JP2009054228A - Magnetic recording medium, manufacturing method thereof, and magnetic recording unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic recording medium having a thin protection layer while maintaining anti-abrasion and anticorrosion properties. <P>SOLUTION: The magnetic recording medium includes a substrate 1, a magnetic layer 3 formed over the substrate 1, a protection layer 4 made of an amorphous silicon nitride film, having a density of 2.2 g/cm<SP>3</SP>or more, being formed over the magnetic layer 3, and a lubrication layer 5 on the protection layer 4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a magnetic recording medium, a method for manufacturing the same, and a magnetic recording apparatus including the magnetic recording medium.

  A magnetic recording device called a hard disk drive (HDD) has been widely used as an external storage device such as a computer or various information terminals.

  The magnetic recording apparatus includes a magnetic disk (magnetic recording medium) and a magnetic head that floats on the surface of the magnetic disk and writes information on the magnetic disk or reads information recorded on the magnetic disk.

  The magnetic disk includes a substrate, a magnetic layer formed above the substrate, a protective layer, and a lubricating layer. The magnetic layer is made of a cobalt-based alloy that exhibits good magnetic properties. However, this type of magnetic material is extremely inferior in wear resistance (durability) and corrosion resistance. Mechanical damage to the layer is likely to occur, and chemical damage to the magnetic layer due to surface corrosion is likely to occur due to adsorption of moisture in the air. Such damage causes deterioration of the magnetic properties of the magnetic layer. Therefore, the magnetic disk has a structure in which a protective layer is provided on the magnetic layer, and a lubricating layer made of a lubricant is provided on the magnetic layer, so that mechanical and chemical damage loss is unlikely to occur.

As the conventional protective layer, films made of various materials such as silicon oxide (SiO ₂ ) and alumina (Al ₂ O ₃ ) are used. Particularly recently, carbon films excellent in corrosion resistance and wear resistance (durability) have been used as in Patent Documents 1 and 2.
JP 2002-175616 A JP 2006-277779 A

  Incidentally, the amount of information handled has been increasing in recent years, and the recording density of magnetic disks has been further increased. Therefore, it has become essential to shorten the distance from the magnetic layer surface of the magnetic disk to the recording / reading portion of the magnetic head, that is, the magnetic spacing.

  In this case, simply shortening the magnetic spacing causes fly stiction that the lubricant on the surface of the magnetic disk is transferred to the magnetic head, thereby attracting the magnetic head to the magnetic disk. In order to solve this problem, Patent Document 1 has a structure in which the facing surface of the magnetic head with respect to the surface of the magnetic disk is covered with a silicon nitride film or the like by an ECR sputtering method in which lubricant is difficult to adhere.

  On the other hand, when the protective layer is thinned according to the shortening of the magnetic spacing, there is a problem that the protective layer is easily peeled due to the internal stress of the carbon film that is the protective layer. In addition, since the carbon film has a thickness of 4 nm and has reached the limit of thinning, if it is made thinner than that, a pinhole is generated, and there is a problem that moisture penetrates into the magnetic layer and the magnetic layer is corroded. . In order to solve these problems, Patent Document 2 has a structure in which a carbon film is a discontinuous film, and a silicon nitride film formed by an RF sputtering method having excellent corrosion resistance is provided below the carbon film.

  The present invention was created in view of the problems of the above-described conventional example, and a magnetic recording medium capable of reducing the thickness of the protective layer while maintaining wear resistance and corrosion resistance, a method for manufacturing the same, and An object of the present invention is to provide a magnetic recording apparatus provided with a magnetic recording medium.

According to an aspect of the present invention, a substrate, a magnetic layer formed above the substrate, and an amorphous silicon nitride film having a film density of 2.2 g / cm ³ or more formed above the magnetic layer. And a lubricating layer formed on the protective layer. A magnetic recording medium is provided.

  According to the magnetic recording medium of the present invention, from the viewpoint that the wear resistance (durability) and the corrosion resistance of the protective layer are increased in proportion to the density of the film constituting the protective layer, the magnetic recording medium is more than the amorphous carbon film. An amorphous silicon nitride film that easily increases the film density is used as a protective layer.

In the amorphous silicon nitride film, the film density is set to 2.2 g / cm ³ or more which is equal to or higher than that of the amorphous carbon film, and thereby the film density and film hardness which are equal to or higher than those of the amorphous carbon film are obtained. I was able to. From the same viewpoint, the ratio of the nitrogen concentration to the silicon concentration in the amorphous silicon nitride film (N / Si ratio) may be 1 or more.

  Thereby, since the wear resistance (durability) and corrosion resistance of the protective layer can be enhanced, the protective layer can be further thinned while maintaining the wear resistance (durability) and corrosion resistance. For example, the protective layer can be thinned to a thickness of 3 nm or less, which is smaller than the thickness of the amorphous carbon film.

  In addition, since the amorphous silicon nitride film has a high surface free energy, adhesion of the lubricating layer to the protective layer can be strengthened. As a result, the wear resistance (durability) and corrosion resistance of the magnetic layer can be enhanced in combination with the protective layer and the lubricating layer.

  According to another aspect of the present invention, the magnetic recording medium and a magnetic surface that floats on the surface of the magnetic recording medium and writes information to the magnetic recording medium or reads information recorded on the magnetic recording medium. There is provided a magnetic recording apparatus having a head.

  According to the magnetic recording apparatus of the present invention, since the amorphous silicon nitride film as the protective layer of the magnetic recording medium can strengthen the adhesion of the lubricating layer on the surface, the magnetic head slides on the surface of the magnetic recording medium. The lubrication layer is prevented from peeling from the protective layer against movement. Moreover, the protective layer itself can be thinned while maintaining wear resistance (durability) and corrosion resistance. Furthermore, since the protective layer is amorphous, the surface unevenness is small unlike the case of polycrystal. As a result, the magnetic recording apparatus can reduce the magnetic spacing and thereby increase the recording density while maintaining or further improving the wear resistance (durability) and the corrosion resistance.

According to still another aspect of the present invention, an amorphous film having a film density of 2.2 g / cm ³ or more is formed above the magnetic layer by a step of forming a magnetic layer above the substrate and a plasma chemical vapor deposition method. There is provided a method for manufacturing a magnetic recording medium, comprising a step of forming a protective layer made of a quality silicon nitride film and a step of forming a lubricating layer on the protective layer.

  According to the method for manufacturing a magnetic recording medium of the present invention, the amorphous silicon nitride film is formed by plasma enhanced chemical vapor deposition (PECVD). It has been found that the amorphous silicon nitride film formed by plasma chemical vapor deposition can be easily increased in film density as compared with the silicon nitride film formed by sputtering. It has been found that it is easy to increase the ratio of the nitrogen concentration to the silicon concentration in the amorphous silicon nitride film (N / Si ratio) that has a corresponding relationship with the film density.

Thereby, it is easy to increase the denseness and film hardness of the film. Furthermore, the film density and N / Si ratio could be adjusted by adjusting the film forming conditions such as the flow rate of the film forming gas, the gas pressure, the substrate heating temperature, and the plasma power in the plasma chemical vapor deposition method. As a result, a film density of 2.2 g / cm ³ or more and an N / Si ratio of 1 or more were obtained, and accordingly a film density and film hardness equivalent to or higher than those of the carbon film were obtained. Thereby, it is possible to reduce the thickness of the protective layer while maintaining wear resistance (durability) and corrosion resistance to the magnetic layer.

According to the magnetic recording medium of the present invention, since the protective layer is formed of an amorphous silicon nitride film having a film density of 2.2 g / cm ³ or more, the wear resistance (durability) and the corrosion resistance are maintained. However, it is possible to reduce the thickness of the protective layer. In addition, since the adhesion of the lubricating layer to the protective layer can be strengthened, the wear resistance (durability) and corrosion resistance of the magnetic layer can be further enhanced by combining the protective layer and the lubricating layer.

  In addition, according to the magnetic recording apparatus of the present invention, since the magnetic recording medium is provided, the magnetic spacing can be shortened and thus increased while maintaining or further improving wear resistance (durability) and corrosion resistance. Recording density can be increased.

Furthermore, according to the method for manufacturing a magnetic recording medium of the present invention, the amorphous silicon nitride film as the protective layer is formed by plasma chemical vapor deposition. In amorphous silicon nitride film by plasma enhanced chemical vapor deposition, a film density of 2.2 g / cm ³ or more can be obtained, and accordingly a film density and film hardness equivalent to or higher than that of a carbon film can be obtained. The protective layer can be made thin while maintaining the wear resistance (durability) and corrosion resistance of the protective layer.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

(Magnetic disk)
The magnetic disk is an element constituting a hard disk drive (HDD) described later, and can be applied to any recording medium such as an in-plane recording medium, SFM (Synthetic Ferri Coupled Media), a perpendicular recording medium, and a patterned medium. .

(1) Description of Structure of Magnetic Disk FIG. 1A is a sectional view showing a magnetic disk (magnetic recording medium) according to the first embodiment of the present invention.

  As shown in FIG. 1A, a magnetic disk (magnetic recording medium) 11 according to a first embodiment of the present invention is provided on a substrate 1 from the lower layer, an underlayer 2, a magnetic layer 3, and a protective layer. 4 and the lubricating layer 5 are laminated.

As the substrate 1, a glass plate, an AlTiC (AL ₂ O ₃ —TiC) plate, an aluminum alloy plate, or the like can be used.

  The underlayer 2 can be a single layer of a chromium (Cr) film or other metal film, or can be a laminate of a plurality of different types of films, and the thickness of the underlayer 2 is appropriately determined depending on the material used. It can be changed. Here, a chrome (Cr) film is used, and the thickness is about 10 nm. The magnetic layer 3 can be appropriately changed in material, thickness and structure depending on the type of medium such as in-plane recording medium, SFM (Synthetic Ferri Coupled Media), perpendicular recording medium, and patterned medium. A cobalt (Co) alloy film constituting the recording medium is used, and the film thickness is set to about 50 nm.

The protective layer 4 is an amorphous silicon nitride film having a nitrogen concentration ratio (N / Si ratio) to silicon concentration in the film of 1 or more and a film density of 2.2 g / cm ³ or more. What was formed below is used.

  According to the experiments by the present inventors, regarding the N / Si ratio of the amorphous silicon nitride film as the protective layer 4, the film density and film hardness are proportional to the N / Si ratio, and the N / Si ratio is If it is 1 or more, the denseness and film hardness of the film equivalent to or higher than the current carbon film can be obtained. Therefore, the protective layer 4 can be made thin while maintaining wear resistance (durability) and corrosion resistance. On the other hand, in the experiment, an N / Si ratio of 1.4 was obtained by adjusting the film formation conditions by chemical vapor deposition (hereinafter referred to as plasma CVD (Chemical Vapor Deposition) method). It can be set within the range obtained by adjusting.

Further, regarding the film density of the amorphous silicon nitride film as the protective layer 4, the film density has a corresponding relationship with the N / Si ratio, and if the lower limit is 2.2 g / cm ³ , the film density is equal to or higher than the current carbon film. Density and film hardness can be obtained. For this reason, the protective layer 4 can be made thin while maintaining wear resistance (durability) and corrosion resistance. On the other hand, a film density of 2.5 g / cm ³ was obtained in the experiment, but the present invention is not limited to this, and the film density can be set within the range obtained by adjusting the film formation conditions by the plasma CVD method. Further, if the thickness of the amorphous silicon nitride film is 3 nm or less, the magnetic spacing can be shortened compared to the current situation. On the other hand, regarding the lower limit of the film thickness, the required wear resistance (durability) and corrosion resistance are obtained, and the range is such that no discontinuity of the film occurs, and is about 0.5 nm.

  The lubricating layer 5 is desirably made of a material that is particularly excellent in adhesion to the amorphous silicon nitride film that is the protective layer 4. Here, the lubricating layer 5 is formed with a thickness of about 1.0 nm using a fluorine-containing polyether whose terminal structure is a molecule composed of a hydroxyl group, a piperonyl group or a carbonyl group. The thickness range of the lubricating layer 5 can maintain the wear resistance (durability) and corrosion resistance equivalent to or higher than those of the current carbon film together with the protective layer, and can reduce the magnetic spacing with respect to the current state. The range is preferably about 0.5 to 1.5 nm.

As described above, the magnetic disk 11 of the present invention has the protective layer 4 made of an amorphous silicon nitride film having an N / Si ratio of 1 or more and a film density of 2.2 g / cm ³ or more. Since the denseness and film hardness of the protective layer 4 equal to or higher than those of the current carbon film can be obtained, the protective layer 4 can be made thin while maintaining the wear resistance (durability) and the corrosion resistance. . Further, since the adhesion of the lubricating layer 5 to the protective layer 4 can be strengthened, the wear resistance (durability) and the corrosion resistance of the magnetic layer 3 can be further enhanced in combination with the protective layer 4 and the lubricating layer 5. it can.

(2) Description of Magnetic Disk Manufacturing Method Next, a magnetic disk manufacturing method according to an embodiment of the present invention will be described.

  2A to 2D are cross-sectional views illustrating a method of manufacturing a magnetic disk according to an embodiment of the present invention.

  First, as shown in FIG. 2A, a chromium (Cr) film to be the underlayer 2 is formed on the glass substrate 1 by a sputtering method with a thickness of about 10 nm. Subsequently, as shown in FIG. 2B, a cobalt (Co) alloy film to be the magnetic layer 3 is formed with a film thickness of about 50 nm on the underlayer 2 by sputtering.

Next, as shown in FIG. 2C, an amorphous silicon film to be the protective layer 4 is formed with a film thickness of 3 nm on the magnetic layer 3 by plasma CVD. For the amorphous silicon film, the film forming conditions are appropriately adjusted so that the ratio of the nitrogen concentration to the silicon concentration in the film (N / Si ratio) is 1 or more and the film density is 2.2 g / cm ³ or more. Form. Adjustable film forming conditions that affect the film quality include the substrate temperature, the flow rate of each gas constituting the film forming gas, the pressure of the film forming gas, and the discharge power applied between the counter electrodes.

  Below, the film-forming method by plasma CVD method is demonstrated concretely.

First, the substrate 1 laminated up to the magnetic layer 3 is placed on one electrode of the counter electrode installed in the chamber of the plasma CVD apparatus and facing the other electrode. Next, the substrate 1 is heated to keep the temperature of the substrate 1 within a predetermined range. According to the experiment, an amorphous silicon nitride film having a substrate 1 temperature of 230 ° C., 2.2 g / cm ³ which is the lower limit of the film density in the present invention, and 1 which is the lower limit of the N / Si ratio is obtained. It was. On the other hand, a film density of 2.5 g / cm ³ and an N / Si ratio of 1.4 were obtained at a temperature of 330 ° C. of the substrate 1, but the substrate 1, the underlayer 2 and the magnetic layer 3 were not adversely affected, and a higher film density and N As long as the / Si ratio is obtained, it can be appropriately increased. Therefore, the temperature of the substrate 1 is set to an appropriate temperature of 230 ° C. or higher.

Next, silane (SiH ₄ ) and ammonia (NH ₃ ) are introduced into the chamber at predetermined flow rates as film forming gases, respectively, and after adjusting the pressure, discharge power is applied between the counter electrodes. As a result, the film forming gas is converted into plasma and reacts, and an amorphous silicon nitride film that becomes the protective layer 4 starts to be formed on the magnetic layer 3 of the substrate 1. By maintaining this state for a predetermined time, a desired film thickness can be obtained.

  Next, as shown in FIG. 2D, a lubricant solution is applied on the protective layer 4 by a pulling method or a spin coating method to form the lubricating layer 5. As the lubricant solution, a fluorine-containing polyether whose terminal structure is a molecule composed of a hydroxyl group, a piperonyl group or a carbonyl group is appropriately diluted with a solvent. An example of a lubricant is Fomblin TETRAOL (manufactured by Solvay Solexis, Italy). The lubricating layer 5 is formed with a film thickness of 0.5 to 1.5 nm. Thereby, the magnetic disk is completed.

According to the method for manufacturing a magnetic disk of the embodiment of the present invention as described above, the film density is 2.2 g / cm in the protective layer 4 by forming the protective layer 4 by appropriately adjusting the film formation conditions by the plasma CVD method. ³ or more, an N / Si ratio of 1 or more can be obtained, and accordingly a film density and film hardness equal to or higher than that of the carbon film can be obtained, so that the magnetic layer 3 has wear resistance (durability) and The protective layer 4 can be made thinner while maintaining the corrosion resistance.

(3) Performance Comparison of Magnetic Disk Next, the results of an investigation of the performance of the magnetic disk of the example of the present invention compared with the performance of the magnetic disk of the comparative example will be described. They are summarized in the table of FIG. However, since Comparative Examples 2 and 3 are samples only for film hardness measurement, the description is omitted.

(Conditions for magnetic disk production)
Hereinafter, conditions for producing the magnetic disk according to the example of the present invention and the magnetic disk according to the comparative example will be described.

(Example 1)
A magnetic disk according to Example 1 was manufactured by the method described in (2) above. However, the protective layer 4 is used by adjusting the flow rate of silane (SiH ₄ ) as a film forming gas to a flow rate of 5 sccm and adjusting the flow rate of ammonia (NH ₃ ) to a flow rate of 167 sccm by plasma CVD, and keeping the substrate temperature at 330 ° C. The discharge power was adjusted to 700 W, and an amorphous silicon nitride film was formed with a thickness of 3 nm. The lubricating layer 5 was formed to have a film thickness of 1 nm by immersing and lifting for 30 seconds in a lubricant solution in which Fomblin TETRAOL (manufactured by Solvay Solexis, Italy) was diluted to about 0.001 wt%.

(Example 2)
A magnetic disk according to Example 2 was manufactured by the method described in (2) above. However, the protective layer 4 is used by adjusting the flow rate of silane (SiH ₄ ) as a film forming gas to a flow rate of 5 sccm and adjusting the flow rate of ammonia (NH ₃ ) to a flow rate of 167 sccm by plasma CVD, and keeping the substrate temperature at 230 ° C. Then, the discharge power was adjusted to 700 W, and an amorphous silicon nitride film was formed with a film thickness of 3 nm. The lubricating layer 5 was formed to have a film thickness of 1 nm by immersing and lifting for 30 seconds in a lubricant solution in which Fomblin TETRAOL (manufactured by Solvay Solexis, Italy) was diluted to about 0.001 wt%.

(Comparative Example 1)
A magnetic disk according to Comparative Example 1 was fabricated in substantially the same manner as in the above item (2) except that the protective layer 4 was formed of amorphous carbon. The protective layer 4 is an amorphous carbon film formed by adjusting the flow rate of C ₂ H ₄ to a flow rate of 100 sccm by plasma CVD, maintaining the substrate temperature at 200 ° C., and adjusting the discharge power to 1000 W. Was formed with a film thickness of 4 nm. The lubricating layer 5 was formed to have a film thickness of 1 nm by immersing and lifting for 30 seconds in a lubricant solution in which Fomblin TETRAOL (manufactured by Solvay Solexis, Italy) was diluted to about 0.02 wt%.

(Comparative Example 2)
As a sample for measuring the film hardness of the protective layer 4, the protective layer 4 is formed on the substrate / underlayer / magnetic layer, and the sputtering method is used to adjust the nitrogen gas flow rate around the Si target so as to have four different N / Si ratios. SiNx films (N / Si ratio: 0.05, 0.6, 1.0, 1.2) were formed.

(Comparative Example 3)
As a sample for measuring the film hardness of the protective layer 4, diamond-like carbon (DLC) was formed as a protective layer 4 on the substrate / underlayer / magnetic layer by a filtered cathodic arc (FCA) method.

(Evaluation)
(Characteristic evaluation method and conditions of protective layer)
The characteristic evaluation of the protective layer 4 was performed before forming the lubricating layer 5. Film density was measured by Rutherford Backscattering Spectroscopy. The N / Si ratio was measured by X-ray photoelectron spectroscopy. The film hardness was measured using a nanoindentation method. The nanoindentation method is a method for evaluating mechanical characteristics by measuring a minute deformation when a diamond indenter is pushed into a material with a minute load of about μN and unloaded. Since the amount of indentation can be controlled to about several nanometers, it is suitable for evaluating the characteristics of thin film samples.

(Durability test methods and conditions)
The test method is shown in FIG. As shown in FIG. 4, the test magnetic disk 11 is placed on the test magnetic disk 11 in contact with a pin 6 made of AlTiC (Al ₂ O ₃ —TiC) and pressed with a load of 30 g. Slide in sec. The number of turns at the time when the protective film of the test magnetic disk 11 was broken was measured.

(Method and conditions of corrosion resistance test)
2 cc of dilute nitric acid was dropped on the test magnetic disk surface, and the amount of Co in the dilute nitric acid collected after standing for 1 hour was measured with an inductively coupled plasma mass spectrometer (ICP-MS).

(Adhesion rate test methods and conditions)
The lubricating layer was washed away with 2,3-dihydrodecafluoropentane. The ratio (percentage) of the thickness of the lubricating layer after washing to the initial lubricating layer thickness before washing was evaluated as the adhesion rate.

(Evaluation results)
The film density was 2.5 g / cm ³ in Example 1, 2.2 g / cm ^{3 in} Example 2, and 1.8 g / cm ³ in Comparative Example 1. The film density of the amorphous silicon nitride film by the plasma CVD method is considerably higher than that of the amorphous carbon film by the plasma CVD method, and it can be said that the film density is high. Therefore, the protective layer made of the amorphous silicon nitride film formed by the plasma CVD method has high corrosion resistance.

  The N / Si ratio was 1.4 in Example 1 and 1.0 in Example 2. There is a corresponding relationship with the film density, and the denseness of the film can be evaluated by evaluating the N / Si ratio.

  The measurement results of the film hardness are shown in FIG. According to FIG. 5, it was about 21 GPa in Example 1 and about 18 GPa in Example 2. It was 11 to 17 GPa in Comparative Example 2, and 17 GPa in Comparative Example 3. The film hardness of the amorphous silicon nitride film formed by plasma CVD is higher than that of the SiNx film formed by sputtering in Comparative Example 2. In the sputtering method, it is difficult to increase the N / Si ratio due to the manufacturing method of adjusting the N / Si ratio by adjusting the flow rate of nitrogen gas around the Si target, and therefore increasing the film hardness of the SiNx film by the sputtering method. Is difficult. The film hardness of the amorphous silicon nitride film formed by the plasma CVD method is considerably higher than the film hardness of the DLC of Comparative Example 3. Therefore, the amorphous silicon nitride film formed by the plasma CVD method has high wear resistance.

  The durability measurement results are shown in FIG. According to FIG. 6A, the protective film was broken in 4300 rounds in Example 1, 1800 rounds in Example 2, and 850 rounds in Comparative Example 1. In agreement with the evaluation results of the film hardness, it was demonstrated that the amorphous silicon nitride film formed by the plasma CVD method has higher wear resistance than the amorphous carbon film formed by the plasma CVD method.

FIG. 6B shows the measurement results of the corrosion resistance. According to FIG. 6B, in Example 1, the Co elution amount was 0.2 μg / m ² , in Example 2, the Co elution amount was 0.4 μg / m ² , and in Comparative Example 1, the Co elution amount was 0.4 μg / m ^{2. 2} . Consistent with the evaluation results of the film density, it was demonstrated that the amorphous silicon nitride film formed by the plasma CVD method has higher corrosion resistance than the amorphous carbon film formed by the plasma CVD method.

  Regarding the adhesion rate evaluation, it was 96% in Example 1, 90% in Example 2, and 85% in Comparative Example 1. It was proved that the adhesion between the amorphous silicon nitride film by plasma CVD method and Fomblin TETRAOL which is a lubricating layer is strong. This can be extended to a lubricant which is the same fluorine-containing polyether as Fomblin TETRAOL and whose terminal structure is a molecule composed of a hydroxyl group, a piperonyl group or a carbonyl group.

(Hard disk drive structure)
FIG. 7A is a plan view showing the internal structure of a hard disk drive (magnetic recording apparatus) equipped with the magnetic disk 11 according to the embodiment of the present invention. FIG.7 (b) is sectional drawing which follows the II line | wire of Fig.7 (a).

  As shown in FIG. 7A, the hard disk drive includes a magnetic disk (magnetic recording medium) 11, a spindle motor (not shown) that rotates the magnetic disk 11, a magnetic head 12, and a magnetic head in a housing. The suspension 13 that supports the suspension 12, the actuator 14 that drives and controls the suspension 13 in the radial direction of the magnetic disk 11, and the spindle motor and actuator 14 are driven and controlled, and information is written to the magnetic disk 11 via the magnetic head 12. And an electronic circuit 15 for performing reading.

As shown in FIG. 1, the magnetic disk 11 is formed by laminating a base layer 2, a magnetic layer 3, a protective layer 4, and a lubricating layer 5 on a substrate 1 from the lower layer. As described above, the protective layer 4 is composed of an amorphous silicon nitride film having an N / Si ratio of 1 or more, a film density of 2.2 g / cm ³ or more, and a thickness of 3 nm. Yes. The lubricating layer 5 is a fluorine-containing polyether and is composed of a lubricant whose terminal structure is a molecule composed of a hydroxyl group, a piperonyl group, or a carbonyl group.

  The magnetic head 12 includes a writing element (inductive head) that converts an electric signal into a magnetic signal and a reading element (magnetoresistance effect element) that converts a magnetic signal into an electric signal. The magnetic disk 11 is provided with a bit pattern for recording information and a bit pattern for tracking control on the surface.

  This hard disk drive operates as follows. When the magnetic disk 11 is rotated at a high speed by the spindle motor, the magnetic head 12 slightly floats from the surface of the magnetic disk 11 due to the air flow generated by the rotation of the magnetic disk 11 as shown in FIG. At this time, the distance D from the surface of the magnetic layer 3 of the magnetic disk 11 to the surface facing the magnetic disk 11 of the recording / reading part 12a of the magnetic head 12 is called magnetic spacing. In this state, the actuator 14 moves the magnetic head 12 in the radial direction of the magnetic disk 11, and information is written to or read from the magnetic disk 11.

  According to the hard disk drive of the embodiment of the present invention as described above, the amorphous silicon nitride film that is the protective layer 4 of the magnetic disk 11 can strengthen the adhesion of the lubricating layer 5 on the surface. The lubricating layer 5 is prevented from peeling off from the protective layer 4 against the sliding of the magnetic head 12 on the surface of the disk 11. Moreover, the protective layer 4 itself can be thinned while maintaining wear resistance (durability) and corrosion resistance. Furthermore, since the protective layer 4 is amorphous, the surface unevenness is small unlike the case of polycrystal. As a result, the hard disk drive can maintain the wear resistance (durability) and the corrosion resistance, or can further increase the recording density while shortening the magnetic spacing D and further increasing the recording density. In this case, since the protective layer 4 is made thin, fly stiction can be prevented even when the magnetic spacing D is shortened.

  Hereinafter, various aspects of the present invention will be collectively described as supplementary notes.

(Appendix 1) A substrate, a magnetic layer formed above the substrate, a protective layer made of an amorphous silicon nitride film having a density of 2.2 g / cm ³ or more formed on the magnetic layer, and the protection A magnetic recording medium comprising a lubricating layer formed on the layer.

  (Supplementary note 2) The magnetic recording medium according to supplementary note 1, wherein the amorphous silicon nitride film constituting the protective layer has a ratio of nitrogen concentration to silicon concentration (N / Si ratio) of 1 or more.

  (Supplementary note 3) The magnetic recording medium according to any one of Supplementary notes 1 and 2, wherein the protective layer has a thickness of 3 nm or less.

  (Additional remark 4) The said lubricating layer is fluorine-containing polyether, The terminal structure of this fluorine-containing polyether is a molecule | numerator which consists of a hydroxyl group, a piperonyl group, or a carbonyl group, Any of the additional statements 1 thru | or 3 characterized by the above-mentioned. A magnetic recording medium according to claim 1.

  (Supplementary Note 5) Information recorded on or recorded on the magnetic recording medium according to any one of Supplementary notes 1 to 4 and the surface of the magnetic recording medium, and writing information on the magnetic recording medium And a magnetic head for reading out the data.

(Supplementary note 6) A protective layer made of an amorphous silicon nitride film having a density of 2.2 g / cm ³ or more is formed above the magnetic layer by a step of forming a magnetic layer above the substrate and plasma chemical vapor deposition. A method for manufacturing a magnetic recording medium, comprising: a step of forming; and a step of forming a lubricating layer on the protective layer.

  (Supplementary Note 7) The amorphous silicon nitride film constituting the protective layer has a ratio of nitrogen concentration to silicon concentration (N / Si ratio) of 1 or more. Production method.

  (Appendix 8) The plasma chemical vapor deposition method is characterized in that the substrate is heated, and a film forming gas containing silane and ammonia is converted into plasma and reacted to form the amorphous silicon nitride film. The method for manufacturing a magnetic recording medium according to any one of appendix 6 or 7.

  (Supplementary note 9) The method for manufacturing a magnetic recording medium according to supplementary note 8, wherein the temperature of the substrate is maintained at 230 ° C. or higher while the amorphous silicon nitride film is formed.

1 is a cross-sectional view showing a structure of a magnetic disk according to an embodiment of the present invention. (A) thru | or (d) are sectional drawings which show the manufacturing method of the magnetic disc based on Embodiment of this invention. It is a table | surface which shows the item and result of a test sample about the performance comparison of the magnetic disc which concerns on embodiment of this invention. It is a perspective view which shows the method of measuring the durability of the magnetic disc which concerns on embodiment of this invention. It is a graph which shows the comparative evaluation result of N / Si ratio of a magnetic disc concerning an embodiment of the invention, film density, and film hardness. (A) is a graph which shows the comparative evaluation result of durability of the magnetic disc which concerns on embodiment of this invention, (b) is a graph which similarly shows the comparative evaluation result of corrosion resistance. (A) is a graph which shows the structure of the hard-disk drive based on embodiment of this invention, (b) is sectional drawing which similarly shows operation | movement of a hard-disk drive.

Explanation of symbols

1 ... substrate,
2 ... Underlayer,
3 ... magnetic layer,
4 ... protective layer,
5 ... Lubrication layer,
11 ... Magnetic disk,
12 ... Magnetic head,
12a: Recording / reading unit,
D: Magnetic spacing.

Claims (5)

A substrate,
A magnetic layer formed above the substrate;
A protective layer made of an amorphous silicon nitride film having a density of 2.2 g / cm ³ or more formed above the magnetic layer;
A magnetic recording medium comprising a lubricating layer formed on the protective layer.   2. The magnetic recording medium according to claim 1, wherein the amorphous silicon nitride film constituting the protective layer has a ratio of nitrogen concentration to silicon concentration (N / Si ratio) of 1 or more.   The magnetic recording medium according to claim 1, wherein the protective layer has a thickness of 3 nm or less. A magnetic recording medium according to any one of claims 1 to 3,
A magnetic recording apparatus comprising: a magnetic head for writing information on the magnetic recording medium or reading information recorded on the magnetic recording medium. Forming a magnetic layer above the substrate;
Forming a protective layer made of an amorphous silicon nitride film having a density of 2.2 g / cm ³ or more above the magnetic layer by plasma enhanced chemical vapor deposition;
And a step of forming a lubricating layer on the protective layer.

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