JPH10244382A - Texture device and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a texture device and its method capable of a superior CSS characteristic, sticking characteristic, and low floating of a magnetic head simultaneously. SOLUTION: A laser beam outputted from a laser beam generator 1 is emitted on a substrate 6 through a modulator 2, polarizing beam splitter 3, 1/4λ plate 4, mirror 5a, and a condensing mechanism 5. This substrate 6 is rotated by a substrate rotating mechanism 7, the modulator 2 is ON/OFF-controlled by a timing controller 11, the condensing mechanism 5 is moved in the radial direction of the substrate 6 by a transfer mechanism 12, and the substrate is thereby texture-processed. Reflection light from the substrate 6 is returned to the polarizing beam splitter 3 through the condensing mechanism 5, mirror 5a and, 1/4λ plate 4, reflected by a prism mating face, and received by a light receiving system 9, with the reflected light quantity monitored by a monitoring device 10 for reflected light. Incident light passing through the modulator 2 is monitored by a monitoring device 8 for incident light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a texture apparatus and a texture processing method, and more particularly, to the above apparatus and processing method using a laser beam.

[0002]

2. Description of the Related Art In a magnetic disk drive, in order to stably maintain a minute gap between a magnetic disk and a magnetic head, the magnetic head is in contact with the surface of the magnetic disk when stopped, and stopped when the drive is started. A so-called contact start / stop (CSS) system in which a magnetic head slides on a magnetic disk surface and travels while flying is employed. In order to prevent sticking between the magnetic head and the substrate, a texture processing for forming minute projections (streak patterns) on the surface of the substrate is performed.

In the conventional texturing, mechanical grinding using a polishing tape coated with abrasive particles dispersed in a binder or a slurry in which abrasive particles are dispersed has been mainly employed.
As a texturing method capable of controlling the uniformity and the processing height, U.S. Pat. No. 5,062,021 proposes a texturing using a Q-switched YAG laser beam. This method is a method of forming crater-shaped projections and depressions composed of a melt-formed hole and an annular rim in which the periphery is raised by surface tension and solidified.

As a texturing method using a laser beam, Japanese Patent Application Laid-Open No. Hei 8-224677 discloses a method for controlling a laser beam output, an irradiation time, a spot diameter and the like by using a gas laser such as Ar so that the height can be reduced to one. ~ 100
A texturing method is described in which 10 ¹ to 10 ⁸ protrusions and recesses adjacent to the protrusions are formed per ¹ mm ² .

[0005]

When a substrate is textured by using a laser beam, the height of the projections and the depth of the concave holes vary due to, for example, a focus shift due to an abnormal autofocus, a power variation of a laser light source, and the like. So, for example, measure the height of all generated protrusions,
If it is out of the predetermined range, a method of determining an abnormality is adopted. Since this method measures the actual projection height, it takes time for the measurement when the projection density is high, and it is practically impossible to measure all the projection heights industrially. There was a problem.

The present invention has been made in view of the above circumstances, and an object of the present invention is to improve the processing productivity of texture processing using a laser beam. Another object of the present invention is to provide a texture device and a texture processing method that can simultaneously achieve good CSS characteristics and sticking characteristics and a low flying height of a magnetic head.

[0007]

A texture device according to the present invention is a texture device for forming minute projections on the surface of a magnetic disk substrate, comprising: a laser beam oscillator; and ON / OFF control of a laser beam from the oscillator. Modulator, a condensing mechanism for irradiating the substrate surface with a laser beam from the modulator, and a texture device having a moving unit for relatively moving the laser beam and the substrate, the amount of light incident on the substrate of the laser beam and A monitor means for measuring the amount of reflected light from the substrate is provided.

According to the texture processing method of the present invention, when minute projections are formed on a magnetic disk substrate by using this texture device, the amount of incident light and the amount of reflected light measured by the monitor means are within a predetermined range. It is characterized by doing.

As described above, the incident light amount and the reflected light amount are monitored, and the incident light amount and the reflected light amount are set in a predetermined range, so that the height of the minute projections generated by the texture processing and the arrangement position with respect to the concave hole can be made predetermined. it can.

In the present invention, when monitoring the amount of reflected light from the substrate, it is preferable that the reflected light is condensed through the condensing mechanism, separated from the incident optical axis, and guided to the reflected light amount monitoring means.

In a conventional texture apparatus using a laser beam, a method of obliquely incident light on a substrate may be employed in order to prevent reflected light from returning to a laser beam oscillator. This is because laser beam oscillation becomes unstable when the reflected light returns to the laser beam oscillator. However, in this case, the optical axis of the reflected light deviates from the optical axis of the incident light, so that another optical system for condensing the reflected light is required to monitor the reflected light. In the present invention, as described above, if the reflected light is guided to the means for monitoring the amount of reflected light through the mechanism for condensing the incident light, such another optical system becomes unnecessary.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a texture device according to an embodiment, and FIG. 2 is a schematic cross-sectional view showing an uneven portion formed on a substrate surface by texture processing.

The laser beam output from the laser beam oscillator 1 is applied to a modulator 2, a polarization beam splitter 3, 1 /
The light is applied to the substrate 6 via the 4λ plate 4, the mirror 5a, and the light collecting mechanism 5. The substrate 6 is rotated by the substrate rotation mechanism 7 and the modulator 2 is
The N / OFF control is performed and the mirror 5a and the condensing mechanism 5 are moved in the radial direction of the substrate 6 by the moving mechanism 12, whereby the substrate 6 is textured. Note that instead of moving the light collecting mechanism 5, the substrate 6 may be moved, or both may be moved.

The reflected light from the substrate 6 returns to the polarization beam splitter 3 through the light collecting mechanism 5, the mirror 5a, and the λλ plate 4. The light returning to the polarization beam splitter 3 is
The reflected light is reflected by the prism mating surface of the polarizing beam splitter 3, is received by the light receiving system 9, and is monitored by the reflected light amount monitoring device 10.

The amount of incident light passing through the modulator 2 is monitored by an incident light amount monitor 8, but as described later, when the modulator 2 has a monitor function, the monitor 8 can be omitted.

As described above, the incident light amount and the reflected light amount are monitored by the monitor devices 8 and 10 for the incident light amount and the reflected light amount, and these are set in a predetermined range, so that the height of the minute projections formed on the substrate 6 is set to a predetermined value. In addition, as shown in FIG. 2, it is possible to form an uneven portion in which the minute projections are arranged so as to be adjacent to one side of the concave hole.

In the present invention, minute projections can be simultaneously formed on the back surface as well as the front surface of the magnetic disk substrate. Such an embodiment is, for example, a laser beam oscillator 1
This can be realized by dividing the laser beam emitted from the substrate and irradiating the divided laser beam to the back surface of the substrate which is rotatably supported by the substrate rotating mechanism.

The preferred structure of the above-described texture device will be described in more detail below.

As the laser beam oscillator 1, a gas laser such as a CO ₂ gas laser or an Ar gas laser, a YAG laser capable of continuous oscillation, or the like is preferable, and an Ar gas laser is particularly preferable. Gas laser is Q switch YA
Compared with a G laser, an excimer laser, or the like, the phase is uniform and the beam spot can be easily narrowed, which is advantageous in that a sharp projection can be formed.

As for the wavelength of the laser, a higher output is usually easier to obtain in the visible region. The Ar gas laser beam typically has a wavelength of 488 nm or 514.5 nm. When directly irradiating the glass substrate, the glass substrate is passed through a relatively low-power ultraviolet region, for example, 350 nm argon or FHG (fourth harmonic generator).
A 6 nm YAG laser is preferred.

The laser beam emitted from the laser beam oscillator 1 to the surface of the substrate 6 is controlled to an energy capable of forming a concave / convex portion having a concave hole near the microprojection as shown in FIG. Preferably.

The modulator 2 is preferably capable of high-speed modulation. Further, it is preferable that the rise time is 50 ns or less, and the pulse width including the rise time and the fall time is 50 ns to 2 μs. If the pulse width is less than 50 ns, no projections are formed or it is difficult to form minute projections having a desired shape. If the pulse width exceeds 2 μs, the area of the minute projections tends to be large, and the CSS characteristics tend to deteriorate.

It is preferable that the modulator 2 can be turned on / off with good rise. Since the rise time of the modulator affects the sharpness of the protrusion, the use of a modulator having a long rise time results in the formation of a minute protrusion having a large contact area with the head. As a modulation element used for such a modulator, an electro-optic modulation element (EOM) is preferable. The electro-optic modulator uses high-speed modulation (ON / OF) up to several hundred Mbps.
F) is possible. In addition, analog modulation can be performed at the time of ON. Note that the EOM is normally used for its ABC (Auto Bi
Since a light amount monitoring function is provided for the “As Control”, if this is used as a signal for monitoring the incident light amount, there is no need to separately install the incident light monitoring device 8.

The modulation frequency is 0.5 to 10 MHz
Is particularly preferable, and 0.5 to 5 MHz is particularly preferable. If the modulation frequency is less than 0.5 MHz, the contact area between the protrusion and the head increases. If the frequency exceeds 10 MHz, adjacent projections interfere with each other, and it is difficult to form independent projections. Also,
The pulse width (irradiation time required to form one uneven portion) is preferably 40 nsec to 100 μsec, and 50 μsec.
Particularly preferred is nsec to 2 μsec. As the pulse width increases, the projections continue, and the contact area with the head increases.

The polarizing beam splitter 3 and the ４λ plate 4 are used to separate the reflected light from the substrate 6 from the incident optical axis. The principle is as follows. A laser beam that is linearly polarized is used as the laser beam. In the case of a gas laser, it is originally linearly polarized and can be used as it is.
Linear polarization is performed by a polarizing plate or the like. The direction of the linearly polarized light of the incident light is set to the direction of transmission through the polarization beam splitter 3. The direction of the ４λ plate is set to a direction that converts linearly polarized light into circularly polarized light. The direction of rotation of the laser beam converted to circularly polarized light is reversed when reflected by the disk, so that when the reflected light again passes through the ４λ plate and becomes linearly polarized light, the polarization angle differs from the incident light by 90 degrees. . Therefore, the reflected light does not pass through the polarizing beam splitter, the optical axis is bent by 90 degrees, and the reflected light can be separated from the incident optical axis.

The light collecting mechanism 5 is formed by combining an objective lens and an auto focus (AF) system. It is preferable to provide a beam expander in front of the objective lens and to increase the beam diameter to an extent equal to the effective diameter of the objective lens in order to form a clear spot. The effective diameter of the lens is usually about 50 to 80% of the lens diameter.

In order to uniformly provide minute irregularities on the substrate, the spot diameter, uniformity and sharpness of the laser beam applied to the substrate are important factors. The spot diameter is 0.2-4 μm, especially 0.2-2 μm
Is preferred. (Note that the spot diameter indicates the diameter of a circle whose intensity is reduced to e- ^2, which is the highest intensity at the central portion of the light.) The numerical aperture of the objective lens is NA, and the wavelength of the laser beam is λ. When NA is 0.3 to 0.8,
And it is preferable that (lambda) / NA is 0.16-3.3.

From the viewpoint of the sharpness of the spot, the focal length of the objective lens is preferably 20 mm or less, particularly preferably 5 mm or less. In the case of such a focal length,
Since the substrate and the objective lens are arranged very close to each other, it is preferable that the substrate and the objective lens have a sufficient shape that enables stable attachment / detachment and rotation of the substrate and high-speed rotation, and does not hinder the movement of the objective lens, It is preferable that the distance between the upper surface of the substrate and the tip of the rotation axis of the spindle protrudes from the substrate surface at a ratio of 0.8 or less, particularly 0.6 or less with respect to the distance (working distance) between the substrate upper surface and the objective lens. . Working distance is usually 10
mm or less. In addition, it is preferable that a notch is provided near the back surface of the substrate on the rotation axis of the spindle to stably move the objective lens.

By using an aspherical lens as the objective lens, the weight of the lens can be reduced, the light transmittance can be increased, and the working distance can be widened. Since the distance between the objective lens and the substrate fluctuates due to the waviness of the substrate or the shaft movement of the spindle, the focusing mechanism is further equipped with an autofocus (A
F) It is preferable to have a mechanism. In particular, the response frequency of the autofocus mechanism is preferably 90 Hz or more.

When the response frequency decreases, the size of the beam spot varies, and the size and height of the projection become non-uniform. In addition, it is preferable to improve the control efficiency of the AF mechanism by utilizing the result of the surface shake learning function, that is, the AF control result in the portion where the laser irradiation has been performed, in the AF control in a feedforward manner in synchronization with the rotation of the disk, for example.

As the mechanism 12 for relatively moving the substrate rotating mechanism 7 and the light condensing mechanism 5, a linear slider is suitable, and the moving speed of the linear slider (the relative moving speed of the substrate 6 in the radial direction) is as follows. 0.03 to 60 mm / sec
The degree is preferred. As described above, the moving mechanism 12
May move the condensing mechanism 5, may move the substrate rotating mechanism 7, or may move both.

If the relative movement speed between the beam and the substrate 6 is too slow, it is difficult to improve the CSS characteristics, and if it is too fast, the contact area between the projection and the head becomes large, so that the CSS characteristics are selected to be good. . Usually, the relative scanning speed of the beam on the irradiation surface is 2 m / s or more, especially 2 to 5 msec.
It is preferably 0 m / s. The substrate 6 is supported on a rotating shaft of a spindle motor of the substrate rotating mechanism 7 so as to have such a relative speed, and is rotated at a constant rotation speed or linear speed. In a normal case, the number of rotations of the substrate is preferably 900 to 7200 rpm, particularly 1800 rpm.
m or more is preferable, and 3600 rpm or more is most preferable.

If the rotating shaft of the spindle motor is shaken, the surface shake becomes large, the focus becomes difficult to stop, and the projection shape varies, and in some cases, a desired projection shape cannot be obtained. It is preferred that

The texture apparatus shown in FIG. 1 is provided with a timing control section 11 for controlling the modulation timing of a laser beam as a means for forming minute projections on the surface of the substrate in a constant pattern at the same or different intervals.

That is, for example, when forming the fine projections at the same interval which is usually adopted, when the substrate 6 is moved at a constant rotation speed and a constant speed by the constant speed operation of the moving mechanism 12 and the substrate rotating mechanism 7, The interval between the minute projections formed on the surface becomes wider toward the outer periphery. Therefore, the laser beam spot position on the substrate is checked, and the modulation timing (irradiation time) of the laser beam is controlled by the timing control unit 11 in accordance with the spot position signal, and the interval between the minute projections formed on the substrate surface is reduced. Keep it constant. As a mechanism for detecting the position of the laser beam spot, for example, a laser displacement meter, an encoder, or the like can be used.

The speed control of the moving mechanism 12 and the substrate rotating mechanism 7 may be performed without controlling the modulation timing of the laser beam.

In order to make the shape of the concavo-convex portion shown in FIG. 2 uniform, even if the spot position of the laser beam changes in the radial direction of the disk, the laser spot of the laser beam based on the relative movement of the condensing mechanism and the substrate rotating mechanism. It is preferable to keep the sweep distance constant. In this case, it is preferable to change the pulse width or the number of rotations of the substrate according to the irradiation position.

When the spindle speed is constant, the position of the laser spot in the radial direction is measured by the measuring means, and the sweep distance of the laser spot is constant for each position in the radial direction measured by the measuring means. The calculated pulse width is calculated by the calculation means, and the laser beam is modulated based on the calculation result.

When the pulse width is constant, the position of the laser spot in the radial direction is measured by measuring means, and the position of the laser spot is measured with respect to each position in the radial direction measured by the measuring means. The arithmetic unit calculates the spindle rotation speed for keeping the sweep distance constant, and modulates the laser beam based on the calculation result.

When texturing of the surface of a magnetic disk substrate is performed using such a texture device, an uneven portion as shown in FIG. 2 composed of minute projections having a height of 1 to 100 nm and concave holes adjacent to the minute projections is used. Is 10 ¹ per mm ²
10 ⁸ preferably is preferably the amount of incident light and reflected light as formed at the same interval in the CSS zone is monitored. In particular, the average value of the area of the figure surrounded by the contour at a height 1 nm below the vertex of each projection is 1 μm.
^It is preferable to monitor so as to obtain a relatively steep value of ² or less.

The substrate having such irregularities has good CSS characteristics and sticking characteristics as well as low flying height of the magnetic head, as is clear from the examples described later.

By setting the amount of incident light and the amount of reflected light monitored by the monitoring devices 8 and 10 within a predetermined range, power fluctuation of the laser light source, abnormality of the autofocus mechanism, and the like can be detected. Even without measuring the height of each projection, it is possible to manage the height of the projection and the depth of the concave hole of the formed uneven portion.

In order to form the concave and convex portion composed of the fine protrusion and the concave hole adjacent to the fine protrusion shown in FIG. 2, it is important to make the output of the laser beam appropriate. The laser beam output varies somewhat depending on the surface material of the substrate and the like, but it is generally preferable to use a light source in the range of 50 to 2000 mW, particularly 50 to 1000 mW, particularly 50 to 400 mW on the irradiation surface. If it is less than 50 mW, it is difficult to form protrusions, and if it exceeds 2000 mW, it becomes difficult to perform texture processing with excellent CSS characteristics. Further, it is preferable to use a laser capable of continuous output.

For a typical Ni-P layer, 50-700
It is preferable to use a light source of mW, especially 50 to 700 mW, and the average irradiation time is preferably 0.04 to 100 μsec. The average irradiation time indicates the irradiation time required to form one projection.

When the output of the laser beam exceeds the above-mentioned range, a crater-like structure in which a convex portion surrounds a concave hole in a circular shape described in US Pat. No. 5,062,021 is used. An uneven portion is formed. Such a crater-shaped uneven portion is insufficient for the problem of sticking between the magnetic disk and the magnetic head. In addition, Ni-P
The thickness of the layer is between 50 and 20000 nm, preferably 100
It is good to make it the range of-15000 nm.

In the present invention, an Ni-P electroless plating base layer is provided on the surface of a substrate called a substrate, that is, a substrate made of an Al alloy, for example, an Al-Mg alloy. A substrate or a glass substrate, a silicon substrate, or the like having a base layer subjected to mirror finishing (polishing) can be used, but other metal substrates such as copper and titanium, a carbon substrate, a ceramic substrate, and a resin substrate can also be used. . Even after the layers such as the underlayer, the magnetic layer, the protective layer, and the lubricant layer are provided on the substrate, those in the process (only one or two or more of these layers may be used) Provided) can be textured by the present invention.

[0047]

【Example】

Example 1 A disk-shaped Al alloy substrate having a diameter of 95 mm was subjected to Ni-P electroless plating with a thickness of 15 μm and then polished so that the surface roughness (Ra) became 1 nm or less. Was textured on one side using the texture device of FIG.

As a laser beam light source, an Ar gas laser beam tube (wavelength 488 nm, maximum output 2 W),
The modulator has an electro-optic modulator (response frequency: 2 MHz,
(Rise time: 15 ns). The fluctuation rate of the incident light amount and the reflected light amount was ± 1% or less. The light collection mechanism
It was configured as a combination of an objective lens combining a beam splitter cube and an autofocus system.

The other conditions were as follows.

Laser beam output: 400 mW Pulse width: 0.156 μsec Beam spot diameter: 1 μm Auto focus response frequency: 180 Hz Substrate rotation speed: 2400 rpm Moving speed (relative speed) of linear slider: 0.6 mm
The relative scanning speed on the irradiation surface of the / sec beam: 4.8 m / s The variation in the height of the protrusions was evaluated by σ using a surface shape measuring device (“ZYGO” manufactured by Zigo, USA) using laser interference. As a result of observing the surface shape of the substrate after the texture processing, it was confirmed that minute projections having a shape having a concave portion connected to the convex portion were formed near the convex portion. The average projection density was 9260 / mm ² and the average projection height was 33.
The average value of the area of the figure surrounded by the contour line at a height of 1 nm below the vertex in nm was 0.12 μm ² .

By a sputtering method, a Cr intermediate layer (thickness: 100 nm), a Co—Cr—Ta alloy magnetic layer (thickness: 50 nm), and a carbon protective layer (thickness: 20 nm) were sequentially formed on the above substrate surface.
m), and a 2 nm-thick fluorinated liquid lubricant (“DOL-20” manufactured by Monte Edison Co., Ltd.) is formed on the surface of the carbon protective layer.
00 ") by dip coating to obtain a magnetic disk.

For the above magnetic disk, the static friction coefficient (initial stiction) and CSS before the CSS test
The friction force after 20,000 times was measured. The CSS test was performed on a thin film head with a load gram of 6 gf (slider material: Al ₂ O ₃
Using TiC), the head flying height was 2 μ inch. Further, a glide tester was used to evaluate the flying height of the head at the time of seeking between the data zone and the CSS zone. Table 1 shows the results.

Comparative Example 1 Example 1 except that the laser light source was intentionally made unstable and the variation rate of the incident light amount was set to ± 10%.
In the same manner as described above, a micro projection was formed and evaluated. Table 1 shows the results.

[Comparative Example 2] Microprojections were formed and evaluated in the same manner as in Example 1 except that the autofocus system was intentionally out of order and the variation in the amount of reflected light was set to ± 10%. Table 1 shows the results
Shown in

[0055]

[Table 1]

As shown in Table 1, when the fluctuation rate of the incident light and the reflected light is small, the variation in the height of the protrusion is small, and the initial stiction, the frictional force and the flying height are extremely excellent.

[0057]

According to the present invention described above, it is possible to control the height of the generated minute projections to be within a predetermined range when the substrate is textured by using the laser beam. In addition, the stability of texture processing productivity is improved. In addition, the CSS characteristics and sticking characteristics of the textured substrate can be improved, and the flying height of the magnetic head can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of a texture device of the present invention.

FIG. 2 is a schematic sectional view of a substrate surface.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser beam oscillator 2 Modulator 3 Polarization beam splitter 4 1/4 (lambda) plate 5 Condensing mechanism 6 Substrate 7 Substrate rotation mechanism 8 Incident light quantity monitoring apparatus 9 Reflected light receiving system 10 Reflected light quantity monitoring apparatus 11 Timing control part 12 Moving mechanism

Claims (5)

[Claims] 1. A texture device for forming minute projections on a surface of a magnetic disk substrate, comprising: a laser beam oscillator; and a laser beam from the oscillator.
In a texture device having a modulator for performing N / OFF control, a condensing mechanism for irradiating a laser beam from the modulator onto a substrate surface, and a moving unit for relatively moving the laser beam and the substrate, And a monitor for measuring the amount of incident light and the amount of light reflected from the substrate. 2. The texture device according to claim 1, wherein the reflected light from the substrate is condensed through the light condensing mechanism and then guided to a reflected light amount monitoring means. 3. The texture apparatus according to claim 2, wherein the reflected light is separated from an incident optical axis by a polarizing beam splitter and a λλ plate, and then guided to a reflected light amount monitoring means. 4. A modulator according to claim 1, wherein the modulator for controlling ON / OFF of the laser beam is an electro-optical modulator, and the incident light monitoring means is for automatic bias control of the electro-optical modulator. A texture device, which is an incident light measuring device. 5. The method according to claim 1, wherein when forming the fine protrusions on the magnetic disk substrate using the texture device according to claim 1, the incident light amount and the reflected light amount measured by the monitor means are within a predetermined range. A texture processing method for a magnetic disk substrate.