TW201912304A - Double-sided grinding device for the object to be used for grinding - Google Patents

Abstract

The purpose of the invention is to provide a carrier for holding a ground object, which is a ground object holding carrier used for a double-sided grinding device and configured to obtain a ground object with the delicate upper and lower surface roughness and excellent parallelism and excellent flatness. The problem addressed by the present invention is solved by a carrier for holding a ground object used for a double-sided grinding device. The carrier for holding a ground object has one or more holding holes for holding the ground object and is characterized in that a plurality of small holes are formed in the carrier substrate through hole at an inner side of an imaginary concentric circle which has the same center as the holding hole for holding the ground object and has a radius larger than the radius of the holding hole for holding the ground object, and a plurality of small holes each of which has a larger diameter than that of the aforementioned small hole are formed in the carrier substrate through hole at an outer side of the imaginary concentric circle.

Description

   Star wheel for holding object to be ground for double-side grinding device   

The present invention relates to a caster wheel for holding an object to be polished, which is used for a double-side grinding device, and a small hole for passing the abrasive is provided around the holding hole of the object to be ground. The object to be ground is clamped and crimped between the upper and lower fixed plates to which the abrasive cloth is attached, while at least one of the upper and lower fixed plates and the object to be ground are rotated to simultaneously perform grinding processing on both sides of the object to be ground.

During polishing of both sides of an object consisting of a silicon wafer, a compound semiconductor wafer, an aluminum magnetic hard disk substrate, a glass magnetic hard disk substrate, or glass for a photomask, a crystal oscillator, ceramics, etc. It is held in a holding hole of a caster wheel for holding an object to be polished. The above-mentioned caster wheel for holding an object has a holding hole that conforms to the shape of the object to be polished. The gear and the sun gear mesh with the outer peripheral teeth. The object to be ground is rotated in a planetary motion by the rotation of the internal gear and the sun gear. At the same time, the upper and lower fixed disks are rotated to drive the object to be ground. Both sides are simultaneously ground. The planetary gear train for holding an object to be polished is used as a member of a polishing device for simultaneously performing polishing processing or mirror polishing processing on both surfaces of the object to be polished.

Conventionally, a star wheel for holding an object to be ground is generally manufactured by using a metal material such as steel or stainless steel, fiber-reinforced resin (FRP), and the like, and holding holes having a size capable of holding the object to be ground. Processing is performed in such a manner that the outer periphery thereof is processed so as to have outer peripheral teeth that mesh with the gear shapes of the internal gear and the sun gear.

In the above-mentioned polishing process, during the polishing process, the polishing liquid is supplied from the polishing liquid supply hole formed on the upper platen to the processing portion, and the gap between the self-holding holes also enters the lower platen side, and the upper and lower surfaces of the object to be polished are simultaneously polished. . However, in the case where the hole for perforating the caster wheel for holding the object to be polished is only the part for holding the object wheel for holding the object, the caster wheel for holding the object and the object to be ground become as described below. The shape of the disk is substantially the entire surface, so that the inflow of the polishing liquid downward to the disk side becomes insufficient, and homogeneous processing becomes difficult. Therefore, it is pointed out that the following phenomena occur: the shape of the object to be ground becomes tapered after processing, or peripheral collapse, or deviation in the roughness of the finished surface, or the surface roughness of the upper and lower surfaces is different. Furthermore, a problem was also pointed out that the polishing liquid was easily discharged out of the system before centrifugal force due to the rotation was enough to contribute to the polishing process, so it wasted much.

In particular, in recent years, the manufacturing technology of the object to be ground has been improved, so the above-mentioned problem about the star wheel for holding the object to be ground has become more obvious, and it is strongly demanded to solve the problem.

In order to avoid the phenomenon described above, a method has been proposed previously, which is to perforate a dummy hole (also called a dummy hole) at a position other than the holding hole, and use it as a polishing liquid through the hole to make the polishing liquid downward. The inflow on the disk side becomes smooth (Patent Document 1 or Patent Document 2).

In addition, Patent Document 3 discloses a method in which a mesh-shaped void portion is provided in a region other than the holding hole of the caster wheel for holding an object to be polished to improve the inflow of the polishing liquid downward to the platen side and prevent the after-processing. Fluctuations of the object to be ground.

Patent Document 4 proposes a caster wheel for holding an object to be polished, which restricts the amount of displacement of the caster wheel for holding an object by specifying the diameter of the polishing liquid passage hole or the distance between the polishing liquid passage holes. No strain.

[Prior technical literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 11-170164

[Patent Document 2] Japanese Patent Laid-Open No. 2004-291115

[Patent Document 3] Japanese Patent Laid-Open No. 2000-84835

[Patent Document 4] Japanese Patent Laid-Open No. 2016-22542

However, even with these methods, the supply (inflow) of the polishing liquid to the back surface (lower platen side) of the object to be polished is not necessarily sufficient, so that the amount of supply of the polishing liquid to the upper and lower platen is not uniform. That is, it is by no means easy to obtain an object to be polished which has a fine upper and lower surface roughness and has excellent parallelism and excellent flatness.

The present inventors have made intensive research on a caster wheel for holding an object to be polished for polishing both sides of an object to be polished, such as a silicon wafer, and have thus completed the present invention. An object of the present invention is to provide an object for holding an object to be polished that solves the above-mentioned problems. Star wheel. That is, the present inventors have discovered that small holes with fixed apertures are arranged at fixed intervals in the region of the base member of the planetary wheel for holding the object other than the holding holes of the object to be ground, and the holes have a hole diameter from the base material. The method of increasing the inner side to the outer side is arranged in a gradient manner, so that the flow of the polishing liquid is homogenized, so that the surface roughness of the upper and lower surfaces is uniform without unevenness, and the object to be polished has high parallelism and high flatness. .

The above-mentioned problem is achieved by a caster wheel for holding an object to be polished for a double-side polishing device. The star wheel system for holding an object has one or more holding holes for holding the object to be polished. It is characterized in that a plurality of small holes are perforated in the star wheel base material which is more inside than the imaginary concentric circle drawn in the same way as the above-mentioned holding hole and has a radius larger than its radius, and is more than the above imaginary concentric circle The substrate of the star wheel further outside is perforated with a plurality of small holes having a diameter larger than the small holes.

In the planetary wheel for holding an object to be polished of the present invention, it is preferable that the difference between the radius of the object to be ground (workpiece) and the radius of the imaginary concentric circle is equal to or less than the radius of the holding hole. If the difference between the radii of the two circles exceeds the radius of the holding hole, the area of the perforated small hole in the star wheel base material that is more inward than the imaginary concentric circle is wider, and the star wheel base material is more outside than the imaginary concentric circle The area of the perforation having a small hole larger than the diameter of the small hole is narrowed, so that the homogenization of the flow of the polishing liquid based on the gradient of the size of each small hole becomes insufficient. Specifically, it is set in the range of 10% to 70% of the radius of the object to be polished.

In the planetary wheel for holding an object to be grounded in the present invention, it is preferable that the diameter of the plurality of small holes perforated by the planetary wheel base material which is more inward than the imaginary concentric circle above is 3% of the radius of the object (workpiece). To 15%. If it is less than 3%, even if the surface tension of the polishing liquid in the small hole acts, the function of the polishing liquid passing hole as the inflow of the polishing liquid downward to the plate side is reduced. If it exceeds 15%, the ability to maintain the polishing liquid supplied from the small holes perforated by the star wheel base material which is more outward than the concentric circle is reduced, and the balance between the polishing surface of the upper and lower plates and the polishing liquid supplied by the object to be polished is balanced. The properties are deteriorated, and homogeneous grinding cannot be performed. Specifically, it is set in a range of Φ3mm to Φ15mm.

In the planetary wheel for holding an object to be ground of the present invention, it is preferable that a plurality of small holes perforated on the planetary wheel base material which is further outside than the imaginary concentric circle described above, that is, the diameter of the larger small hole is the object to be grounded ( Workpiece) radius of 6% to 30%. If it is less than 6%, the difference between the diameter of the small hole with the smaller hole, that is, the hole perforated on the star wheel base material which is more inward than the imaginary concentric circle, becomes smaller, and the grinding based on the gradient of the size of the above hole is realized. The homogenization of the liquid flow becomes insufficient. In addition, if it exceeds 30%, the ability to retain the abrasive liquid in the small holes perforated by the star wheel base material which is more outward than the concentric circle is reduced, and the smaller the perforation of the star wheel base material which is more inside than the hypothetical concentric circle The supply of the polishing liquid to the holes becomes insufficient, and the balance between the polishing surfaces of the upper and lower platens and the polishing liquid supplied to the object to be polished deteriorates, making it impossible to perform homogeneous polishing. Specifically, it is set in a range of Φ10 mm to Φ30 mm.

Further, in the planetary wheel for holding an object to be polished according to the present invention, it is preferable that a plurality of small holes other than the object holding hole to be held are spaced closer to each other than the above-mentioned imaginary concentric circles. Is less than the diameter of the small hole. If arranged at intervals larger than the diameter, the arrangement of the holes becomes too sparse, and the target effect of the present invention cannot be obtained. Specifically, it is set in a range of 30% to 100% with respect to the small hole diameter.

Further, in the caster wheel for holding an object to be polished according to the present invention, it is preferable that a plurality of small holes other than the object holding hole is spaced from adjacent small holes at a position closer to the outside than the imaginary concentric circles. Is less than the diameter of the small hole. If arranged at intervals larger than the diameter, the arrangement of the holes becomes too sparse, and the target effect of the present invention cannot be obtained. Specifically, it is set in a range of 30% to 100% with respect to the small hole diameter.

The present invention is characterized in that a plurality of small holes are provided in an area other than the object holding hole of the star wheel for holding the object, and the hole diameter of the small hole becomes larger from the inner side of the star wheel base toward the outer side. The method is arranged in a gradient manner, and the diffusion of the polishing liquid to the polishing surfaces of the two fixed plates becomes smooth, and the distribution of the polishing liquid becomes homogeneous. In the description of the present invention shown below, a case where the distribution area of the pinholes becomes double is listed, but it is not particularly limited, and it may be set to triple or more.

With the planetary wheel for holding an object to be polished according to the present invention, the supply of the polishing liquid used as the abrasive in the double-side polishing to the polishing surfaces of the two fixed plates becomes equal, and at the same time, the distribution of the polishing liquid on the polished surface of the fixed plate can be changed. Get homogeneous. This makes it possible to obtain an object to be polished, in which both the upper and lower surfaces of the object to be polished have a fine surface roughness, a non-uniform surface, and excellent flatness. In addition, the consumption of the polishing liquid is reduced, and the cost in the polishing process can be reduced.

1‧‧‧ Retaining hole for holding abrasive

2‧‧‧ An imaginary concentric circle with the same center point as the holding hole

3‧‧‧Φ10mm abrasive liquid through the small hole

4‧‧‧Φ15mm abrasive liquid through the small hole

5‧‧‧Φ100mm abrasive liquid through the small hole

6‧‧‧Φ50mm abrasive liquid through the small hole

7‧‧‧Φ30mm polishing liquid through small holes

FIG. 1 is a plan view of a star wheel for holding an object to be polished according to the present invention.

FIG. 2 is an enlarged plan view of a main part of a star wheel for holding an object to be polished according to the present invention.

FIG. 3 is a plan view of an example of a caster wheel for holding an object to be ground obtained by a conventional technique.

FIG. 4 is a plan view of another example of a star wheel for holding an object to be ground obtained by a conventional technique.

FIG. 5 is a plan view of another example of a star wheel for holding an object to be ground obtained by a conventional technique.

FIG. 6 is a graph showing a measurement result of a thickness distribution (Y-axis) in a diameter direction (X-axis) of a Φ300 mm silicon wafer obtained by polishing using a planetary wheel for holding an object to be polished according to the present invention.

FIG. 7 is a graph showing a measurement result of a thickness distribution (Y-axis) in a diameter direction (X-axis) of a silicon wafer Φ300 mm obtained by polishing using a conventional star wheel for holding an object to be polished shown in FIG. 3.

FIG. 8 is a graph showing a measurement result of a thickness distribution (Y-axis) in a diameter direction (X-axis) of a silicon wafer of Φ300 mm obtained by polishing using a conventional caster wheel for holding an object to be polished shown in FIG. 4.

FIG. 9 is a graph showing a measurement result of a thickness distribution (Y-axis) in a diameter direction (X-axis) of a silicon wafer of Φ300 mm obtained by polishing using a conventional star wheel for holding an object to be polished shown in FIG. 5.

Next, the content of this invention is demonstrated using drawing. FIG. 1 is a top view of a caster wheel for holding an object to be polished as an embodiment of the present invention, and FIG. 2 is an enlarged view of a main part thereof. There are a plurality of holding holes 1 (three in this embodiment) of holding holes 1 for holding objects to be ground Φ300 mm. For each of the three holding holes for holding the object to be ground, draw an imaginary concentric circle 2 having the same center point as each holding hole and having a radius of 210 mm, from the periphery of the holding hole 1 for holding the object to be ground to the imaginary A region up to the inner periphery of the concentric circle 2 is referred to as an A region, and a region further outside than the A region is referred to as a B region. In addition, in the area A, a hole Φ10mm is used to pass through the small holes 3 so that the distance between the small holes passing through the holes is 7.5 mm, and in the area B is a small hole that is adjacent to the liquid passing through the holes. A small-diameter Φ15 mm polishing liquid is passed through the small hole 4 so as to be 10 mm.

In the case of a star wheel for holding an object to be polished shown in FIG. 1 and FIG. 2, there are three holding holes 1 with a radius of 150 mm and an imaginary concentric circle 2 with the same center point having a radius of 210 mm. The difference between the radii is 60 mm, which is smaller than the 150 mm radius of the holding hole for holding the object to be ground. Because the diameter of the plurality of polishing liquids perforated in the area A is Φ10 mm, the diameter of the small holes becomes 6.67% of the 150 mm radius of the silicon wafer to be polished. In addition, since the diameter of the plurality of polishing liquids perforated in the B region is Φ15 mm, the diameter of the small holes is 10.0% of the 150 mm radius of the silicon wafer to be polished.

The object to be polished (workpiece) referred to in the present invention refers to silicon wafers, compound semiconductor wafers, aluminum magnetic hard disk substrates, glass magnetic hard disk substrates, or glass for photomasks, crystal oscillators, ceramics, etc. It is particularly limited, but mainly targets silicon wafers. In addition, although its shape is approximately circular, its size (diameter) or shape is not particularly limited. For example, a large-diameter object such as a silicon wafer with a diameter of 300 mm can be cited. The present invention has a significant effect on such objects. . In addition, the so-called double-sided polishing referred to in the present invention refers to polishing, pre-polishing, polishing, and the like, and is not particularly limited.

The material used for the planetary wheel for holding the abrasive object of the present invention can be stainless steel, carbon tool steel (SK steel), high-carbon chromium bearing steel, high-speed tool steel, alloy tool steel, high tension steel, or titanium and other metals and ceramics. , Polyamide, polyacetal, polyvinyl chloride, polycarbonate, polyimide, polyimide, epoxy and other resins, or glass fiber, carbon fiber, aromatic polyimide fiber, cloth glue A fiber-reinforced plastic (FRP) in which a fiber material such as cloth (bakelite) is compounded with an epoxy resin, a polyamide resin, a phenol resin, or the like is not particularly limited. Resin or diamond-like carbon such as polypropylene can also be used to cover the surface of the caster wheel for holding such abrasives. In addition, in order to prevent damage to the outer edge portion of the object to be polished, the star wheel for holding the object of the present invention is provided with a resin frame such as an aromatic polyamide resin at the inner peripheral portion of the object holding hole.

FIG. 3 is an explanatory diagram of a star wheel for holding an object to be ground obtained by a conventional technique. In addition to the holding hole 1 for holding the object to be polished, an irregular polishing liquid passage hole is formed. The shape of the passage hole has an irregular shape such as a substantially rhombic shape and a substantially triangular shape.

FIG. 4 is an explanatory diagram of a star wheel for holding an object to be ground obtained by a conventional technique. The perforation has a plurality of (3) holding holes for holding an object to be ground with a diameter of 300 mm. Grinding liquid passing holes having different sizes are formed in areas other than the respective holding holes. In the conventional technique, the polishing liquid passing through the small hole system is composed of 3 Φ100 mm polishing liquid passing through the small holes 5, and 6 Φ50 mm polishing liquid passing through the small holes 6. Although these polishing liquids are composed of a smaller hole and a larger hole by using small holes, they are not arranged in such a manner as to have a gradient from a side closer to each holding hole toward a side farther away as in the present invention.

FIG. 5 is also an explanatory diagram of a star wheel for holding an object to be ground obtained by a conventional technique. There are a plurality of (3) holding holes 1 for holding an object to be ground Φ300 mm. A plurality of Φ30 mm polishing liquid passing small holes 7 are perforated in a region other than each of the holding holes so that the distance from the adjacent small holes becomes 22 mm. There is only one kind of pore size of the polishing liquid by using small pores, and those with different pore sizes are not mixed as in the present invention.

In FIGS. 1 and 2, as an embodiment of the caster wheel for holding an object to be grounded according to the present invention, it is shown that one object is used for holding the object to be ground with three holding holes for holding the object with a diameter of Φ300 mm. Star wheel. In this case, the area of the area outside the holding hole is relatively small, so in this embodiment, the area for the perforated small hole is separated by an imaginary concentric circle (a double imaginary concentric circle), but if the If the number of holes is set to one, the area where the perforated polishing liquid passes through the small holes separated by a plurality of imaginary concentric circles with different radii may be set to one or more. When it is assumed that only one Φ300mm silicon wafer holding holding hole is used for holding a grinding wheel for holding an abrasive, a plurality of imaginary concentric circles with different radii (here, two imaginary concentric circles) will be determined by The area formed by the imaginary concentric circles is set to triple, that is, A area, B area, and C area. In this case, for example, it is possible to perforate a polishing liquid of Φ5 mm (the ratio with respect to the radius of the object to be polished is 3.33%) in area A, and use a small hole to perforate Φ10 mm (the ratio to the radius of the object to be ground). (6.67%) The polishing liquid passes through the small hole, and the C area is punched with Φ15mm (the ratio of the radius to the object to be polished is 10.00%). The polishing liquid passes through the small hole, and higher effects can be expected. In the case of perforating the polishing liquid through the small holes in the area separated by a plurality of imaginary concentric circles, the polishing liquid with the smallest perforation diameter in the area closest to the holding hole can pass through the small holes on the outer side adjacent to the area. The perforation of the area has a perforation which is more perforated in the area closest to the holding hole. The perforation of the larger diameter of the small diameter hole is passed through the small hole, and the perforation of the area adjacent to the outer area is more perforated to the nearest. The polishing liquid passing through a small hole with a large diameter is passed through the small hole through the polishing liquid in the region adjacent to the outer side of the hole holding hole. That is, when there are three or more regions separated by a plurality of imaginary concentric circles, perforation can be performed in such a manner that the polishing liquid passes through the small hole diameter and the polishing liquid passing through the area closest to the holding hole passes through the small hole. The diameter of the hole is used as a reference, and the diameter of the small hole for polishing liquid passing becomes larger as it reaches the outer region.

[Example]

Example 1

A star wheel for holding an object having the same shape as that of the star wheel for holding an object shown in FIG. 1 is prepared. The material of the prepared star wheel for holding an object to be polished is stainless steel, and its thickness is set to 774 μm. In order to prevent damage to the outer edge portion of the object to be polished, the caster wheel system for holding the object is provided with a resin frame made of an aromatic polyurethane resin on the inner peripheral portion of the object holding hole.

A polishing test of a silicon wafer having a diameter of 300 mm was performed using the above-mentioned planetary wheel for holding an object to be polished. The polishing machine and polishing processing conditions are as follows.

Grinder: Double-side grinding device manufactured by SpeedFam Co., Ltd.

Abrasive cloth: MH (registered trademark) series made by NITTA HAAS

Abrasive: GLANZOX (registered trademark) series manufactured by Fujimi Incorporated

Upper platen rotation: counterclockwise

Lower platen rotation: clockwise

Internal gear rotation: clockwise

Sun gear rotation: clockwise

Load (upper plate load): 10kPa surface pressure

Processing time: 30 minutes

The thickness distribution in the diameter direction of the silicon wafer after polishing processing under the above conditions was measured. As a measuring device, a known thickness measuring device (made by Hamamatsu Photonics) was used. The measurement results are shown in FIG. 6. The P-V (Peak to Valley) value, which represents the thickness distribution in the diameter direction, that is, the difference between the maximum measured value and the minimum measured value of the workpiece is 0.048 μm. According to the graph of FIG. 6, it can be seen that almost no deviation in the diameter direction of the silicon wafer after polishing using the planetary wheel for holding an object to be polished according to the present invention, nor a phenomenon such as a surface collapse, was confirmed. The P-V value of 0.048 μm is an extremely excellent value.

Comparative Example 1

A conventional grinding wheel for holding an object to be polished shown in FIG. 3 was used to perform a grinding experiment under the same conditions as in Example 1. The specifications of the caster wheel for holding an object to be polished used in this comparative example are the same as the caster wheel for holding an object to be polished according to the present invention used in Example 1, except for the shape and arrangement of the polishing liquid passage holes.

The thickness distribution in the diameter direction of the silicon wafer after the polishing process using the caster wheel for holding an object to be polished was measured. The measurement results are shown in FIG. 7. The obtained P-V value was 0.524 μm. As can be seen from the graph of FIG. 7, the tendency of the outer peripheral portion to be thinner than the central portion was confirmed. The so-called face collapse phenomenon is apparent. The P-V value was 0.524 μm, which was a value that was 10 times or more worse than that in Example 1. In addition, it was confirmed that the variation in the thickness in the diameter direction was larger than that in Example 1.

Comparative Example 2

A conventional grinding wheel for holding an object to be polished shown in Fig. 4 was used to perform a grinding experiment under the same conditions as in Example 1. The specifications of the caster wheel for holding an object to be polished used in this comparative example are the same as the caster wheel for holding an object to be polished according to the present invention used in Example 1, except for the diameter and arrangement of the polishing liquid passage holes.

When the holding hole 1 for holding an object to be ground of the conventional wheel for holding an object to be ground is drawn, imaginary concentric circles 2 having the same center point as each holding hole are drawn, even on the inner periphery of the imaginary concentric circle. Dispose Φ50mm abrasive liquid through the small hole and Φ100mm abrasive liquid through the small hole, and arrange Φ50mm abrasive liquid on the inner periphery of the imaginary concentric circle by using the small hole 6 and arrange Φ100mm so as to overlap the circumference of the imaginary concentric circle. The polishing liquid of Φ50mm and Φ100mm is arranged by using small holes 5 or superimposed on the circumference of an imaginary concentric circle. By setting a imaginary concentric circle with an arbitrary radius by using a small hole, it also does not meet the constitutional requirements of the present invention. Its configuration.

In the case of a star wheel for holding an object to be polished as shown in FIG. 4, the radius of the plurality of holding holes 1 is 150 mm, and the radius of an imaginary concentric circle 2 having the same center point is 210 mm as in the present invention. The area from the peripheral edge of the holding hole to the inner peripheral edge of the imaginary concentric circle is set as the A area, and the area further outside than the A area is set as the B area. In addition, if the Φ50mm polishing liquid passes through the small hole 6 and Φ100mm polishing liquid passes through the small hole 5 in the area other than the holding hole, the Φ50mm and Φ100mm polishing liquid passes through the small hole to overlap the circumference of the imaginary concentric circle. It is configured in the above manner, that is, a small hole of Φ50mm and Φ100mm is used for perforating the polishing liquid passing through the area A and the area B.

The Φ50mm polishing liquid passes through the small hole 6 and Φ100mm polishing liquid passes through the small hole, so it becomes a reference value, but the Φ50mm polishing liquid passing hole becomes the radius of the silicon wafer 150mm. 33.33%. In addition, the Φ100mm polishing liquid passing hole becomes 66.67% of the 150mm radius of the silicon wafer.

The thickness distribution in the diameter direction of the silicon wafer after the polishing process using the caster wheel for holding an object to be polished was measured. The measurement results are shown in FIG. 8. The obtained P-V value was 0.206 μm. As can be seen from the graph of FIG. 8, the outer peripheral portion of the silicon wafer has a convex shape that is thinner than the central portion. In addition, a surface collapse phenomenon occurred at the outer periphery. The P-V value was 0.206 μm, which was a value that was 4 times or more worse than that of Example 1. In addition, it was confirmed that the variation in the thickness in the diameter direction was larger than that in Example 1.

Comparative Example 3

A conventional grinding wheel for holding an object to be polished shown in FIG. 5 was used to perform a polishing experiment under the same conditions as in Example 1. In addition, the specifications of the caster wheel for holding an object to be polished used in this comparative example are the same as those of the caster wheel for holding an object to be polished according to the present invention used in Example 1, except for the diameter and arrangement of the polishing liquid passage hole. the same.

When the holding hole 1 for holding the ground object of the conventional wheel for holding the object to be ground is drawn, the imaginary concentric circles 2 having the same center point as the holding holes are drawn. The arrangement of the Φ30mm polishing liquid passage holes in both areas is an arrangement that does not satisfy the constitutional requirements of the present invention even if an imaginary concentric circle is set at an arbitrary radius.

In the case of a planetary wheel for holding an object to be polished as shown in FIG. 5, as in FIG. 4, the radius of the three holding holes is 150 mm, and the radius of the imaginary concentric circle 2 having the same center point is set as in the present invention. 210mm. The area from the peripheral edge of the holding hole to the inner peripheral edge of the imaginary concentric circle is set as the A area, and the area further outside than the A area is set as the B area. In addition, in the areas A and B, which are areas other than the holding holes, a polishing liquid passing hole 7 having a diameter of 30 mm is punched so that the interval between the adjacent holes is 22 mm.

The diameters of the plurality of polishing liquids perforated in the A area and the B area are Φ30mm, so they become 20% of the 150mm radius of the silicon wafer as the object to be polished.

The thickness distribution in the diameter direction of the silicon wafer after the polishing process using the caster wheel for holding an object to be polished was measured. The measurement results are shown in FIG. 9. The obtained P-V value was 0.231 μm. It can be seen from the graph of FIG. 9 that the outer peripheral portion of the silicon wafer has a convex shape that is thinner than the central portion. In addition, a surface collapse phenomenon occurred at the outer periphery. The P-V value was 0.231 µm, which was a value about 5 times worse than that of Example 1. In addition, it was confirmed that the variation in the thickness in the diameter direction was larger than that in Example 1.

As described above, when the results of Example 1 and Comparative Examples 1 to 3 are compared, it can be seen that there is a significant difference in quality. The results of the thickness measurement of Comparative Example 1 were inferior to the results of the thickness measurement of Example 1. It was confirmed that if it is a star wheel for holding an object to be polished used in Comparative Example 1, the polishing liquid for polishing diffuses up and down the two fixed disk surfaces, In particular, the inflow to the lower plate side was not smooth, and the distribution of the polishing liquid was uneven. In other words, the caster wheel for holding an object to be polished according to the present invention particularly improves the shape accuracy and thickness deviation of the object after polishing, and solves the problems of the conventional caster wheel for holding objects to be polished.

[Industrial availability]

According to the present invention, the planetary wheel for holding abrasives of the present invention solves the problem of the conventional planetary wheel for holding abrasives, that is, the uneven supply of the polishing liquid to the upper and lower fixed disk surfaces, and the polishing liquid for polishing is applied to the substrate. The inflow of the back surface of the abrasive (the lower plate side) is insufficient, so it can effectively solve the problem that the shape accuracy (flatness) of the object to be polished cannot be satisfied after processing. According to the planetary wheel for holding an object to be polished according to the present invention, the top and bottom surfaces of the object to be polished, such as silicon wafers, are fine and non-uniform surfaces, and the object is excellent in flatness. The quality of the object to be polished is improved and Increased productivity has helped a lot. In addition, it has the effect of reducing the consumption of polishing liquid, and has made great contributions to the industry.

Claims (6)

    A caster wheel for holding an object to be polished for a double-side grinding device, which is a caster wheel for holding an object with one or more holding holes for holding the object, which is characterized in that: The imaginary concentric circle which has the same center as the above-mentioned holding hole and has a radius larger than its radius is perforated with a plurality of small holes on the star wheel base material of the inner side, and is located on the star wheel which is further outside than the imaginary concentric circle. The substrate is perforated with a plurality of small holes having a diameter larger than the small holes.         The star wheel for holding an object to be polished used in the double-side polishing device according to claim 1, wherein a difference between a radius of the object to be polished and a radius of the imaginary concentric circle is equal to or less than a radius of the holding hole.         The planetary wheel for holding an object to be ground used in the double-sided grinding device as described in claim 1 or 2, wherein the diameter of the plurality of small holes perforated in the planetary wheel base material which is more inside than the imaginary concentric circle described above is the object to be polished 3% to 15% of the radius.         The planetary wheel for holding an object to be polished used in the double-sided grinding device according to claim 1 or 2, wherein the diameter of the plurality of small holes perforated in the substrate of the planetary wheel further outside than the imaginary concentric circle described above is the object to be polished The radius is from 6% to 30%.         As described in claim 1 or 2, the star wheel for holding an object to be ground is used for the double-side grinding device, wherein the space between the small hole perforated by the star wheel base material which is more inward than the imaginary concentric circle above and the adjacent small hole It is equal to or smaller than the diameter of the small hole.         As described in claim 1 or 2, the star wheel for holding the object to be ground is used for the double-side grinding device, wherein the space between the small hole perforated by the star wheel base material which is more outside than the above imaginary concentric circle and the adjacent small hole It is equal to or smaller than the diameter of the small hole.