JP2001357516A - Method for assembling substrate surface of glass substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form surface irregularity by converging a coherent energy beam on an exposed surface of a magnetic recording medium. SOLUTION: This is a method for assembling a substrate surface of a glass substrate prior to film-deposition of a magnetic thin film. Non-magnetic metal is worked to form a non-magnetic metal layer having uniform thickness of 5 nm on the glass substrate. Coherent radiation energy is converged selectively on plural positions on a region to be processed of the metal layer to controllably change substrate topography in each position. The surface irregularity is formed in each position so as to have a height in 3-200 nm range from the nominal plane of the substrate surface to an upper part. The surface irregularity consists of roundish small lumps formed by slight destruction of the glass adjacent to the metal layer or formed in the metal layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION The present invention relates to media for recording, storing and reading magnetic data, and more particularly to the use of radiant energy beams to control the topography of such media.

[0002] Magnetic disks use thin films of magnetic material to store data in magnetic form. Typical magnetic disks are rotatably mounted, each having a magnetic data transducing head located in close proximity to one of the magnetic disk recording surfaces. Each head rotates when the disk rotates.
Move generally radially relative to the associated disk. In a drive mechanism using a solid magnetic disk, the disk rotates at a high speed during reading and recording operations. The rotation speed is fast enough to produce an air cushion or air bearing that supports each transducing head at a controlled distance from the associated recording surface of the head, resulting in consistent head "flying height"
To maintain. The transducing head is always in contact with the associated disk when the disk is stationary, accelerating from a stop, or decelerating just before reaching a complete stop.

[0003] Designers are constantly striving to increase the density at which magnetic data is recorded. One way to increase storage density is to reduce the flying height of the transducing head. The use of a smooth, mirrored recording surface and a similar facing surface of the conversion head allows the head to be closer to the recording surface. A smooth surface not only can increase data density, but also makes the behavior of the air bearing and head during operation more consistent and predictable.

At the same time, good smoothness also leads to friction and stiction problems when the transducing head is in contact with the disk. One method is Ranja
n) Other US Pat. No. 5,108,781 that selectively textures certain portions of the disk surface, sometimes referred to as landing or contact zones. ). Further, when the disk decelerates toward the stop state, the position of the conversion head is controlled so that the head always stays on the landing band, not on the relatively smooth recording surface of the disk. This patent also discloses using a laser to prepare the texture of the landing zone. More specifically, neodymium: yttrium aluminum garnet (Nd
-YAG) laser generates a pulsed laser beam;
The beam is focused on the upper surface of the aluminum nickel-phosphorus substrate. As the laser forms a series of laser marks or spots, each has a central depression surrounded by an annular raised rim.

While this method is satisfactory for most applications, there may be special demanding environments where the depression and the surrounding rim result in transient surface roughness and lack of sufficient uniformity. . In these applications, the flying height of the conversion head is further reduced to, for example, 1 microinch (25.4 nm). The low flying height imposes strict requirements on the data recording surface of the magnetic disk with relatively high smoothness. More specifically, the recording surface is polished extremely smoothly, preventing the occurrence of sharp points and other needle-like features,
It is necessary to prevent the low-floating conversion head from touching.

[0006] Means for mechanically polishing a disk, ie, using a cloth, paper, or pad saturated with cerium oxide, silicon carbide, or other suitable grit applied or filled, are well known. 0.1 microinch (2.
In order to reach a roughness level of 54 nm), the polishing process usually takes several steps and progressively refines the grit. Alternatively, mechanical polishing can be performed in a single step over time using very fine grit material. In either case, a large amount of material consumption, a significant increase in media production costs, and potential media quality degradation due to unwanted curvature near the edges must result.
Since the magnetic recording film to be coated later is a copy of the surface topography, a residual scratch formed by mechanical polishing may cause a defect in the magnetic recording film. Trace scratches also reduce the uniformity of the protective carbon film formed on the magnetic recording layer and weaken the resistance to corrosion.

It is, therefore, an object of the present invention to provide a magnetic data recording medium in which the structure of the dedicated transducer head contact zone is more uniform and more precisely controlled.

Another object is to provide a process for directing a coherent energy beam to an exposed surface of a magnetic recording medium and controlling the beam to control the height and structural properties of nodules and other discontinuities. It is.

Yet another object is to selectively direct laser energy to the data recording surface of a magnetic media substrate after mechanical polishing of the substrate surface to remove trace scratches without altering the properties of the processed substrate. Is to provide a process.

Yet another object is to provide a magnetic data recording medium that is smooth, essentially free of trace scratches and other needle-like features, and has increased resistance to corrosion.

(Abstract of the Invention) In order to achieve such an object, a non-magnetic substrate is polished in a process of manufacturing a medium for reading and recording magnetic data by coating a magnetic recording layer on the non-magnetic substrate. Process is provided. The process comprises: a. Mechanically polishing the non-magnetic substrate to form a substantially flat substrate surface on the substrate such that the surface roughness due to trace scratches formed by mechanical polishing is at most about 25 nm; b. . Subsequent to mechanical polishing, radiant energy is injected into a selected surface portion of the substrate surface, and the selected surface portion has a depth above the roughness, which is within a surface reference plane of the substrate surface. Fusing, melting the substrate in the melted region, thereby causing the substrate material in the melted region to flow and substantially eliminate trace scratches; and c. Solidifying the substrate material to form a selected surface portion to be specular and substantially free of trace scratches.

Preferably, the injection of radiant energy is such that the beam of coherent energy is directed at the surface of the substrate, defines an irradiation area of the beam impinging on said surface, and translates the substrate and the beam relative to each other. , By moving the illuminated area along a path that substantially includes the selected surface portion in the coverage area. The beam profile and the angle of incidence of the beam on the substrate surface determine the shape of the illuminated area, for example, circular, elliptical, etc. In one useful combination, a beam having a circular profile, ie, a cross section, is oriented perpendicular to the substrate surface to form a circular illumination area.

[0013] The degree of surface heating, and thus the depth of the fusion zone, is primarily controlled by the level and duration of energy in the illuminated area, ie, the time period during which a particular location on the substrate surface is illuminated. If the coherent energy is pulsed, the duration is controlled by the pulse width and pulse frequency. Although the duration is slightly affected by the velocity of the irradiation area relative to the substrate, the pulse time is very short and this factor is usually not significant. The energy level is controlled by the power at which the beam is generated, the attenuation between the beam source and the collision area, the degree of beam convergence, and other spatial properties of the beam.

A preferred energy source is a solid state laser, more preferably a neodymium: yttrium lithium fluoride (Nd: YLF) laser. Compared to the Nd: YAG laser discussed in the aforementioned US Pat. No. 5,108,781, the Nd: YLF laser is operable at lower energy levels and is substantially more stable with respect to pulse level and pulse width. is there. This results in a significant improvement in the laser's surface processing capabilities, since it improves uniform and repeatable properties such as the rimmed depression disclosed in US Pat. No. 5,108,781. In addition, it has been found that solid state lasers allow for surface polishing and formation of unique surface irregularities.

As an example of the obtained improvement, Nd: YLF
The laser is pulsed and focused to create a localized but relatively large illumination area, and to select a pulse width to melt the substrate surface, but to be extremely instantaneous and at most about 40 microinches (1 micron) ), More preferably about 25
It can be melted down to 0 nm, most preferably 38 nm. This method is particularly effective in removing trace scratches after mechanical polishing of conventional substrate disks (aluminum plated with a 3-10 micron thick layer of nickel-phosphorous alloy). The material melting depth is more than sufficient to remove trace scratches. In addition, since the depth of fusion is selected to be at most 10% of the thickness of the Ni-P layer in any case, the depth of fusion is insignificant with respect to the thickness of the Ni-P layer. Due to the rapid cooling and resolidification of the melting zone and the low melting depth compared to the alloy layer thickness, it must be lost if the alloy layer receives sufficient heating and causes more general crystallization The non-magnetic properties of the alloy layer are preserved. More specifically, the initial structure of the Ni-P layer is preserved over most of its depth.

It has been found that laser polishing does not always reduce surface roughness. For example, the maximum roughness is approximately 2
Surfaces that have been mechanically polished down to nm may increase in roughness when subjected to the laser polishing discussed herein, for example, to a maximum peak height of approximately 3 nm. However, the resulting roughness is a relatively low frequency waveform or undulation as compared to the high frequency needle-like features of trace scratch peaks and valleys.
Thus, the performance of the media is improved with respect to noise reduction and corrosion resistance, while keeping sufficiently low roughness.

In another case, for example, if the substrate surface is approximately 25
with a trace roughness of at least 25 nm or approximately 25 nm
When mechanically polished to the above roughness, laser polishing not only removes needle-like features, but also reduces surface roughness.

In addition to polishing, lasers can be used to control the surface composition of selected surface zones that are dedicated to contacting the transducing head and thus have greater roughness than adjacent or close data recording zones. Consequently, the exclusive band is selectively surface-machined by forming a laser mark or spot. A laser beam generated at a power level similar to that used for laser polishing, but focused on a substantially smaller illumination area,
It was found that a nodule or dimple protruding outward from the substrate surface was formed. Nodule formation is due to lower energy levels and convergence to the illuminated area.
Apart from this, the exact reason for the formation of nodules opposite to the formation of depressions is not fully understood. In both cases, the Gaussian nature of the impinging laser beam concentrates heat at the beam center. One hypothesis for the formation of bumps is that if the beam impinges instantaneously melts the material in the beam-irradiated area, it will form waves in the center of the irradiated area that tend to travel radially outward. That is what you think. The waves are preserved by rapid cooling and solidification of the substrate material. At relatively high energy levels, the waves travel outward before the material solidifies, forming a ring or rim surrounding the depression. At relatively low energy levels, the solidification of the molten substrate material is so rapid that the waves have not yet begun to move radially outward. Thus, instead of sinking, bumps or nodules are formed.

The level of energy at which a rimbed depression becomes a nodule (and vice versa) varies with the substrate material. Furthermore, it has been found that there is a high degree of consistency within a given batch, although varying between different sets of aluminum nickel-phosphorus substrates or batches, and that there is a close relationship between energy level and nodule size. Therefore, determining the appropriate energy level in different situations requires several trials.

The formation of nodules, rather than rimmed depressions, is a surprising and useful outcome. Nodules produced on a given substrate under the same conditions (pulse level, attenuation and pulse width) often exhibit very high uniformity in height, eg, less than about 1 nm standard deviation. More generally,
Nodules are a preferred discontinuity because they are less likely to form debris and enhance liquid lubricant replenishment as compared to sinking.

Accordingly, another aspect of the present invention is a process for selectively surface-treating a magnetic recording medium, comprising: a. Forming a specular substrate surface on the non-magnetic substrate body so that the substrate surface is substantially flat and has a nominal roughness; b. The radiant energy is selectively focused at a plurality of locations to cover the processing area of the substrate surface to controllably change the selected surface topography, and at each location, the surface reference plane of the selected surface. Upward approximately 2.5-2
Causing a hemispherical nodule to form in the range of 5 nm and having a height greater than said standard roughness, c. Depositing the magnetic film as a substantially uniform thickness layer on the substrate surface to create a recording surface.

A preferred application of the processing area is an annular band which provides a dedicated transducing head contact area adjacent to a smoother data recording area. Typically, this band is relatively narrow and located on the radially inner edge of the data recording area.

Depending on the degree of control of the nodule size, a further improvement is provided, namely an annular transition zone between the contact zone and the recording zone. In particular, over the entire area of the annular transition zone between the contact zone and the recording zone, it can be controllably varied to reduce the nodule size in the radial direction, for example to reduce the height from approximately 20 nm. . The slope across the transition zone reduces disturbances as the transducing head moves radially between the contact zone and the data zone, reducing the likelihood of head failure.

Still another embodiment of the present invention is a process for preparing the texture of a glass substrate in preparation for a subsequent step of coating a magnetic thin film. The process comprises: a. Depositing a metal as a metal layer of uniform thickness of at least 5 nm on a glass substrate, b. Concentrating coherent radiant energy at a plurality of locations covering the processing area of the metal layer to controllably change the substrate topography at each of said locations to form a surface irregularity at each of said locations, forming said irregularities; Making the regularity have a height of 3 to 200 nm from a surface reference plane of the substrate surface.

Thus, according to the present invention, radiant energy is selectively injected into a magnetic recording medium to control surface topography over the data, contact and transition zones. Radiative energy polishing removes trace scratches and other needle-like features created by mechanical tissue preparation and polishing and enhances data band smoothness, corrosion resistance and signal reproduction characteristics. The formation of nodules by radiant energy tissue preparation results in a very uniform roughness across the contact zone and, if desired, a controlled roughness gradient across the transition zone. A lower flying height of the conversion head is realized, and data can be recorded at a higher density.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, FIGS. 1 and 2 show a magnetic data recording and reading medium, in particular a substantially flat and horizontal rotatable rotatable about vertical axis. Magnetic disk 1 with upper surface 18
6, is shown. Rotary actuator (not shown)
Support the conversion head support arm 20 in a cantilever manner. The magnetic data transducing head 22 is attached to the free end of the support arm 20 via a suspension 24, which provides gimbal movement of the head, i.e., finite vertical movement and rotation about the pitch and roll axes. enable. The rotary actuator and the support arm are pivotally mounted to move the head 22 in an arcuate path along a generally radial direction of the disk 16.

An opening 26 is provided in the center of the disk 16 to receive a disk drive shaft (not shown) used to rotate the disk. Disk opening 26
Between the outer peripheral edge 28 and the outer peripheral edge 28, the upper surface 18 has four sectors: a radially inner sector 30 for fastening the disk 16 to the shaft, a dedicated transducing head contact zone 32, and a transition zone 3.
4 and a data band 36 serving as an area for recording and reading magnetic data.

When the disk 16 is stationary or spinning at a speed substantially below its normal operating range, the head 22 contacts the top surface 18. However, when the disk is rotating within the normal operating range, the head 22 and the upper surface 18 are moved along the rotation direction of the disk.
An air bearing or air cushion is formed by the air flowing between the head and the head, and supports the head at a distance from and parallel to the recording surface. Typically, the distance between the flat bottom surface 38 and the top surface 18 of the head 22, known as the head "fly height", is approximately 10 microinches (2
54 nm) or less. In order to maximize the data storage density of the disk 16, the flying height must be as low as practicable.

With respect to the recording and reading operations, the rotation of the disk and the rotation of the rotating arm are controlled in harmony, so that the transducing head 22 is positioned near a desired position in the data band 36. After the reading and recording operations, when the disk 16 is decelerated, the support arm 20 is moved radially inward so as to place the head 22 directly above the contact zone 32. In this manner, when the disk 16 is sufficiently decelerated so that the head and upper surface can engage, the head is positioned to engage only the contact band. Prior to the next data recording and reading or retrieval, the disk 16 is accelerated from the stopped state,
Are engaged with the disk in the contact zone 32. Head 22
The rotating arm does not pivot until is separated from the contact zone and supported by the air bearing.

The magnetic disk 16 is polished and ground on an aluminum substrate disk.
nding or other mechanical finish to provide a substantially flat top surface 40. Next, a nickel-phosphorous alloy is plated on the top surface of the substrate disk to obtain a non-magnetic layer 42 having a uniform thickness in the range of approximately 2-10 microns. Following the plating step, Ni-P
The top surface of the alloy layer, ie, the substrate surface 44, is polished to a roughness of less than approximately 0.1 microinches (2.54 nm). For this purpose, a cloth, paper or pad saturated with cerium oxide, silicon carbide or other suitable grit is applied or filled. Liquid slurry containing grit can also be used.

The laser treatment is preferably performed after mechanical polishing of the substrate surface 44. Processing is performed using a laser texture preparation and polishing apparatus. As shown in FIG. 3, apparatus 46 includes a shaft 48 for rotatably holding a substrate disk labeled 50. The laser module 52
Carriage 54 reciprocates in the radial direction of the substrate disk
Attached to. The laser module includes a neodymium: yttrium lithium fluoride (Nd: YLF) diode laser 56, a collimating optical system for collimating the diode laser power to generate a beam 60 having a radius of about 1 mm, an attenuator 62, and a beam 60. Surface 4
Focusing optical system 64 for converging to or near 4
including. As shown, the attenuator 62 is an ND filter,
For example, it is a glass plate 66 having a thin film 68 formed by changing the thickness by sputtering so that the transmittance is inclined across the glass plate. The movement of the glass plate 66 is along the abscissa relative to the beam direction along the ordinate and controllably alters the percentage of beam energy transmitted to the collection optics 58, thereby changing the energy intensity at the substrate surface. Let it.

The diode laser 56 is, for example, a Spectra Physics company.
Nd: YLF diode-pumped laser, available from Sigma-Aldrich, Inc. Preferably, the diode laser 56 is pulsed for tissue preparation and polishing, but a continuous mode (less preferred) can be used for polishing. Apparatus 46 is controllable in tissue preparation and polishing operations to determine the topography and properties of various substrate surfaces. In essence, tissue preparation and polishing includes means for rotating the substrate disk 50 at a controlled speed, while the carriage 54 moves the laser module at a controlled radial speed. At the same time, the diode laser is controlled to provide a pulsed beam at a predetermined frequency and a predetermined pulse width. If desired, the rotational speed of the disk can be gradually reduced as the laser module moves radially outward to maintain a substantially constant linear velocity.

The beam 60 is perpendicular to the substrate surface 44 and defines an area of the beam impinging on the surface in a substantially circular area 70. If desired, it is of course possible to make the collision area elliptical by changing the beam non-vertically or by changing the collection optics, for example to a cylindrical lens. In any case, the way to change the surface is
The energy distribution and duration of the collision area, i.e., the period during which the collision area 70 matches a particular part of the substrate surface;
Depends on. As a result of the simultaneous disk rotation and laser module movement, the impact area 70 moves in a spiral path across the substrate surface. While a spiral path is preferred, the laser module 52 can be moved stepwise with each revolution of the disk so that the path is concentric.

The energy distribution in the collision area depends on several factors, including the power emitted by the diode laser 56, the attenuation, and the degree of laser beam convergence. The energy distribution also depends on the mode in which the diode laser 56 operates. For example, the TEM ₀₀ mode results in a Gaussian distribution of energy and concentrates energy in the center of the collision area. To make the convergence sharp,
This leads to concentration of energy near the collision area.

When the beam 60 is pulsed, the duration is primarily a function of the pulse width. The duration is also slightly affected by the disk rotation speed and the radial speed of the laser module 52. Furthermore, if the diode laser is pulsed, the surface topography is a function of the pulse frequency, ie, the number of pulses per unit time.

Using a lower energy beam 60, there is an energy threshold at the substrate surface that allows the formation of an upwardly protruding nodule rather than a rimged depression. The operating ranges of several parameters required to produce nodules having a height ranging from approximately 0.1 to approximately 2 microinches (2.5 to 51 nm) have been found. More specifically, the diode laser 56 is emitted at a level ranging from 1 to 50 μJ, more preferably 1 to 6 μJ. Given a low energy level, the beam 60 is sharply focused to a focal diameter, i.e., the impact area diameter, more preferably in the range of 5 to 15 microns. The diode laser 56 operating in the TEM ₀₀ mode produces a Gaussian distribution of energy in the beam 60 and thus over the collision area 70. The concentration of energy obtained near the center of the collision area promotes nodule formation. Diode laser 56 is preferably pulsed as described above and has a duration including a time when the pulse level is greater than or equal to 10% of the peak amplitude;
That is, the pulse width is preferably in the range of 5 to 200 ns (more preferably about 20 to 40 ns).

A typical nodule formed by the diode laser 56 is shown in a perspective view in FIG. Nodules are
It protrudes above the plane of the specular surface of the substrate surface, the reference plane 72, by a height "h" of 0.3 micron inches (7.6 nm). Nodule 74 has a diameter "d" of approximately 5 microns. At its base, the nodule is surrounded by a small annular depression. Increasing the power at which the diode laser 56 is emitted within the operating range described above tends to increase the height and diameter of the nodule. Reducing the collision area 70 with a sharp focus tends to increase the height of the nodule. However, when increasing the firing power and / or pulse width, avoid increasing the energy distribution beyond the threshold, the energy value at which the laser will form a rimmed depression instead of a nodule due to thermal infiltration. You need to be careful.

As will be described in more detail below, the texture preparation of the substrate surface 44 may be accomplished by contacting the contact zone 32 or any other surface area designated for texture modification, such as a nodule 74. Forming a number of nodules. Compared to the rimbed depression described above, the nodule is preferred for various reasons. Perhaps most apparently, the roughness obtained by using lumps that can be formed as high as approximately 0.1 micron inches (2.54 nm) is reduced. A closely related advantage is the enhancement of uniformity due to nodule formation, which is mainly due to Nd: YLF diode lasers, especially Nd: YLF at low peak power levels.
Diode laser. Compared to a mechanically polished surface needle-like feature with similar roughness,
The rimmed depression shows excellent uniformity, but with regard to uniformity, the nodule provides a further substantial improvement.

Nodule tissue preparation enhances surface toughness with respect to damage due to repeated contact with the transducing head. FIG.
5 and FIG. 5 shows that although the height is exaggerated relative to the diameter of the nodule, the nodule 74 is rounded and slightly convex, ie, the diameter “d” is the height “h”. More than
, It can be seen that it is more stable than a rim-filled depression of the same size. In conclusion, presumably with substantially no depression, the nodule tissue preparation surface is better replenished with smoothness to improve frictional properties and make it difficult to collect or trap debris.

In addition to controlling the properties of the individual nodules 74, the device 46 is controlled to impart the desired pattern or distribution of nodules throughout the tissue preparation area of the substrate surface. To give an example of the above control parameters, the substrate disk 50 rotates at a speed that can vary depending on the radial rotation of the diode laser, resulting in a linear (arc) speed of approximately one meter per second. A pulse with a pulse width of 10 nanoseconds has a frequency of 50,000 pulses per second, ie, 2
One pulse is given every 0 microseconds. as a result,
The distance between the centers of adjacent nodules will be 20 microns. Furthermore, the laser module 52 moves in the radial direction at a speed that varies with the disk rotation speed, for example, about 20 microns per rotation. As a result, a spiral pattern of the nodules is obtained in which both the distance between the adjacent nodules and the adjacent distance between the circular loci of the nodules are 20 microns.

As another example, even if the speed of the disk rotation and the radial movement of the laser module is kept constant,
The pulse frequency is 5 per second depending on the radial position of the beam.
A similar pattern can be formed by controllably changing the average value of 0000 pulses.

In any case, at the aforementioned linear velocity, the beam impact area 70 will be only 10n at each pulse width time.
Only move m. Since this distance is small with respect to the diameter of the collision area, it can be considered that the collision area is essentially stationary during the formation of each nodule.

The spiral pattern of the nodule is preferred because it involves a single, continuous path and requires only a few seconds for complete tissue preparation, ie, completion of nodule formation across contact zone 32.

Apparatus 46 is not limited to surface texture preparation, but may also be used to polish data bands 36 and other selected areas on the substrate surface. Laser polishing is shown schematically in FIGS. As can be seen in FIG. 6, the laser beam 60 is focused on the substrate surface 44, ie, the upper surface of the nickel-phosphorous layer 42. The beam 60 is not as sharply focused as in the case of nodule formation. For polishing, the preferred diameter of the focal spot or beam impact area is 50
In the range of １００100 microns. The diode laser is emitted at a power level in the range of 1-50 μJ, more preferably 1-6 μJ. The use of a spatial filter allows for a more uniform distribution of power over the surface (ie, a non-Gaussian distribution). The energy distribution within beam 60 and collision area 70 is fairly uniform, ie, non-Gaussian. Thus, the tendency to form nodules is significantly reduced. However, there is sufficient energy distribution to melt the nickel-phosphorous material inside and near the collision zone, the zone where the material is melted has a diameter of at least about 30 microns. The pulse width is the same as when forming the nodule,
That is, 5 to 200 ns, more preferably approximately 20 to 40 ns
ns.

Once the pulse is instantaneous, the nickel-phosphorous melting range is limited, as shown in FIG. Most preferably, the fusion zone is very thin, for example, on the order of 38 nm (1.5 microinches). However, if the thickness of the nonmagnetic layer 42 is sufficient, good results can be obtained if the thickness is up to about 250 nm (10 micron inches), and satisfactory results can be obtained if the thickness is up to about 1000 nm. Can be More specifically, the depth of the molten region 76 is approximately 10% of the nickel-phosphorus layer thickness.
% Should not be exceeded. The minimum depth of the fusion zone 76 is determined by heat loss to the surrounding disk material substantially immediately after the end of the pulse. This property is important in the polishing process because substantial heating over the entire thickness of layer 42 will cause undesirable crystallization upon resolidification and magnetize the nickel-phosphorous layer. However, the depth of the fusion zone 76 exceeds the depth of the trace scratches due to mechanical polishing and thus contributes to the removal of peaks and valleys formed by such scratches (and other needle-like features).

As can be seen from FIG. 7, the rightward movement of beam 60 removes the needle-like features, leaving a low frequency waveform or undulation in the trail of the moving liquefaction region. FIG. 8 shows a completely polished surface.

Polishing may be performed by continuous operation of the diode laser 56, but a pulsed laser is preferred. Given a pulse width of nanoseconds and a frequency of 50,000 pulses per second, the substrate disk 50 rotates at a substantially slow speed and is directed such that successive pulses overlap the collision area. Thus, despite relatively large collision areas, laser polishing requires a longer time than tissue preparation, for example, 10 to 330 seconds.

FIGS. 9-12 show traces of surface roughness measured by atomic force microscopy and show two applications of laser polishing. The first is the laser treatment of a mechanically textured surface 77, a dedicated head contact or data band, shown in FIGS. 9 and 10, which is independent of the very low transducing head fly height. FIG. 9 illustrates the needle-shaped features 78 present after mechanical tissue preparation. The surface roughness is approximately 25 nm in terms of the maximum peak height above the surface reference plane 80.

The roughness trace in FIG. 10 is after laser polishing and is an example in which the surface roughness is substantially reduced to approximately 10 nm. Furthermore, the substrate material melted by the laser energy flows to remove substantially all of the needle-like features, leaving a smooth, rounded feature 82 that creates a low frequency waveform. The removal of sharp peaks is particularly advantageous because sharp peaks are likely to cause breakage upon head contact. Therefore, the surface after the laser treatment has an improved ability to withstand intentional or accidental head contact, and generates less debris.

FIG. 11 shows a surface roughness trace 84 of a very finely polished, or "super-polished", substrate disk. The surface roughness based on peak height is less than 2 nm, but trace scratches form needle-like phases 86.

FIG. 12 shows the same substrate after the laser polishing. The roughness of the front substrate has actually increased to approximately 3 nm. However, the removal of trace scratches and the deformation to a more rounded and gentler curvilinear profile outweighs any disadvantages caused by a slight increase in surface roughness. First, as with laser-treated tissue-prepared surfaces, the rounded features 88
Increased compatibility to withstand accidental contact with the transducing head. Second, the increased uniformity of the protective carbon film enhances corrosion resistance because the magnetic film and other layers deposited in subsequent processing tend to duplicate the topography of the substrate surface. By virtually eliminating trace scratches and needle-like features of the layers deposited by subsequent processing,
Signal quality is also improved.

FIGS. 13 to 15 show a method for selectively preparing tissues in different regions of the substrate surface using the apparatus 46. FIG.

FIG. 13 shows a laser-prepared contact zone 9.
4 and mechanically polished and super polished data band 96
Shows a portion of a substrate disk 90 with a substrate surface 92 that has been selectively treated to create a substrate. Along the data band, the substrate 92 is polished to a peak roughness of less than about 3 nm, comparable to the result of the mechanical polishing shown in FIG. The substrate surface is likewise polished along the contact zone, preferably to the edge of the contact zone. Thereafter, the substrate surface is irradiated with a beam 60 over the entire contact band.
To 0.3 to 1.0 microinches (7.6 to 2 micron inches).
(5.4 nm). A major advantage other than tissue preparation of the contact zone is that no steps are required between the data zone 96 and the contact zone 94. Therefore, choose a gradual transition, or choose a step that provides a margin that is used to record data like other methods and a narrow, steep step that increases the risk of transducing head failure, There is no need to make a choice.

In FIG. 14, the substrate surface 100 of the substrate disk 102 is processed by the device 46 to form the contact band 10.
4. A data band 106 and a transition band 108 between the contact band and the data band are provided. Beam 60 is injected over contact zone 104 to provide spaced nodules 110
Is 0.8-1.0 microinch (20.3-25.
4 nm), more preferably about 0.8 microinch (about 20 nm).

Over the radial direction of the transition zone 108, the height of the nodule 112 changes incline, ie, approximately 0.8-1.
0 microinch (20.3-25.4 nm) to approximately 0.1-0.3 microinch (2.5-7.6 nm)
It becomes lower gradually. The nodule 112 is formed by pulsing the diode laser 56 as described above.
Although formed in a continuous spiral path, an additional feature is that the energy in the impact area 70 is gradually reduced as the beam 60 moves radially outward. This means that the emission power of the diode laser is maintained at a constant level, but the ND filter 62 moves gradually in the horizontal axis direction (arrow in FIG. 3), thereby gradually attenuating the beam passing through the glass plate 66. Performed by The slope of the transition zone is a function of the radial width of the transition zone and the maximum and minimum height of the nodule.

Data band 106 is first processed by laser polishing after mechanical fine polishing, as described in connection with FIGS. 6-8, to achieve a surface profile similar to that shown in FIG. Following laser polishing, the data band 106 is further exposed to the beam 60, and
It forms a nodule that is less than 0.3 microinches (2.5-7.6 nm) in height, ie nodule 112. This means that the controlled surface roughness is sufficient for most transducer head flying heights, resulting in a controlled texture that can withstand accidental transducer head contact.

FIG. 15 shows contact band 120 and data band 1
Shown is a substrate disk 116 having a substrate surface 118 that has been processed to form 22. Over the entire contact zone 120, the substrate surface was mechanically textured to 25 nm
A degree of surface peak roughness is provided. The data band 122 is further finely polished to a surface peak roughness of up to approximately 3 nm.

After mechanical polishing, the entire substrate surface is laser polished. Throughout the contact zone 120, laser polishing substantially reduces the surface roughness to a value on the order of 10 nm. Polishing does not significantly change the 3 nm surface roughness across the data band. Laser polishing fluidizes the substrate material across the contact and data bands, eliminating trace scratches and replacing the needle-like features with a rounded shape. Thus, the entire substrate surface exhibits better corrosion resistance.

FIG. 16 shows a glass substrate 124 that has been treated to provide an energy absorbing layer 126. Preferably, the energy absorbing layer is a metal layer, for example a glass substrate 1
Sputtering to a thickness of at least 5 nm on 24,
Chromium applied by vapor phase plating or plating. Other metals such as tungsten or titanium can also be used.

The metal layer 126 is exposed to a pulsed laser beam to prepare a contact zone 128. This is shown in FIG.
And in substantially the same manner as in the formation of the nodule discussed in connection with FIG.
0 μJ, more preferably 1-6 μJ), convergent zone diameter (5-15 microns), and pulse width (5-200 n)
s, more preferably 20-40 ns). Surface topography is affected by changes in these parameters, as discussed above.

Also, the surface topography is affected by the thickness of the chromium layer. When very thin films, for example 5 to 10 nm thick, are deposited, chromium acts virtually exclusively as a cause of local energy absorption, thereby causing local deformation of the glass (surface melting, local melting). Micro-destruction). FIG. 17 shows an irregular, somewhat star-shaped destruction 130.
FIG. 18, while FIG. 18 is an atomic force microscopy profile trace of these fractures showing a needle-like appearance as compared to the nodule described above. The height of the rupture varies over a wider range than the nodule, ie (0.1-8 micron inches).

When the thickness of the chromium layer is increased, for example, 10 to 1
Within a thickness of 00 nm, the resulting topography combines the microfractures described above with rounded nodules of chromium as described in connection with the aluminum nickel-phosphorous substrate. In conclusion, for materials thicker than 100 nm, the topography is virtually exclusively determined by nodule formation.

FIG. 19 shows a laser tissue preparation and polishing apparatus 132 similar to the apparatus 46, including a laser beam 134.
Are focused on the substrate surface 136 of the substrate disk 138. The disk rotates on a shaft 140 while the carriage 142 translates the laser module radially. The laser module includes a diode laser 146 that supplies energy to beam collimating optics 148. The columnar beam passes through the attenuator 150 and is transmitted to the focusing optics 152 and then to the substrate surface.

The difference lies in the structure of the attenuator. Attenuator 150
Is a polarizer, which includes an upstream polarizer 154, a downstream polarizer 156 aligned with the polarizer 154, and a mechanism 158 for rotating the polarizer 156. The rotation of the polarizer 156 aligns the respective polarization axes (indicated by the arrows) of the polarizers 154 and 156 and can be arranged to provide maximum transmission of laser energy. As the polarizer 156 moves out of alignment, the transmittance of the polarizer gradually decreases.
Thus, the rotation of the polarizing plate 156 causes the ND in FIG.
A result similar to the linear movement of the filter is obtained.

Referring to FIG. 2, the fabrication of the magnetic disk 16 involves the selective organization of the substrate disk and the deposition of several layers after polishing. A layer of chromium is sputtered onto substrate surface 44, preferably about 10-100 nm.
Up to a thickness of. Thereby, the underlayer 160
Can advantageously control the epitaxy and crystal structure of the magnetic film, so that an underlayer 160 particularly suitable for forming a magnetic thin film to be formed later can be obtained. The recording layer 162 of a magnetic material, such as cobalt / tantalum / chromium or an alloy of cobalt / platinum / chromium, is approximately 10-50.
Sputter deposited to a thickness of nm. Finally,
A protective layer 164, for example, carbon, is deposited on the recording layer for approximately 5-30.
Sputter deposited to a thickness of nm. As described above, removal of the needle-like phase by laser polishing of the substrate surface
Allowing the carbon layer 164 to be deposited with a more uniform thickness,
Enhance corrosion resistance.

FIG. 20 shows yet another laser tissue preparation and polishing apparatus 166 that focuses a laser beam 168 on a substrate surface 170 of a substrate disk 172. A diode laser 174 generates a laser beam,
The beam is collimated by collimating optics 176 before being provided to scanning assembly 178. Attenuator 180,
For example, an ND filter can be moved horizontally, as indicated by the arrows, to selectively attenuate the beam.

As is well known to those skilled in the art, the optics (including lenses and mirrors) within scanning assembly 178 are operated to translate the beam relative to substrate disk 172. Device 46 and device 132
As in the case of (1), the laser diode moves on a spiral path which reflects the path obtained by the radial movement of the laser diode in accordance with the rotation of the disk. Thus, in apparatus 166, the optics increase in complexity, but the substrate disk to be processed may remain stationary.

As described above, according to the present invention, the tissue of the magnetic recording medium is selectively prepared, and the conversion head contact zone,
A data band and an intermediate transition zone are obtained, with respect to surface roughness, either to enhance the uniformity of the contact or landing zone or to control the radial or roughness gradient across the transition zone. Strictly controlled. Compared to the already known laser discontinuities, especially depressions surrounded by raised rims, nodules improve non-uniformity, increase resistance to head contact when surface roughness is low, and provide additional lubricant. Shows improvement and reduced debris collection. Laser polishing enhances performance in eliminating trace scratches and improving corrosion resistance and signal integrity, even when compared to extremely smooth mechanically polished surfaces.

[Brief description of the drawings]

FIG. 1 is a plan view of a solid-state magnetic disk and a conversion head that moves substantially radially with respect to the disk.

FIG. 2 is an enlarged partial sectional view of the magnetic disk of FIG. 1;

FIG. 3 is a front view of an apparatus for performing polishing and tissue preparation on a magnetic disk.

FIG. 4 is an enlarged perspective view of a lump formed on the surface of a magnetic disk substrate by the apparatus of FIG. 3;

FIG. 5 shows the profile of the nodule of FIG.

FIG. 6 schematically illustrates a laser polishing step of a mechanically polished substrate.

FIG. 7 schematically illustrates a laser polishing step of a mechanically polished substrate.

FIG. 8 schematically illustrates a laser polishing step of a mechanically polished substrate.

FIG. 9 illustrates an atomic force microscope surface profile of a mechanically textured substrate.

FIG. 10 illustrates the surface profile of FIG. 9 after laser polishing of the substrate.

FIG. 11 illustrates an atomic force microscope surface profile of a mechanically polished substrate.

FIG. 12 illustrates the surface profile of FIG. 11 after laser polishing of the substrate.

FIG. 13 illustrates the surface profile of a substrate with a dedicated head contact zone that has been laser textured.

FIG. 14 illustrates the surface profile of a substrate with laser textured contact and transition zones, and a laser polished data zone.

FIG. 15 illustrates the surface profile of a substrate with a mechanically textured contact zone and a mechanically polished data zone, followed by both laser treated zones.

FIG. 16 is a cross-sectional view of a glass substrate near the top surface that has been treated to enhance its energy absorption capability.

FIG. 17 is a plan view of the upper surface of the substrate, illustrating a group of surface breakdown discontinuities.

FIG. 18 illustrates one profile of the discontinuity group of FIG.

FIG. 19 is a front view of another tissue preparation and polishing apparatus.

FIG. 20 is a front view of still another tissue preparation and polishing apparatus.

 ──────────────────────────────────────────────────続 き Continuing the front page (72) Inventor Quo, David S. United States 94546 Castro Valley, California, Sydney Circle 18923 F-term (reference) 5D006 CA01 DA03 DA04 5D112 AA02 AA03 AA24 BA03 KK01

Claims (1)

[Claims] 1. A method for assembling a substrate surface of a glass substrate in preparation for a subsequent magnetic thin film deposition, comprising: depositing a non-magnetic metal on the glass substrate and forming at least 5 n
forming a non-magnetic metal layer having a uniform thickness of m and selectively focusing coherent radiant energy at a plurality of locations on the processing area of the metal layer and controlling the substrate topography at each of those locations Change to
A surface irregularity is formed at each of these locations, the surface irregularities being 3-20 upwards above the nominal plane of the substrate surface.
Having a height in the range of 0 nm, wherein said surface irregularities are caused by (i) microfracture of glass adjacent to said metal layer and (ii) roundness formed by said metal layer. Such a method, which consists essentially of the irregularities selected from the group of nodules.