JPH1148106A - Surface grinding machine, and grinding method using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct highly precise grinding without grinding a dummy made of a material same to a work before actual grinding or with grinding only a reduced number of dummys compared with a conventional case. SOLUTION: In a surface grinding machine provided with a grinding wheel 2 for grinding a work 3 and a driving motor 1 for driving rotationally the grinding wheel 2 via a grinding wheel spindle 7, a brake mechanism is provided in the grinding wheel spindle 7. The brake mechanism is composed of, for example, a generator 8 connected with the grinding wheel shaft 7, and a heat radiator 9 to radiate electrical energy generated in the generator as thermal energy. After the surface grinding machine is brought into warming-up operation under an operating condition of the brake mechanism using the surface grinding machine to proceed to a thermal equibrium condition, the operation of the brake mechanism is released to grind the work 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a surface grinder and a grinding method using the same. More specifically, the present invention relates to a surface grinder capable of grinding a workpiece with high accuracy and stability while maintaining a constant thermal equilibrium state, and a grinding method using the same.

[0002]

2. Description of the Related Art As a technique for flattening the surface of a workpiece such as a semiconductor wafer, there is a technique for performing a grinding process using a surface grinder. FIG. 5 is a schematic configuration diagram showing an example of a conventional surface grinder. In the figure,
The workpiece 3 is placed on a table 4 driven to rotate by a table drive motor 5, and the workpiece 3 rotates together with the table 4. On the other hand, the grindstone 2 is rotatably driven by a grindstone shaft drive motor 1 via a grindstone shaft 7 and is moved up and down by a grindstone shaft elevating motor 6. With such a configuration, the rotating table 4
The grindstone 2 is lowered onto the upper workpiece 3 while rotating at a high speed, and the grinding stone 2 is cut into the workpiece 3 while supplying a grinding liquid to perform grinding. This surface grinder is of a grinding system called in-feed grinding.

In grinding a workpiece using a surface grinder, factors that have a particularly significant effect on the processing accuracy of the workpiece include the distance and parallelism between the grinding wheel shaft and the table. In order to ensure the accuracy of the workpiece, it is necessary to perform the grinding after appropriately adjusting the distance and the parallelism described above.

The above adjustment is performed in a thermally stable state by the heat generated by the operation of the apparatus, similarly to the adjustment of a general high-precision processing apparatus. That is, at the time of operation, each motor and the like generates heat and expands and contracts due to thermal expansion in each part, resulting in dimensional irregularities. As a result, sufficient grinding accuracy cannot be obtained. In order to suppress the influence of such heat generation, a cooling mechanism such as water-cooling or air-cooling is incorporated in the grindstone shaft, and some attempts have been made to maintain a constant temperature around the grindstone shaft, but the effect has not been sufficient.

[0005] Therefore, a warm-up operation (no-load operation) is performed until the thermal equilibrium state is reached. However, the thermal equilibrium state of the apparatus due to the no-load operation is incomplete, and for a while after the actual start of grinding, the workpiece is processed. Dimensional accuracy is unstable. This is because the calorific value of the grinding wheel shaft drive motor differs between during the no-load operation and during the grinding, so that the grinding starts and the heat of the motor causes a change in the state of thermal equilibrium. Therefore, the processing accuracy of the workpiece processed in such a state is unstable, and sometimes it becomes defective. Especially in the latest semiconductor wafer, when the diameter is 200 mm,
TTV (Total Thi) showing wafer thickness unevenness
A flatness of 0.5 μm or less is required, and the influence of instability of processing accuracy is great.

For this reason, after the warming-up operation, a sufficient number of workpieces (dummy) are ground to stabilize the apparatus thermally, and the grinding is performed while measuring the grinding accuracy of the workpiece. It is common to start actual grinding after obtaining high grinding accuracy.

[0007]

As described above, when a workpiece is ground using a conventional surface grinder, not only an extra dummy workpiece is naturally required, but also Since a time loss required for the dummy grinding occurs, the processing cost increases. In particular, as the diameter of the semiconductor wafer to be processed increases, the unit price of the wafer also increases, so that the influence is large.

[0008] Further, there is a problem particularly when the grinding is temporarily stopped and then restarted due to occurrence of a trouble.
In other words, if the device stops once due to some trouble, the thermal equilibrium state will collapse with the stop of the heat generation of the device, so in order to grind the workpiece again, it is necessary to adjust the adjustment again in a stable state. The results must be reproduced and ground. At this time, the apparatus is reproduced in a thermal equilibrium state while the apparatus is operated under no load for several minutes to several hours, or in some cases, a sufficient number of grindings of the workpiece (dummy) are added again as described above. Is generally restored. Needless to say, it is necessary to control the air conditioning, the temperature of the grinding fluid, and the like under certain conditions in reproducing the conditions.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has been described in which the dummy of the same material as the workpiece is not ground at all before the actual grinding, or the dummy is less than the conventional one. It is an object of the present invention to provide a surface grinder capable of performing a high-precision grinding process only by grinding a surface, and a grinding method using the same.

[0010]

The gist of the present invention is to provide a brake mechanism on a grinding wheel shaft for performing surface grinding, and to achieve a thermal equilibrium state of a surface grinding machine by a conventional no-load operation. The purpose of the present invention is to provide a means for adjusting the load of the motor so as to generate heat similar to the actual grinding state by the action of the brake mechanism, and for stably reproducing high-precision grinding.

That is, the invention described in claim 1 of the present application is:
A surface grinding machine comprising a grinding wheel for grinding a workpiece and a drive motor for rotating the grinding wheel via a grinding wheel shaft, wherein a brake mechanism for applying a load to the grinding wheel shaft is provided. Provide a board.

The invention described in claim 2 of the present application is claim 1
The surface grinding machine according to claim 1, wherein the brake mechanism is an electric brake mechanism that converts a part of the driving energy of the grinding wheel shaft into electric energy.

The invention described in claim 3 of the present application is claim 2
In the above described surface grinding machine, the electric brake mechanism includes a generator connected to the grinding wheel shaft, and a heat radiating device that emits electric energy generated by the generator as heat energy. Provide a surface grinder.

The invention described in claim 4 of the present application is claim 1
The surface grinding machine according to claim 1, wherein the brake mechanism is a mechanical brake mechanism that consumes a part of driving energy of the grinding wheel shaft by mechanical resistance.

The invention described in claim 5 of the present application is claim 4
The surface grinding machine according to claim 1, wherein the mechanical brake mechanism includes an interlocking rotating body connected to the grinding wheel shaft, and a brake body that comes into contact with the interlocking rotating body.

[0016] The invention described in claim 6 of the present application is directed to claim 5.
The surface grinding machine according to claim 1, wherein the mechanical brake mechanism comprises an interlocking rotating blade connected to the grinding wheel shaft, and a fluid housed in a container and in contact with the interlocking rotating blade. I will provide a.

The invention described in claim 7 of the present application is the invention according to claim 1.
7. The surface grinding machine according to any one of items 6 to 6, wherein the brake mechanism is provided so as to be able to arbitrarily release the operation of the grinding wheel shaft.

[0018] The invention described in claim 8 of the present application is claim 1.
7. A grinding method, characterized by using the surface grinding machine according to any one of (1) to (7) and grinding the workpiece while constantly maintaining a thermal equilibrium state by the brake mechanism during operation of the surface grinding machine.

The invention described in claim 9 of the present application is claim 8
In the described grinding method, the surface grinding machine is operated in a warm-up state while the brake mechanism of the surface grinding machine is operated, and after the surface grinding machine shifts to a substantially equal thermal equilibrium state at the time of grinding the workpiece, A grinding method is provided in which the operation of the brake mechanism is released to grind the workpiece.

The brake mechanism that applies a load to the grinding wheel shaft means a mechanism that can apply an arbitrary magnitude of braking torque to the rotation of the grinding wheel shaft.

[0021]

FIG. 1 shows an example of a surface grinder according to the present invention, particularly an example using an electric brake mechanism. The basic configuration of this surface grinder is substantially the same as that of the conventional surface grinder shown in FIG. That is, in the drawing, the workpiece 3 is placed on a table 4 that is driven to rotate by a table drive motor 5, and the workpiece 3 is
It rotates with it. On the other hand, whetstone 2
The motor is driven to rotate by a grinding wheel shaft driving motor 1 via a grinding wheel shaft 7 and is moved up and down by a grinding wheel shaft lifting motor 6.

In the surface grinding machine of the present embodiment, a DC generator 8 is provided between the grinding wheel 2 and the grinding wheel shaft 7 and directly above the grinding wheel 2.
Is provided, and a radiator 9 electrically connected to the DC generator 8 is provided at a location away from the grinding position.
These constitute a brake mechanism. This brake mechanism applies a load to the grinding wheel shaft drive motor 1 so that the heat generated by the motor, which is not during the grinding process, is brought into the same state as during the grinding process. The operation of the DC generator 8 can be arbitrarily released. Also, the heat radiating device 9
Is a device that converts electric energy into heat energy and emits it. Specific examples thereof include a heater having an electric resistance, and other means for consuming the electric energy generated by the DC generator 8. It can be replaced.

To describe the specific operation, the DC generator 8 is operated at the start of the warming-up operation of the surface grinder, and the same load as that at the time of grinding the workpiece 3 is applied to the grinding wheel drive motor 1 by The heat generated by the grinding wheel shaft drive motor 1 is the same as when grinding is performed. Naturally, the energy supplied from the grinding wheel shaft drive motor 1 is converted into electric energy by the DC generator 8. At this time, if the DC generator 8 itself generates heat, it will be in a state different from the originally intended thermal equilibrium state. To prevent this, the electric energy converted by the DC generator 8 affects the accuracy of the surface grinding machine. Is released as heat energy by the heat radiating device 9 connected to the DC generator 8 so as not to cause the heat generation. At this time, by controlling the electric resistance value of the heat radiating device 9, the load applied to the grinding wheel shaft driving motor 1 can be freely controlled. In practice, some heat generation of the DC generator 8 itself is unavoidable due to efficiency problems, but this heat does not affect the grinding wheel shaft 7 by the grinding fluid supplied between the grinding wheel 2 and the workpiece 3. Cool to a degree. Then, after the surface grinder reaches a thermal equilibrium state equivalent to that at the time of actual grinding of the workpiece 3, the operation of the DC generator 8 is released, and the workpiece 3 can be ground.

When the grinding of the workpiece 3 is temporarily stopped, the DC generator 8 is operated again while the grinding is not performed, and the grinding wheel shaft driving motor 1 is operated in the same manner as when the workpiece 3 is ground. By applying the above load and maintaining the thermal equilibrium state at all times, the grinding of the workpiece 3 can be restarted with almost no adjustment.

FIG. 2 shows another embodiment. In this example,
The DC generator 10 is linked to the grinding wheel shaft 7 via a belt 12 and is provided at a position close to the grinding wheel shaft drive motor 1. The brake mechanism is desirably installed at a position as close as possible to the grindstone 2 of the grindstone shaft 7 connecting the grindstone shaft drive motor 1 and the grindstone 3 so that the braking torque of the brake mechanism is applied so as to approximate the actual grinding state. . In that respect, the configuration of FIG. 1 is advantageous, but there is no particular need to be particular if the desired accuracy is obtained.

As the brake mechanism, an electric brake using the above-described DC generator is advantageous in terms of installation freedom and ease of releasing absorbed energy, but other types are also possible. . FIG. 3 shows an example using a mechanical brake mechanism by friction. In the figure, a disk-shaped interlocking rotator 15 attached to a brake shaft 14 that rotates interlockingly with the grindstone shaft 7 via a belt 13 contacts a brake body 16 and applies a load to the grindstone shaft 7 by friction.

FIG. 4 shows an example in which a mechanical brake mechanism using a fluid is used. In the figure, an interlocking rotating blade 21 attached to a brake shaft 18 interlockingly rotating with the grindstone shaft 7 via a belt 17 is installed so as to be immersed in a fluid 20 contained in a container 19. When rotating in the fluid 20 in conjunction with the rotation of the shaft 7, a load is applied to the grinding wheel shaft 7 by the flow friction with the fluid 20.

[0028]

EXAMPLE Using the surface grinder shown in FIG. 2, the evaluation items include the temperature near the bearing portion 23 of the grinding wheel shaft 7 and the displacement of the grinding wheel shaft 7 during the warm-up operation and during the actual grinding cycle of the workpiece 3. And the TT of the workpiece 3 after grinding.
V was evaluated. The displacement of the grindstone shaft 7 was measured by measuring the minute displacement of the grindstone shaft 7 by installing a push-in type minute displacement meter 22 in the gap between the grindstone shaft drive motor 1 and the grinding machine body.
In this state, a load is applied to the grinding wheel drive motor 1 by the DC generator 10, and a warm-up operation is performed under conditions equivalent to actual grinding, that is, under the condition that the motor shaft current value of the grinding wheel drive motor 1 becomes the same. After the was stabilized, actual grinding was performed, and the processing accuracy (TTV) of the workpiece 3 was measured. These results are shown in FIG.

For comparison, an evaluation experiment similar to that described above was performed with the belt 12 connecting the grinding wheel shaft 7 of the grinding machine and the DC generator 10 removed. FIG. 7 shows the result.

In the graphs shown in FIGS. 6 and 7, the temperature near the bearing portion 23 of the grinding wheel shaft 7, the displacement of the grinding wheel shaft 7, and the work The time change of each measured value was expressed as a relative value based on the TTV after grinding of the object 3. Note that the horizontal axis of the graph indicates time with the grinding cycle as a unit time.

As is clear from FIGS. 6 and 7, in the case of the embodiment, since the processing load does not change even when the actual grinding starts from the warm-up operation, the temperature and the displacement hardly change, and the grinding start 1 High-precision machining can be performed from the cycle. on the other hand,
In the comparative example corresponding to the prior art, even if the actual grinding starts when the temperature and the displacement become constant by the warm-up operation, the processing load changes, so that the temperature and the displacement change. Processing accuracy will deteriorate for a while.

That is, in order to obtain stable processing accuracy, in the prior art, after performing a warm-up operation, it is necessary to grind a dummy made of the same material as the actual workpiece, but in the present invention, Not only is the dummy unnecessary or the required amount is reduced, but also the time required for grinding the dummy can be saved, so that the processing efficiency is increased. Also, by setting the load by the brake mechanism during the warm-up operation to be larger than the load during the actual grinding, the warm-up operation itself can be shortened.

[0033]

As described above, according to the present invention, it is possible to obtain a high precision by performing no or no dummy grinding of the same material as the workpiece before actual grinding. Grinding can be performed, and the processing efficiency is improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing another embodiment of the present invention.

FIG. 3 is a schematic configuration diagram showing another embodiment of the present invention.

FIG. 4 is a schematic configuration diagram showing another embodiment of the present invention.

FIG. 5 is a schematic configuration diagram showing an example of a conventional surface grinder.

FIG. 6 is a graph showing evaluation results using the surface grinder shown in FIG. 2;

FIG. 7 is a graph showing evaluation results using the conventional surface grinder shown in FIG.

[Description of sign]

 1: Wheel spindle drive motor 2: Grindstone 3: Workpiece 4: Table 5: Table drive motor 6: Grindstone spindle elevating motor 7: Grindstone spindle 8: DC generator 9: Heat radiator 10: DC generator 11: Heat radiator 12: Belt 13: Belt 14: Brake shaft 15: Interlocking rotating body 16: Brake body 17: Belt 18: Brake shaft 19: Container 20: Fluid 21: Interlocking rotating blade

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Okuni ▲ Tadayuki Odakura Osaikura, Nishigo-mura, Nishishirakawa-gun, Fukushima Prefecture 150 Semiconductor Shirakawa Research Laboratory, Shin-Etsu Semiconductor Co., Ltd. 596, Jono-Koshishinda, Naoetsu Electronics Co., Ltd. (72) Inventor Keiichi Okabe 1393, Ojiyashiro, Koshoku-shi, Nagano Nagano Electronics Industry Co., Ltd. (72) Inventor, Tadahiro Kato Ohira 150 Shin-Etsu Semiconductor Co., Ltd.

Claims (9)

[Claims] 1. A surface grinding machine having a grinding wheel for grinding a workpiece and a drive motor for rotating the grinding wheel via a grinding wheel shaft, wherein a brake mechanism for applying a load to the grinding wheel shaft is provided. Characteristic surface grinder. 2. The surface grinding machine according to claim 1, wherein the brake mechanism is an electric brake mechanism that converts a part of driving energy of the grinding wheel shaft into electric energy. 3. The electric brake mechanism according to claim 1, wherein the electric brake mechanism includes a generator connected to the grinding wheel shaft, and a radiator for releasing electric energy generated by the generator as heat energy. 2. The surface grinder according to 2. 4. The surface grinding machine according to claim 1, wherein the brake mechanism is a mechanical brake mechanism that consumes a part of driving energy of the grinding wheel shaft by mechanical resistance. 5. The surface grinding machine according to claim 4, wherein the mechanical brake mechanism comprises an interlocking rotating body connected to the grinding wheel shaft, and a brake body contacting the interlocking rotating body. 6. The mechanical brake mechanism according to claim 5, wherein said mechanical brake mechanism comprises an interlocking rotating blade connected to said grinding wheel shaft, and a fluid housed in a container and in contact with said interlocking rotating blade. Surface grinder. 7. The surface grinding machine according to claim 1, wherein the brake mechanism is provided so as to be able to arbitrarily release operation of the grinding wheel shaft. 8. A surface grinding machine according to any one of claims 1 to 7, wherein the workpiece is ground while constantly maintaining a thermal equilibrium state by the brake mechanism during operation of the surface grinding machine. How to grind. 9. A warm-up operation of the surface grinder in a state where the brake mechanism of the surface grinder is operated, and after the surface grinder shifts to substantially the same thermal equilibrium state as when grinding a workpiece, The grinding method according to claim 8, wherein the work is ground by releasing the operation of the brake mechanism.