JPH09254021A - Highly flat grinding method and highly flat grinding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the deterioration of flatness of an object to be ground as much as possible by forming a plurality of recessed parts which are substantially continuous, have specific values of width and depth, and are in the shape of a belt or a fan from the vicinity of inner periphery of a pad which is in contact with the object to be ground on a grinding surface plate to the vicinity of outer periphery thereof on a surface of the pad and making the width of a projection part which is equivalent to an interval of the recessed parts a specific value. SOLUTION: A projection part 2 and a recessed part 3 are provided on a surface of a pad 4 which is in contact with an object to be ground on a grinding surface plate 1. The width and depth of a plurality of recessed parts 3 which are formed substantially continuous from the vicinity of inner periphery to the vicinity of outer periphery of the pad 4 and are in the shape of a belt or a fan are 50mm or less and 1mm or more, respectively, to improve fluidity of grinding slurry. If the width is increased, grinding speed is reduced, and smooth slide movement of the object to be ground is prevented. Moreover, it is preferable that the width of the projection part 2 which is equivalent to an interval of the recessed parts is two-thirds or less of a long side or a long diameter of the dimension of outer shape of the object to be ground in the vicinity of outer periphery of the grinding surface plate 1 to suppress the deterioration of flatness during polish grinding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly flat polishing method for polishing the surface of a glass substrate for a photomask, a glass substrate for a magnetic disk, a silicon semiconductor wafer, etc. to a highly flat surface, and a highly flat polishing apparatus therefor.

[0002]

2. Description of the Related Art Since a glass substrate for a photomask, a glass substrate for a magnetic disk or a silicon semiconductor wafer is required to have high flatness, it is polished by improving a lapping machine using a cast iron surface plate or devising a device operating method. The demand has been addressed by increasing the flatness of the substrate by making the surface pressure and the relative movement velocity uniform, and by reducing the polishing amount of the polish polishing performed thereafter as much as possible. That is, polishing for a long time deteriorates the flatness of the object to be polished. In order to suppress this deterioration to some extent, a method of controlling the temperature of the polishing platen has been used for a silicon semiconductor wafer or the like, but it has not always been sufficient.

Further, there is adopted a method in which grooves called "cuts" are formed in a grid pattern on the surface of the polishing pad and the polishing abrasive liquid is supplied to the surface to be polished as uniformly as possible to make the polishing uniform. However, there is a problem that when this polishing pad is used for polishing, fine undulations corresponding to the pitch of the slits are formed on the surface of the object to be polished, and this method is adopted especially at the stage of finish polishing. I couldn't do that.

[0004]

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art. That is,
An object of the present invention is to newly provide a polishing method and an apparatus for polishing, which can suppress deterioration of flatness of an object to be polished as much as possible.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a pair of polishing surface plates to which pads are attached and a carrier sandwiched between the polishing surface plates rotate. Thereby, in the high flatness polishing method of simultaneously polishing both the front and back surfaces of the object to be polished inserted in the carrier,
A plurality of strip-shaped or fan-shaped recesses having a width of 50 mm or less, which are substantially continuous from the inner periphery to the outer periphery, are formed on the pad surface of the polishing platen which is in contact with the object to be polished,
The width of the protrusion corresponding to the interval between the recesses is not more than two-thirds of the long side or major axis of the outer shape of the object to be polished in the vicinity of the outer periphery of the polishing platen, and the depth of the recess is 0.1 mm or more. Is a highly flat polishing method.

Further, a pair of polishing surface plates to which pads are attached and a carrier sandwiched between the polishing surface plates each rotate, so that both the front and back surfaces of an object to be polished inserted into the carrier are polished at the same time. In the polishing apparatus, the surface of the polishing platen to which the pad in contact with the object to be polished is attached has a substantially continuous width 5 from the inner periphery to the outer periphery of the polishing platen.
A plurality of strip-shaped or fan-shaped recesses of 0 mm or less are provided, and the width of the protrusion corresponding to the interval between the recesses is two-thirds of the long side or the long diameter of the outer dimension of the object to be polished near the outer periphery of the polishing platen. And the depth of such a recess is 0.1 m
It is a highly flat polishing apparatus characterized in that it is at least m.

[0007]

1 is a perspective view of a part of a polishing platen according to one embodiment of the present invention, in which 1 is a polishing platen, 4 is a pad, 2 is a convex portion (thick portion) of the pad. ) 3 is a recess (thin portion) of the pad.

As the polishing apparatus of the present invention, a Hoffman type double side polishing machine or the like can be used. As the carrier of the present invention, a stainless steel sheet, a polyimide resin sheet, a glass fiber laminated epoxy resin sheet or the like can be used.

As the pad of the present invention, soft foamed polyurethane, non-woven fabric made of polyester fiber, a combination of both of them, a hard foamed polyurethane impregnated with an abrasive and the like can be used.

In the present invention, the surface of the pad is provided with the convex portion and the concave portion. The convex portion and the concave portion can correspond to the thick portion and the thin portion of the pad, respectively. As the method of forming the convex portion and the concave portion, a method of forming a concave portion on the surface of the polishing surface plate to which the pad is attached by machining, or a plastic sheet cut to a predetermined size on the surface of the polishing surface plate to form the concave portion Method (in this case, the thickness of the concave portion, that is, the thickness of the thin portion of the pad is 0 mm), the method of using the pad with the back surface layer partially removed, and the concave portion was formed by heating and pressing the surface layer. It is possible to use a method of using a pad or a method of using a plurality of pads cut into a predetermined size.

The width and depth of the band-shaped or fan-shaped concave portion to be formed are set to a width of 1 in order to improve the flow of the polishing slurry.
mm or more and a depth of 0.1 mm or more,
Further, in order to reduce the deviation in the polishing amount caused by the difference in the relative speed between the object to be polished and the pad between the inner and outer circumferences of the polishing platen, it is desirable to make the width of the recess on the outer circumference side wider than that on the inner circumference side. . However, if the width is too wide, the polishing rate is lowered and the smooth sliding motion of the object to be polished is hindered. Therefore, the width is preferably 50 mm or less.

It is desirable that the width of the convex portion is not more than two-thirds of the long side or the long diameter of the outer dimension of the object to be polished in the vicinity of the outer periphery of the polishing platen in order to suppress the flatness deterioration during polishing. .

In a Hoffman type double-side polishing machine, etc.,
Normally, the upper and lower polishing platens are rotated in the opposite directions.Therefore, polishing on the platen side, which rotates in the opposite direction to the rotation direction of the carrier, is the relative speed between the object to be polished and the pad between the inner and outer circumferences of the platen. Will be performed under the condition that the difference between the two increases. In order to reduce this effect, for a surface plate that rotates in the opposite direction of the carrier rotation direction, the contact time of the pad and the object to be polished on the outer surface of the surface plate should be shorter than that of a surface plate that rotates in the same direction. In addition, it is more desirable to reduce the width of the convex portion on the outer peripheral side or increase the number of concave portions. That is, on the pad surface, the ratio n · b of the cumulative length n · b (where n is the number of protrusions) of the convex length b to the circumferential length a at a certain radius.
It is preferable that / a = c is smaller on the outer peripheral side and the value of c on the outer peripheral side is different between both polishing surface plates.

In the present invention, the recesses on the pad surface serve to uniformly supply the polishing slurry to the surface of the object to be polished. Generally, the unevenness of the pad surface causes a local deviation of the polishing amount, but by providing this recess continuously from the vicinity of the inner circumference to the vicinity of the outer circumference of the polishing platen, the deviation is averaged without being amplified. be able to. This can be realized when the relative speed between the object to be polished and the pad due to the rotation of the carrier is sufficiently smaller than the relative speed between the object to be polished and the pad due to the rotation of the polishing platen.
It is considered that setting the rotation speeds of the carrier and the polishing platen under such conditions will not cause any problems.

Further, in the present invention, since the substantial polishing time at the predetermined radius of the polishing platen can be changed by arbitrarily setting the width of the convex portions × the number of the protrusions, it occurs between the inner and outer circumferences of the polishing platen. Polishing deviation can be suppressed.

[0016]

EXAMPLES Examples and comparative examples of the present invention will be described below.

[Example 1] The outer diameter of the polishing platen was 1325 m.
m 4 way Hoffman type double side polishing machine
A total of 15 pieces of synthetic quartz glass substrates of × 152 × 6.4 mm were inserted into 5 pieces of carriers, 3 pieces each, and polishing was performed.

A 0.5 mm thick rigid PVC sheet with a width of 1
It was cut into 5 mm strips, and 90 strips were respectively radially attached and fixed to the surfaces of the upper and lower surface plates by a double-sided tape to form recesses having a width of 2 to 31 mm on the surface of the surface plate. A polishing pad made of soft foamed polyurethane having a nonwoven fabric layer on the back surface was attached thereon.

The polishing pressure was 80 g / cm ² as a value obtained by dividing the total pressure by the area in which the convex portions of the pad contact the object to be polished. The number of rotations of the upper platen and the lower platen is 15 rpm, respectively.
And -45 rpm (where the-sign represents counterclockwise rotation). The number of carrier revolutions and the number of revolutions are -15 each
rpm and 3 rpm. Polishing was performed for 40 minutes while supplying a polishing slurry in which cerium oxide was suspended in pure water.

As a result, the change in the flatness of each glass substrate before and after polishing was 0.3 μm on average and 1.5 μm at the maximum, and the surface roughness _Ra was 0.2 nm and the surface was smooth and free from creaking. Got

[Comparative Example 1] Polishing was carried out under the same conditions as in Example 1 except that the recesses were not formed on the surface of the polishing platen, and the flatness change of each glass substrate before and after polishing was 1. It was 2 μm, and the maximum was 8 μm. The surface roughness _Ra was 0.2 nm.

[Example 2] Hard PVC with a thickness of 0.5 mm
The sheet is cut into strips with a width of 15 mm, and 90 strips are radially affixed to the surface of the lower surface plate by double-sided tape to form a concave portion with a width of 2 to 31 mm on the surface of the lower surface plate. For the same PVC sheet, the short side is 15m
m, long side 30 mm, height 418 mm, cut into 90 trapezoidal pieces, and radially stick to the surface of the upper surface plate with double-sided tape to fix it, and the width of the upper surface plate is 2 to 16
mm recesses were formed.

Polishing was performed in the same manner as in Example 1 using these platens. As a result, the flatness change of each glass substrate before and after polishing was 0.2 μm on average and 0.8 μm at the maximum, and a smooth mirror-free mirror surface with _a surface roughness _Ra of 0.2 nm was obtained.

[0024]

The present invention has the following effects because it is possible to suppress the deterioration of flatness caused by polishing. (1) A glass substrate or semiconductor wafer having a high flatness and a smooth surface can be manufactured. (2) Even when surface defects such as scratches and stains are generated and polishing is performed again, regenerated polishing can be performed without degrading flatness. (3) Since the flatness is hardly deteriorated, the re-polishing by polishing with hard foamed polyurethane or the like can be omitted, so that the material yield is improved. (4) Defects in flatness are reduced and the yield is improved.

[Brief description of drawings]

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

[Explanation of symbols]

 1: Polishing surface plate 2: Convex part 3: Concave part 4: Pad

Claims (4)

[Claims] 1. A high flatness for simultaneously polishing both front and back surfaces of an object to be polished inserted in a carrier by rotating a pair of polishing surface plates to which pads are attached and a carrier sandwiched therebetween. In the polishing method, a plurality of strip-shaped or fan-shaped recesses having a width of 50 mm or less, which are substantially continuous from the inner periphery to the outer periphery, are formed on the pad surface of the polishing platen in contact with the object to be polished. The width of the convex part corresponding to the interval is 2/3 or less of the long side or the major axis of the outer shape of the object to be polished near the outer periphery of the polishing platen, and the depth of the concave part is 0.1 mm or more. High flatness polishing method. 2. A cumulative total of n · b (where n is n) of the length b of the convex portion with respect to the circumferential length a at a certain radius on the pad surface.
The ratio n · b / a = c of the number of convex portions is smaller on the outer peripheral side, and the value of c on the outer peripheral side is different between both polishing platens. Flat polishing method. 3. A high flatness for simultaneously polishing both front and back surfaces of an object to be polished inserted in a carrier by rotating each of a pair of polishing surface plates having pads attached thereto and a carrier sandwiched therebetween. In the polishing apparatus, on the surface of the polishing platen to which the pad in contact with the object to be polished is adhered, a width of 50 mm which is substantially continuous from the inner periphery to the outer periphery of the polishing platen.
The following strip-shaped or fan-shaped recesses are provided, and the width of the protrusion corresponding to the interval between the recesses is less than ⅔ of the long side or the long diameter of the outer dimension of the work piece in the vicinity of the outer periphery of the polishing platen. The high flatness polishing apparatus is characterized in that the depth of the recess is 0.1 mm or more. 4. A ratio n.b / a = c of a cumulative total n.b (where n is the number of protrusions) of the length b of the protrusions to the circumferential length a at a certain radius on the surface of the polishing platen. However, the value of c on the outer peripheral side is smaller and the value of c on the outer peripheral side is different between both polishing surface plates.