JPH05303735A - Magnetic disk and magnetic disk device - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to provide a magnetic disk and a magnetic recording device that have a small flying height and are compatible with high density recording. [Structure] A substrate for a magnetic disk having a small surface roughness (1 nmRmax or less) and a high flatness (1 μm or less) is used. In order to obtain such a substrate, double-side grinding is performed while the amount of elastic deformation of the substrate 3 is kept within a certain range by monitoring the amount of positional displacement of the upper surface plate 4 by the positional displacement sensor 13. As a result, the warp of the substrate 3 is removed and the flatness is increased. In addition, the upper and lower surface plate 4, which has a dynamic pressure generating surface
5, the substrate 3 is placed between the surface plates 4 and 5 and the surface of the substrate 3 is not in contact with the surface plates 4 and 5 due to the dynamic pressure effect of the polishing agent interposed between the surface plates 4 and 5 and the substrate 3. To reduce the surface roughness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk having a higher flatness and a smaller surface roughness, and a magnetic disk device using the magnetic disk.

[0002]

2. Description of the Related Art Magnetic disks are widely used as recording media because of their characteristics such as random access.

The magnetic disk is formed by forming a magnetic thin film on a substrate by using a thin film forming technique such as sputtering or plating. Usually, the magnetic disk is produced by the steps described below (see FIG. 13).

First, an aluminum alloy substrate is prepared.
For example, for a 5.25-inch magnetic disk (outer diameter 130 mm, inner diameter 40 mm, plate thickness 1.9 mm), a punched substrate is formed from an aluminum alloy plate material to the above dimensions, and this is pressure-molded in a high temperature furnace (step 131). The pressure forming process is performed in order to correct a processing strain when forming an aluminum alloy ingot into a plate material by rolling and a deformation due to punching from the plate material.

Next, double-sided simultaneous grinding in which an elastic grindstone is installed in order to improve the parallelism, flatness and surface roughness of the substrate itself (for example, double-sided processing machine manufactured by Speed Fam Co .; model SF
DL-1000 is used). In some cases, surface finishing is further performed by double-sided simultaneous polishing using a polishing cloth and a free abrasive grain abrasive. Then, after cleaning the substrate, the surface thereof is treated with Ni—P plating having a thickness of about 10 μm (step 132).

Then, the plated surface is subjected to double-sided grinding (step 133) and polishing processing using abrasive grains of various grain sizes (step 134).
And surface roughness 0.001-0.003 μm Ra, 0.005-0.020
Polished to a range of μmRmax. This surface roughness is determined by the material of the polishing cloth used for double-sided simultaneous polishing and the material and particle size of the free abrasive grains, and the current polishing method, that is, Ni-P plating of the polishing cloth and the workpiece. In the method of polishing by contacting with the substrate, the above surface roughness is the best surface precision at present.

Thereafter, the Ni-P plated substrate is further subjected to so-called texturing on the polished surface thereof to form fine grooves in the circumferential direction of the substrate by using finer abrasive grains (step). 135). This has a surface roughness of 0.004 to 0.0
By making it rough to 08 μmRa and forming minute irregularities on the substrate surface, CSS (Cont.
avoid head sticking in act-Start-Stop),
This is to improve the magnetic characteristics of the magnetic medium formed on this surface. The texture processing is described in JP-A-59
-82626 (NTT; Akio Tako), JP-A-62-203748 (NEC), U.S. Pat. S. Patent: 4,735,840.

Finally, a magnetic film and a protective film are formed on the substrate, and a lubricating film is further formed to produce a magnetic disk (step 136).

The above-mentioned grinding and polishing will be described with reference to FIG.

The substrate 3 is bonded to the jig 31. Then, the surface of the substrate 3 to be processed faces downward and is placed on the lower surface plate 5 (when polishing is to be performed, it is placed on the polishing cloth 5 disposed on the lower surface plate 5). ..).
Then, while a certain load is applied from the upper side, the lower surface plate 5 is rotated while supplying the working liquid to perform grinding and polishing. In this case, the load applied to the substrate does not take into consideration the warpage of the substrate.

[0011]

There is a great demand for miniaturization, high-density recording, and high speed in magnetic recording devices. In order to increase the recording capacity of the magnetic disk, the magnetic head 2
The flying height Hfly (see FIG. 15) must be extremely small. Recently, this flying height Hfly was 0.2 μm.
.About.0.1 .mu.m or less is required. Also, in order to shorten the writing and reading speed, that is, the access time, the number of rotations of the magnetic disk has been kept at 36%.
It is required to rotate at a high speed of 00 min-1 to 5000 min-1, or 7000 min-1 or more.

However, by the above-mentioned conventional grinding and polishing, it was not possible to obtain a magnetic disk which achieves the above-mentioned target.

It is an object of the present invention to provide a magnetic disk and a magnetic disk device which are compatible with high density recording.

It is an object of the present invention to provide a method of manufacturing a magnetic disk that can be used for high density recording and the like.

An object of the present invention is to provide a surface processing apparatus applicable to the manufacture of a magnetic disk which can be used for high density recording and the like.

[0016]

In order to obtain a magnetic disk satisfying these requirements, the inventors of the present invention have hitherto performed surface processing on the disk surface with an abrasive tape or a head to reduce the fine protrusions. We have conducted tests on the discs that we designed.

For example, the surface roughness after texturing is
The flying characteristics and CSS characteristics have been confirmed using a magnetic disk of 0.004 μmRa to 0.002 μmRa or less. However, the result was not always good. That is, on the surface of the disk, a sliding defect occurs due to polishing marks such as scratches when the substrate is double-sided, that is, minute projections on the groove shoulders of the scratch. Moreover, it became a factor of causing a head crash at a remarkable time. Furthermore, this phenomenon has a large runout of the magnetic disk,
It also became noticeable as the number of rotations of the disk increased.

Further, there are specifications of runout and acceleration which show the dynamic shape accuracy of the disk surface required for the magnetic head to stably fly. It has been found that, as shown in FIG. 16, the acceleration greatly increases in the disk having the same flatness according to the rotational speed of the disk.

From the above results, in order to maintain the reliability and further reduce the flying height of the head or read / write information in a state where the magnetic head is in contact with the disk surface, the surface of the policy surface is processed. The present inventor has clarified that it is necessary to reduce the roughness to reduce the minute protrusions Rp existing on the surface of the magnetic disk.

Further, it is not enough to improve the accuracy of the surface roughness as described above, and Ni of the magnetic disk related to the runout of the magnetic disk, which has not been paid much attention in the past, is used.
The inventor of the present application has made clear that it is important to increase the flatness of the -P plated substrate to reduce the runout, which is the runout of the magnetic disk.

In order to achieve the desired flying height of 0.08 μm or less for the time being, the surface roughness is 0.001 μmRa (desirably 0.0005 μmRa) or less, several nmRmax (desirably 5 nmRmax) or less, and the magnetic disk. It is necessary that the flatness, which is the surface shape of, is 1 μm or less.

As a result of the investigation by the inventor of the shape accuracy of the magnetic disk substrate actually obtained by a general processing process in the present situation, the outer diameter is 130 mm (usually called a 5.25 inch substrate). The Ni-P plated substrate had a flatness of 6.8 μm and a standard deviation of 2.2 μm. Further, in the case of a glass substrate having an outer diameter of 130 mm made of glass, the flatness was 5.1 μm and the standard deviation was 1.3 μm. Therefore, in the magnetic disk using these substrates, the head flying height is limited to about 0.08 to 0.1 μm, and it is stable at 0.0
It was very difficult to reduce the thickness to 8 μm or less. The runout and acceleration, which represent the dynamic surface accuracy of the magnetic disk, were 1 to 15 μm and 1 to 5 m / s ² at a disk rotation speed of 3600 min-1, respectively.

Further, as a result of studying why the above-mentioned conventional processing method could not obtain a magnetic disk satisfying such conditions, the inventor of the present application has the following problems in the conventional method. I found that.

That is, in grinding and polishing a flat surface of a thin disk such as a magnetic disk substrate, both surfaces are simultaneously ground and polished.
Need to be polished. This is because when processing one surface at a time, grinding and polishing are performed in a state where the work piece (substrate) 3 is bonded to the jig and the work piece is deformed, and it is difficult to obtain high flatness. That is why.

Further, even when both sides are simultaneously polished,
Polishing cloth 32 used for conventional mirror polishing
In the method in which the surface to be machined and the polisher are brought into contact with each other and polished, viscoelastic deformation of the polishing cloth 32 due to the pressure of the upper and lower surface plates causes sag in the peripheral part of the workpiece, resulting in highly accurate flatness. It was difficult to get.

The conventional grinding and polishing method is a method in which the Ni-P plated substrate is pressed by the upper and lower surface plates and relatively slid to be polished. Therefore, the thin plate Ni
The -P plated substrate is subjected to processing in a state of being elastically deformed following the surface of the surface plate. Therefore, when the upper and lower surface plates are taken out after the processing is finished, the same warp occurs as before the processing. As described above, the flatness of the Ni-P plated substrate hardly changed by the conventional double-sided simultaneous grinding and double-sided simultaneous polishing, and it was very difficult to obtain high flatness.

Further, since the abrasive grains held by the polishing cloth polish the surface to be processed, the influence of the coarse abrasive grains contained in the free abrasive grains and the presence of polishing debris of the workpiece at the processing interface Machining defects such as scratches are less likely to occur on the polished surface, making it difficult to significantly improve the surface roughness.

From the above, in order to reduce the flying height of the magnetic head and obtain a magnetic disk substrate having excellent sliding characteristics such as CSS characteristics, unlike the conventional processing process, surface roughness and flatness There is a need for a technology that can improve both the degree and the degree. Therefore, the inventor of the present application newly invented the following surface processing apparatus and processing method.

The contents of the present invention will be specifically described below.

Surface roughness 1 nmRa or less and flatness 1 μm
Provided is a magnetic disk including the following annular substrate and a magnetic film formed on the annular substrate.

In this case, the annular substrate has a surface roughness
It is more preferably 0.5 nmRa or less. Further, the flatness is more preferably 0.5 μm or less.

As another aspect of the present invention, in the method of manufacturing a disk-shaped member, the first step of grinding while keeping the elastic deformation amount of the disk-shaped member within a certain range, and the disk-shaped member described above. And a second step of simultaneously non-contact polishing both surfaces of the disc-shaped member.

The annular substrate of the magnetic disk is preferably a glass substrate manufactured by the method of manufacturing the disc-shaped member.

Further, there is provided a magnetic disk substrate including an aluminum substrate processed by the manufacturing method and a Ni-P plating layer formed on the aluminum substrate.

Further, the magnetic disk, a magnetic head for writing and / or reading a signal on the magnetic disk, a driving means for driving the magnetic disk and the magnetic head, and the magnetic head and the driving means are controlled. And a control means for controlling the magnetic disk drive. In this case, the flying height of the magnetic head with respect to the magnetic disk during operation is preferably 0.06 μm or less.

According to another aspect of the present invention, a rotatably configured first surface plate and an object to be processed are disposed between the first surface plate and the first surface plate. No. 2 surface plate, changing means for changing the position of the first surface plate according to a set value, rotation driving means for rotating the first surface plate and the second surface plate, and the first surface plate. A contact detection unit that detects contact between the plate and the object to be processed, and the contact detection unit changes the position of the first surface plate by the changing unit while the first surface plate and the object to be processed are being changed. When the contact is detected, the control means using the position of the first surface plate at that time as a reference point for changing the position by the changing means,
There is provided a surface processing apparatus having:

The control means stops the change of the position of the first surface plate by the change means when the contact is detected during the change of the position of the first surface plate by the changing means. It may be one.

According to another aspect of the present invention, a rotatably configured first surface plate and an object to be machined are arranged between the first surface plate and the first surface plate rotatably configured. No. 2 surface plate, changing means for changing the position of the first surface plate according to a set value, rotation driving means for rotating the first surface plate and the second surface plate, and the first surface plate. The positional deviation detecting means for detecting the positional deviation amount between the actual position of the board and the position corresponding to the set value, and the positional deviation detection during the change of the position of the first surface plate by the changing means. When the means detects the occurrence of displacement, the control means uses the position of the first surface plate at that time as a reference point for changing the position by the changing means. A surface processing device is provided.

The control means changes the position of the first platen by the changing means when detecting the occurrence of the positional deviation while changing the position of the first platen by the changing means. May be stopped.

The control means temporarily stops changing the position of the first surface plate by the changing means when detecting the occurrence of the positional deviation while changing the position of the first surface plate by the changing means. After that, the position of the first surface plate is changed by a preset amount, and at this time, until the position displacement amount detected by the position displacement detecting means becomes 0, the first rotation surface is moved by the rotation driving means. The process of rotating the surface plate and the second surface plate to grind the object to be machined is repeated until the preset amount of positional change and the positional displacement amount detected by the positional displacement detection means become equal. Preferably.

The control means compares the amount of positional change by the changing means with the amount of positional deviation detected by the positional deviation detecting means, and if both are the same, it means that the workpiece is not elastically deformed. It is preferable to judge.

The first surface plate and / or the second surface plate may include a grindstone on a surface facing the object to be processed. Alternatively, the first surface plate and the second surface plate may have a dynamic pressure generating surface on the surface facing the workpiece.

Further, at least a polishing liquid supply means for supplying a polishing liquid is provided between the object to be processed and the first surface plate and the second surface plate, and the control means is the changing means. When the occurrence of the positional deviation is detected during the change of the position of the first surface plate by the, the change of the position of the first surface plate by the changing means is temporarily stopped, and then the position of the first surface plate is changed. The position of the first surface plate is changed by the changing means by a preset amount in the direction in which the distance from the second surface plate increases, and the first surface plate is supplied while supplying the polishing liquid. Alternatively, the second surface plate may be rotated.

[0044]

After the first step of grinding while keeping the elastic deformation amount of the disk-shaped member within a certain range, the second step of simultaneously non-contact polishing both surfaces of the disk-shaped member is performed.

First, the first step will be described.

An object to be processed, for example, a substrate is placed on the second surface plate. Then, the changing means lowers the first surface plate. At this time, the control means monitors the output of the positional deviation detection means. Then, when the occurrence of the positional deviation is detected, it is determined that the first surface plate and the workpiece are in contact with each other, and the first
Stop the descent of the surface plate of. Note that, regarding the detection of the contact, the position shift detecting means functions as the contact detecting means.

After that, the first platen is lowered from the stop position by a preset amount (for example, 5 μm). Then, the object to be processed is elastically deformed by the force received from the first surface plate. On the other hand, the reaction force received from the object to be processed increases the displacement of the first surface plate.

In this state, the object to be processed is ground by rotating the first surface plate or the like. Then, the portion of the object to be processed that is in contact with the first surface plate and the second surface plate is ground, so that the amount of the positional deviation is gradually reduced.

The control means monitors the amount of the positional deviation even during the grinding, and when the value becomes 0, the grinding is temporarily stopped.

Then, again, the first platen is lowered by the preset amount (for example, 5 μm). Then, the amount of positional deviation similarly generated is compared with the amount of fall (in this case, 5 μm). As a result, if they do not match, it is determined that elastic deformation has occurred, and grinding is performed in the same manner. Then, the same processing is repeated until the two match. That is, it is determined whether or not elastic deformation occurs in the workpiece depending on whether the two match, and until elastic deformation does not occur (Note: if there is no warp or other distortion in the workpiece. , Elastic deformation does not easily occur), that is, grinding is continued until the flatness increases.

When the two match, the final grinding is performed, and when the amount of positional deviation at that time becomes 0, the grinding is finished. However, it goes without saying that the grinding may be continued if the desired amount of grinding has not been carried out.

By performing such grinding, since the grinding is performed in a state where the elastic deformation amount is small, that is, the substrate remains warped, distortion such as warpage can be effectively removed.

The second step will be described.

By the same method as in the above-mentioned first step, the descent of the first surface plate is stopped when the object to be processed comes into contact with the first surface plate. Then, the first amount by the preset amount
Raise the surface plate of. Then, in this state, the processing liquid, the first surface plate, and the second surface are processed by the polishing liquid supply means.
The first surface plate and the second surface plate are rotated while the polishing liquid is supplied between the first surface plate and the second surface plate.

Then, the object to be machined is lifted by the dynamic pressure generated by the dynamic pressure generating surfaces of the first surface plate and the second surface plate. That is, a layer of a polishing liquid is formed between the object to be processed and both surface plates, and the polishing is performed in a state of not being in contact with either of the surface plates.

According to this polishing method, polishing can be carried out without deteriorating the flatness obtained in the first step, and high flatness accuracy of flatness of 1 μm or less can be achieved. Furthermore, if a fine grindstone with an abrasive grain size of 0.1 μm or less is used, the surface roughness is 1 nmRa or less and several nmR or less.
It is possible to obtain a processed surface of max or less. In addition, since the shape accuracy of both sides is high and the variation in plate thickness is extremely small,
The runout and acceleration measured by rotating the substrate can also be greatly improved.

[0057]

An embodiment of the present invention will be described with reference to the drawings.

The purpose of this embodiment is to perform double-side grinding and double-side polishing by applying Ni-P plating to a thickness of about 10 μm on an aluminum disc having an outer diameter of 130 mm, an inner diameter of 40 mm and a plate thickness of 1.9 mm, which is a magnetic disk substrate. It is a surface processing device.

The apparatus described below accurately detects that the substrate and the upper surface plate are in contact with each other when the upper surface plate is descended, and the position of the upper surface plate is used as a reference for the upper surface plate. The feature is that the position can be adjusted extremely accurately. Another characteristic of the apparatus is that both surfaces can be simultaneously subjected to contact polishing (float polishing).

This apparatus has an upper surface plate 4 as shown in FIG.
A lower surface plate 5, a carrier 8, a rotation driving means 11,
It is mainly composed of a position shift sensor 13, a vertical drive mechanism 14, and a machining liquid supply device 9.

The upper surface plate 4 and the lower surface plate 5 can be replaced with optimal ones according to the work content. Then, at the time of grinding, the one whose finished surface has a flatness of 1 μm is used. On the other hand, at the time of polishing, a surface having a pattern for generating dynamic pressure is used.
The details of the pattern will be described later.

As shown in FIG. 2, the upper surface plate 4 of this embodiment has its rotation shafts, that is, the spindles 17 and 18,
It is supported by the thrust bearing 20. The thrust bearing 20 uses air sent from the compressor 19 as a lubricant, and has a relatively low bearing rigidity. Therefore, the upper surface plate 4 has a small amount of "play" corresponding to the thickness of the air phase. On the other hand, the support mechanism of the lower surface plate 5 has a sufficiently high vertical bearing rigidity, and the vertical "play" is extremely small. Therefore, when the upper surface plate 4 is lowered by the vertical drive mechanism 14, the force received from the substrate 3 is
The configuration is such that only the vertical position of the upper surface plate 4 can be affected. In other words, when no force is applied from the substrate, that is, when the substrate and the upper platen 4 are not in contact with each other, the thrust collar 201 and the thrust receiver 20
2 has a certain constant value, but when a force is applied from the substrate, that is, when the substrate 3 and the upper surface plate 4 are in contact with each other to generate a reaction force due to elastic deformation of the substrate, The distance between the thrust color 201 and the thrust receiver 202 is changed.

Further, the thrust bearing 20 of the upper surface plate 4
Is a static pressure air bearing, and the air has a configuration in which the upper side and the lower side of the bearing can be adjusted separately. Therefore, by adjusting the air pressure, the support rigidity can be made different between the upper part and the lower part of the bearing. In this embodiment, the upper bearing rigidity is 10 kgf / μm and the lower bearing rigidity is 10 kgf / μm. However, the specific value is not limited to this.

A hole portion 15 through which the working liquid passes is provided at the center of the spindle 17 which is the rotating shaft of the upper surface plate 4. Further, the upper surface plate 4 is provided with holes 16 for passing the processing liquid, and the processing liquid is supplied between the upper surface plate 4 and the lower surface plate 5 through these holes.

As shown in FIG. 3, a center gear 54 is provided at the center of the lower turn table 5. Also lower plate 5
An internal gear 52 is provided on the outer peripheral portion of the device so as to face inward. These are for rotating and revolving the carrier 8 on the lower surface plate 5.

The upper surface plate 4 and the lower surface plate 5 are supported by static pressure air bearings adjusted to air pressures P1 to P6 for both the thrust shaft and the radial shaft.

The displacement sensor 13 is provided below the thrust bearing 20 of the upper surface plate 4 as shown in FIG.
The thrust color 201 of the upper surface plate 4 and the thrust receiver 20
It has a function of detecting a change in the interval between the two. In addition,
The detection result is output to a control device (not shown in FIGS. 1 and 2) described later. In this embodiment, the displacement sensor 13 is a capacitance type displacement meter, but the present invention is not limited to this.

The vertical drive mechanism 14 includes a thrust bearing 20.
At the same time, the upper surface plate 4 can be moved up and down at a pitch of 1 μm or less. The vertical drive mechanism 14
Are controlled by a control device (not shown).

The carrier 8 is a substantially disk-shaped jig for holding the substrate 3 between the upper surface plate 4 and the lower surface plate 5, and has a hole portion 82 for holding the substrate. ..
A stopper for fixing the substrate is provided on the inner surface of the hole 82. As will be described later, the stopper is used only during grinding and is not used during double-side non-contact polishing. A gear 84 is provided on the outer periphery of the carrier 8. The carrier 8 has the gear 84
However, the size is such that it meshes with the internal gear 52 and the center gear 54 of the lower surface plate 5 at the same time. As a result, the carrier 8 is configured to rotate and revolve like a planetary gear during grinding or polishing.

However, the structure of the carrier 8 is not limited to this. For example, it may have a disk surface having substantially the same size as the lower surface plate 5. In this case, the carrier 8 performs only the lower point and the same axis as the lower surface plate 5.

The rotation driving means 11 is for rotating the upper surface plate 4, the lower surface plate 5, and the carrier 8.

The machining liquid supply device 9 has a function of supplying a temperature-controlled machining liquid.

As described above, the vertical drive mechanism 1
4, the operation of each part such as the rotation driving means 11, the machining liquid supply device 9 and the like is controlled by a control device (not shown). The details of the control will be given together with the operation description.

Grinding by the apparatus, that is, the processing method in the "first step" in the claims will be described below with reference to FIGS. 4 and 5.

In this step, as the upper surface plate 4 and the lower surface plate 5, a surface plate made of ceramic or cast iron, or PV is used.
Elastic grindstone such as A (polyvinyl alcohol) grindstone
It is performed using a surface plate held on a US substrate. In this example, a polyvinyl alcohol elastic grindstone C # 1500 was used. A water-soluble grinding liquid (for example, Fujimi Cut manufactured by Fujimi) was used as the working liquid.

The Ni-P plated substrate 3 is set on the carrier 8 and placed on the lower surface plate 5 (step 40,
FIG. 5A). In this example, five substrates 3 are mounted.

Then, the upper surface plate 4 is lowered from this state (step 41). In this case, 200 μm of substrate 3
It descends from the upper position at a low speed of 0.1 mm / min. During this time,
The control device monitors whether or not the upper surface plate 4 and the substrate 3 are in contact with each other by monitoring the output from the displacement sensor 13, that is, the distance between the thrust color 201 and the thrust receiver 202.

When it is detected that the upper surface plate 4 is in contact with any of the substrates 3, the lowering of the upper surface plate 4 is temporarily stopped (step 42, FIG. 5B). Then, with the stop position as the origin, the upper surface plate 4 is further lowered by a preset set fall amount A (here, A = 5 μm) (step 43, FIG. 5C). It should be noted that the set drop amount A can be changed according to the material, the thickness, the size, etc. within a range in which the elastic deformation amount of the substrate 3 does not become too large. As described in the description of the prior art, the warp of the substrate 3 cannot be sufficiently removed.

Then, the substrate 3 is elastically deformed by the amounts shown in the following formulas 1 and 3.

The substrate is warped like an umbrella, for example, the inner circumference is in contact with the upper surface plate and the outer circumference is in contact with the lower surface plate, and the weight is concentrated on both of these circumferences. In

[0081]

[Equation 1]

However,

[0083]

[Equation 2]

Further, in a state where the ring surface of the ring is warped and a concentrated load is applied to the ring surface, for example, both the inner peripheral portion and the outer peripheral portion of the ring contact the lower platen and the ring surface Is in contact with the upper surface plate,

[0085]

[Equation 3]

However,

[0087]

[Equation 4]

In the above formulas ₁ to 4, δ ₁ : vertical deformation amount δ ₂ : vertical deformation amount a: disc outer radius b: disc inner radius I: cross-section secondary moment L: circle Width of ring part of ring P ₁ : load on circumferential part P ₂ : load on ring part t: plate thickness ν: Poisson's ratio E: longitudinal elastic coefficient Then, the reaction force of a magnitude corresponding to the elastic deformation amount Acts on the upper surface plate 4 and the lower surface plate 5.

As a result, the upper stool 4 is pushed upward, and the upper stool 4 does not actually fall by the set drop amount A. That is, a "deviation" occurs between the position where the upper surface plate 4 should be present and the position where the upper surface plate 4 is actually present. And, the amount corresponding to the "deviation" is the thrust color 20
The distance between 1 and the thrust receiver 202 changes. In addition, after that, the position shift sensor 13 detects,
The amount of change in the distance between the thrust color 201 and the thrust receiver 202 is referred to as “variation amount B”.

Therefore, the control device sets the set drop amount A,
The magnitude relationship with the fluctuation amount B is determined (step 44). In this case, if A> B, it means that the substrate 3 is elastically deformed. In this case, the process proceeds to step 45. On the contrary, when A> B is not satisfied, in other words, when A = B is satisfied (assuming that the upper surface plate 4 does not lower due to its own weight, it is impossible that A <B). No deformation has occurred. In this case, the process proceeds to step 47.

At step 45, the working liquid is supplied and the upper surface plate 4, the lower surface plate 5 and the carrier 8 are rotated to start grinding. In this example, the upper surface plate 4
The rotating speed of the lower platen 5 was set to 10 rpm (counterclockwise) and the rotating speed of the lower platen 5 was set to 31 rpm (clockwise). Further, the rotation number and the revolution number of the carrier 8 are set to 12 rpm and 7 rpm, respectively.

During this grinding, it is continuously monitored whether or not the fluctuation amount B becomes 0 (step 46). Board 3
Since the portion in contact with the upper surface plate 4 and the lower surface plate 5 is ground, the reaction force that pushes up the upper surface plate 4 decreases as the processing progresses. As a result, the position of the upper surface plate 4 is lowered from the position that actually existed at the time of starting the grinding, and the above “deviation” becomes smaller.

Finally, when the fluctuation amount B is 0,
That is, when the substrate 3 is not elastically deformed,
Returning to step 43, the position of the upper surface plate 4 is lowered again by the set drop amount A. Then, the same processing is repeated. That is, the processing of steps 43 to 46 is repeated until the distortion of the substrate 3 is removed.

On the other hand, if A = B in step 44, that is, if the distortion of the substrate 3 is completely removed, the process proceeds to step 47. Then, in the same manner as in steps 45 and 46, final grinding is performed (steps 47 and 48), and double-side polishing is completed (step 4).
9).

In the above grinding process, both sides can be ground while the elastic deformation of the substrate 3 due to the processing load is kept small. Therefore, the shape accuracy such as the warp of the thin circular plate and the circumferential waviness is improved, and a substrate having high flatness can be obtained. Actually, the surface roughness is 0.03 μmRa, 0.2 μmRmax, and the flatness is 0.3.
A μm substrate was obtained.

Next, the polishing by the apparatus, that is, the "second step" referred to in the claims will be described with reference to FIGS.

As the upper surface plate 4 and the lower surface plate 5, those having a surface accuracy of 2 μm or less made of a material having a small viscoelasticity, such as ceramic, cast iron, or tin, are used for the surface plate. In addition, as shown in FIG. 8, fine grooves are formed on the surfaces of these surfaces so that a dynamic pressure effect is produced by relative sliding between the surface plate and the substrate 3. However, the shape of the dynamic pressure generating surface is an example, and the shape is not limited to this. In this example, colloidal silica having a particle size of 80 nm was used as the working liquid.

In the thrust bearing 20 of the upper surface plate 4,
Similar to double-sided grinding, the upper bearing rigidity is set to 10 kgf / μm,
The bearing rigidity of the lower part was set to 10 kgf / μm.

Five Ni-P plated substrates having both sides ground are mounted between the upper surface plate 4 and the lower surface plate 5 (step 60, FIG. 7A). In this case, the substrate 3 is the hole 84 of the carrier 8.
It is only placed inside and not fixed to the carrier 8. And
The upper surface plate 4 is lowered (step 61). The substrate 3
From the 200 μm upper azimuth value, the descending speed is reduced to 0.1 mm / min.

During this time, the control device monitors whether or not the upper surface plate 4 has come into contact with any of the substrates 3 by the same principle and method as in the case of the above-mentioned grinding process. Then, when it is detected that the two come into contact with each other, the lowering of the upper surface plate 4 is once stopped (step 62, FIG. 7B). Then, after this, conversely, the upper surface plate 4 is reversed by a preset amount (in this example,
5 μm) (step 63, FIG. 7C). This makes it necessary to perform the float polishing,
A clearance between the substrate 3 and the surface plates 4 and 5 is secured. The amount of the clearance may be changed according to the number of revolutions of the surface plate, the shape of the dynamic pressure generating surface formed on the surface of the surface plate, that is, the magnitude of the generated dynamic pressure, the type of the abrasive 6, and the like. is necessary.

The temperature controlled abrasive was supplied to the upper surface plate 4,
The bath of the apparatus is filled with an abrasive so that the lower platen 5, the substrate 3, and the carrier 8 are in the abrasive. Then, the upper and lower surface plates 4, 5 and the carrier 8 are rotated (step 64).
In this example, the rotation speeds of the upper and lower turn tables 4 and 5 were set to 13 rpm (counterclockwise) and 40 rpm (clockwise), respectively. The rotation number and the revolution number of the carrier 8 are set to 11 rpm and 13 rpm, respectively.

Then, as the upper and lower surface plates 4 and 5 rotate,
A liquid layer of the abrasive 6 is formed between the surface plate surface and the substrate surface,
Polishing is performed while the platens 4 and 5 and the substrate 3 are kept in non-contact with each other (FIG. 7D). That is, by repeatedly colliding the fine colloidal silica particles in the polishing agent 6 with the surface of the substrate, minute irregularities on the surface of the substrate are gradually removed. The shape of the surface plate whose flatness is corrected to 1 μm is transferred to the substrate surface.

As the polishing progresses, the upper platen 4
Is gradually lowered, the liquid layer h becomes smaller, and the polishing load W increases as shown by the following equation. As a result, the polishing efficiency is increased and the polishing can be efficiently advanced.

[0104]

[Equation 5]

W: polishing load μ: viscosity coefficient of polishing agent U: relative velocity D: substrate diameter Kw: correction coefficient Ks: correction coefficient h: distance between the substrate and the upper platen or lower platen in a non-contact state As described above, after performing double-side polishing for a fixed time (here, 10 min) (step 65), the operation of the apparatus is stopped (step 66), and the polishing is completed.

As described above, in the polishing by the apparatus of this embodiment, since both the substrate 3 and the surface plate surface are simultaneously polished in the non-contact state with the temperature controlled abrasive, the periphery of the viscoelastic body is polished. The generation of scratches due to who and coarse abrasive grains is greatly improved, enabling surface polishing in the angstrom order.

The surface precision of the substrate processed by using the apparatus of this example is such that the flatness is 0.5 μm, the surface roughness is 0.3 nm Ra, and the surface roughness is 5 n.
It was mRmax. This is a conventional substrate (flatness 5μ
m, surface roughness 3 nm Ra, 40 nm Rmax), the surface accuracy is significantly improved. In addition, the flatness of these data is measured by an optical interference type flatness measuring instrument (ZYGO, He-Ne laser light: wavelength 0.6328 μ).
m), and the surface roughness was measured by a surface roughness measuring device (manufactured by Rank Taylor Hobson Co., Taristep: stylus shape 0.1 μm × 2.5 μm).

Further, the results of analysis using another device are shown. Fig. 9 shows non-contact micro surface measurement (TO, WYKO, TO
(PO3D). RMS is root mean square roughness, R
a is the centerline average roughness, P-V is the difference in height between the highest peak and the deepest valley, and FIG. 10 shows the surface roughness profile as an ultra-precision surface roughness meter nanostep (rank).・ The results are measured by Thera Hobson Co.). Rq is the root mean square roughness, Ry is the maximum height, Rv is the depth of the deepest valley portion (note: the depth is based on the center line), Rp is the height of the highest mountain portion (note : The height is based on the center line). In all measurements, surface roughness 0.3nmRa
Hereinafter, it is shown that it is 5 nmRmax or less.

A Co--Cr based magnetic film having a thickness of 50 is formed on this substrate.
nm, carbon protective film 40 nm thick, lubrication film approximately 5
A magnetic disk having a thickness of 10 nm was prepared and the head flying characteristics were examined. The result is shown in FIG. Disc speed 3600r.
At pm, runout and acceleration are less than 1 μm each,
Achieved less than 1 m / s ² . The flying height is 0.06 μm
It was possible to obtain stable floating characteristics. In addition, CS
We were able to consistently achieve the S count of 30,000 or more.
As described above, since the shape accuracy of both surfaces is high and the variation of the plate thickness is very small, the runout and the acceleration measured by rotating the substrate could be greatly improved.

As an example, an aluminum substrate obtained by subjecting the substrate material to Ni-P plating has been described, but the same applies to anodized aluminum substrates, glass substrates, ceramic substrates, and carbon substrates using the apparatus of the above-mentioned examples. Can be processed into

Further, although the magnetic disk has been described as an example of the object to be processed in the above description, it is naturally applicable to grinding and polishing of other objects. In particular, it is particularly effective when applied to the processing of a thin plate or the like in which distortion such as warpage is likely to occur.

A magnetic disk device using the magnetic disk of the above embodiment is shown in FIG. This magnetic disk device includes a magnetic disk 1, a magnetic head 2, a magnetic disk 1 (not shown in the drawing), and a magnetic head 2
A drive mechanism such as a motor for moving the motor and a control device for controlling these. In this magnetic disk device, as described above, the flying height of the magnetic head 2 with respect to the magnetic disk 1 can be reduced, so that high density recording is possible.

[0113]

As described above, when the substrate according to the present invention is used, a magnetic disk having high recording density and high floating stability,
A magnetic recording device can be obtained. Further, it is possible to obtain a surface processing apparatus capable of performing grinding and polishing with high flatness and high surface roughness of an object to be processed.

[Brief description of drawings]

FIG. 1 is a side perspective view showing an overall configuration of a surface processing apparatus that is an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing details of a positional deviation detection mechanism of an upper surface plate 4.

FIG. 3 is an explanatory diagram showing a carrier.

FIG. 4 is a flowchart showing a grinding procedure according to the present embodiment.
It is

FIG. 5 is an explanatory diagram showing a grinding procedure according to the present embodiment.

FIG. 6 is a flowchart showing a polishing procedure according to the present embodiment.
It is

FIG. 7 is an explanatory diagram showing a polishing procedure according to the present embodiment.

FIG. 8 is a schematic view showing a state of non-contact polishing.

FIG. 9 is a graph showing the surface accuracy of a magnetic disk substrate manufactured using a substrate processed by the processing apparatus of this example.

FIG. 10 is a graph showing the surface roughness of a magnetic disk manufactured using a substrate processed by the processing apparatus of this example.

FIG. 11 is a table showing characteristics of a magnetic disk manufactured using a substrate processed by the processing apparatus of this example.

FIG. 12 is a perspective view showing an outline of a magnetic disk device.

FIG. 13 is a flowchart showing a manufacturing process of a magnetic disk.
It is

FIG. 14 is an explanatory diagram showing a conventional method for polishing a disk substrate.

FIG. 15 is an explanatory diagram showing a state in which a magnetic head is flying over a magnetic disk.

FIG. 16 is a graph showing the relationship between the rotational speed of the magnetic disk, runout, and acceleration.

[Explanation of symbols]

1 ... magnetic disk, 2 ... magnetic head, 3 ...
..Substrate, 4 ... Upper surface plate, 5 ... Lower surface plate, 6
... Abrasive agent, 8 ... Carrier, 9 ... Abrasive agent supply device, 11 ... Rotation drive means, 13 ... Position shift sensor, 14 ... Up-down drive mechanism, 15 ...
Holes, 16 ... Holes, 17 ... Spindle,
18 ... Spindle, 19 ... Compressor,
20 ... Thrust bearing, 32 ... Polisher,
52 ... internal gear, 54 ... center gear, 82 ... hole, 84 ... gear, 201 ...
..Thrust color, 202 ... Thrust receiver

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiki Kato 2880 Kozu, Odawara City, Kanagawa Stock Company Hitachi Ltd. Odawara Factory

Claims (20)

[Claims] 1. A surface roughness of 1 nm Ra or less and a flatness of 1 μm.
A magnetic disk comprising the following annular substrate and a magnetic film formed on the annular substrate. 2. The surface roughness of the annular substrate is 0.5 nmR.
The magnetic disk according to claim 1, which is a or less. 3. The magnetic disk according to claim 1, wherein the annular substrate has a flatness of 0.5 μm or less. 4. A method for manufacturing a disk-shaped member, the first step of grinding while keeping the elastic deformation amount of the disk-shaped member within a certain range, and non-contact polishing of both surfaces of the disk-shaped member at the same time. And a second step of: 5. The magnetic disk according to claim 1, wherein the annular substrate is a glass substrate manufactured by the method for manufacturing a disc-shaped member according to claim 4. 6. A magnetic disk comprising an aluminum substrate processed by using the method for producing a disk-shaped member according to claim 4, and a Ni—P plating layer formed on the aluminum substrate. Substrate. 7. A magnetic disk according to claim 1, a magnetic head for writing and / or reading a signal to and from the magnetic disk, a drive means for driving the magnetic disk and the magnetic head, the magnetic head, and A magnetic disk device comprising: a control unit that controls the drive unit. 8. The magnetic disk drive according to claim 7, wherein the flying height of the magnetic head with respect to the magnetic disk during operation is 0.06 μm or less. 9. A rotatably configured first stool, and a rotatably configured second stool in which an object to be machined is arranged between the first stool and the first stool. Change means for changing the position of the first surface plate according to a set value, rotation drive means for rotating the first surface plate and the second surface plate, the first surface plate and the workpiece. Contact detection means for detecting the contact between the first surface plate and the processing object while the position of the first surface plate is being changed by the changing means. A surface processing apparatus comprising: a control unit that uses the position of the first surface plate at that point in time as a reference point for changing the position by the changing unit. 10. The control means stops the change of the position of the first surface plate by the changing means when the contact is detected during the change of the position of the first surface plate by the changing means. The surface processing apparatus according to claim 9, wherein 11. A rotatably configured second stool, in which an object to be machined is disposed between the rotatably configured first stool and the first stool. Changing means for changing the position of the first surface plate according to a set value, rotation driving means for rotating the first surface plate and the second surface plate, and an actual position of the first surface plate, The positional deviation detecting means for detecting the positional deviation amount from the position corresponding to the set value, and the positional deviation detecting means for generating the positional deviation during the change of the position of the first surface plate by the changing means. When detected, the surface processing apparatus comprising: a control unit that uses the position of the first surface plate at that time as a reference point for changing the position by the changing unit. 12. The control means changes the position of the first surface plate by the changing means when the occurrence of the positional deviation is detected while changing the position of the first surface plate by the changing means. 12. The surface processing apparatus according to claim 11, which is stopped. 13. The control means changes the position of the first surface plate by the changing means when the occurrence of the positional deviation is detected during the change of the position of the first surface plate by the changing means. After temporarily stopping, the position of the first surface plate is changed by a preset amount, and at this time, the rotational driving means causes the first displacement until the displacement amount detected by the displacement detecting means becomes zero. In the process of rotating the first surface plate and the second surface plate to grind the object to be processed, the preset amount of positional change and the amount of positional deviation detected by the positional deviation detecting means become equal. 12. The surface processing apparatus according to claim 11, wherein the surface processing apparatus is repeated. 14. The control means compares the amount of positional change by the changing means with the amount of positional deviation detected by the positional deviation detecting means, and when both are equal, the workpiece is elastically deformed. The surface processing apparatus according to claim 11, wherein the surface processing apparatus is determined to be absent. 15. The first platen and / or the second platen.
The surface processing apparatus according to claim 11, wherein the surface plate of (1) is configured to include a grindstone on a surface facing the object to be processed. 16. The surface processing apparatus according to claim 11, wherein each of the first surface plate and the second surface plate has a dynamic pressure generating surface on a surface facing the object to be processed. 17. At least the object to be processed and the first object.
Polishing plate supply means for supplying a polishing liquid between the platen and the second platen, and the control part is arranged to change the position of the first platen while the position of the first platen is being changed by the changing part. When the occurrence of misalignment is detected,
The change of the position of the first platen by the changing means is temporarily stopped, and then the first platen is moved by a preset amount in a direction in which the distance between the first platen and the second platen increases. 17. The surface processing apparatus according to claim 16, wherein the position of the surface plate is changed by the changing means, and the first surface plate and the second surface plate are rotated while the polishing liquid is supplied. .. 18. The surface processing apparatus according to claim 11, wherein the rotating shaft supporting the first surface plate is supported by an air bearing. 19. The surface processing apparatus according to claim 18, wherein the rotary shaft has a thrust portion composed of a thrust receiver and a thrust color. 20. The surface processing apparatus according to claim 19, wherein the positional deviation detecting means detects a variation in the size of the clearance between the thrust receiver and the thrust color.