WO2009157306A1

WO2009157306A1 - Apparatus for polishing both sides of glass substrate for magnetic disk, polishing method, and production process

Info

Publication number: WO2009157306A1
Application number: PCT/JP2009/060554
Authority: WO
Inventors: 満堀江; 正文伊藤; 憲昭下平
Original assignee: 旭硝子株式会社
Priority date: 2008-06-25
Filing date: 2009-06-09
Publication date: 2009-12-30
Also published as: JPWO2009157306A1

Abstract

A polishing pad (24) of an upper platen (22) and a polishing pad (25) of a lower platen (23) have grooves (24a and 25a) formed therein so that when the upper platen (22) and the lower platen (23) are in the state of not rotating, the polishing pad (24) of the upper platen (22) has a smaller area of contact with a glass substrate (10) than the polishing pad (25) of the lower platen (23).

Description

Double-side polishing apparatus, polishing method and manufacturing method for glass substrate for magnetic disk

The present invention relates to a double-side polishing apparatus, a polishing method and a manufacturing method for a glass substrate for a magnetic disk constituting a magnetic disk used in a hard disk drive (HDD) which is a magnetic disk apparatus.

A personal computer (PC) or the like is provided with a hard disk drive (HDD) or the like as an external storage device. Usually, this hard disk drive is equipped with a magnetic disk known as computer storage. This magnetic disk has a structure in which a magnetic layer or the like is formed on an appropriate substrate such as an aluminum alloy substrate.

In recent years, glass substrates, which are high-strength and high-rigidity materials, are frequently used as magnetic disk substrates instead of fragile metal substrates. Further, glass substrates have attracted attention as magnetic disk substrates for server applications.

In addition, as the capacity of hard disks is being increased, in order to achieve higher density storage and improved recording / reading accuracy, this magnetic disk glass substrate is required to have higher precision flatness. There is a demand for further reducing the fine waviness that greatly affects the flying performance of the magnetic head.

As a polishing apparatus for manufacturing such a glass substrate, Patent Document 1 discloses a double-side polishing apparatus shown in FIG. The double-side polishing apparatus 100 includes a polishing carrier mounting portion having an internal gear 101 and a sun gear 102 that are driven to rotate at a predetermined rotation ratio, and an upper surface that is driven to rotate reversely with respect to the polishing carrier mounting portion. A panel 103 and a lower surface plate 104 are provided. A polishing pad 106 is mounted on the surface of the upper surface plate 103 and the lower surface plate 104 facing the glass substrate 105. The polishing carrier 107 mounted so as to mesh with the internal gear 101 and the sun gear 102 performs planetary gear motion. In this planetary gear movement, the polishing carrier 107 rotates while rotating around its center and revolving around the sun gear 102 as an axis. Both surfaces of the glass substrate 105 are simultaneously polished with friction between the polishing pad 106 and the glass substrate 105 due to the planetary gear motion. In this double-side polishing machine 100, after polishing the glass substrate 105, it is necessary to raise the upper surface plate 103 in order to take out the polished glass substrate 105.

On the other hand, in order to reduce the micro-waviness of the glass substrate and ensure flatness, the polishing pads mounted on the upper and lower surface plates shift from rough to flat, thereby improving the polishing accuracy of the glass substrate. Secured. Such a polishing pad has elasticity. For example, as described in Patent Document 2, a polishing pad having a groove formed on its surface is known.

Japanese Unexamined Patent Publication No. 2008-103061 Japanese Unexamined Patent Publication No. 11-77518

However, since the glass substrate for magnetic disks is thin and light, it is easily adsorbed to a polishing pad having elasticity. When the double-side polishing machine 100 of Patent Document 1 is used, when the upper platen 103 is raised, the glass substrate 105 is There was a risk that the glass substrate 105 stuck to the upper surface plate 103 would fall and be damaged.

In view of the above circumstances, the present invention suppresses sticking of an upper surface plate of a glass substrate to a polishing pad, and prevents the glass substrate from dropping and breaking. And it aims at providing a manufacturing method.

The present invention provides a magnetic disk glass substrate double-side polishing apparatus for simultaneously polishing both surfaces of a magnetic disk glass substrate disposed between an upper surface plate and a lower surface plate each having a polishing pad. The contact area between the polishing pad and the glass substrate is smaller than the contact area between the polishing pad of the lower surface plate and the glass substrate.

Further, in the double-side polishing apparatus, it is preferable that grooves of the same width are formed in a lattice pattern at different pitches on the polishing pad of the upper surface plate and the polishing pad of the lower surface plate.

The present invention also relates to a method for polishing a glass substrate for a magnetic disk, in which both surfaces of a glass substrate for a magnetic disk disposed between an upper surface plate and a lower surface plate each having a polishing pad are simultaneously polished. Polishing is performed using a polishing pad having a smaller contact area between the polishing pad and the glass substrate than a contact area between the polishing pad of the lower surface plate and the glass substrate.

The present invention also includes an attachment step of attaching a magnetic disk glass substrate between an upper surface plate and a lower surface plate each having a polishing pad, a polishing step of simultaneously polishing both surfaces of the magnetic disk glass substrate, A step of taking out the glass substrate for magnetic disk disposed between the upper surface plate and the lower surface plate, and a method for producing the glass substrate for magnetic disk, comprising: Is smaller than the contact area between the polishing pad of the lower surface plate and the glass substrate.

In the present invention, the contact area of the polishing pad with the glass substrate refers to the contact area of the polishing pad with the glass substrate when the upper surface plate and the lower surface plate are stationary with respect to the glass substrate.

According to the double-side polishing apparatus, polishing method and manufacturing method of the magnetic disk glass substrate of the present invention, the contact area between the polishing pad of the upper surface plate and the glass substrate is larger than the contact area of the polishing pad of the lower surface plate with the glass substrate. Even if it is a thin glass substrate for a magnetic disk that is thin and light, when the upper platen is raised to take out the glass substrate after polishing using a double-side polishing machine, the glass substrate is It can suppress sticking to the polishing pad with which it was mounted | worn. Thereby, it can prevent that the glass substrate stuck to the polishing pad falls and is damaged.

The flowchart which shows the manufacturing method of the glass substrate for magnetic discs which concerns on this invention. Sectional drawing of the double-side polish apparatus of the glass substrate for magnetic discs which concerns on this invention. The front view of the polishing pad of an upper surface plate. The front view of the polishing pad of a lower surface plate. Cross-sectional view showing a groove of a square cross-section polishing pad Sectional drawing which shows the groove | channel of the polishing pad of a trapezoidal cross section. The flowchart which shows the process sequence of the double-side polish apparatus of the glass substrate for magnetic discs which concerns on this invention. A double-side polishing apparatus described in Patent Document 1.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
A method for producing a magnetic disk glass substrate 10 (hereinafter referred to as a glass substrate) of the present invention will be described with reference to FIG. The manufacturing method of this glass substrate 10 is as follows:
(1) Shape processing step (S1);
(2) a first polishing step (S2);
(3) a first cleaning step (S3);
(4) a second polishing step (S4);
(5) a second cleaning step (S5).

The shape processing step (S1) is a step of preparing a circular glass substrate 10 (for example, a glass substrate having a diameter of 65 mm), and a through hole (inner hole) is formed in the center of a rectangular plate glass to be processed into a circular glass. Cutting step, chamfering step of chamfering the cut circular glass edge (intersection line between main surface and inner peripheral end surface forming through-hole and intersection point of main surface and outer peripheral end surface), inner periphery and outer periphery And a grinding process for adjusting the thickness of the glass substrate to 110% or less of the final product thickness (699 μm or less when the final plate thickness is 635 μm). The main surface refers to an annular portion including the front surface and the back surface of the glass substrate 10.

In the first polishing step (S2), the main surface of the glass substrate 10 was polished by using a double-side polishing apparatus 20 to be described later, so that the main surface of the sheet glass was formed in the shape processing step (S1). It is possible to obtain a mirror-finished main surface by reducing the fine uneven shape.

Specifically, in the first polishing step (S2), in the double-side polishing apparatus 20 described later, while supplying ceria slurry containing cerium oxide having an average particle size of 0.5 μm to 2.0 μm, a urethane polishing pad For example, polishing is performed using a hard foam urethane pad. The reduction amount (polishing amount) of the plate thickness is typically 20 μm to 65 μm. As described above, the main surface of the glass substrate 10 is polished by the polishing process in the first polishing process (S2), and then the polishing process in the second polishing process (S4) to be described later is performed. In time, a mirrored main surface can be obtained.

Subsequently, in the first cleaning step (S3), the glass substrate 10 that has finished the first polishing step (S2) is cleaned. For example, ultrasonic cleaning using water, detergent, strong acid or strong alkali is performed.

Next, in the second polishing step (S4), so-called final polishing, the main surface is polished so as to have a desired surface roughness, and the main surface of the glass substrate 10 is finished into a mirror surface.

Specifically, in the second polishing step (S4), a colloidal silica slurry containing colloidal silica abrasive grains having an average particle diameter of 0.01 μm to 0.1 μm is supplied using a double-side polishing apparatus 20 described later. Polishing is performed using a urethane polishing pad such as a suede pad, and the surface roughness (Ra) measured using an AFM (atomic force microscope) is set to 0.05 nm to 0.2 nm, for example. The reduction amount (polishing amount) of the plate thickness is typically 0.3 μm to 3 μm.

Subsequently, in the second cleaning step (S5), the glass substrate 10 that has finished the second polishing step 4 is cleaned. For example, ultrasonic cleaning using water, detergent, strong acid or strong alkali is performed.

In addition, the manufacturing method of the glass substrate 10 for magnetic disks in this invention is not limited to such a thing, What is necessary is just to provide the polishing process of at least 1 time, and includes the polishing process of an inner peripheral end surface and an outer peripheral end surface. Alternatively, an additional polishing step for the main surface may be included.

Next, the double-side polishing apparatus 20 used in the first polishing step (S2) and the second polishing step (S4) described above will be described.
As shown in FIG. 2, the double-side polishing apparatus 20 of the present invention includes a carrier 21 that holds a glass substrate 10, and an upper surface plate 22 and a lower surface plate 23 that can be driven in reverse rotation with respect to the glass substrate 10. The

polishing pads

24 and 25 are mounted on the surfaces of the upper surface plate 22 and the lower surface plate 23 facing the glass substrate 10, respectively.

The upper surface plate 22 is movable up and down with respect to the lower surface plate 23 to attach and remove the glass substrate 10 before and after the polishing process, and during polishing, the

polishing pads

24 and 25 are respectively the main surfaces of the glass substrate 10. It is comprised so that reverse rotation is possible, contacting. As in the conventional double-side polishing apparatus 100 shown in FIG. 6, the carrier 21 and the lower surface plate 23 are used with respect to the upper surface plate 22 and the lower surface plate 23 using the internal gear 101 and the sun gear 102 that are driven to rotate at a predetermined rotation ratio. May be rotated relative to each other.

As shown in FIGS. 3A and 3B, the polishing pad 24 mounted on the upper surface plate 22 and the polishing pad 25 mounted on the lower surface plate 23 have

grooves

24a and 25a having substantially the same width, respectively, at equal intervals. The

grooves

24a and 25a of the

polishing pads

24 and 25 have substantially the same width, and the pitch between the grooves is that of the polishing pad 24 of the upper surface plate 22 (for example, P1 = 10 mm) is the lower surface plate. 23 is smaller than the polishing pad 25 (for example, P2 = 30 mm).

Accordingly, the polishing pad 24 of the upper surface plate 22 has more grooves than the polishing pad 25 of the lower surface plate 23, and the polishing pad is in a state where the upper surface plate 22 and the lower surface plate 23 are not rotating before and after the operation of the polishing machine. The area of the region where 24 and 25 can come into contact with the glass substrate 10 is smaller in the polishing pad 24 of the upper surface plate 22 than in the polishing pad 25 of the lower surface plate 23.

In the present embodiment, the groove pitch P1 of the polishing pad 24 of the upper surface plate 22 is set to three times the groove pitch P2 of the polishing pad 25 of the lower surface plate 23. However, the present invention is not limited to this. .

Further, the arrangement of the

grooves

24a and 25a with respect to the surfaces of the

polishing pads

24 and 25 is not necessarily a lattice shape, and extends radially from the center of the

polishing pads

24 and 25 toward the outer diameter side in a straight line or a curved line. The polishing pad 24 of the upper surface plate 22 has a contact area with the glass substrate 10 that is gradually increased in the radial direction from the center to the outer shape side, and the polishing pad 24 of the lower surface plate 23 has a contact area with the glass substrate 10. Any arrangement can be adopted as long as it is smaller than 25. Further, the combination of the arrangement of the grooves 24 a of the polishing pad 24 mounted on the upper surface plate 22 and the arrangement of the grooves 25 a of the polishing pad 25 mounted on the lower surface plate 23 is not necessarily the same. As long as the contact area of the polishing pad 24 of the upper surface plate 22 is smaller than the polishing pad 25 of the lower surface plate 23, any combination can be adopted.

Further, the cross-sectional shape of the

grooves

24a and 25a of the

polishing pads

24 and 25 can be any shape such as a square shown in FIG. 4A or a trapezoid shown in FIG. 4B.

As the

polishing pads

24 and 25, in addition to the above-described polishing pads, non-woven fabrics, velor-like, suede-like polishing pads, other fibers, resin materials, or composite materials of these materials can be used. In particular, as a polishing pad for a glass substrate for a magnetic recording medium having a surface roughness of about 0.05 nm to 0.2 nm, a suede-like polishing pad using a polymer foamed body, particularly a foamed polyurethane, is 0 to 15%. And preferably have a compression modulus of 80 to 99%.

Next, the processing procedure of the double-side polishing apparatus 20 of the present invention will be described with reference to FIG.
The processing procedure of this double-side polishing apparatus 20 is as shown in FIG.
・ Attaching process of substrate (SA1),
・ Upper platen lowering process (SA2),
・ Pressurization / acceleration process (SA3);
・ This polishing step (SA4);
・ Depressurization / deceleration process (SA5),
・ Upper platen rising process (SA6),
A substrate take-out step (SA7).

First, the glass substrate 10 is attached to the carrier 21 (SA1), and after attaching the glass substrate 10, the upper surface plate 22 is lowered (SA2). Subsequently, the upper surface plate 22 and the lower surface plate 23 are started to rotate while the polishing pad 24 of the upper surface plate 22 and the polishing pad 25 of the lower surface plate 23 are brought into contact with the glass substrate 10 while supplying a predetermined slurry. And accelerate (SA3). Then, after polishing for a predetermined time (SA4), the rotational speeds of the upper surface plate 22 and the lower surface plate 23 are reduced and the pressure is reduced (SA5). After stopping, the upper surface plate 22 is raised (SA6), and the glass substrate 10 is taken out from the carrier 21 (SA7).

According to the present embodiment, by providing the

grooves

24 a and 25 a in the polishing pad 24 of the upper surface plate 22 and the polishing pad 25 of the lower surface plate 23, the slurry can be spread over the plurality of glass substrates 10 in the polishing process. In addition, when the upper surface plate 22 and the lower surface plate 23 are not rotating, the polishing pad 24 of the upper surface plate 22 has a contact area with the glass substrate 10 of the

polishing pads

24, 25. It is set smaller than 25.

Therefore, the surface tension due to the liquid component such as the slurry staying between the polishing pad 24 of the upper surface plate 22 and the surface of the glass substrate 10 facing the surface of the glass substrate 10 facing the polishing pad 25 of the lower surface plate 23 It becomes smaller than the surface tension due to the liquid component such as the slurry staying between. Thus, even if the polishing process is performed using a polishing pad that is thin and light and has a soft and easy-to-adsorb polishing pad for high precision flatness. When the upper surface plate 22 of the apparatus 20 is raised (SA6), the glass substrate 10 can be prevented from sticking to the polishing pad 24 of the upper surface plate 22. Accordingly, it is possible to prevent the glass substrate 10 from being dropped and damaged by raising the upper surface plate 22 of the double-side polishing apparatus 20.

The ratio of the contact area between the polishing pad 24 of the upper surface plate 22 and the glass substrate 10 to the contact area between the polishing pad 25 of the lower surface plate 23 and the glass substrate 10 is preferably 1: 1.005 to 1: 1. 5, more preferably 1: 1.01 to 1: 1.3. If it is smaller than 1: 1.005, the glass substrate 10 may stick to the polishing pad 24 of the upper surface plate 22, and if it is larger than 1: 1.5, the surface roughness between the front surface and the back surface of the glass substrate 10 is large. , End shapes, or micro swell may vary.

In addition, the present invention can be applied to any polishing process (for example, the first and second polishing processes), but it is necessary to use a polishing pad that is softer and easier to adsorb as the surface roughness is smaller. Therefore, it is particularly useful in the final polishing step (second polishing step).

Hereinafter, the present invention will be specifically described by giving examples and comparative examples. In addition, this invention is not limited to the structure of these Examples.
[Disc drop test]
In order to verify the disk fall prevention performance, the following tests were performed using a small-size double-side polishing apparatus capable of polishing both surfaces of four glass substrates simultaneously. The examples and comparative examples were all performed under the same conditions except that the groove pitch of the polishing pad was changed, and after finishing polishing (SA1 to SA5 in FIG. 5), the upper surface plate was raised (SA6 in FIG. 5), The number of glass substrates attached to the polishing pad of the upper surface plate was counted. The test was repeated 5 times under the same conditions.

In Example 1, a 1 mm wide groove formed in a grid pattern with a pitch of 10 mm is used as an upper surface plate polishing pad, and a 1 mm wide groove formed in a lattice pattern at a pitch of 30 mm is used as a lower surface plate polishing pad. Thus, the contact area ratio between the polishing pad of the upper surface plate and the polishing pad of the lower surface plate was set to 1: 1.154. In Example 2, a 1 mm wide groove formed in a grid pattern with a pitch of 20 mm was used as a polishing pad for an upper surface plate, and a 1 mm wide groove formed in a grid pattern at a pitch of 30 mm was used as a polishing pad for a lower surface plate. Thus, the contact area ratio between the polishing pad of the upper surface plate and the polishing pad of the lower surface plate was set to be 1: 1.035. On the other hand, in the comparative example, as the polishing pads for the upper surface plate and the lower surface plate, a common 1 mm wide groove formed in a lattice shape at a pitch of 30 mm is used, and the contact area with the glass substrate is the same as that of the upper surface plate. The same setting was applied to the polishing pad and the polishing pad of the lower surface plate. A polyurethane suede pad was used as the polishing pad. Table 1 shows the results of the disk drop test.

According to this comparative experiment, in the comparative example, it can be seen that more than half of the glass substrate is stuck to the polishing pad of the upper surface plate from the total of five tests. On the other hand, in Example 1 of the present invention, the glass substrate did not stick to the polishing pad of the upper surface plate through five tests. Also in Example 2, only two sheets stuck to the polishing pad of the upper surface plate through five tests.

From the above results, in the present invention, the polishing process was performed using a thin and light glass substrate for a magnetic disk, and a soft and easily adsorbing polishing pad in order to provide high-precision flatness. Even if it is a case, when raising the upper surface plate of the double-sided polishing apparatus after the polishing treatment, it is possible to suppress the glass substrate from sticking to the polishing pad of the upper surface plate, thereby dropping and damaging the glass substrate. Can be prevented.

The present invention is not limited to the embodiment described above, and can be implemented in various forms without departing from the scope of the invention.

This application is based on a Japanese application (Japanese Patent Application No. 2008-165853) filed on June 25, 2008, the contents of which are incorporated herein by reference.

DESCRIPTION OF SYMBOLS 10 Glass substrate 20 Double-side polish apparatus 22 Upper surface plate 23

Lower surface plate

24, 25

Polishing pad

24a, 25a Groove

Claims

In a double-side polishing apparatus for a magnetic disk glass substrate that simultaneously polishes both surfaces of a glass substrate for a magnetic disk disposed between an upper surface plate and a lower surface plate each having a polishing pad,
A double-side polishing apparatus for a glass substrate for a magnetic disk, wherein a contact area of the polishing pad of the upper surface plate with the glass substrate is smaller than a contact area of the polishing pad of the lower surface plate with the glass substrate.
2. The double-side polishing of a glass substrate for a magnetic disk according to claim 1, wherein grooves of the same width are formed in a lattice pattern at different pitches on the polishing pad of the upper surface plate and the polishing pad of the lower surface plate. apparatus.
In the method for polishing a glass substrate for a magnetic disk, which simultaneously polishes both surfaces of the glass substrate for a magnetic disk disposed between an upper surface plate and a lower surface plate each having a polishing pad,
A method for polishing a glass substrate for a magnetic disk, wherein polishing is performed using a polishing pad having a smaller contact area with the glass substrate than the polishing pad of the lower surface plate as the polishing pad of the upper surface plate.
A mounting step of attaching a magnetic disk glass substrate between an upper surface plate and a lower surface plate each having a polishing pad;
A polishing step of simultaneously polishing both surfaces of the magnetic disk glass substrate;
An extraction step of taking out the magnetic disk glass substrate disposed between the upper surface plate and the lower surface plate;
In a method for manufacturing a glass substrate for a magnetic disk comprising:
A method of manufacturing a glass substrate for a magnetic disk, wherein a contact area of the polishing pad of the upper surface plate with the glass substrate is smaller than a contact area of the polishing pad of the lower surface plate with the glass substrate.