JP2000076645A - Precision substrate for optical and magnetic medium and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a precision substrate for optical and magnetic medium consisting of synthetic quartz glass and having <=10 Å surface roughness (Ra), <=0.03 μm/500μm× 500 μm surface waviness by PV value, <=1 μm/100 mmϕ parallel degree, and <=2 μm/100 mmϕ flatness degree. SOLUTION: This method includes a process to polish a substrate material consisting of synthetic quartz glass by using a double-face plane polishing machine equipped with an elastic deforming means. The elastic deforming means is interposed between an upper surface plate and a doughnut plate suspended from the upper surface plate and elastically deforming the substrate material by gravity. Thus, the objective precision substrate consisting of synthetic quartz glass having <=10 Å surface roughness (Ra), <=0.03 μm/500 μm ×500μm surface waviness by PV value, <=1 μm/100 mmϕparallel degree and <=2 μm/100 mmϕ flatness degree is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precision substrate for optical and magnetic media, such as a substrate for an elastic wave element and a substrate for magneto-optical recording, utilizing an elastic wave generated by an ultrasonic magnetic material, and a method of manufacturing the same.

[0002]

2. Description of the Related Art As the degree of integration of optical and magnetic media increases, it is clear that the inherent physical properties and processing accuracy of substrate materials for optical and magnetic media will determine the success or failure of the degree of integration. It is becoming.

[0003] For example, in the case of magnetic disks, aluminum alloys,
Various substrate materials such as chemically strengthened glass and crystallized glass have been developed.

[0004] This change in material is aimed at improving the recording density, and the use conditions are inevitably changing. Accordingly, the required characteristics of the substrate have changed. In other words, the material properties and the processing method corresponding to the new specification of the precision substrate for optical and magnetic media are not an extension of the conventional technology, but the characteristics of the substrate material and the processing method that matches the material must be newly created. It has become a challenge.

[0005]

From the above situation, various conditions required for a substrate for optical and magnetic media to be developed in the future are listed as follows.

(1) In the case of a recording medium substrate that requires rotation, it is necessary to reduce the flatness (flatness) of the substrate to 2 μm / 100 mmφ or less from the viewpoint of tribology.

(2) In the field of perpendicular magnetic recording, it is necessary to reduce the thickness of the magnetic film to 0.02 to 0.05 μm in the future. The undercoat of this magnetic film is 0.1 ~
0.5 μm, and the substrate heating temperature during magnetic film deposition was 50 μm.
0 ° C. or higher is required. Substrate flatness (flatness)
In consideration of the fact that the thickness of the substrate is required to be at least 2 to 3 times the film thickness and the warpage of the substrate caused by heating at the above temperature, the flatness of the substrate is 2 μm / 100 mmφ or less, and the surface waviness is 0. 03μm / 500μm × 500μ
m or less. In addition, the surface roughness (Ra) of the substrate must be reduced to 10 ° or less as the flying height of the recording / reproducing head decreases.

(3) As one type of a substrate for a magnetic medium, a substrate for a surface acoustic wave element utilizing an elastic wave of an ultrasonic magnetic material (eg, permalloy) is disclosed in, for example, Japanese Patent Application Laid-Open No. 5-111515.
And an ultrasonic delay medium (substrate) disclosed in JP-A-6-350368 and the like. In these elastic wave element substrates and magneto-optical recording substrates, the parallelism of the substrate is a decisive factor that governs the direction of propagation for accurate propagation of ultrasonic waves and light in the thickness direction of the substrate. is there. Also, for the purpose of minimizing the acoustic wave device and making the device compact, the ultrasonic wave is accurately reflected between the front surface and the back surface of the extremely thin acoustic wave device substrate having a thickness of about 0.5 to 1.0 mm. To achieve this, the flatness between the front surface and the back surface becomes extremely important in addition to the parallelism of the substrate. Therefore, a substrate for an elastic wave element such as an ultrasonic delay medium to be developed in the future will require a parallelism of 1 μm / 100 mmφ or less and a flatness of 2 μm / 100 mmφ or less. Such substrate conditions are the same whether rotation is required or not.

(4) In order to exhibit the characteristics of a perpendicular magnetic film for improving the recording density, it is required to reach the limit of the intrinsic physical properties of the magnetic material, and the chemical component of the substrate material does not include a component deteriorating the characteristics of the magnetic film. In addition, it is desired that a deteriorating component is not contained as an impurity.

(5) In addition to the chemical components of the substrate material, homogeneity of the components is required, and an amorphous material free from uneven distribution and grain boundaries has been desired.

(6) It is desired that a substrate material requiring rotation has mechanical properties that can withstand high-speed rotation.

(7) It is desired that the substrate material has chemical durability that can withstand cleaning, etching, and the like as the density increases.

When examining a substrate material that can satisfy the above conditions (1) to (7), the synthetic quartz glass is composed of a single component of SiO ₂ , and substantially contains a composition component or an impurity that deteriorates the magnetic film characteristics. Amorphous material that is homogeneous, free from uneven distribution and without grain boundaries, etc., and has excellent chemical durability. Promising to satisfy the above conditions (4), (5), (7) Material. However, looking at (1) to (3) among other conditions, the surface roughness (Ra) of the substrate can be reduced to 10 ° or less by the current polishing technology, but the other necessary condition, PV Surface undulation 0.03 μm / 500 μm × 500 μm or less, parallelism 1 μm / 100 mmφ or less, flatness 2 μm /
It is impossible to obtain a synthetic quartz glass substrate having an ultra-precision surface characteristic of 100 mmφ or less by a conventional polishing technique, and at present these conditions (1) to
(3) cannot be satisfied. Further, the synthetic quartz glass has a rigidity ratio (rigidity / specific gravity) of 32.7. At such a rigidity ratio, when the substrate is rotated at a high speed exceeding 6,000 rpm, the substrate vibrates and cannot be used. ) Can not be satisfied.

The present invention has been made in view of the above circumstances, and has the above-mentioned conditions (1) to (3) and (6).
It is an object of the present invention to provide a novel synthetic quartz glass substrate for optical and magnetic media which can satisfy the above, and a method for producing the same.

[0015]

The present inventor has developed a novel manufacturing method including a polishing step using a polishing machine in which a new structure is added to a double-sided plane polishing machine conventionally used for polishing such a substrate. By using this, a new synthetic quartz glass substrate having surface waviness, parallelism and flatness, which was impossible with conventional polishing techniques, was successfully obtained.

That is, the precision substrate for optical and magnetic media made of synthetic quartz glass according to the present invention has a surface roughness (R).
a) 10 ° or less, surface waviness due to PV value 0.03 μm
/ 500μm × 500μm or less, parallelism 1μm / 100
mmφ or less and a flatness of 2 μm / 100 mmφ or less.

Further, the method of manufacturing a precision substrate for optical and magnetic media made of synthetic quartz glass according to the present invention is conventionally caused between the upper platen and the upper platen hanging donut plate due to bending of the upper platen due to its own weight. Elastic deformation is the fulcrum P of the tightening bolt 10
(FIG. 4) Double-sided surface polishing with elastic deformation means interposed between the upper platen and the donut plate and the upper platen, the elastic deformation means for expanding the area from the fulcrum P to the inner peripheral side of the upper platen. By polishing a substrate machine made of synthetic quartz glass with a machine, the surface roughness (Ra) is 10 ° or less, the surface undulation by PV value is 0.03 μm / 500 μm × 500 μm or less, the parallelism is 1 μm / 100 mmφ or less, and the flatness is 2 μm / 100m
This is a method for manufacturing a precision substrate for optical and magnetic media made of synthetic quartz glass capable of obtaining characteristics of mφ or less.

[0018]

The substrate according to the present invention has a surface undulation of 0.03 μm / 500 μm × 500 μm or less, a parallelism of 1 μm / 100 mmφ or less, and a flatness of 2 μm / 10 or less.
When the thickness is 0 mmφ or less, when used as a substrate for a recording medium that requires rotation, tribology is small, and excellent performance can be exhibited as a substrate for perpendicular magnetic recording. When used as a substrate for an elastic wave element, it can be used as an extremely thin substrate having a thickness of about 0.5 to 1.0 mm, which can contribute to miniaturization of the apparatus. Further, since the substrate according to the present invention has the above-mentioned surface characteristics, it can cope with high-speed rotation without generating vibration even when rotated at 7,000 rpm, despite its low rigidity ratio. Therefore,
According to the present invention, there is provided an excellent synthetic quartz optical and magnetic medium substrate that satisfies all of the conditions required for a next-generation optical and magnetic medium substrate.

Further, according to the method of manufacturing a substrate according to the present invention, it is possible to manufacture a precision substrate for optical and magnetic media made of synthetic quartz glass having the above-mentioned surface characteristics, which has been impossible to realize conventionally. .

[0020]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

Since the synthetic quartz glass substrate of the present invention has been realized for the first time by a manufacturing method including a polishing step using a novel double-sided plane polishing machine, this novel double-sided plane polishing machine will be described. First, for convenience of understanding, a conventional double-sided surface polishing machine will be described with reference to FIGS.

FIG. 5 shows a main part of a conventional double-sided surface polishing machine.
7 and a partial perspective view of FIG. 7, an upper surface plate 2, a lower surface plate 3, an upper surface plate drive unit 4, a sun gear 5 rotatably fitted to the upper surface plate drive unit 4, and a lower surface plate 3. And a carrier 8 having holes 8a (FIG. 7) formed as gears meshing with the internal gear 6, the sun gear 5 and the internal gear 6, respectively, provided on the outer peripheral side of the gear 8 and accommodating the workpiece 7. Usually, four to six carriers 8 are arranged, but in FIG. 7, only one carrier is shown for simplification. The workpiece 7 is accommodated in the hole 8a of the carrier 8 and is thicker than the carrier 8, so that the workpiece 7 is arranged to protrude upward from the upper surface of the carrier 8. During the polishing operation, the workpiece 7
Are in close contact with the lower surface of the upper surface plate 2 and the upper surface of the lower surface plate 3. A polishing cloth is attached to the lower surface of the upper stool 2 and the upper surface of the lower stool 3, respectively.

FIG. 6 shows an upper surface plate 2 of the conventional double-side polishing machine 1.
FIG. 3 is a plan view showing only a part of the upper platen hanging donut board 9. The upper stool 2 has a center hole 2a slightly larger in diameter than the upper stool drive unit 4 at the center, and is fitted to the drive unit 4. A plurality (four in the illustrated example) of claws 2b are provided at predetermined intervals in the circumferential direction of the center hole 2a and extend in the height direction.
On the other hand, as shown in FIG.
b is formed, and the claw 2 of the upper surface plate 2 is formed.
The upper platen 2 rotates integrally with the upper platen drive unit 4 by the rotation of the upper platen drive unit 4 by fitting the b into the groove 4 a.

On the upper surface of the upper surface plate 2, an upper surface plate hanging donut plate 9 made of a metal donut-shaped disk having a smaller diameter than the upper surface plate 2 (for example, a diameter of about 60% of the upper surface plate) is in close contact. They are arranged concentrically and fastened to the upper surface plate 2 by bolts 10 at appropriate intervals in the circumferential direction (90 ° intervals in the illustrated example). The upper surface plate hanging donut board 9 has a plurality (4 in the illustrated example).
The lower end of the upper platen hanging column 11 is fixed,
The upper ends of the upper platen suspension columns 11 are fixed to the lower surface of a powder ring 12 for supplying a polishing liquid to the workpiece. A plurality of through-holes 2c are formed in the outer peripheral portion of the upper platen 2. These through-holes 2c are connected to the inside of the powder ring by a hose 13, and the polishing liquid inside the powder ring 12 passes through the hose 13, the through-hole. Workpiece 7 via 2c
Supplied to

A piston rod 14 of an air cylinder 16 disposed above the powder ring 12 is fixed, and the upper platen 2 is raised and lowered by operating the air cylinder 16. The air cylinder 16 suspends the upper stool 2 via the upper stool donut board 9 so that the workpiece 7 can be polished at a predetermined polishing pressure during the polishing operation.
The total load can be adjusted.

The upper platen driving unit 4, the lower platen 3, the sun gear 5,
The four internal gears 6 are rotationally driven by respective drive mechanisms, the upper stool 2 is driven in the opposite direction to the lower stool 3, the internal gear 6 is driven in the opposite direction to the upper stool 2, and the carrier 8 Is configured to rotate clockwise or counterclockwise while moving in the same direction of the lower platen 3 depending on the rotation ratio of the sun gear 5 and the internal gear 6.

Next, a new double-sided plane polishing machine used in the manufacturing method of the present invention will be described with reference to FIGS.

FIG. 1 is a sectional view similar to FIG. 5 showing a main part of a polishing machine used in the manufacturing method of the present invention, FIG. 2 is a plan view of an upper platen and an upper platen hanging donut plate, and FIG. FIG. 3 is an enlarged sectional view showing an upper surface plate and a part of the upper surface plate hanging donut plate, and FIG.
FIG. 6 is an enlarged cross-sectional view showing a part of the upper platen and the upper platen hanging donut plate of the conventional polishing machine shown in FIG. 5 for comparison with FIG.

In the polishing machine shown in FIGS. 1, 2 and 4,
The same components as those of the conventional polishing machine of FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted.

In this polishing machine, an elastic donut disk 15 having a predetermined thickness made of an elastic material such as rubber such as neoprene rubber or a synthetic resin is used as an elastic deformation means. The elastic material donut board 15 is an upper surface plate hanging donut board 9
, And is arranged concentrically with the donut board 9 between the donut board 9 and the upper surface plate 2. As the elastic material, a material having an elasticity corresponding to the elasticity caused by the rigidity of the upper stool 2 and the elasticity generated by the polishing pressure of various polishing cloths is selected.

A bolt insertion hole 9a (FIG. 4) is formed in the thickness direction at an appropriate interval (in the illustrated example, at an interval of 90 degrees) in the circumferential direction of the upper surface plate hanging donut board 9. 15 also has a bolt insertion hole 1 communicating with the bolt insertion hole 9a.
5a is drilled. A screw hole 2d is formed at a position on the upper surface of the upper surface plate 2 corresponding to the bolt insertion holes 9a and 15a. A bolt 20 is inserted into each of the insertion holes 9a and 15a, and a tip portion 20a of the bolt 20 is screwed into a screw hole 2d of the upper surface plate 2. A well-known elastic washer 21 made of a leaf spring is mounted between the bolt head 20b and the upper surface of the upper platen hanging donut plate 9. When the bolt 20 is tightened, the upper platen hanging donut plate 9 becomes elastic. It is fastened to the upper platen 2 via a material donut plate 15. The elastic washer 21 has a function of adjusting the compression degree of the elastic material donut board 15 by adjusting the tightening force of the bolt 20, and has a function of adjusting the compression degree of the elastic material donut board 15, and the mechanical vibration of the upper platen hanging donut board 9 due to the rotational motion of the bolt 20. Has a function to prevent loosening. The elastic washer is not limited to the one made of the above-described leaf spring, and another elastic washer such as a rubber ring may be used.

Next, the operation of the novel polishing machine used in the manufacturing method of the present invention will be described in comparison with the operation of the conventional polishing machine shown in FIG.

The inventor of the present invention has found that, with the conventional polishing machine, the parallelism of not more than 1 μm / 100 mmφ is 2 μm / 100 m.
Flatness less than mφ and 0.03 μm / 500 μm × 5
As a result of studying the reason why the surface cannot be polished to a surface undulation of 00 μm or less, in the conventional polishing machine, the upper platen 2
Is bent downward (in the direction of arrow A) from the point P as a starting point due to its own weight, due to its own weight, the portion 2e of the upper platen 2 on the outer peripheral side of the point P fastened to the upper platen hanging donut plate 9 by the bolts 10. Outer side of panel (side closest to internal gear 6)
The polishing pressure applied to the workpiece 7 located at the point P gradually increases toward the outer peripheral side, and the uniformity of the polishing pressure between the inner peripheral side and the outer peripheral side at the point P is impaired. As a result, it has been found that the desired parallelism, flatness and surface undulation cannot be obtained. Based on this discovery, in the manufacturing method of the present invention, an elastic deformation means that is elastically deformed by the deflection of the upper surface plate 2 due to its own weight is interposed between the upper surface plate hanging donut plate 9 and the upper surface plate 2. And succeeded in solving the problem.

That is, in the polishing machine used in the manufacturing method of the present invention shown in FIG. 4, the upper platen 2 is different from the case of FIG. 3 in that the bolt 20 of the elastic donut disk 15 constituting the elastic deformation means is provided. The lower part of the upper surface plate 2 is compressed by the downward bending of the upper surface plate 2 so as to gradually increase the amount of compression toward the inner surface side as shown by a dotted line B in the figure. The starting point of the downward bending of the upper platen shifts from the point P toward the point Q on the inner peripheral side of the upper platen 2, and the upper platen 2 bends more smoothly than the case of FIG. The upper platen 2 can move upward by compressing the elastic donut disk 15 by the reaction force of the workpiece 7 on the outer peripheral side. As a result, the workpiece 7 located on the outer peripheral side of the upper platen 2 can be moved. Excessive polishing pressure applied to the substrate can be reduced over the entire circumference.

Further, by interposing the elastic material donut disk 15, it is possible to control the fine vertical position change of the air cylinder 16 and the rotation of each rotating part such as the upper and lower plates 2 and 3, the sun gear 5, and the internal gear 6. The accompanying vibration can be absorbed. In other words, it is possible to obtain the same effect as when a kind of dashpot mechanism is mechanically assumed in order to equalize the fluctuation of the pressure applied to the workpiece 7 during driving caused by these various causes. By interposing an elastic deformation means between the upper surface plate hanging donut wheel 9 and the upper surface plate 2, the work to be processed is 1 μm / 100 m as a combined effect.
It can be polished to a parallelism of mφ or less, a flatness of 2 μm / 100 mmφ or less, and a surface waviness of 0.03 μm / 500 μm × 500 μm or less.

The positions of the bolts 20 (hanging positions of the upper stool 2) are determined on the circumference of a circle concentric with the upper stool 2 having a radius of 55 to 57% of the radius of the upper stool 2 as a result of the experiment. At one time it was found that the best parallelism and flatness were obtained.

Next, one embodiment of polishing the synthetic quartz glass substrate of the present invention using the above-mentioned polishing machine will be described.

An upper surface plate (radius 435 mm) made of FCD45 of a 12B double-sided surface polishing machine was replaced with the above-mentioned elastic material donut disk (radius 2).
Example of the manufacturing method of the present invention using a double-sided plane polishing machine fastened to an upper surface plate (suspending donut machine (radius: 274 mm)) with four bolts via 74 mm, thickness 2 mm, made of neoprene rubber and elastic material A comparative example was prepared in which the same upper platen as above was directly attached to the same upper platen hanging donut plate with four bolts without using a donut plate. Of the circle having a radius of 55% of the average particle size of 0.4 to 0.1 as a secondary abrasive.
A 6 μm cerium oxide abrasive was used, colloidal silica was used as the final abrasive, and glycerin was also used as an anti-agglomeration agent. The polishing cloth used was Seagull MD-1800. As a workpiece (polishing target), a synthetic quartz glass substrate (substrate size 100 mmφ × 0.8 t) of SK-1300 manufactured by Sumikin Quartz Co., Ltd. manufactured by the VAD method was selected, and 18 wafers / batch, polishing time 60 minutes, Polishing number 180
Polishing was performed under the polishing conditions of one sheet. The parallelism, flatness, and surface waviness after the secondary polishing are as shown in the following table. The surface undulation is PV value μm / 500 μm × 5
The value is 00 μm.

[0039]

[Table 1] From the above results, according to the manufacturing method of the present invention, 1 μm / 1
It can be seen that a synthetic quartz glass substrate having a parallelism of 00 mmφ or less, a flatness of 2 μm / 100 mmφ or less, and a surface waviness of 0.03 μm / 500 μm × 500 μm or less can be obtained.

The synthetic quartz glass substrate after the secondary polishing was subjected to final polishing using colloidal silica as an abrasive and glycerin as an anti-agglomeration agent. Surface roughness of synthetic quartz glass substrate after final polishing (R
a) was 0.47 °.

This synthetic quartz glass substrate has a rigidity ratio of 3
Although it was 2.7, no vibration was generated even if it was rotated at 7,000 rpm, and it was found that high-speed rotation was adequately dealt with.

In the above embodiment, an example was described in which an elastic donut disk made of an elastic material such as rubber or synthetic resin was used as the elastic deformation means of the polishing machine. However, the elastic deformation means is not limited to this. Elastic deformation means may be used in which the upper ends of the plurality of coil springs are in contact with the lower surface of the upper platen, and the lower ends are in contact with the upper surface of the upper platen. Further, a large number of elastic washers may be used as the elastic deformation means, and an air cushion or a plurality of small air cylinders may be used. In other words, a material or a device which elastically deforms due to bending of a workpiece is particularly limited. There is no.

The precision substrate for optical and magnetic media made of synthetic quartz glass of the present invention is not only a substrate for an elastic wave element such as an ultrasonic delay medium, but also a substrate for a magneto-optical recording medium and a substrate for a magnetic information storage medium such as a hard disk. Can be used for

[0044]

As described above, the substrate according to the present invention has a surface waviness based on the PV value of 0.03 μm / 500 μm.
When the substrate is used as a substrate for a recording medium that requires rotation, it has a small tribology and has a parallelism of 1 μm / 100 mmφ or less and a flatness of 2 μm / 100 mmφ or less. Can also exhibit excellent performance. When used as a substrate for an elastic wave device, the thickness is 0.5 to 1.0 m.
m can be used as a very thin substrate, which can contribute to miniaturization of the device. further,
Since the substrate according to the present invention has the above-mentioned surface characteristics, the substrate has a rigidity ratio of 7,000 r.
Even when rotating at pm, vibration does not occur and high-speed rotation can be dealt with. Therefore, according to the present invention, there is provided an excellent synthetic quartz glass optical and magnetic medium substrate that satisfies all of the conditions required for a next-generation optical and magnetic medium substrate.

Further, according to the method of manufacturing a substrate according to the present invention, it is possible to manufacture a precision substrate for optical and magnetic media made of synthetic quartz having the above-mentioned surface characteristics, which has been impossible to realize conventionally.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one example of a polishing machine used in a manufacturing method of the present invention.

FIG. 2 is a plan view of the upper platen and the upper platen hanging donut plate in the embodiment of FIG. 1;

FIG. 3 is a partially enlarged sectional view corresponding to FIG. 4 of a conventional polishing machine.

FIG. 4 is a partially enlarged cross-sectional view of the polishing machine of FIG.

FIG. 5 is a sectional view of a main part of a conventional polishing machine.

FIG. 6 is a plan view of a middle upper platen and an upper platen hanging donut plate of the polishing machine of FIG. 5;

FIG. 7 is a perspective view showing a part of the polishing machine of FIG. 5;

Claims (2)

[Claims] 1. Surface roughness (Ra) 10 ° or less, surface waviness based on PV value 0.03 μm / 500 μm × 500 μm
Below, parallelism 1μm / 100mmφ or less, flatness 2μm
/ Precision substrate for optical and magnetic media made of synthetic quartz glass having a diameter of 100 mmφ or less. 2. A double-sided plane polishing machine in which an elastic deformation means for elastically deforming a substrate material made of synthetic quartz glass between an upper platen and a donut plate and an upper platen by the deflection of the upper platen by its own weight is provided. Surface roughness including polishing step (R
a) 10 ° or less, surface waviness due to PV value 0.03 μm
/ 500μm × 500μm or less, parallelism 1μm / 100
A method for producing a precision substrate for optical and magnetic media made of synthetic quartz glass having a diameter of not more than mmφ and a flatness of not more than 2 μm / 100 mmφ.