KR20010040843A - Magnetic recording medium with patterned substrate - Google Patents

Abstract

The magnetic recording medium of the present invention exhibits an improved Hr, SNR and S * suitable for the high density of the recording area, and the continuous layers 22, 22 ', 23, 23', 24, 24 ', 25, It is obtained by forming a uniformly patterned Al or Al alloy layer 21, 21 'on a nonmagnetic substrate 20 that is substantially replicated to 25', 26, 26 '. In one embodiment, sputter deposition of Al or Al alloy layers 21, 21 'onto the substrate 20, and sputtering layers 21, 21' to form a plurality of substantially uniform hexagonal cells comprising aluminum dioxide. Forming an oxide film). Hexagonal patterns are replicated in successively deposited and epitaxially grown magnetic layers 24, 24 'such that the magnetic gains are separated.

Description

Magnetic recording medium with patterned substrate {MAGNETIC RECORDING MEDIUM WITH PATTERNED SUBSTRATE}

Magnetic disks and disk drives are typically used to store magnetizable data. Typically one or more discs are located proximate to the recording surface of the disc and rotate in the central axis along with the radially moving data conversion head. The magnetic disk is generally housed in the magnetic disk unit in a stationary state with a magnetic head having a specific rod that presses in elastic contact with the disk surface. For ultra-high density recording, which exhibits adequate mechanical properties for write-read performance, such as high magnetic force above 2500 Hersted and high magnetic overlites of about 40 dB and small glide height avalanches from about 0.75 to about 0.85 μinch. It is very difficult to manufacture a magnetic recording medium.

In operation, the magnetic disk is generally driven by the contact start stop (CSS) method, where the head starts to slide to the surface of the disk when the disk starts to rotate. When a certain high rotational speed is reached, the head floats in the air while maintaining a certain distance from the surface due to the dynamic pressure effect of the air flow generated between the disk and the sliding surface of the head. In the write and read operation, the conversion head is supported by the air bearing as the disc rotates to be kept at the control distance of the recording surface. The magnetic head unit is arranged so that the head can move freely in both the periphery and the radial direction of the disc, and in the floating state, data can be recorded or retrieved on the surface of the disc at a desired position.

In the shutdown operation of the disc drive, the rotational speed of the disc decreases and the head slides onto the surface of the disc, eventually stopping in contact with the disc and being pressed. Therefore, the conversion head is in contact with the recording surface while the disc is fixed and accelerated from the stop and just before it comes to a complete stop. Each time the head and disk assembly are driven, the sliding surface of the head stops and slides to the disk surface, floats in air and slides and stops to the surface of the disk.

It is desirable to keep each conversion head as close to the associated recording surface as possible during the write and read operations, ie to minimize the flying height of the head. This purpose is particularly important as the recording density per area increases. Density per area (Mbits / in ² ) is the recording density per unit area and corresponds to the track density (TPI) multiplied by the tracks per inch and bits per inch (BPI). Therefore, a smooth recording surface is preferred, and also a smooth facing of the conversion head is desired, so that the head and the disk are located in close proximity to the air bearing with constant motion supporting the head with an additional increase in predictability. However, other factors work the opposite way. If the head surface and the recording surface are too flat, the exact matching of the surface will cause excess stiction and friction during the start and stop phases. Thus, the head and the recording surface are worn out and finally "head crash" occurs. Therefore, there is a purpose against each other that reduces head / disk friction and minimizes the transducer flying height.

In order to satisfy the above objects, the recording surface of the magnetic disk is provided with a rough surface to reduce the friction of the head / disk, typically by a technique such as "texturing". Conventional texturing techniques include trimming the surface of the disk substrate to provide texture before successively depositing coatings such as underlayers, substrate layers, carbon overcoats and lubricious topcoats. Here the textured surface of the substrate is regenerated on the surface of the magnetic disk.

A typical longitudinal recording medium is shown in FIG. 1 and includes a substrate 10 made of an aluminum alloy, such as an aluminum (Al) or aluminum-magnesium (Al-Mg) alloy, plated on an amorphous nickel-phosphorus (NiP) layer. do. Optionally the substrate comprises glass, ceramics, glass-ceramic materials and graphite. Substrate 10 is typically a chromium (Cr) or chromium alloy underlayer (11, 11 '), cobalt (Co) based alloy magnetic layers (12, 12'), protective overcoat (13) 13 '), carbon and lubricity topcoats 14, 14'. As the Cr underlayers 11 and 11 ', a composite including a plurality of sub-sublayers 11A and 11A' may be used. Cr underlayers 11, 11 ′, Co base magnetic alloy layers 12, 12 ′ and protective overcoats 13, 13 ′ are typically sputtered in an apparatus comprising a continuous deposition chamber. Conventional Al-alloy substrates have NIP plating primarily serving as a suitable surface to provide texture for increasing the hardness of Al substrates. The texture is reproduced on the disk surface to serve substantially as a landing area.

Higher density and larger capacity magnetic disks require a smaller flying height, i.e. the distance between the disk surface of the CSS drive and the head floating. The requirement to reduce the flying height of the head due to high recording density and capacity makes it difficult to control the texturing accurately to avoid head crash.

Conventional techniques for providing a textured surface to a disk substrate include mechanical processes such as polishing. For example, U.S. Patent No. 5,202,810 to Nakamura et al. Conventional mechanical texturing techniques have several drawbacks. For example, it is difficult to provide a clean textured surface due to debris formed by mechanical polishing. In addition, surfaces are inevitably scratched during mechanical processes, which leads to inefficient glide properties and large defects. Many preferred substrates are also difficult to process by mechanical texturing. The limited facet by the above undesirable mechanical texturing leads to the use of substantially many inexpensive substrates and also to the use of conductive graphite substrates which facilitates achieving high coercive forces.

Optionally, mechanical texturing can use a laser to form a landing area. For example, U.S. Patent No. 5,062,021 to Ranjan et al. Another optional mechanical texturing is disclosed in U.S. Patent No. 5,166,006 to Lal et al. And includes chemical etching.

U.S. Patent No. 08 / 608,072, filed February 28, 1996, discloses a non-magnetic substrate comprising glass, glass-ceramic material, and a metal layer such as titanium or titanium alloy formed on a NiP chemically plated Al-Mg alloy substrate. A magnetic recording medium having a texturing surface is disclosed. However, it is difficult to manufacture a magnetic recording medium having a moderately high coercive force of more than 3000 Ersted, in particular more than 2500 Ersted, such as 3300 Ersted, together with sputter texturing.

The requirement for high recording density per area increases the requirement of thin film magnetic recording media for coercivity, residual squareness, low media noise and narrow track recording performance. It is extremely difficult to produce a magnetic recording medium that satisfies the above requirements, in particular fixed high density magnetic disk medium for longitudinal recording.

The linear recording density can be increased by increasing the coercive force of the magnetic recording medium. However, the above object can only be achieved by reducing the medium noise and at the same time maintaining the pieces which are not very finely magnetically coupled. Media noise is an important factor limiting the increased recording density of high density magnetic hard disk drives. The media noise in thin films is mainly due to the size of the different pieces and the exchange coupling between the grains. Therefore, to increase the linear density, the media noise can be minimized by controlling the appropriate microstructure.

The magnetic properties associated with residual coercivity (Hr), residual magnetism (Mr), and coercive squareness (S *) depend on the performance of thin magnetic alloy films that are primarily dependent on the microstructure of the magnetic layer affected by the deposited underlying layer. It is important. Typical underlayers include Cr alloyed with various alternative elements in addition to Cr, molybdenum (Mo), tungsten (W), titanium (Ti), chromium-vanadium (CrV). Sublayers with fine flake structures are highly desirable for growing fine flakes of deposited hexagonal closed packed (HCP) magnetic Co or Co alloy layers.

In order to meet the demand for high data storage capacity, it is necessary to manufacture a magnetic recording medium exhibiting high Hr and low medium noise, i.e., high SNR. High Hr is effectively limited to PW50 (pulse width at half of maximum) and can reduce the bit length for high write density. Research on micromagnetics has been underway for many years to reduce Hr and media noise. When the mutual response of the magnetic pieces decreases, Hr decreases and medium noise decreases. Since medium noise is mainly caused by the exchange of magnetic pieces and the electromagnetism interaction, a method of effectively suppressing these elements is to physically or chemically separate the magnetic pieces. Early work in this area focused mainly on the magnetic and lower layers. However, there are limitations to the manner in which the lower and magnetic layers can be grown.

In the past, substrate processing or substrate-related approaches that finally separate the magnetic pieces to reduce the magnetostatic interaction and exchange to increase Hr have not received much attention. For example, previous efforts in this area include photolithographic techniques with high accuracy, but this is very time consuming and expensive. Therefore, large capacity production is virtually impossible.

Application No. 08 / 699,759, filed August 20, 1996, experiences that the Cr film deposited on the surface of the oxidized NiP layer is smaller than the Cr film deposited on the non-oxidized NiP layer. Application No. 08 / 586,529, filed Jan. 16, 1996, discloses a method of depositing a Cr film on the surface of an oxidized NiP film and the deposited Cr film represents the major crystal orientation of (200).

Application No. 08 / 945,084 filed on Oct. 17, 1997 (applicant's case number 2674-052; 50103-092) discloses a magnetic recording medium having a high magnetic force, which has an oxide surface formed on a nonmagnetic substrate. And a seed layer having chromium, a sub-underlayer comprising chromium on the oxide surface of the seed layer, a nickel-aluminum or iron-aluminum underlayer on the underlayer, an intermediate layer on the underlayer containing chromium and a magnetic layer on the interlayer.

Application number 09 / 043,610, filed March 19, 1998 (applicant's case number 2674-057; 50103-098), discloses a magnetic recording medium comprising a surfer textured layer.

Appl. No. 08 / 972,229, filed Nov. 17, 1997, and Applicant No. 2674-072; 50103-118, filed Oct. 21, 1997, Applicant No. 2674-073, filed Oct. 21, 1997; 50103-119 discloses a method of using a laser beam for texturing a data region.

U.S. Patent No. 5,470,636, filed by Wakui et al. On November 28, 1995, forms an oxide film on an Al substrate or Al layer on a substrate and fills the final pores with a nonmagnetic material on the surface. Or a method of forming a landing region by treating an oxide film forming layer having a base is disclosed.

There is a continuing need for a magnetic recording medium that is suitable for high Hr, high SNR and high S * and high recording density per area exhibiting improved flying characteristics. There is also a continuing need for effective costs and methods of producing magnetic recording media having high Hr, SNR and S * and high recording density per area exhibiting improved flying characteristics.

This application claims the priority of February 10, 1998, split application No. 60 / 074,253 as the name of the invention "PATTERN SUBSTRATE FOR HIGH COERCIVITY AND LOW NOISE MEDIA", the entire disclosure of which is cross-referenced herein.

TECHNICAL FIELD The present invention relates to the recording, storage and reading of magnetic data, and more particularly to a rotatable magnetic recording medium such as a thin film magnetic disk having a textured surface for contacting an extrinsic magnetic recording medium. The present invention is particularly applicable to high density magnetic recording media exhibiting low noise, reduced flying height and high coercive force.

1 is a schematic diagram of a conventional magnetic recording medium structure.

2 is a schematic diagram of a magnetic recording medium structure according to the present invention.

3 shows an image of an atomic force microscope (AFM) of a NiP / Al substrate before and after oxide film formation according to one embodiment of the invention.

4A and 4B respectively show Hr and SNR of one embodiment of the present invention for a conventional magnetic recording medium.

An advantage of the present invention is in a magnetic recording medium suitable for longitudinal magnetic recording having a high per-area density showing low medium noise, high Hr, high S * and improved flying characteristics.

Another advantage of the present invention lies in the effective cost and method of producing a magnetic recording medium having high Hr, SNR and S * and high recording density per area exhibiting improved flying characteristics.

According to the present invention, the above advantages and other advantages include: a magnetic recording medium: a nonmagnetic substrate; A layer comprising Al or an Al alloy on a substrate, the Al or Al alloy having a substantially uniform pattern; And a magnetic layer; Here the pattern is replicated on the magnetic layer to form a data region: in part by.

Another aspect of the invention relates to a method of manufacturing a magnetic recording medium. The method above forms Al or an Al alloy on a nonmagnetic substrate; Forming a substantially uniform pattern in the layer; And forming a magnetic layer, wherein the pattern includes replicating the magnetic layer to form a data region.

One embodiment of the invention includes a method of forming an oxide film on an Al or Al alloy layer to form a honeycomb-shaped uniform pattern comprising a substantially hexagonal aluminum oxide cell. One embodiment of the invention further includes a method of texturing a surface of a substrate to form a replicated texturing area on a substantially deposited layer comprising a magnetic layer to form a recording data area.

Other advantages of the present invention are more readily apparent to those skilled in the art from the following description, and one embodiment of the present invention is described with reference to the drawings of the best mode for carrying out the present invention. Those skilled in the art can make various modifications without departing from the present invention. Accordingly, the drawings and the embodiments are only examples, and are not limited thereto.

The present invention addresses the problem of increasing the data storage capacity of a magnetic recording medium by increasing Hr and reducing medium noise. Increased Hr can narrow the pulse width and reduce the bit length to increase the write density. Low medium noise produces high SNR. In one embodiment of the present invention, the above object can be achieved by physically separating the magnetic pieces of the magnetic layer. The separation of the physical magnetic pieces is accomplished by forming a pattern on the substrate that initiates the magnetic film growth pattern. The pattern minimizes the irregularities in the growth of the pieces and narrows the distribution of the magnetic piece units, thereby reducing the generation of zigzag variations. As a result, the interaction of the magnetic pieces is suppressed and the SNR is improved.

One embodiment of the present invention includes the formation of a continuous film on many conventional nonmagnetic substrates. The continuous film is patterned to provide a substantially uniform matrix for thin film growth, which matrix is replicated in a continuously deposited layer comprising a magnetic layer to form a data region. That is, the uniform pattern formed on the substrate according to an embodiment of the present invention serves as a template for the film deposited on the lower layer and the magnetic layer, for example. Therefore, the magnetic unit clusters are replicated according to the substrate pattern and the magnetic fragment clusters are separated by the pattern boundary. In this way the interaction of the fragments is minimal and the SNR is increased.

According to one embodiment of the present invention Al or Al alloy is sputter deposited on a NiP plated Al or Al alloy substrate or a nonmagnetic substrate such as glass, ceramic or glass-ceramic substrate. Al or an Al alloy film may be sputter deposited to a thickness of about 50 kPa to about 5000 kPa, for example from about 500 kPa to about 1500 kPa. According to one embodiment of the invention a substantially uniform pattern is formed on a sputter deposited Al or Al alloy film to serve as a template such that the magnetic piece clusters of the continuously deposited magnetic layer are separated by the pattern boundary. The sputter deposited Al or Al alloy film is formed with an oxide film to form a pattern comprising aluminum oxide, such as a pattern in a substantially honeycomb form. The anodization process may take from about 1 to about 15 mA / cm ² at room temperature for about 1 hour, for example about 10 minutes, for example from about 1% to about 10% at about 5 mA / cm ² , for example about 4% Is treated with hydrogen phosphate (H ₃ P0 ₄ ). The final honeycomb pattern includes hexagonal aluminum oxide cells. The hexagonal cell serves as a template suitable for the deposited magnetic layer to be effective in producing a hexagonal closed packed (HCP) crystal structure in which epitaxial growth is desirable. In addition, the boundary of the hexagonal cell separates the magnetic fragment clusters due to the replication of the magnetic layer, thus minimizing fragment interactions and increasing SNR.

An oxide film forming process Next, the magnetic recording medium is completed by depositing a lower layer and a magnetic layer on the surface where the oxide film is formed on the surface and duplicating the pattern on the substrate. For example, a seed layer such as nickel aluminum (NiAl) is deposited on an Al or Al alloy layer on which an oxide film is formed. The cell is not fully filled. A bottom layer such as CrV is sputter deposited on the NiAl seed layer and a magnetic layer such as a cobalt-chromium-platinum-tantalum (CoCrPtTa) alloy layer is sputter deposited on the bottom layer. A protective overcoat comprising carbon is sputter deposited on the magnetic layer and a lubricious topcoat is formed on the protective oboecoat. This layer is 2 × 10 ^-7 Torr in the base pressure, at about 200 ℃ substrate temperature of 300 ℃, about -250V and the substrate bias sputtering of 30W / cm ² from the 2W / cm ² using a sputtering gas flow rate of about 15sccm of Sputtered deposition can be used to optimize magnetic properties using power density.

One embodiment of the present invention is schematically illustrated in FIG. 2 and includes a nonmagnetic substrate 20 such as NiP plated Al. On each side of the substrate 20, an oxide film sputter deposited Al layer 21, 21 'comprising a uniform honeycomb pattern of substantially hexagonal aluminum oxide cells is formed. Seed layers 22 and 22 ', such as NiAl, are sputter deposited in a honeycomb pattern. Lower layers 23, 23 ', such as CrV, are sputter deposited on seed layers 22, 22', and magnetic layers 24, 24 ', such as CoCrPtTa, are sputter deposited on lower layers 23, 23'. During epitaxial growth, the HCP pattern is formed along the template of the patterned layers 21, 21 'such that the patterned boundaries separate the magnetic pieces, thus minimizing the interaction of the pieces and improving the SNR. . Conventional protective overcoats 25 and 25 ', such as protective overcoats comprising carbon, are sputter deposited on magnetic layers 24 and 24' and conventional lubricating layers 26 and 26 'are also formed thereon.

One embodiment

The magnetic recording medium according to the present invention sputters an Al layer on NiP / Al to form a honeycomb-shaped aluminum oxide pattern comprising a hexagonal cell having a depth of about 500 mm 3 and a diameter of about 500 mm suitable for a magnetic recording bit size. It is made by depositing and forming an oxide film on the Al layer. The NiAl seed layer is deposited on the anodized Al layer, the CrV bottom layer is deposited on the NiAl seed layer, and the CoCrPtTa magnetic layer is deposited on the CrV bottom layer. A protective overcoat comprising carbon is deposited on the CoCrPtTa layer. The Al layer is formed of an oxide film with 4% H ₃ PO ₄ solution and the result is shown in FIG. 3. The left part of Fig. 3 shows the Al layer before the oxide film is formed and the right part shows the honeycomb structure after the oxide film is formed.

The comparative (standard) magnetic recording medium is made using substantially the same layer and deposition state in forming a magnetic recording medium representing the present invention. Here, the Al layer is not sputter deposited on the substrate, except that an oxide film is formed. The magnetic properties of both media are tested using a non-destructive rotating disk magnetometer. Recording characteristics and media noise were measured at a linear density of 240 kfci (kilo flux change per inch) using a Guzik 1601 tester with a magnetoresistive (MR) head with a 0.35 μin gap length and a nominal flying height of 2.1 μin.

The test results are shown in FIGS. 4A and 4B. 4A shows the magnetic properties of a medium (patterned underlayer) and a comparative (standard) medium according to the present invention. Using a patterned Al layer on the substrate in FIG. 4A increases Hr.

4b shows a magnetic recording medium according to the present invention showing an improved SNR of about 0.5 to about 1 dB for a comparative (standard) magnetic recording medium.

According to the present invention, an Al oxide layer patterned to form an oxide film is formed on a nonmagnetic substrate to increase the recording density per area. The oxide film pattern can be formed on any nonmagnetic substrate and is typically a substantially hexagonal honeycomb form comprising a single hexagonal unit cell having a depth of about 50 microns to about 10,000 microns and a diameter of about 50 microns to about 5000 microns. It shows the structure of. Conventional magnetron sputtering techniques can be used to produce the magnetic recording medium according to the present invention. Thus, the present invention can be easily integrated into existing manufacturing apparatus. The present invention makes it possible to form a magnetic recording medium suitable for high density per area recording density with improved Hr, SNR and S *. The present invention also improves SNR by separating magnetic cells at pattern boundaries and thus magnetic interaction is suppressed. The present invention makes it possible to produce any of several types of magnetic recording media, in particular magnetic recording media such as thin film discs with improved flying heights.

One embodiment of the invention is shown or recorded herein, and various modifications and variations are possible within the scope of the invention.

Claims (20)

Nonmagnetic substrates; A layer comprising aluminum (Al) or an Al alloy on the substrate, the layer having a substantially uniform pattern; And And a magnetic layer, wherein said pattern is substantially replicated in said magnetic layer to form a data area. The magnetic recording medium of claim 1, further comprising a laser texturing landing area. 2. The magnetic recording medium of claim 1, wherein the pattern comprises aluminum oxide having a substantially honeycomb pattern formed by an oxide film. 4. The magnetic recording medium of claim 3, wherein the honeycomb-shaped pattern includes substantially hexagonal cells. 5. The magnetic recording medium of claim 4, wherein the cell has a diameter of about 50 mm 3 to about 5000 mm 3 and a depth of about 50 mm 3 to about 10000 mm 3. 2. The magnetic recording medium of claim 1, wherein the Al or Al alloy layer has a thickness of about 50 kPa to about 5000 kPa. 7. The magnetic recording medium of claim 6, wherein the Al or Al alloy layer has a thickness of about 500 ms to about 1500 ms. The method of claim 1, A seed layer directly over the patterned Al or Al alloy layer; An underlayer on the seed layer; And And a magnetic layer on the lower layer. The method of claim 8, The substrate comprises nickel phosphorus plated Al or an Al alloy; The lower layer comprises chromium vanadium; And And the magnetic layer comprises a cobalt-chromium-platinum-tantalum alloy. 2. The magnetic recording medium of claim 1, wherein the substrate comprises nickel-phosphorus plated aluminum or aluminum alloy or glass, ceramic or glass-ceramic material. In the method for manufacturing a magnetic recording medium, Forming an aluminum (Al) or Al alloy layer on the nonmagnetic substrate; Forming a substantially uniform pattern on the Al or Al alloy layer; And Forming a magnetic layer, wherein the pattern is replicated on the magnetic layer to form a data region. 12. The method of claim 11 including forming an oxide film on an Al or Al alloy layer to form a pattern comprising aluminum oxide. 13. The method of claim 12 including forming an oxide film on the Al or Al alloy layer to form a honeycomb pattern comprising substantially hexagonal cells. 15. The method of claim 13, wherein the cell has a diameter of about 50 mm 3 to about 5000 mm 3 and a depth of about 50 mm 3 to 10,000 mm 3. 12. The method of claim 11 including sputter depositing an Al or Al alloy layer at a thickness of about 50 kPa to about 5000 kPa. The method of claim 15 including sputter depositing an Al or Al alloy at a thickness of about 500 kPa to about 1500 kPa. The method of claim 13 comprising producing an oxide film with a solution comprising from about 1% to about 15% hydrogen phosphate for about 1 to 15 minutes. 12. The method of claim 11 including texturing the substrate with a laser to form a texturing region that is substantially replicated in the magnetic layer to form a landing region. The method of claim 11, Sputter depositing a seed layer directly over the patterned Al or Al alloy layer; Sputter depositing a magnetic layer on the seed layer; And And sputtering deposition of a magnetic layer on the underlying layer. The method of claim 19, The substrate comprises nickel-phosphorus plated Al or an Al alloy; The seed layer comprises nickel aluminum; The lower layer comprises chromium vanadium; And The magnetic layer comprises cobalt-chromium-platinum-tantalum.