting the feed speed of the spindle unit 12, for example, means for judging whether the polishing resistance value is above or below a predetermined threshold value to accelerate or decelerate the feed speed of the spindle unit 12 (on / off) Control means) or means for changing the feed speed of the spindle unit 12 based on the deviation of the polishing resistance value from a predetermined threshold value (proportional control means).

[0023]

As described above, according to the present invention,
When polishing a workpiece such as a semiconductor wafer with a polishing apparatus, since the feed rate of the spindle unit is appropriately adjusted while constantly detecting the polishing resistance value so that the polishing resistance value falls within a predetermined threshold value, There is no problem such as surface scorching, breakage, and damage to the device itself due to excessive shaving of the workpiece. Thereby, there is an effect that the polishing accuracy can be improved. In addition, the problem that the amount of shaving of the workpiece is small and the polishing ability cannot be sufficiently exhibited and the productivity is deteriorated can be solved, and the effect that the workpiece can always be efficiently polished in an optimum state can be obtained. .

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of a polishing apparatus according to the present invention.

FIG. 2 is an explanatory view showing a mechanism for controlling a polishing resistance value.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cassette 2 ... Carry-in / out means 3 ... Center alignment table 4 ... 1st conveyance means 5 ... Chuck table 6 ... Turntable 7 ... Polishing means 8 ... Polishing part 9 ... Mounter 10 ... Spindle 11 ... Rotation drive source 12 ... Spindle unit 13 ... Spindle feeding means 14 ... Polishing resistance value detecting means 15 ... Determining means 16 ... Speed control means 17 ... Second conveying means 18 ... Spinner cleaning means

Claims (3)

[Claims] A chuck table for holding a workpiece;
Polishing means for polishing the surface of the workpiece held by the chuck table, the polishing means comprising: a polishing section for polishing the workpiece; a mounter to which the polishing section is mounted; A spindle unit that rotatably supports the spindle and has a rotation drive source, and a spindle feed unit that sends the spindle unit at a predetermined feed speed in a direction approaching or moving away from the workpiece. A chuck table, wherein the chuck table includes a holding unit for holding the workpiece, and a support unit for supporting the holding unit. The polishing apparatus further includes a polishing resistance generated when the workpiece is polished. Polishing resistance value detecting means for detecting a value, and a resistance value signal from the polishing resistance value detecting means is received and the signal is within a predetermined threshold value A polishing apparatus, comprising: a determination unit for determining whether or not the spindle speed is higher than a predetermined threshold; and a feed speed control unit for appropriately adjusting a feed speed of the spindle feed unit when the determination unit determines that the predetermined speed is exceeded. . 2. The polishing resistance value detecting means is a stress detector (Kistler dynamometer) for detecting a stress generated in a supporting portion of the chuck table, and the determining means is configured such that the stress is within a predetermined threshold value. The polishing apparatus according to claim 1, wherein it is determined whether or not the polishing is performed. 3. The polishing resistance value detecting means is a current value detecting means for detecting a load current value (spindle current) of a current supplied to a drive source of the spindle unit. The polishing apparatus according to claim 1, wherein it is determined whether the value is within a predetermined threshold.