JP2000218515A - Polishing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an operator to substantially ignore a temperature rise in a working surface of a surface plate even after the start of operation by providing a temperature controller at a speed reducer installed at a lower part of the surface plate. SOLUTION: Upper and lower surface plates 1, 2, a sun gear 4 and an internal gear 5 constituting a polishing machine is driven by a drive motor 8 and a speed reducer 9 installed in a device body box 7. A cooling jacket 10 is arranged to spirally surround the reducer 9. Refregerant for cooling is controlled in its temperature at a preliminarily set temperature by a refregerant temperature controller 11 and circulated in the jacket 10 by a circulation pump to control temperature increase in the reducer 9. Accordingly, the temperature increase in the reducer 9 is restrained, and though raised temperature is transmitted to the lower surface plate 2 the temperature increase is prevented, and further the whole system is maintained in its temperature at the temperature around the room temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing machine having a rotatable surface plate, and more particularly to an apparatus for processing a material having a high flatness which requires extremely high flatness and parallelism. More particularly, the present invention relates to a polishing machine capable of accurately controlling the temperature of a platen and a peripheral device therefor.

[0002]

2. Description of the Related Art Conventionally, in order to obtain precise dimensional accuracy and shape accuracy in a manufacturing process of a plate-like material such as glass, metal material, ceramics or semiconductor material which requires extremely high flatness and parallelism. The flat surface processing is performed by placing a rotatable surface plate or a rotatable surface plate with a polishing pad attached on the surface on both upper and lower surfaces or one surface, sandwiching the workpiece, and polishing the abrasive fine powder slurry as an abrasive. Pressing and rotating the platen and workpiece while supplying quantitatively,
A lapping or polishing method for making the thickness uniform and improving the flatness and parallelism by the action is performed.

In recent years, especially in recent years, ICs, LSIs,
For electronic components made from semiconductor materials such as semiconductor materials, the uniformity of the thickness of silicon wafers or compound-based wafers (hereinafter collectively referred to as wafers), which are the raw materials, is required due to the need to increase storage capacity and improve productivity. In particular, there is a remarkable tendency to increase the size of the wafer itself at the same time as improving the processing accuracy and dimensional stability, and extremely precise management is also required for the accuracy and stability of the apparatus itself in lapping and polishing processing. It is becoming. Above all, in the case of silicon wafers, the technique of pulling silicon single crystal as a raw material has been improved, and the diameter is 12 inches and 16 inches.
Production of large-diameter products such as inches has been started. Therefore, in order to efficiently perform lapping and polishing of such a large-diameter wafer, a large-sized double-sided processing machine having a large-diameter platen having a carrier diameter of 24 inches or 32 inches is becoming popular in recent years. . Even in such a background, improvement in TTV (Total Thickness Variation) or GBIR, which is an index indicating the thickness variation in one wafer, has been increasingly demanded.

The lapping plate referred to here is a disk having a certain thickness made of a metal such as cast iron, copper, tin and soft iron, or a non-metal such as ceramics and glass. On the surface used for processing, for example, a thin lattice-like groove is cut, and is arranged on both upper and lower surfaces or one of them so that the surfaces are aligned. In the case of a double-sided processing machine, hold the workpiece between the upper and lower stools, apply pressure from the upper stool and rotate the workpiece or the stool or both to grind the abrasive The slurry is supplied quantitatively. The surface of the work piece is gradually removed by the action of the abrasive grains, and the work surface is created with a flat and uniform surface roughness. The flatness is obtained by transferring the flatness of the upper and lower platens as it is. Therefore, the shape and flatness of the platen must be kept extremely accurately. When a hard and brittle material such as a silicon wafer is used as a workpiece, a plate made of cast iron is generally used. In the case of polishing, a polishing surface plate is used in which a polishing pad made of a synthetic resin foam, synthetic leather, non-woven fabric, or the like is attached to a surface plate made of the same material. In the case of a single-side polishing machine, the workpiece, which is the workpiece, is affixed to the lower surface of the pressure plate and pressed against the rotating platen surface, but the motor and reduction gear are also arranged on the pressure plate itself. There is also a type to do.

As described above, particularly in the case of a silicon wafer, if the required accuracy for the wafer is increased, the polishing heat generated by the processing or the heat generated by a motor or a reduction gear for rotating the surface plate causes an effect. First, the heat of the lower surface plate rises, and the shape of the surface plate slightly changes due to the effect of the increased heat.
It was undeniable that it had a subtle effect on the dimensional accuracy of the processed wafer. Further, a double-sided processing machine generally incorporates a motor and a speed reducer for driving the upper and lower platens, and a motor and a speed reducer for driving the sun gear and the internal gear, respectively. Here, the sun gear and the internal gear are for rotating a carrier plate that holds a wafer as a workpiece and performs a movement different from that of the surface plate. Since fine mist, dust, oil droplets, etc. are generated from these drive systems and reduction gears, and there is a risk of contaminating the product, as a countermeasure, attach an exhaust duct directly to the processing machine body. A method of processing at a remote place is used. for that reason,
The temperature of the processing machine itself becomes unstable due to the airflow and operating conditions of the exhaust duct, and the temperature of the surface plate can be affected and slightly fluctuated even while the machine is operating, increasing the variation in product quality. I could not deny that.

In order to eliminate such adverse effects, a method has been already proposed in which a rise in temperature is suppressed by passing a cooling medium through the inside of the surface plate to process the surface plate at a stable temperature in a cooled state. For example, JP-A-63-245368 and JP-A-4-53671) disclose that the temperature of the platen is controlled by cooling, so that the temperature following the temperature change is slightly slow.
In addition, it has been pointed out that a refrigerant having a high heat capacity such as water is disadvantageous in terms of energy. In addition, measures have been taken, such as performing idle operation at the start of operation and performing warm-up operation. However, it has been difficult to reduce the operation rate of the machine and to have sufficient effects. The applicant has already filed Japanese Patent Application No.
No. 293841 proposes an apparatus and a method for maintaining the temperature of the surface of the surface plate at the saturation temperature at the time of operation even at the time of stoppage and performing stable processing from the first batch at the start of operation.

[0007]

In order to solve the above-mentioned problems, the present inventors have made it easier and more efficient to control the temperature of the heating element itself instead of controlling the temperature of the platen surface. The present inventors have conducted intensive studies focusing on obtaining a good effect. That is, for several batches from the start of operation after the standstill of the machine stand, the dimensional accuracy of the processed wafer is not stable, the processing accuracy is poor, and the factors that cause a phenomenon that significantly lowers the product yield are thoroughly studied. As a result, they have clarified the following. That is, the shape (radial linearity and diametrical unevenness) of the upper and lower stools are matched (matching).
Determines the processing accuracy. During continuous processing, the surface plate expands due to a rise in temperature, causing a volume change, and this volume change delicately changes the shape (flatness) of the surface plate. Although it has a large effect on the machining accuracy, it has been found that the main factor of the temperature change is not the frictional heat due to the machining but the heat generated and transmitted by the speed reducer in the drive system. Therefore, if the machine that has been operating stably for a long time with the temperature reached the saturation value (maximum temperature reached in that condition) due to the temperature rise of the speed reducer, the temperature of the surface plate will gradually decrease. As it approaches room temperature, its shape is slightly deformed in the direction of contraction due to the effect of the temperature drop. Immediately after restarting after the stop, the machine starts in such a state, so that the dimensional accuracy of the processed wafer is not good and the product yield is poor. When several batches of processing are continued, the temperature of the surface plate gradually rises and returns to the state immediately after the stop, and the state of the upper and lower surface plates also returns to the original state, thus enabling stable processing.

The present inventors have conducted intensive studies on the above-mentioned problems of the existing grinding machine, and as a result, have found that the rotation of a motor for driving a surface plate, a sun wheel, and an internal gear is reduced and transmitted. If the temperature of the machine is controlled so as to keep it constant during operation, the temperature rise of the surface plate during operation is found to be extremely small, and a mechanism for controlling the temperature of the speed reducer is provided. The purpose of the present invention is to provide a polishing machine in which the temperature rise on the working surface of the surface plate is substantially negligible even after the start of operation. Is to do.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a processing machine having a rotatable surface plate, a motor for driving the surface plate, and a reduction gear, which is installed below the surface plate. This is achieved by a polishing machine characterized in that the speed reducer is provided with a temperature control device. The above-mentioned temperature control device,
It is more preferable that the cooling liquid medium is circulated and cooled. Further, the above-mentioned temperature control device may be a system in which air or a substitute gas for chlorofluorocarbon or another cooling gas medium is blown or circulated for cooling.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A polishing machine according to the present invention is composed of a machine part which is a main part of the apparatus and peripheral equipment comprising a temperature control mechanism, an example of which will be described with reference to the drawings. FIG. 1 shows a double-sided polishing machine according to the present invention, in which a rotatable disk-shaped upper platen 1 and a lower platen 2 made of cast iron or the like are arranged on the upper and lower surfaces thereof,
It comprises a carrier plate 3 that performs planetary motion, a sun gear 4 that moves the carrier plate, and an internal gear 5. The workpiece 6 such as a wafer set on the carrier plate while supplying a slurry containing fine abrasive particles as a working liquid is supplied. Processing is performed, and abrasive particles act on the surface of the work and are removed by the pressing force and rotation of the surface plate. The purpose is to correct the unevenness of the thickness of the wafer after slicing, to remove unevenness, and to obtain a fine flatness.

The upper and lower stools 1 and 2, the sun gear 4 and the internal gear 5 are driven by a drive motor 8 and a speed reducer 9 installed in an apparatus body box 7. There is a type in which these are moved by using a single motor, but in recent years, there are many so-called 4-way types in which each is driven by its own motor and moves independently. A cooling medium jacket 10 is provided so as to circumvent the speed reducer 9, and the cooling medium is controlled to a preset temperature by a separately installed refrigerant temperature controller 11, and a circulation pump (not shown)
Circulated in As a result, the temperature rise of the speed reducer 9 is suppressed, the increased temperature is transmitted to the lower platen by conduction, and the temperature is prevented from being increased, and the whole system is maintained at a temperature near room temperature.

Next, the temperature control of the polishing machine of the present invention will be described in detail. As described above, in the case of a double-sided processing machine, up to four motors 8 and reduction gears 9 are mounted (only one machine is shown in the drawing), and these are generated when the machine starts operating. In general, heat is transmitted through a rotating shaft or the like, and first, the lower platen 2 is gradually heated. As the temperature rises, the lower platen changes its volume due to thermal expansion, causing subtle changes in the flatness of the platen, the parallelism of the upper and lower platens (gap at the same interval), and the matching of the shape, deteriorating the processing accuracy . If the temperature does not change from the start of operation, the surface plate is not deformed and is stable. The temperature of the surface plate is stabilized at a specific temperature (saturation temperature) if the machine base is used several times under constant conditions without controlling the temperature of the speed reducer. As long as a general large lapping double-sided processing machine is used under general processing conditions, this temperature rise is at most about 5 ° C., and with the double-sided processing machine of the present invention, the temperature rise is substantially zero. ° C. Temperature control is performed by a temperature control device 11 equipped with a cooler.
The cooling medium cooled by the circulation pump to the required temperature circulates through the jacket 10 and controls the temperature rise of the speed reducer 9.

[0013] The cooling medium used herein is one used in ordinary cooling machines and is not particularly limited, but one having a large heat transfer coefficient and a small specific heat, for example, water, glycerin, ethylene glycol And an aqueous solution of sodium chloride. Further, as a cooling medium, a substitute gas such as Freon may be sealed and used in addition to the liquid. Alternatively, a simple type in which cooled air is blown may be used.

[0014]

EXAMPLES and COMPARATIVE EXAMPLES The method of the present invention will be specifically described below with reference to examples, but the present invention is not particularly limited thereby. The equipment, consumables, processing conditions, and the like used in the following examples and comparative examples are as shown below. Processing machine: A double-sided lapping machine 24B-5L (manufactured by Speed Fam Japan) is modified and equipped with a cooling jacket, a temperature controller and a circulation pump on the reduction gear. Spindle oil is used as the cooling medium. Board outer diameter: 1,592 mm Platen inner diameter: 554 mm Platen thickness: 70 mm Working fluid: FO1200, 30% by weight slurry Work: 200 mm as-cut silicon wafer Processing conditions: Working pressure: 15 kPa Batching number of batches: 25 Board rotation speed: -10 rpm (clockwise) Lower platen rotation speed: 40 rpm (counterclockwise) Sun gear rotation speed: 18 rpm (counterclockwise) Internal gear rotation speed: 10 rpm (counterclockwise) Processing time per batch: 10 Min Work exchange time; 2 min Machining fluid flow rate: 1000 mL / min Machining removal amount: 80 μm TTV Joki: Microscan 9500 (ADE Corporation) TTV Measurement conditions: measured five samples from each batch

Example The above-mentioned lapping machine was operated under the above-mentioned processing conditions after a two-day holiday. At this time, the room temperature was about 23 ° C., and the temperature controller was set to this temperature and started. From the first batch to the fifth batch after the start, the TTV after the processing was continuously measured, and at the same time, the temperature of the speed reducer was measured. The results are illustrated in the graph of FIG. The temperature of the speed reducer is maintained at 23 ° C., and the T
As is apparent from the results shown in FIG. 2, the TV was in the range of about 0.7 to 0.8 μm, and the fluctuation range was suppressed to about 0.1 μm.

COMPARATIVE EXAMPLE An operation experiment was conducted using the same apparatus and conditions as in the example except that the control mechanism was not provided. The surface plate surface temperature in the early morning after 2 days was 23 ° C. In this state, processing under the same processing conditions as in the example was started. The results are also shown in FIG. The TTV of the first batch after the start was poor at about 1.3 μm. When the lapping process was continuously performed from the second batch to the fifth batch as it was, the TTV started to decrease linearly and improved to 0.9 μm in the fifth batch. The temperature of the speed reducer rose to 42 ° C. in the fifth batch.

As is apparent from the results shown in the graph of FIG. 2, in the case of the conventional lapping machine in which the temperature of the speed reducer is not controlled, the surface temperature of the platen is maintained during five batches of continuous processing.
The temperature rises from 23 ° C. to 42 ° C., during which time the value of TTV gradually becomes stable, and reaches a good level only in the fifth batch. On the other hand, in the case of the lapping machine according to the present invention, which controls the temperature of the speed reducer, the surface temperature of the platen is always maintained at 23 ° C., and the TTV value is changed from the first batch. A good value is shown at 1 μm or less, and the effect of controlling the temperature of the speed reducer according to the present invention is very clear.

[0018]

As described above, according to the polishing machine of the present invention, in a lapping process of a semiconductor material such as a silicon wafer, which is further increased in size and further refined, it is referred to as the enlargement and refinement. In pursuing practical application while balancing extremely difficult technologies, it is possible to produce a tremendous effect of increasing the yield of products that occupy a large weight in achieving them. That is, if a product having a good TTV value is obtained from the first batch at the start of the process and the variation among the products is small, the product yield is naturally improved. Along with this, carrier diameter 24B
Alternatively, full-scale practical use of a large lapping machine such as 32B has become possible.

[Brief description of the drawings]

FIG. 1 is a sectional view of a polishing machine according to the present invention.

FIG. 2 is a graph showing a change in TTV from the first batch to the fifth batch after the operation of the example and the comparative example starts.

[Explanation of symbols]

1: Upper surface plate, 2: Lower surface plate, 3: Carrier plate, 4: Sun gear, 5: Internal gear,
6: Wafer, 7: Main body box, 8: Driving motor, 9: Reduction gear, 10: Cooling jacket, 1
1: Refrigerant temperature controller ● ─ ●: Change in TTV when reduction gear temperature control is performed ▲ ─ ▲: Change in TTV when reduction gear temperature control is not performed

Claims (3)

[Claims] 1. A processing machine comprising a rotatable surface plate, a motor for driving the surface plate, and a speed reducer, wherein a temperature control device is provided in a speed reducer installed below the surface plate. Polishing machine characterized by the following. 2. The polishing machine according to claim 1, wherein the temperature control device is of a type that circulates and cools a cooling liquid medium. 3. The polishing process according to claim 1, wherein the temperature control device is of a type in which air, a substitute gas for chlorofluorocarbon, or another cooling gas medium is blown or circulated for cooling. Machine.