JP2005353129A - Manufacturing method of substrate for magnetic recording medium and magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a substrate for substrates for magnetic recording media which can manufacture the substrate for magnetic recording medium corresponding to high recording density at a low cost and high throughput. <P>SOLUTION: The manufacturing method of a substrate for the magnetic recording medium includes a process to contact a mold 2 on a surface of the substrate 1 and stress pressure to a surface of the substrate 1, and a transfer process which heats a surface of the substrate 1 by irradiating the surface of the substrate 1 with a laser beam 3 and transcribe the surface shape of the mold 2 on the surface of the substrate 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a substrate for a magnetic recording medium in which the surface of a substrate is flattened with high accuracy and a nano-order level uneven shape is formed as necessary. The present invention also relates to a magnetic recording medium including a magnetic recording medium substrate manufactured by such a manufacturing method.

  In the hard disk drive (HDD), there is an increasing need for recording large-capacity data such as images and moving images, and the use for home appliances such as a video recorder is rapidly expanding in addition to the use as a storage device for computers. For this reason, technological development for providing a magnetic recording medium with a further increased storage capacity at a low price has been actively promoted.

  In order to improve the recording density of the magnetic recording medium, it is possible to increase the flatness on the surface of the substrate used for the magnetic recording medium and intentionally form a nano-order level uneven shape on the substrate surface as necessary. Required.

  First, improvement in flatness on the surface of the magnetic recording medium substrate will be described.

  As the recording density of the magnetic recording medium increases, the flying height of the magnetic head decreases, so that the flatness of the magnetic recording medium substrate is strictly controlled so as to cope with this. For example, in a 2.5 inch substrate with a recording density of about 50 Gbit / square inch, the height difference of the substrate surface is set to a maximum of about 5 μm in order to prevent the magnetic head from crashing. It has been demanded.

  Further, in order to keep the flying height of the magnetic head stable, it is necessary to strictly control the surface roughness of the magnetic recording medium substrate. Specifically, the surface roughness (Wa) having a wavelength of about 50 μm or more, called “microwaviness”, is suppressed to about 0.5 nm or less, or a short wavelength component that can be measured by using an atomic force microscope. It is required to suppress the surface roughness (Ra) to about 0.5 nm or less.

  In addition, as a nano-order level uneven shape intentionally formed on the surface of the magnetic recording medium substrate, there is an uneven shape (circular groove) with a pitch of several tens of nm called a texture. By forming the texture on the surface of the substrate, the magnetic anisotropy of the recording layer is controlled and the magnetic characteristics of the magnetic recording medium are improved.

  In order to manufacture a magnetic recording medium substrate that satisfies these requirements, a sophisticated and complicated manufacturing technique such as a polishing technique is required, and the number of processes is increased, so that the manufacturing cost tends to increase.

  On the other hand, in recent years, a substrate for a magnetic recording medium using a glass-based material substrate and applying a glass forming technique has been developed. Glass-based materials have advantages such as higher hardness and lower coefficient of thermal expansion than materials such as aluminum, but in order to form textures uniformly on each substrate, advanced microfabrication processes are required. It becomes necessary and causes an increase in cost.

  In order to solve such a problem, Patent Document 1 uses a molding die (mold) having a circumferential groove formed with a predetermined roughness, and heats the mold and the glass substrate to a predetermined temperature. A method of pressing is disclosed. According to the method of patent document 1, the process of forming a texture by the microfabrication technique on each glass substrate becomes unnecessary.

  In order to improve the recording density of the magnetic recording medium, it is necessary to solve the problems associated with thermal disturbance. Thermal disturbance is a phenomenon that occurs when the recording density is increased by reducing the bit area (magnetization reversal unit) of a magnetic recording medium. (Energy to be directed in one direction) also decreases, so that the thermal energy for disaggregating the magnetization direction cannot be ignored, the magnetization is reversed, and the recorded information is lost.

  Therefore, a patterned medium (discrete medium) or a discrete track medium has been proposed as a medium that can overcome the thermal disturbance without requiring a means for refining the magnetization reversal unit.

  The patterned medium is a medium in which the magnetic film carrying the recording information of the magnetic recording medium is patterned and the magnetic film isolated magnetically is used as a magnetization reversal unit. According to this, since the noise based on the nonuniformity of the shape of the magnetization reversal unit can be reduced, the recording density can be increased. On the other hand, a discrete track type medium is a medium in which a magnetic film is patterned for each recording track and the magnetic film magnetically separated is used as a magnetization reversal unit. According to this, since the noise called side fringe (recording blur) that increases with the narrowness of the recording track can be reduced, the recording density can be increased.

  However, the above-described patterned medium and discrete track type medium require an extremely fine patterning technology of the order of several tens of nanometers in order to achieve a high recording density of several hundred Gbit / square inch level. Processing costs for forming (costs such as photolithography and etching processes) have hindered practical use.

  In recent years, an imprint method capable of achieving nanometer-level patterning at a low cost has been actively researched. The imprint method is a method of transferring a shape formed on the surface of a mold onto a transfer object by pressing a mold (mold) onto the transfer object. Typically, there are a “resist imprint method” using a resist and a “heating direct imprint method” not using a resist.

  Among these, the “resist imprint method” is a method of transferring the shape of the mold to the resist by pressing the mold onto the resist using a substrate coated with the resist. According to this method, the exposure in the photolithography process, which is the main cause of the cost increase, can be omitted, so that the above-described patterned medium and discrete track type medium can be manufactured at a low cost (see, for example, Patent Document 2). . However, it is necessary to further etch the base using the patterned resist as a mask.

  On the other hand, the “heating direct imprint method” is a method in which the surface shape of a mold is directly transferred to a substrate such as glass without using a resist. Patent Document 3 discloses a method of directly forming a nano-order level groove on the surface of a substrate by pressing a molding die having fine processed grooves formed on the surface thereof onto a glass substrate.

  According to the heating direct imprint method, not only the exposure step but also the etching step can be omitted. Therefore, it is considered that the cost reduction effect is greater than the resist imprint method in which only the exposure step can be omitted.

Note that the method of Patent Document 1 described above is also included in the heating direct imprint method because the shape (texture pattern) of the mold is directly transferred to the glass substrate.
JP 2003-85740 A JP 2003-16621 A Japanese Patent Laid-Open No. 9-245345

  However, according to the heating direct imprint method described above, although the exposure process and the etching process can be omitted, it is necessary to heat the substrate and the mold to a high temperature with a heater or the like. For example, in order to transfer the shape of the mold to the surface of the glass substrate, the substrate is in a temperature range from the glass transition point to the softening point (specific temperature varies depending on the glass composition, etc., but is generally 500 to 700 ° C.). Must be heated and heated. Further, after the transfer is completed, the glass substrate must be cooled until the surface of the glass substrate is sufficiently cured. For this reason, time is required for temperature rise and cooling, and the throughput cannot be increased.

  Furthermore, in the heating direct imprint method, it is required to control the surface shape of the substrate with high accuracy by suppressing the shrinkage of the substrate that occurs during the cooling process. For this reason, when the substrate is cooled, imprint conditions such as temperature profiles and pressure profiles of the two molds respectively corresponding to the two substrate surfaces must be precisely controlled. Therefore, it is very difficult to increase the cooling rate of the substrate, and it is impossible to improve both the throughput and the yield.

  The present invention has been made in view of the above circumstances, and an object of the present invention is for a magnetic recording medium in which the surface of a substrate is flattened with high accuracy and a nano-order level uneven shape can be formed with high throughput as required. It is to provide a method for manufacturing a substrate.

  Another object of the present invention is to provide a magnetic recording medium provided with the magnetic recording medium substrate.

  Still another object of the present invention is to provide an apparatus capable of manufacturing the above-mentioned magnetic recording medium substrate, or a transfer capable of efficiently transferring the nano-order level uneven shape formed on the mold to the surface of the substrate. It is to provide a method.

  The method for manufacturing a substrate for a magnetic recording medium according to the present invention includes a step of bringing a mold into contact with the surface of the substrate, applying pressure to the surface of the substrate, and irradiating the surface of the substrate with laser light, thereby And a transfer step of transferring the surface shape of the mold onto the surface of the substrate by heating the surface of the mold.

  In a preferred embodiment, the transfer step is a step of heating and melting the surface of the substrate to a temperature not lower than the melting point of the substrate, or heating the surface of the substrate to a temperature not lower than the glass transition point on the surface of the substrate. And softening process. Here, the light absorption coefficient of the substrate with respect to the laser light is preferably larger than the light absorption coefficient of the mold with respect to the laser light.

  In another preferred embodiment, the substrate includes a transfer layer and a base material that supports the transfer layer, and the transfer step irradiates the transfer layer with the laser light, thereby transferring the transfer layer. In this step, the surface of the mold is transferred to the transfer layer by heating the layer. Here, the transfer step includes a step of heating and melting the transfer layer to a temperature equal to or higher than the melting point of the transfer layer, or a step of heating and softening the transfer layer to a temperature equal to or higher than the glass transition point of the transfer layer. Including. It is preferable that the light absorption coefficient of the transfer layer with respect to the laser light is larger than the light absorption coefficient of the base material with respect to the laser light. The light absorption coefficient of the mold with respect to the laser light is preferably smaller than the light absorption coefficient of the transfer layer with respect to the laser light. The laser beam is preferably irradiated through the mold. The substrate preferably has a transfer layer formed of silicon or germanium and a base material formed of glass that supports the transfer layer. In the transfer step, it is preferable to heat the transfer layer by transferring a laser beam having a wavelength of 200 to 300 nm to the transfer layer.

  In a preferred embodiment, the mold has a concavo-convex shape corresponding to a recording bit or a recording track of a magnetic recording medium. Here, the thickness of the transfer layer is preferably larger than the height of the concavo-convex shape formed in the mold.

  The magnetic recording medium of the present invention includes a magnetic recording medium substrate obtained by any one of the above manufacturing methods, and a recording layer or a high magnetic permeability soft magnetic layer formed on the substrate.

  In a preferred embodiment, the recording layer or the high magnetic permeability soft magnetic layer comprises a plurality of portions magnetically separated in recording bit units or recording track units according to the shape transferred onto the surface of the magnetic recording medium substrate. Have.

  The apparatus for manufacturing a substrate for a magnetic recording medium according to the present invention comprises a pressure applying means for bringing a mold into contact with the surface of the substrate and applying pressure to the surface of the substrate, and laser light irradiation for irradiating the surface of the substrate with laser light. Means for transferring the surface shape of the mold to the surface of the substrate by heating the surface of the substrate by the laser beam irradiation means.

  In the transfer method of the present invention, the mold is brought into contact with the surface of the substrate, pressure is applied to the surface of the substrate, and the surface of the substrate is irradiated with laser light to heat the surface of the substrate and And a transfer step of transferring the surface shape of the mold to the surface of the substrate.

  In a preferred embodiment, the substrate includes a transfer layer and a base material that supports the transfer layer. In the transfer step, the transfer layer is transferred by transferring the laser light to the transfer layer. Heating and transferring the surface shape of the mold to a transfer layer.

  According to the method for manufacturing a magnetic recording medium substrate according to the present invention, the surface of the substrate is heated to a high temperature in a short time by the irradiation of the laser beam, and the surface of the substrate after completion of the transfer is quickly solidified. Both high throughput and high yield, which could not be realized by the “heating direct imprint method”, can be achieved at low cost.

  In the production method of the present invention, a method of using a substrate having a transfer layer and a base material supporting the transfer layer and irradiating the transfer layer with laser light is a preferred embodiment. According to this embodiment, it is possible to perform transfer to a transfer object with a laser beam having a lower output than in an embodiment using a substrate having no transfer layer. Further, when the same laser light source is used, the present invention capable of processing at a lower output can also provide an effect that the substrate can be easily increased in area because the irradiation area can be increased.

  According to the transfer method of the present invention, it is possible to transfer a nano-order level uneven shape formed on the surface of the mold to the surface of the substrate in a very short time with low cost and high throughput.

  When manufacturing a substrate for a magnetic recording medium by a conventional heating type direct imprint method, it is necessary to heat the substrate to a predetermined temperature (a temperature from the glass transition point to the softening point) by a heating means such as a heater. The manufacturing cost is rising. The inventor has found that the transfer of a fine pattern can be realized at a high throughput by irradiating the surface of a substrate, which is a pattern transfer target, with a laser beam and heating the substrate, and arrived at the present invention.

(Embodiment 1)
First, with reference to FIGS. 1A to 1C, a first embodiment of a method for manufacturing a magnetic recording medium substrate according to the present invention will be described. FIGS. 1A to 1C are process cross-sectional views schematically showing a process for manufacturing a magnetic recording medium substrate in the present embodiment.

  In the present embodiment, a magnetic recording medium substrate is manufactured using a mold 2 having a surface with high flatness on which no uneven pattern is formed.

  First, as shown in FIG. 1 (a), the mold 2 is brought into contact with the surface of the substrate 1 in a roughly processed state, and pressure is applied to the surface of the substrate 1 using a press device (not shown). Details of a press apparatus (imprint apparatus) that can be suitably used in the present embodiment will be described later.

  Next, as shown in FIG. 1B, the surface of the substrate 1 pressed by the mold 2 is irradiated with the laser beam 3 to heat the surface of the substrate 1. The laser beam 3 preferably has a wavelength that passes through the mold 2 and is efficiently absorbed by the surface of the substrate 1. The intensity and irradiation time of the laser beam 3 need to be at a level at which the surface of the substrate 1 is heated to a temperature at which the pattern of the mold 2 can be transferred with an applied pressure.

  In this embodiment, before the heating of the substrate 1 by the irradiation of the laser beam 3 is started, the surface of the mold 2 is brought into contact with the substrate 1 to apply pressure. The pressure applied to the surface of the substrate 1 can be set in the range of 0.1 to 100 MPa, for example, but may be set appropriately according to the material, shape, size, etc. of the substrate 1 and the mold 2 to be used.

  According to the present embodiment, since the surface of the substrate is heated to a temperature that can be processed in a short time (for example, 1 millisecond or less) by laser light irradiation, the processing time in the imprint method using the conventional heating means However, the pattern can be transferred in a very short time.

  Here, the depth of the “surface of the substrate 1” heated by the irradiation of the laser beam 3 only needs to include at least the depth at which the shape of the mold 2 is transferred. For example, when using the mold 2 on which a concavo-convex pattern having a depth of several tens of nm is used, the depth of the region heated to the transferable temperature on the surface of the substrate 1 is within a range of about several tens to 200 nm. It is enough. However, when a surface with high flatness is formed on the roughly processed substrate 1 as in this embodiment, the surface of the substrate 1 has a large unevenness, or the substrate 1 is curved and the flatness is high. It may have declined. In such a case, it is preferable to heat from the surface of the substrate 1 to a deep portion to soften and melt.

  In this embodiment, the surface pattern of the mold 2 is transferred to the substrate 1 by heating the surface of the substrate 1 by irradiation with the laser beam 3 and melting at least the surface region. However, depending on the material of the substrate 1, it is not always necessary to melt the surface, and it may be sufficient to raise the temperature to a softening level.

  When the surface of the substrate 1 is softened by irradiation with the laser beam 3, it is necessary to heat the surface of the substrate 1 to a temperature above the glass transition point, but the surface of the substrate 1 is heated to a temperature above the melting point. There is no need to melt. On the other hand, when the surface of the substrate 1 is melted by irradiation with the laser beam 3, it is necessary to heat the surface region of the substrate 1 to a temperature equal to or higher than the melting point. Specifically, when silicon (melting point: about 1414 ° C.) is used as a substrate, the mold pattern can be effectively transferred by controlling the pressure within a range of 0.1 to 100 MPa and irradiating laser light under the following conditions. Can be done.

Wavelength: 248nm
Pulse width: 20 nanoseconds Irradiation frequency: 1
Power density: 1.5 J / cm ²

  According to this embodiment, since the surface of the substrate 1 melts in a short time, the shape formed on the surface of the mold 2 is transferred to the surface of the substrate 1 in an extremely short time (within about 1 millisecond). become. In the conventional heating type direct imprinting method, considering that the transfer to the substrate 1 generally takes 5 minutes or more including heating and cooling required before and after the transfer, this embodiment significantly increases the production efficiency. To do.

  When the output of the laser light source is low, the irradiation area is narrowed to ensure a predetermined power density (the value obtained by dividing the output of the light source by the irradiation area), and the mold is moved repeatedly while moving within the substrate. It is also possible to perform so-called step-and-repeat, which performs a transfer process.

  According to the conventional heating direct imprint method, it is necessary to heat not only the substrate but also the mold, for example, to a temperature above the glass transition point (about 500 to 700 ° C.) at the time of transfer. For example, there is no need to intentionally heat the mold 2 to a high temperature.

  After completion of the laser light irradiation, the transfer process is completed by separating the substrate 1 onto which the shape of the mold 2 has been transferred from the mold 2 as shown in FIG. According to this embodiment, the surface of the substrate 1 is quickly cooled and solidified after the laser irradiation is stopped. For this reason, the mold 2 can be separated from the substrate 1 within 10 seconds after the laser irradiation is stopped. As a result, one press (transfer) process cycle can be reduced to 15 seconds or less. In consideration of the fact that the conventional heating direct imprint method requires a time of about 5 to 10 minutes, the transfer time can be greatly shortened by this embodiment.

  The substrate 1 used in this embodiment needs to have a light absorption coefficient of the substrate 1 as large as possible with respect to the irradiated laser light 3 so that the surface of the substrate 1 is efficiently heated by the irradiation of the laser light 3. On the other hand, in this embodiment, since the surface of the substrate 1 is irradiated with the laser beam 3 so as to pass through the mold 2, it is preferable that the light absorption coefficient of the mold 2 with respect to the laser beam 3 is as small as possible. Further, since the mold 2 is brought into contact with the surface of the substrate 1 and pressure is applied, the mold 2 is preferably formed of a material having as high a mechanical strength as possible. For example, sapphire or quartz is preferable as the material of the mold 2 that satisfies such requirements.

  The surface shape of the mold 2 may be any shape as long as a predetermined shape can be imparted to the surface of the substrate 1. That is, a mold whose surface is flattened with high accuracy as in this embodiment may be used, or a mold whose surface is processed so as to have a fine uneven pattern as in Embodiment 2 described later. May be used.

(Embodiment 2)
Next, a second embodiment of the method for manufacturing a magnetic recording medium substrate according to the present invention will be described with reference to FIGS.

  The manufacturing method in the second embodiment and the manufacturing method in the first embodiment are the same except that the surface shapes of the substrate 1 and the mold 2 to be used are different. Therefore, the details of the pressure application method and the laser beam irradiation means are the same as those in the first embodiment, and the detailed description will not be repeated here.

  In this embodiment, a flat substrate whose surface is not processed is used. Further, as shown in FIG. 2A, the surface of the mold 2 has a fine concavo-convex pattern, that is, a concavo-convex shape in which both the pitch and the depth are on the order of nanometers. An uneven pattern corresponding to the track is formed.

  First, as shown in FIG. 2A, a micro-processed mold 2 is brought into contact with the surface of the substrate 1, and pressure is applied to the surface of the substrate 1 using a press device (not shown). The pressure applied to the surface of the substrate 1 can be set, for example, in the range of 0.1 to 100 MPa.

  Next, as shown in FIG. 2B, the surface of the substrate 1 pressed by the mold 2 is irradiated with the laser beam 3, and the surface of the substrate 1 is heated and melted. The irradiation condition of the laser beam 3 is the same as the condition described in the first embodiment. By this laser irradiation process, the fine uneven pattern of the mold 2 is transferred to the molten surface of the substrate 1.

  After the irradiation of the laser beam 3 is stopped and the melted portion on the surface of the substrate 1 is solidified, the mold 2 is pulled away from the substrate 1 as shown in FIG. At this stage, the surface of the substrate 1 has an uneven shape to which the fine pattern of the mold 2 is transferred.

  Next, as shown in FIG. 2D, the recording layer 4 is deposited on the surface of the substrate 1 where the irregularities are formed. The recording layer 4 is formed of a magnetic film usually used in the field of magnetic recording media, and is formed of, for example, a cobalt-based alloy (CoCr, CoCrPt, CoPt, etc.). The recording layer 4 can be easily formed on the substrate by a known method such as sputtering.

  Thereafter, as shown in FIG. 2E, the upper surface of the recording layer 4 is flattened by polishing or the like. At this time, the portion of the recording layer 4 located on the convex portion of the substrate surface is removed, and the planarization is performed so that only the portion located in the concave portion remains. As a result, the recording layer 4 is composed of regions 4A and 4B magnetically separated in recording bit units or recording track units defined by the concavo-convex pattern transferred to the surface of the substrate 1.

  By sequentially depositing a protective layer and a lubricating layer (not shown) on the recording layer 4 thus obtained, the magnetic recording medium of this embodiment can be obtained.

  The laminated structure including the recording layer 4 is formed by a known method such as a sputtering method.

  The magnetic recording medium obtained in this way was provided with a recording layer in which a fine concavo-convex pattern was not formed because the recording layers 4A and 4B were magnetically separated in units of recording bits or recording tracks. Compared with a “continuous recording medium”, noise caused by a transition region and a recording fringe can be remarkably reduced. As a result, a high recording density magnetic recording medium is obtained.

  Furthermore, according to the present embodiment, a nanometer-order shape corresponding to a recording bit or a recording track can be formed on the surface of the substrate in a short time, so that mass production of a magnetic recording medium with high throughput and low cost is possible. Is possible. Therefore, the above-described patterned medium and discrete track type medium can be provided at low cost.

  FIG. 3 is a cross-sectional view schematically showing another configuration example of the magnetic recording medium according to the present embodiment. The configuration of the magnetic recording medium in FIG. 3 is the same as the configuration of the magnetic recording medium shown in FIG. 2E in that it has a high magnetic permeability soft magnetic layer 5 formed between the substrate 1 and the recording layer 4. Is different.

  The high magnetic permeability soft magnetic layer 5 shown in FIG. 3 can be formed on the substrate 1 by the same method as the method of forming the recording layer 4 described with reference to FIGS. 2 (d) and 2 (e). Specifically, first, after the concave / convex pattern of the mold 2 corresponding to the recording bit or the recording track is transferred to the surface of the substrate 1 by the above-described method, the high permeability soft magnetic layer 5 is sputtered on the surface of the substrate 1. It is deposited by a known method. The high magnetic permeability soft magnetic layer 5 is formed of a magnetic film usually used for a magnetic recording medium, and is formed of a magnetic material such as NiFe (Permalloy), NiFeMo, FeTaC, or FeAlSi. Next, the high magnetic permeability soft magnetic layer 5 is planarized by polishing or the like, thereby magnetically separating the high magnetic permeability soft magnetic layer 5 in units of recording bits or recording tracks. Thereafter, after depositing the recording layer 4 on the high magnetic permeability soft magnetic layer 5 by a method such as sputtering, a protective layer and a lubricating layer (not shown) may be sequentially laminated.

(Embodiment 3)
Next, a third embodiment of the method for manufacturing a magnetic recording medium substrate according to the present invention will be described with reference to FIGS. 4A to 4C are process cross-sectional views schematically showing the manufacturing process of the magnetic recording medium substrate in this embodiment. In the present embodiment, a substrate on which a transfer layer 6 is formed on a base material 7 is used, and transfer is performed with a mold 2 having a high degree of flatness on which no concavo-convex pattern is formed.

  First, as shown in FIG. 4A, a substrate on which a transfer layer 6 that efficiently absorbs laser light is formed on a base material 7 is prepared. The surface of the substrate 7 is in a roughly processed state, and the surface of the transfer layer 6 deposited thereon is also rough.

  Next, the mold 2 is pressed against the transfer layer 6 by a press device (not shown), and then the laser beam 3 is irradiated.

  In this embodiment, since the transfer layer 6 is formed on the base material 7, it is possible to use the base material 7 formed of a material (such as glass) that hardly absorbs the laser light 3. Furthermore, in this embodiment, the transfer layer 6 can be sufficiently heated with a laser beam having a lower output than in the first embodiment in which a substrate that does not have the transfer layer 6 is used. This is because the base material 7 formed of a material having a relatively low thermal conductivity, such as glass, is used, so that the heat diffusion from the transfer layer 6 heated by the laser beam 3 to the base material 7 is performed. This is because the transfer layer 6 is efficiently heated. Further, since the reflection of the laser beam 3 at the interface between the substrate 7 and the transfer layer 6 occurs, the amount of absorption of the laser beam 3 by the transfer layer 6 increases, and this also efficiently heats the transfer layer 6. Is possible.

  A preferable material for the transfer layer 6 varies depending on the wavelength of the laser beam 3, but when the laser beam 3 having a wavelength of 200 to 300 nm is irradiated, the transfer layer 6 can be formed from a semiconductor material such as silicon or germanium. Since the light absorption coefficient of silicon is maximized with respect to laser light having a wavelength of 200 to 300 nm, it is efficiently heated. On the other hand, germanium has a light absorption coefficient comparable to that of silicon with respect to a laser beam having a wavelength of 248 nm, a specific heat smaller than that of silicon, and a low melting point. Therefore, when the transfer layer 6 is formed from germanium, the pattern can be transferred with a laser beam having a lower output than when the transfer layer 6 is formed from silicon.

  The preferable thickness of the transfer layer 6 is determined according to the shape to be transferred. When the mold 2 having a flat surface is used as in the present embodiment, the thickness of the transfer layer 6 can be made very thin as 10 to 100 nm. It is possible to melt the whole.

  The transfer layer 6 is formed on the base material 7 with an arbitrary thickness by using a known thin film deposition method represented by a sputtering method or the like. The surface shape of the transfer layer 6 is not particularly limited, and as shown in FIG. 4A, the surface may be uneven, or the transfer may be performed with a flat surface as in Embodiment 5 described later. Layers may be used.

  In this embodiment, a substrate in which the transfer layer 6 is directly formed on the base material 7 is used, but the present invention is not limited to such a case. For example, an intermediate layer such as a high magnetic permeability soft magnetic layer may be inserted between the base material 7 and the transfer layer 6.

  The pressure applied to the substrate by the mold 2 can be set, for example, in the range of 0.1 to 100 MPa, but can be appropriately set according to the material, shape, size, etc. of the transfer layer 6, the base material 7, and the mold 2 to be used. It ’s fine.

  In the present embodiment, as shown in FIG. 4B, the laser beam 3 is irradiated to the transfer layer 6 pressed by the mold 2 so as to pass through the mold 2. For this reason, it is preferable that the laser beam 3 has a wavelength that passes through the mold 2 and is efficiently absorbed by the transfer layer 6.

  Note that the irradiation direction of the laser light 3 in the present embodiment is not limited to the direction shown in FIG. 4B, and even if the transfer layer 6 is irradiated so as to pass through the substrate 7 from below the substrate 7. good. In this case, the substrate 7 is preferably transparent to the laser light 3.

  When the transfer layer 6 is softened by irradiation with the laser beam 3, it is necessary to heat the transfer layer 6 to a temperature not lower than the glass transition point. However, the transfer layer 6 is melted by heating to a temperature not lower than the melting point. There is no need. On the other hand, when the transfer layer 6 is melted by irradiation with the laser beam 3, it is necessary to heat the transfer layer 6 to a temperature equal to or higher than the melting point.

  After the end of the laser beam irradiation, as shown in FIG. 4C, the transfer process is completed by separating the transfer layer 6 onto which the shape of the mold 2 has been transferred and the substrate 7 from the mold 2. According to this embodiment, the transfer layer 6 is quickly cooled and solidified after the laser irradiation is stopped. For this reason, the mold 2 can be separated from the transfer layer 6 and the substrate 7 within 10 seconds after the laser irradiation is stopped. As a result, one press (transfer) process cycle can be reduced to 15 seconds or less.

  The transfer layer 6 used in the present embodiment needs to have a light absorption coefficient as large as possible with respect to the laser beam 3 to be irradiated so that the transfer layer 6 is efficiently heated by the irradiation of the laser beam 3.

Example 1
Hereinafter, specific examples of the present embodiment will be described.

  First, by using an RF sputtering method, a silicon transfer layer having a thickness of 50 nm is formed on a glass substrate having a Ra of 1.2 nm and a Wa of 0.8 nm, so that the surface roughness (Ra) is 1.1 nm and a minute amount. A substrate having a swell (Wa) of 0.8 nm was prepared. Here, Ra is a value measured by an atomic force microscope, and Wa is a value measured by passing through a low-pass filter having a cutoff wavelength of 50 μm as a result of measurement by a scanning white interference method.

  Next, using a quartz mold having both Ra and Wa on the surface of 0.3 nm, transfer to the transfer layer was performed according to the following conditions.

Pressure: 1 MPa
Wavelength: 248nm
Pulse width: 20 nanoseconds Irradiation frequency: 1 shot Power: 0.12 J / cm ²

  The Ra and Wa of the transfer layer after transfer were both 0.3 nm, and the time required for the transfer process was 1 second or less. According to this example, a sufficient 1 nm level concavo-convex pattern formed on the mold could be transferred in a short time with high accuracy.

(Embodiment 4)
Next, a fourth embodiment of the method for manufacturing a magnetic recording medium substrate according to the present invention will be described with reference to FIGS.

  The manufacturing method in the fourth embodiment and the manufacturing method in the third embodiment are the same except that the surface shapes of the base material 7, the transfer layer 6, and the mold 2 to be used are different. Therefore, details of the pressure application method and the laser beam irradiation means are the same as those in the third embodiment, and a detailed description thereof is omitted.

  In this embodiment, the surface shape of the mold 2 is transferred to the transfer layer 6 formed on the substrate 7 having a flat surface.

  First, as shown in FIG. 5 (a), the mold 2 whose surface is finely processed is brought into contact with the transfer layer 6, and pressure is applied to the transfer layer 6 using a press device (not shown). The pressure applied to the transfer layer 6 can be set in the range of 0.1 to 100 MPa, for example. The pitch and depth of the concavo-convex pattern formed on the mold 2 used in this embodiment has a nano-order level size, and has a shape that defines recording bits or recording tracks of the magnetic recording medium. .

  Next, as shown in FIG. 5B, the transfer layer 6 pressed by the mold 2 is irradiated with the laser beam 3, and the transfer layer 6 is heated and melted. The irradiation condition of the laser beam 3 is the same as the condition described in the third embodiment. By this laser irradiation step, the fine uneven pattern of the mold 2 is transferred to the molten surface of the transfer layer 6.

  After the irradiation of the laser beam 3 is stopped and the melted portion in the transfer layer 6 is solidified, the mold 2 is separated from the substrate composed of the transfer layer 6 and the base material 7 as shown in FIG. At this stage, the transfer layer 6 has an uneven shape to which the fine pattern of the mold 2 is transferred.

  Next, as shown in FIG. 5D, the recording layer 4 is deposited on the surface of the transfer layer 6 on which the concavo-convex pattern is formed. The type and formation method of the recording layer 4 are the same as those in the second embodiment.

  Next, as shown in FIG. 5E, the upper surface of the recording layer 4 is flattened by polishing or the like. At this time, the portion of the recording layer 4 located on the convex portion of the transfer layer is removed, and flattening is performed so that only the portion located in the concave portion remains. As a result, the recording layer 4 is composed of regions 4A and 4B magnetically separated in recording bit units or recording track units defined by the concavo-convex pattern transferred to the transfer layer 6. By sequentially depositing a protective layer and a lubricating layer (not shown) on the recording layer 4 thus obtained, the magnetic recording medium of this embodiment can be obtained. The laminated structure including the recording layer 4 is formed by a known method such as a sputtering method.

  In the magnetic recording medium of the present embodiment, since the regions 4A and 4B of the recording layer 4 are magnetically separated in units of recording bits or recording tracks, the recording layer 4 includes a recording layer in which a fine uneven pattern is not formed. Compared with a “continuous recording medium”, noise caused by a transition region and a recording fringe can be remarkably reduced. As a result, a high recording density magnetic recording medium is obtained.

  Furthermore, according to the present embodiment, a nanometer-order shape corresponding to a recording bit or a recording track can be formed on the surface of the substrate in a short time, so that a high recording density magnetic recording medium can be produced with high throughput and low cost. Provided in.

  FIG. 6 is a cross-sectional view schematically showing another configuration example of the magnetic recording medium manufactured by the manufacturing method of the present embodiment. The magnetic recording medium shown in FIG. 6 is the same as the magnetic recording medium shown in FIG. 4E except that an intermediate layer composed of the high permeability soft magnetic layer 5 is formed between the base material 7 and the transfer layer 6. It has the same configuration as the configuration.

  The high magnetic permeability soft magnetic layer 5 may be formed on the transfer layer 6 by the same method as the method for forming the recording layer 4 in the second embodiment. Specifically, first, after transferring the concavo-convex pattern of the mold 2 corresponding to the recording bit or recording track to the transfer layer 6 by the above-described method, a high permeability soft magnetic layer 5 is applied to the transfer layer 6 by a known method such as sputtering. It is formed by the method. Next, the high permeability soft magnetic layer 5 is planarized by polishing or the like, so that the high permeability soft magnetic layer 5 is magnetically separated in units of recording bits or recording tracks.

  Thereafter, the recording layer 4 is deposited on the high magnetic permeability soft magnetic layer 5 by a known forming method such as sputtering, and then a protective layer and a lubricating layer (not shown) are sequentially laminated to obtain a magnetic recording medium. It is done.

  FIG. 7 is a cross-sectional view schematically showing another configuration example of the magnetic recording medium manufactured by the manufacturing method of the present embodiment. The magnetic recording medium of FIG. 7 is different from the configuration of FIG. 5 in that a high magnetic permeability soft magnetic layer 5 is formed between the recess formed in the transfer layer 6 and the recording layer 4. The high magnetic permeability soft magnetic layer 5 can be formed on the substrate by the same procedure as that for forming the recording layer 4 in the magnetic recording medium of FIG. The soft magnetic layer 5 shown in FIG. 7 is composed of a plurality of regions separated from each other by the convex portions of the transfer layer 6.

(Embodiment 5)
Next, an embodiment of a magnetic recording medium substrate manufacturing apparatus (imprint apparatus) according to the present invention will be described with reference to FIG. The illustrated apparatus includes pressure applying means for bringing the mold 2 into contact with the surface of the substrate and applying pressure to the surface of the substrate, and laser light irradiation means for irradiating the surface of the substrate with laser light.

  The pressure application means in this embodiment includes a base 10 that holds the substrate, a pressing plate 8 that brings the mold 2 into contact with the surface of the substrate, and a clamp that is disposed at both ends of the pressing plate 8 and holds the base 10 and the pressing plate 8 together. 9 and a screw 11 that fixes the clamp 9 and the base 10 and applies pressure to the surface of the substrate.

  In the apparatus shown in FIG. 8, the mold 2 and the pressing plate 8 are not integrated, and each is composed of independent parts. The reason for this is to make the mold 2 as thin as possible, as will be described below. That is, in order to form a fine pattern on the surface of the mold 2, it is necessary to execute a microfabrication process using an exposure apparatus or an etching apparatus. Typically, these apparatuses have a thickness of 1 mm or less. Designed to form a pattern on a semiconductor wafer. For this reason, when the mold 2 becomes too thick, it becomes difficult to form a fine pattern on the surface of the mold 2 using these existing apparatuses. In order to form the mold 2 thinly, it is preferable to configure the pressing plate 8 as a component different from the mold 2. A preferable thickness range of the mold 2 is 0.5 mm to 50 mm.

  In addition, after forming a fine pattern on the surface of the mold 2, you may affix the pressing plate 3 on the back surface of the mold 2, and integrate these. In addition, if there is an exposure apparatus or an etching apparatus that can perform fine processing on the relatively thick mold 2, the mold 2 and the pressing plate 8 can be integrally formed from the same material (for example, quartz). It is.

  In the imprint apparatus of FIG. 8, the transfer layer 6 is pressed by the mold 2 by tightening the screw 11, but the method of applying pressure to the substrate is not limited to such a case. Instead of using the screw 11, pressurization may be performed using a gas such as compressed air or a liquid.

  The laser beam irradiation means in this embodiment is arranged at a position where the laser beam 3 is irradiated from the back surface of the pressing plate 8 toward the transfer layer 6. For this reason, the laser beam 3 emitted from the laser beam irradiation means passes through the pressing plate 8 and the mold 2 and enters the transfer layer 6. Therefore, it is necessary that not only the mold 2 but also the holding plate 8 is made of a material that efficiently transmits laser light.

  However, the irradiation direction of the laser beam 3 is not limited to the example shown in FIG. When the base 10 and the base material 7 are formed of a material that transmits laser light, the transfer layer 6 may be irradiated with the laser light from below so as to transmit these.

  The type of the laser beam 3 is not particularly limited as long as it can sufficiently heat the transfer layer 6 in a short time. In order to melt the transfer layer 6 at a high output in a short time, it is preferable to use an excimer laser device as the laser beam irradiation means.

(Example 2)
Next, an example of manufacturing the magnetic recording medium of the present invention using the imprint apparatus of FIG. 8 will be described.

  In this example, a substrate having a flat surface was prepared by forming a silicon transfer layer 6 having a thickness of 50 nm on a disk-shaped glass substrate 7 having a diameter of 26 mm by using an RF sputtering method. The mold 2 is made of quartz having the same diameter as the substrate. On the surface of the mold 2, 1000 concentric lines having a width of 70 nm and a step of 30 nm were formed with a period of 150 nm centered on a position having a radius of 10 mm by a dry etching apparatus equipped with an inductively coupled plasma source.

Next, after setting the substrate and the mold 2 on the pedestal 10, the screw 11 was tightened to apply a pressure of about 5 MPa to the surface of the substrate. Thereafter, the laser beam 3 was irradiated from the back surface of the pressing plate 8 toward the transfer layer 6. The wavelength of the laser light was 248 nm, the pulse half width was 25 ns, and an excimer laser device was used as the light source. The laser beam intensity (power) at the time of irradiation was 0.12 J / cm ² , the shape of the irradiated region was a circle with a diameter of about 30 mm, and the number of times of irradiation was one.

The laser beam intensity in this embodiment corresponds to about 1 or less of the sufficient laser beam intensity (about 1.5 J / cm ² ) applied when a substrate having no transfer layer is used.

  After the laser beam irradiation, the screw 11 was loosened, and the mold 2 was released from the substrate on which the surface shape of the mold 2 was transferred. As a result of observing the substrate surface after completion of the transfer with an atomic force microscope, it was confirmed that the same 30 nm step as the step applied to the mold 2 was also formed on the surface of the substrate.

  As described above, according to this example, the uneven shape of the order of several tens of nanometers formed on the surface of the mold 2 could be accurately transferred to the transfer layer of the substrate in a very short time.

  In the transfer method according to the present invention, the mold is brought into contact with the surface of the substrate, the pressure is applied to the surface of the substrate, and the surface of the substrate is irradiated with laser light to heat the surface of the substrate. And a transfer step of transferring the surface shape of the mold. This transfer method is not only useful for producing the magnetic recording medium substrate of the present invention, but also suitably used for producing electronic devices that require microfabrication, such as semiconductors and display devices. It is done.

  INDUSTRIAL APPLICABILITY According to the present invention, a substrate for a high recording density magnetic recording medium having a surface shape adjusted at a nano-order level can be mass-produced at low cost and with high throughput, which is extremely useful industrially.

  In the magnetic recording medium according to the present invention, since the recording layer or the high magnetic permeability soft magnetic layer is magnetically separated in units of recording bits or recording tracks, the recording density is improved.

FIGS. 3A to 3C are process cross-sectional views schematically showing a manufacturing process in the first embodiment. (A) to (e) are process cross-sectional views schematically showing the manufacturing process in the second embodiment. 6 is a cross-sectional view schematically showing another configuration example of a magnetic recording medium that can be manufactured by the manufacturing method of Embodiment 2. FIG. (A) to (c) is a process cross-sectional view schematically showing a manufacturing process in the third embodiment. (A) to (e) are process cross-sectional views schematically showing the manufacturing process in the fourth embodiment. 10 is a cross-sectional view schematically showing another configuration example of a magnetic recording medium that can be manufactured by the manufacturing method of Embodiment 4. FIG. FIG. 11 is a cross-sectional view schematically showing still another configuration example of a magnetic recording medium that can be manufactured by the manufacturing method of Embodiment 4. It is sectional drawing which shows typically the structure of the typical shape transfer apparatus used for this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Mold 3 Laser beam 4 Recording layer 4A, 4B Each area | region magnetically isolate | separated in the recording layer 5 High magnetic permeability soft magnetic layer 6 Transfer layer 7 Base material 8 Holding plate 9 Clamp 10 Base 11 Screw

Claims (19)

Contacting the mold with the surface of the substrate and applying pressure to the surface of the substrate;
A transfer step of irradiating the surface of the substrate with a laser beam to heat the surface of the substrate and transfer the surface shape of the mold to the surface of the substrate;
A method for manufacturing a magnetic recording medium substrate comprising:   The method for manufacturing a substrate for a magnetic recording medium according to claim 1, wherein the transfer step includes a step of heating and melting the surface of the substrate to a temperature equal to or higher than a melting point of the surface of the substrate.   2. The method for manufacturing a substrate for a magnetic recording medium according to claim 1, wherein the transfer step includes a step of heating and softening the surface of the substrate to a temperature equal to or higher than a glass transition point on the surface of the substrate.   4. The method of manufacturing a magnetic recording medium substrate according to claim 1, wherein a light absorption coefficient of the substrate with respect to the laser light is larger than a light absorption coefficient of the mold with respect to the laser light. The substrate has a transfer layer and a base material that supports the transfer layer,
2. The magnetic recording medium substrate according to claim 1, wherein the transfer step is a step of irradiating the transfer layer with the laser beam to heat the transfer layer to transfer the surface shape of the mold to the transfer layer. Manufacturing method.   The method of manufacturing a magnetic recording medium substrate according to claim 5, wherein the transfer step includes a step of heating and melting the transfer layer to a temperature equal to or higher than a melting point of the transfer layer.   6. The method of manufacturing a magnetic recording medium substrate according to claim 5, wherein the transfer step includes a step of heating and softening the transfer layer to a temperature equal to or higher than a glass transition point of the transfer layer.   The method for manufacturing a substrate for a magnetic recording medium according to claim 5, wherein a light absorption coefficient of the transfer layer with respect to the laser light is larger than a light absorption coefficient of the base material with respect to the laser light.   The method for manufacturing a substrate for a magnetic recording medium according to claim 5, wherein a light absorption coefficient of the mold with respect to the laser light is smaller than a light absorption coefficient of the transfer layer with respect to the laser light.   The method for manufacturing a substrate for a magnetic recording medium according to claim 5, wherein the laser beam is irradiated through the mold.   The magnetic recording medium according to claim 5, wherein the substrate includes a transfer layer formed of silicon or germanium, and a base material formed of glass that supports the transfer layer. Manufacturing method for industrial use.   The method for manufacturing a substrate for a magnetic recording medium according to claim 5, wherein the transfer step melts the transfer layer by transferring a laser beam having a wavelength of 200 to 300 nm to the transfer layer.   The method for manufacturing a substrate for a magnetic recording medium according to claim 1, wherein the mold has an uneven shape corresponding to a recording bit or a recording track of the magnetic recording medium.   The method for manufacturing a magnetic recording medium substrate according to claim 13, wherein a thickness of the transfer layer is larger than a height of the concavo-convex shape formed on the mold.   A magnetic recording medium comprising: a magnetic recording medium substrate obtained by the manufacturing method according to claim 1; and a recording layer or a high magnetic permeability soft magnetic layer formed on the substrate.   The recording layer or the high magnetic permeability soft magnetic layer has a plurality of portions magnetically separated in units of recording bits or recording tracks by a shape transferred onto the surface of the magnetic recording medium substrate. Item 16. The magnetic recording medium according to Item 15. Pressure applying means for bringing the mold into contact with the surface of the substrate and applying pressure to the surface of the substrate;
Laser light irradiation means for irradiating the surface of the substrate with laser light;
With
An apparatus for manufacturing a substrate for a magnetic recording medium, wherein the surface of the mold is transferred to the surface of the substrate by heating the surface of the substrate by the laser light irradiation means. Contacting the mold with the surface of the substrate and applying pressure to the surface of the substrate;
A transfer step of irradiating the surface of the substrate with a laser beam to heat the surface of the substrate and transfer the surface shape of the mold to the surface of the substrate;
A transcription method comprising: The substrate has a transfer layer and a base material that supports the transfer layer,
The transfer method according to claim 18, wherein the transfer step includes a step of transferring the laser light to the transfer layer to heat the transfer layer to transfer the surface shape of the mold to the transfer layer.