WO2010038754A1 - Method for manufacturing magnetic recording medium and magnetic recording medium - Google Patents

Abstract

A magnetic recording medium can be provided with a protective layer which achieves an improvement in durability such as sliding resistance and corrosion resistance while maintaining high coercive force. A method for manufacturing a magnetic recording medium is characterized by comprising a magnetic recording layer deposition step for depositing a magnetic recording layer (122), and a protective layer deposition step for depositing a protective layer (126) by a CVD (Chemical Vapour Deposition) method, wherein in the protective layer deposition step, the protective layer (126) is deposited in an atmosphere with a second pressure after being deposited in an atmosphere with a first pressure, and the second pressure is less than the first pressure.

Description

Method for manufacturing magnetic recording medium and magnetic recording medium

The present invention relates to a method for manufacturing a magnetic recording medium mounted on an HDD (Hard Disk Drive) or the like and a magnetic recording medium.

With the recent increase in information processing capacity, various information recording technologies have been developed. In particular, the surface recording density of HDDs using magnetic recording technology continues to increase at an annual rate of about 100%. Recently, a 2.5-inch diameter magnetic disk (magnetic recording medium) used for an HDD or the like has been required to have an information recording capacity exceeding 200 GB per disk. Is required to realize an information recording density exceeding 400 GBit per square inch.

In order to achieve a high recording density in a magnetic recording medium used for an HDD or the like, it is necessary to refine the magnetic crystal grains constituting the magnetic recording layer for recording information signals and reduce the layer thickness. there were. However, in the case of magnetic recording media of the in-plane magnetic recording method (also called longitudinal magnetic recording method or horizontal magnetic recording method) that has been commercialized conventionally, as a result of the progress of miniaturization of magnetic crystal grains, superparamagnetic phenomenon As a result, the thermal stability of the recording signal is lost, the recording signal disappears, and a thermal fluctuation phenomenon occurs, which is an obstacle to increasing the recording density of the magnetic recording medium.

Therefore, in recent years, a perpendicular magnetic recording type magnetic recording medium (perpendicular magnetic recording medium) has been proposed. In the conventional in-plane magnetic recording method, the easy axis of magnetization of the magnetic recording layer is aligned in the plane direction of the substrate surface, but in the perpendicular magnetic recording method, the easy magnetization axis is adjusted to be aligned in the direction perpendicular to the substrate surface. ing. In the perpendicular magnetic recording system, the demagnetizing field (Hd) decreases as the magnetic grains become finer and the coercive force Hc improves and the thermal fluctuation phenomenon can be suppressed as the magnetic grains become finer. It is suitable for. As such a perpendicular magnetic recording medium, a so-called two-layer perpendicular magnetic recording medium comprising a soft magnetic underlayer made of a soft magnetic material and a perpendicular magnetic recording layer made of a hard magnetic material on a substrate is known (for example, a patent). Reference 1).

As the information recording density increases, both the linear recording density in the circumferential direction (BPI: Bit Per Inch) and the track recording density in the radial direction (TPI: Track Per Inch) continue to increase. Yes. Also, in order to effectively use the limited disk area, the HDD start / stop mechanism is replaced with a LUL (Load ： Unload) type HDD instead of the conventional CSS (ContactStart 方式 and Stop) type. I came.

In the LUL method, when the HDD is stopped, the magnetic head is retracted to an inclined table called a ramp located outside the magnetic recording medium, and during the start-up operation, the magnetic recording medium starts to rotate and then the magnetic head is removed from the ramp. It is slid on the medium and flies over to perform recording and reproduction. During the stop operation, the magnetic head is retracted to the lamp outside the magnetic recording medium, and then the rotation of the magnetic recording medium is stopped. This series of operations is called LUL operation.

The magnetic recording medium mounted on the LUL type HDD does not need to be provided with a contact sliding area (CSS area) with the magnetic head as in the CSS system, and the recording / reproducing area can be expanded and the information capacity can be increased. Preferred for. In addition, unlike the CSS method, the LUL method does not require an uneven CSS region on the surface of the magnetic recording medium, and the surface of the magnetic recording medium can be extremely smoothed. Therefore, in the magnetic recording medium mounted on the LUL type HDD, the flying height of the magnetic head can be further reduced as compared with the CSS type, so that the S / N ratio of the recording signal can be increased and the magnetic recording medium can be achieved. There is also an advantage that the recording capacity of the apparatus can be increased.

Under these circumstances, in order to improve the information recording density, the gap between the magnetic recording layer of the magnetic recording medium and the recording / reproducing element of the magnetic head (magnetic spacing) is reduced by reducing the flying height of the magnetic head. ) Is narrowed to improve the S / N ratio. In recent years, the flying height of a magnetic head desired is 10 nm or less, and in order to achieve an information recording density of 400 Gbit or more per square inch, it is necessary to make it at least 5 nm or less. Therefore, it has been demanded that the magnetic recording medium operates stably even at an extremely low flying height of 5 nm or less. In particular, as described above, in recent years, the magnetic recording medium has shifted from the in-plane magnetic recording system to the perpendicular magnetic recording system, and there is a strong demand for an increase in capacity of the magnetic recording medium and a reduction in flying height associated therewith.

As a technique for narrowing the magnetic spacing described above, during operation of the magnetic head element, a thin film resistor provided inside the head element is energized to generate heat, and the heat causes the magnetic head (magnetic pole tip) to thermally expand. A DFH (Dynamic Flying Height) head that slightly protrudes in the ABS (the Air Air Bearing Surface) direction has been proposed. Thereby, the gap between the magnetic head and the magnetic recording medium is adjusted (magnetic spacing is reduced), and the magnetic head can always fly stably with a narrow magnetic spacing. Currently, it is necessary to develop a medium that satisfies the back-off margin of 2 nm or less of the DFH element. As described above, there is a demand for the realization of a magnetic recording medium having high durability and high reliability under the reduction of the flying height of the magnetic head and the reduction of magnetic spacing accompanying the recent increase in recording density.

Also, as the magnetic head has been reduced in flying height, the possibility that the magnetic head comes into contact with the surface of the magnetic recording medium due to external impact or flight disturbance has increased. For this reason, the magnetic recording medium is provided with a protective layer that protects the surface of the magnetic recording layer from being damaged when the magnetic head collides with the magnetic recording medium (for example, Patent Document 2). The protective layer is formed of a carbon overcoat (COC), that is, a high hardness film by a carbon (carbon) film.

In addition, since the protective layer requires strength and chemical resistance to maintain excellent wear resistance and corrosion resistance even in a thin film, diamond-like carbon having low friction, high strength, and high chemical stability is required. It is preferably used. As a conventional protective layer, a diamond-like carbon protective layer is formed on a magnetic recording medium by a CVD method using a hydrocarbon gas or a sputtering method. The film thickness was about 10 nm or less.

In addition, there is a protective layer in which a hard diamond-like bond of carbon and a soft graphite bond are mixed (for example, Patent Document 3). Also disclosed is a technique for producing a diamond-like bond protective film by a CVD (Chemical Vapor Deposition) method (for example, Patent Document 4).

Further, a lubricating layer is formed on the protective layer to protect the protective layer and the magnetic head when the magnetic head collides. The lubricating layer is formed, for example, by applying perfluoropolyether and sintering.

JP 2002-74648 A JP 2000-282238 A Japanese Patent Laid-Open No. 10-11734 JP 2006-114182 A

As described above, a protective layer and a lubricating layer are necessary on the magnetic recording layer, but there is a demand for further narrowing the gap (gap) between the magnetic head and the magnetic recording layer as the recording density increases. In particular, in a perpendicular magnetic recording medium, a soft magnetic layer is often formed to apply a strong magnetic field in the perpendicular direction to the magnetic recording layer, but the distance between the magnetic head and the soft magnetic layer is further increased. For this reason, it is preferable to make the layer on the substrate surface side from the soft magnetic layer, particularly the layer on the substrate surface side from the magnetic recording layer, as thin as possible.

However, even if the protective layer is simply thinned by using the conventional CVD method and sputtering method described in Patent Documents 1 and 2, the protective layer itself has durability such as sliding resistance (mechanical strength) and corrosion resistance. It will deteriorate.

For example, a protective layer formed by plasma CVD can easily change the film quality depending on process parameters such as gas pressure, gas flow rate, applied bias, and input power, but it is resistant to corrosion, metal ion elution, and mechanical strength. There is a trade-off relationship, and it has been difficult to establish these simultaneously. Therefore, in order to provide a function as a protective layer, it is necessary to increase the thickness of the protective layer so that the weakest characteristic satisfies the required quality. However, if the thickness of the protective layer is increased, the magnetic spacing cannot be reduced, and it becomes difficult to achieve a higher recording density.

Recently, magnetic recording media devices are not only used as storage devices for conventional personal computers, but are also widely used in mobile applications such as mobile phones and car navigation systems. As a result, the environmental resistance required for magnetic recording media has become very severe. Therefore, in view of these circumstances, further improvement in the stability and reliability of the magnetic recording medium is urgently required than before.

In view of such problems, the present invention provides a method for manufacturing a magnetic recording medium and a magnetic recording medium including a protective layer with improved durability such as sliding resistance and corrosion resistance while maintaining a high coercive force. The purpose is that. Another object of the present invention is to provide a method for manufacturing a magnetic recording medium having high stability and reliability by providing a protective layer having sufficient mechanical strength as well as corrosion resistance and metal ion elution resistance even when the film thickness is reduced.

In order to solve the above-mentioned problems, the inventors of the present invention diligently studied. As long as a protective layer harder than the protective layer formed by the conventional method can be formed, the durability can be improved even if the protective layer itself is thinned. We thought that we can maintain. As a method of forming a protective layer harder than the conventional protective layer, a method of increasing the bias voltage or a method of decreasing the atmospheric pressure in the CVD method can be considered.

However, in the CVD method, when the bias voltage is increased, the coercive force (Hc) of the magnetic recording medium is lowered. In the perpendicular magnetic recording medium, the protective layer is formed on the auxiliary recording layer provided on the magnetic recording layer in order to improve the writing characteristics. When a high bias voltage is applied when forming the protective layer by the CVD method, the carbon particles violently collide with the auxiliary recording layer with high energy, so a hard protective layer is formed, but a film is formed immediately below the protective layer. This is probably because the auxiliary recording layer for improving the write characteristics of the magnetic recording layer is partially broken.

Also, the lower the atmospheric pressure during film formation in the CVD method, the longer the mean free path and the lower the collision frequency between plasma ions. In other words, the lower the atmospheric pressure, the more the plasma gas reaches the substrate surface (auxiliary recording layer) without significant energy reduction. Therefore, even if the atmospheric pressure is lowered, the carbon particles violently collide with the auxiliary recording layer with high energy.

In addition, if the atmospheric pressure is lowered, a protective layer harder than the conventional protective layer can be formed, but as the stress in the film increases, pinholes, cracks, etc. tend to be formed in the film and the corrosion resistance deteriorates. To do.

Therefore, the inventors controlled the atmospheric pressure in the CVD method when forming the protective layer, thereby preventing damage to the surface of the substrate (auxiliary recording layer) and improving the hardness of the surface of the protective layer. As a result, the present invention has been completed.

That is, in order to solve the above problems, a typical configuration of a method for manufacturing a magnetic recording medium according to the present invention is a method for manufacturing a magnetic recording medium comprising a magnetic recording layer and a protective layer in this order on a substrate. A protective layer forming step including a magnetic recording layer forming step for forming a magnetic recording layer and a protective layer forming step for forming a protective layer using a CVD (Chemical Vapor Deposition) method. The protective layer is formed in the atmosphere of the second pressure after the film formation in the atmosphere of the first pressure, and the second pressure is less than the first pressure.

In the protective layer forming step, the protective layer is formed with a configuration in which the pressure (second pressure) when forming the upper part is lower than the pressure (first pressure) when forming the lower part of the protective layer. While the protective layer is formed at a pressure (first pressure) that does not damage the previously formed layer, a layer having higher hardness than the lower portion can be formed on the upper portion.

In the CVD method, the higher the atmospheric pressure, the shorter the mean free path, that is, the higher the collision frequency. In other words, the higher the pressure of the atmosphere, the more the gas that has become plasma loses energy due to repeated collisions and reaches the surface of the substrate. Therefore, by increasing the pressure of the atmosphere, the protective layer can be formed at a pressure that does not damage the layer formed before the protective layer is formed. And the structure which forms a protective layer further by reducing a pressure makes it possible to form the upper part (surface) of a protective layer with high density and hardness.

The magnetic recording medium is a perpendicular magnetic recording medium, and may include an auxiliary recording layer film forming step of forming an auxiliary recording layer magnetically substantially continuous in the plane direction of the substrate before the protective layer forming step. .

In a perpendicular magnetic recording medium, if the coercive force Hc of the magnetic recording layer is improved, a high recording density can be achieved, but writing with a magnetic head tends to be difficult. Therefore, the saturation magnetization Ms is improved by forming a single film (auxiliary recording layer) that is substantially magnetically continuous in the in-plane direction of the main surface of the substrate and has a high perpendicular magnetic anisotropy on the magnetic recording layer. It is possible to improve the ease of writing, that is, the overwrite characteristic. In other words, the purpose of providing the auxiliary recording layer on the magnetic recording layer is to improve the reverse domain nucleation magnetic field Hn to reduce noise, to improve the saturation magnetization Ms, and to improve the overwrite characteristics. The auxiliary recording layer may be called a continuous layer or a cap layer.

Here, since the layer immediately below the protective layer is the auxiliary recording layer, the above-described effect of the auxiliary recording layer is effectively reduced by reducing damage to the auxiliary recording layer accompanying the formation of the protective layer. Obtainable.

It should be noted that the auxiliary recording layer being “magnetically continuous” means that the magnetic material is continuous or undivided, that is, a single magnet as a whole. “Substantially continuous” means that since the auxiliary recording layer is a thin film, it does not necessarily form a complete film, and therefore includes the case where the film partially breaks and is not continuous. is there.

After the protective layer forming step, the method further includes a nitriding step for nitriding the surface of the protective layer and a lubricating layer forming step for forming a lubricating layer, and the nitriding step is for doping the protective layer with nitrogen It may be performed by a method, a CVD method or a sputtering method.

PFPE widely used as a lubricating layer has a hydroxyl group (OH ⁻ ) at the terminal, and the hydroxyl group has high affinity with nitrogen present on the surface of the protective layer. Therefore, with the above-described configuration that can improve the nitrogen content on the surface of the protective layer, the adhesion ratio (BR: Bonding Ratio) of the lubricating layer to the protective layer can be improved.

The protective layer may contain diamond-like carbon. Thereby, it can be set as a precise | minute and durable protective layer.

In order to solve the above-described problems, a typical configuration of the magnetic recording medium according to the present invention is characterized by being manufactured using the above-described method for manufacturing a magnetic recording medium.

In order to solve the above problems, a typical configuration of another magnetic recording medium according to the present invention is a magnetic recording medium including at least a magnetic recording layer and a protective layer containing diamond-like carbon in this order on a substrate. In the Raman spectroscopy, the G peak height due to the graphite carbon is Gh, the D peak height due to the diamond-like carbon D peak is Dh, and the background includes the fluorescence of the G peak. When the intensity is B and the peak intensity excluding the fluorescence of the G peak is A, the measurement result of the protective layer by Raman spectroscopy is Dh / Gh of 1.05 or less and B / A is 1.5 or less. It is characterized by being.

The components based on the technical idea of the magnetic recording medium manufacturing method described above and the description thereof can be applied to the magnetic recording medium.

By the way, in order to improve the durability such as wear resistance and impact resistance of the protective layer, carbon having diamond-like bonds (diamond-like carbon Diamond 原子 Like ダ イ ヤ モ ン ド Carbon) is simply referred to as DLC. Need to be increased.

However, even if the film formation conditions by the CVD method are optimized in order to improve the wear resistance, the corrosion resistance is greatly deteriorated. In other words, the lower the pressure when depositing the protective layer by the CVD method, the longer the mean free path, the lower the collision frequency, and the higher energy is deposited on the substrate. Although the film can be formed, the coverage of the medium protective film and the uniformity in the radial direction are deteriorated, so that the corrosion resistance is deteriorated. In particular, since the coverage of the protective layer at the end of the magnetic recording medium is deteriorated, the occurrence of corrosion at the end becomes remarkable.

On the other hand, even if the film formation conditions by the CVD method are optimized in order to improve the corrosion resistance, the wear resistance is greatly deteriorated. That is, the higher the pressure when forming the protective layer by the CVD method, the shorter the mean free path, the higher the collision frequency, and the lower the energy is deposited on the substrate. The uniformity of the layer is increased. Therefore, the corrosion resistance of the outer peripheral portion including the end portion is improved, but the wear resistance is deteriorated because the film has a low density and is soft. Therefore, it has been difficult to reduce the thickness of the protective layer while improving wear resistance and corrosion resistance.

For this reason, it has been a problem to reduce the thickness of the protective layer while improving the wear resistance and corrosion resistance of the protective layer. Therefore, in order to solve such a problem, the inventors have intensively studied. As a result, when forming the protective layer, by controlling the pressure of the atmosphere in the CVD method, the corrosion resistance of the protective layer is improved, and The present inventors have found that the surface hardness of the protective layer can be improved and have completed the present invention.

That is, in order to solve the above-mentioned problem, another typical configuration of the present invention is a magnetic recording medium comprising a magnetic recording layer and a protective layer containing diamond-like carbon in this order on a substrate. In the spectroscopic method, the area intensity of the G peak due to the graphite carbon is Ig, the area intensity of the D peak due to the diamond-like carbon is Id, the background intensity including the fluorescence of the G peak is B, and the fluorescence of the G peak. Assuming that the peak intensity excluding A is A, the measurement results by Raman spectroscopy of the protective layer are Id / Ig of 2.20 to 2.45, B / A of 1.45 to 1.60, When Id / Ig is X and B / A is Y, Y / X is 0.7 to 0.8. The protective layer may have a thickness of 5.0 nm or less.

When forming the magnetic recording layer and forming the protective layer using the CVD method, the film is first formed in an atmosphere of a first pressure, and then at a pressure lower than the first pressure. By forming the film in an atmosphere of a certain second pressure, a perpendicular magnetic recording medium having a protective layer having the above-described configuration can be obtained.

Therefore, the measurement result by Raman spectroscopy in the protective layer is that Id / Ig is 2.20 to 2.45, B / A is 1.45 to 1.60, Id / Ig is X, B / A When Y is set to Y, Y / X can be set to 0.7 to 0.8, and the protective layer can be made thinner while suppressing the occurrence of corrosion (improving corrosion resistance) and improving wear resistance. It becomes possible to plan. Here, B / A means the background intensity (B) including fluorescence of the G peak due to graphite and the peak intensity (A) excluding fluorescence when the protective layer is analyzed using Raman spectroscopy. Ratio. B / A indicates the ratio of the polymeric bond between carbon and hydrogen in the protective layer, and the larger the B / A, the higher the hydrogen content. That is, the lower the B / A, the more DLC is contained in the protective layer.

After about 3% nitric acid is dropped on the surface of the magnetic recording medium and left at room temperature for about 1 hour, the Co contained in the nitric acid is preferably 0.2 ng / ml or less.

When about 3% nitric acid is dropped on the surface of the magnetic recording medium and left at room temperature for about 1 hour, Co contained in the magnetic recording layer is eluted in the nitric acid. Since the magnetic recording medium according to the present invention includes the protective layer, Co elution from the medium surface can be suppressed to 0.1 ng / ml or less. That is, the corrosion resistance can be improved.

In order to solve the above problems, another typical configuration of the present invention is a method of manufacturing a magnetic recording medium comprising a magnetic recording layer and a protective layer containing diamond-like carbon in this order on a substrate. A magnetic recording layer forming step for forming a magnetic recording layer, and a protective layer forming step for forming a protective layer using a CVD (Chemical Vapor Deposition) method. After forming a film in an atmosphere of 1 pressure, a protective layer is formed in an atmosphere of a second pressure that is less than the first pressure. The film thickness of the protective layer formed in the first pressure is M, and the second pressure is M / N is 0.25 to 1 where N is the thickness of the protective layer when the film is formed. The first pressure may be a pressure that is 2 Pa or more higher than the second pressure.

In the protective layer forming step, magnetic recording is performed at the first pressure by a configuration in which the pressure (second pressure) when forming the upper part is lower than the pressure (first pressure) when forming the lower part of the protective layer. The uniformity of the protective layer in the in-plane direction of the medium is increased, and by forming the film at the second pressure, a layer having higher hardness than the lower part can be formed on the upper part.

In the CVD method, the higher the atmospheric pressure, the shorter the mean free path, that is, the higher the collision frequency. In other words, the higher the pressure of the atmosphere, the more the gas that has become plasma loses energy due to repeated collisions and reaches the surface of the substrate. Therefore, by increasing the atmospheric pressure, the plasma gas uniformly covers the substrate surface up to the end, so that the coverage is improved and the corrosion resistance can be ensured. And the structure which forms a protective layer further by reducing a pressure makes it possible to form the upper part (surface) of a protective layer with high density and hardness.

Therefore, by manufacturing a perpendicular magnetic recording medium with the above configuration, the measurement results of the protective layer by Raman spectroscopy have Id / Ig of 2.20-2.45 and B / A of 1.45-1. When Id / Ig is X and B / A is Y, Y / X can be set to 0.7 to 0.8.

The above-described constituent elements based on the technical idea of the magnetic recording medium and the description thereof can also be applied to the manufacturing method of the magnetic recording medium.

Furthermore, in order to solve the above-mentioned problem, another typical configuration of the present invention is a method for manufacturing a magnetic recording medium in which at least a magnetic recording layer and a carbon-based protective layer are sequentially provided on a substrate. When the protective layer is formed, the relationship between the gas flow rate in the chamber and the gas pressure is such that the ratio of the gas flow rate (unit: sccm) to the gas pressure (unit: Pa) (gas flow rate / gas pressure) is 75 (sccm / Pa). ) Or more.

The gas pressure in the chamber when forming the carbon-based protective layer is preferably in the range of 1 to 3 Pa. The carbon-based protective layer is preferably formed by a plasma CVD method. Preferably, the carbon-based protective layer has a thickness of 5 nm or less.

The magnetic recording medium is preferably a magnetic recording medium having a start / stop mechanism mounted on a load / unload type magnetic disk device and used under a head flying height of 5 nm or less.

The carbon-based protective layer has an Id / Ig ratio of 2.4 or less, which is a ratio of the area intensity Ig of the G peak attributed to graphite carbon in Raman spectroscopy to the area intensity Id of the D peak attributed to diamond-like carbon. There should be.

According to the above configuration, it is possible to provide a method of manufacturing a magnetic recording medium including a protective layer having sufficient mechanical strength as well as corrosion resistance and metal ion elution resistance even when the film is thinned. As a result, magnetic spacing can be further reduced, and even under the low flying height of magnetic heads due to the recent rapid increase in recording density, and extremely severe environmental resistance due to diversification of applications. In this case, a magnetic recording medium having high durability and high reliability can be obtained.

The method for manufacturing a magnetic recording medium according to the present invention can include a protective layer with improved durability such as sliding resistance and corrosion resistance while maintaining a high coercive force.

It is a figure explaining the structure of the perpendicular magnetic recording medium as a magnetic recording medium concerning 1st Embodiment. It is explanatory drawing for demonstrating the pressure change and bias change in a CVD chamber in a protective layer film-forming process. It is the comparison figure which compared the Example and the comparative example. It is explanatory drawing for demonstrating Dh / Gh and corrosion resistance of a protective layer. It is explanatory drawing for demonstrating B / A and a scratch test of a protective layer. It is explanatory drawing for demonstrating the relationship between the film thickness of a protective layer, Dh / Gh, and the film thickness of a protective layer, and B / A. It is a figure explaining evaluation of an Example and a comparative example. It is explanatory drawing for demonstrating the image of a Raman spectrum. It is a figure which shows the measurement result which measured the Example and the comparative example by the Raman spectroscopy. It is a figure which shows the result of having performed Co elution test with respect to the Example and the comparative example. It is explanatory drawing for demonstrating the result of a sliding tolerance test. It is explanatory drawing for demonstrating the result of having performed the Co elution test by changing the ratio which forms a protective layer into 2 Pa, and the ratio which forms into 4 Pa. It is a figure explaining the structure of the perpendicular magnetic recording medium as a magnetic recording medium concerning 3rd Embodiment. It is a figure which shows the film-forming conditions and evaluation of a protective layer in the Example concerning 3rd Embodiment, and a comparative example. It is a figure which shows the change of the Co elution amount test result by the film-forming conditions of the Example shown in FIG. 14, and a comparative example. It is a figure which shows the change of the pin-on test result by the film-forming conditions of the Example shown in FIG. 14, and a comparative example.

DESCRIPTION OF SYMBOLS 100 ... Perpendicular magnetic recording medium, 110 ... Disk substrate, 112 ... Adhesion layer, 114 ... Soft magnetic layer, 114a ... First soft magnetic layer, 114b ... Spacer layer, 114c ... Second soft magnetic layer, 116 ... Pre-underlayer, 118 ... Underlayer, 118a ... First underlayer, 118b ... Second underlayer, 120 ... Non-magnetic granular layer, 122 ... Magnetic recording layer, 122a ... First magnetic recording layer, 122b ... Second magnetic recording layer, 123 ... Split layer, 124 ... auxiliary recording layer, 126 ... protective layer, 128 ... lubricating layer, 200 ... perpendicular magnetic recording medium

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

(First embodiment)
A method for manufacturing a magnetic recording medium according to a first embodiment and an embodiment of the magnetic recording medium will be described. FIG. 1 is a diagram for explaining the configuration of a perpendicular magnetic recording medium 100 as a magnetic recording medium according to the first embodiment. The perpendicular magnetic recording medium 100 shown in FIG. 1 includes a disk substrate 110, an adhesion layer 112, a first soft magnetic layer 114a, a spacer layer 114b, a second soft magnetic layer 114c, a pre-underlayer 116, a first underlayer 118a, and a second layer. The underlayer 118b, the nonmagnetic granular layer 120, the first magnetic recording layer 122a, the second magnetic recording layer 122b, the auxiliary recording layer 124, the protective layer 126, and the lubricating layer 128 are included. The first soft magnetic layer 114a, the spacer layer 114b, and the second soft magnetic layer 114c together constitute the soft magnetic layer 114. The first base layer 118a and the second base layer 118b together constitute the base layer 118. The first magnetic recording layer 122a and the second magnetic recording layer 122b together constitute the magnetic recording layer 122.

[Substrate molding process]
As the disk substrate 110, a glass disk obtained by forming amorphous aluminosilicate glass into a disk shape by direct pressing can be used. The type, size, thickness, etc. of the glass disk are not particularly limited. Examples of the material of the glass disk include aluminosilicate glass, soda lime glass, soda aluminosilicate glass, aluminoborosilicate glass, borosilicate glass, quartz glass, chain silicate glass, or glass ceramic such as crystallized glass. It is done. The glass disk is subjected to grinding, polishing, and chemical strengthening sequentially to obtain a smooth non-magnetic disk substrate 110 made of a chemically strengthened glass disk. The surface roughness of the main surface of the disk substrate 110 is preferably 2.18 nm or less in Rmax and 0.3 nm or less in Ra.

[Film formation process]
On the disk substrate 110 obtained by the substrate molding process described above, the adhesion layer 112, the soft magnetic layer 114, the pre-underlayer 116, the underlayer 118, the nonmagnetic granular layer 120, the magnetic recording layer 122 (by the DC magnetron sputtering method) The magnetic recording layer forming step) and the auxiliary recording layer 124 (auxiliary recording layer forming step) are sequentially formed, and the protective layer 126 is formed by the CVD method (protective layer forming step). Thereafter, the lubricating layer 128 is formed by dip coating (lubricating layer forming step). Note that it is also preferable to use an in-line film forming method in terms of high productivity. Hereinafter, the configuration and manufacturing method of each layer will be described.

The adhesion layer 112 is formed in contact with the disk substrate 110, and has a function of increasing the peel strength between the soft magnetic layer 114 formed on the disk substrate 110 and the disk substrate 110, and the crystal grains of each layer formed thereon are finely divided. It has a function to make it uniform and uniform. When the disk substrate 110 is made of amorphous glass, the adhesion layer 112 is preferably an amorphous (amorphous) alloy film so as to correspond to the amorphous glass surface.

The adhesion layer 112 can be selected from, for example, a CrTi amorphous layer, a CoW amorphous layer, a CrW amorphous layer, a CrTa amorphous layer, or a CrNb amorphous layer. Among these, a CrTi alloy film is particularly preferable because it forms an amorphous metal film containing microcrystals. The adhesion layer 112 may be a single layer made of a single material, or may be formed by laminating a plurality of layers.

The soft magnetic layer 114 is a layer that temporarily forms a magnetic path during recording in order to pass magnetic flux in a direction perpendicular to the recording layer in the perpendicular magnetic recording method. The soft magnetic layer 114 is provided with AFC (Antiferro-magnetic exchange coupling) by interposing a nonmagnetic spacer layer 114b between the first soft magnetic layer 114a and the second soft magnetic layer 114c. Can be configured. As a result, the magnetization direction of the soft magnetic layer 114 can be aligned along the magnetic path (magnetic circuit) with high accuracy, and the vertical component of the magnetization direction is extremely reduced, so that noise generated from the soft magnetic layer 114 is reduced. Can do. The composition of the first soft magnetic layer 114a and the second soft magnetic layer 114c includes a cobalt alloy such as CoTaZr, a Co—Fe alloy such as CoCrFeB, CoFeTaZr, CoFeTaZrAlCr, and CoFeNiTaZr, and a [Ni—Fe / Sn] n multilayer structure. Ni—Fe based alloys such as can be used. The composition of the spacer layer can be, for example, Ru.

The film thickness of the soft magnetic layer 114 varies depending on the structure and the structure and characteristics of the magnetic head, but is preferably 15 nm to 100 nm as a whole. The film thicknesses of the upper and lower layers (the first soft magnetic layer 114a and the second soft magnetic layer 114c) may be slightly different for optimization of recording and reproduction, but should be approximately the same. desirable.

The pre-underlayer 116 is a non-magnetic alloy layer, and has an effect of protecting the soft magnetic layer 114 and the easy axis of the hexagonal close-packed structure (hcp structure) included in the underlayer 118 formed thereon. It has a function of orienting the disk in the vertical direction. The pre-underlayer 116 preferably has a (111) plane of a face-centered cubic structure (fcc structure) parallel to the main surface of the disk substrate 110. Further, the pre-underlayer 116 may have a configuration in which these crystal structures and amorphous are mixed. The material of the pre-underlayer 116 can be selected from Ni, Cu, Pt, Pd, Zr, Hf, Nb, and Ta. Furthermore, it is good also as an alloy which has these metals as a main component and contains any one or more additional elements of Ti, V, Cr, Mo, and W. For example, NiW, CuW, or CuCr can be suitably selected as an element having an fcc structure. Note that it is desirable that the film thickness of the pre-underlayer 116 be a minimum film thickness necessary for controlling crystal growth of the underlayer 118. If it is too thick, it may cause a decrease in signal writing capability.

The underlayer 118 is used for suitably controlling the crystal orientation of the magnetic recording layer 122 (orienting the crystal orientation in a direction perpendicular to the substrate surface), crystal grain size, and grain boundary segregation. The underlayer 118 has an hcp structure, and has a function of growing the crystal of the Co hcp structure of the magnetic recording layer 122 as a granular structure by controlling the crystal axis (c-axis) to be oriented in the vertical direction. . Therefore, the higher the crystal orientation of the underlayer 118, that is, the more the (0001) plane of the crystal of the underlayer 118 is parallel to the main surface of the disk substrate 110, the more the orientation of the magnetic recording layer 122 is improved. Can do. Ru is a typical material for the underlayer 118, but in addition, it can be selected from RuCr and RuCo. Since Ru has an hcp structure and the lattice spacing of crystals is close to Co, the magnetic recording layer 122 containing Co as a main component can be well oriented.

When the underlayer 118 is made of Ru, a two-layer structure made of Ru can be obtained by changing the gas pressure during sputtering. Specifically, when forming the first underlayer 118a on the lower layer side, the Ar gas pressure is set to a predetermined pressure, that is, a low pressure, and when forming the second underlayer 118b on the upper layer side, the first lower layer 118b on the lower layer side is formed. The gas pressure of Ar is set higher than when forming the first underlayer 118a, that is, the pressure is increased. Thereby, the crystal orientation of the magnetic recording layer 122 can be improved by the first underlayer 118a, and the grain size of the magnetic particles of the magnetic recording layer 122 can be reduced by the second underlayer 118b.

Further, when the gas pressure is increased, the mean free path of the plasma ions to be sputtered is shortened, so that the film formation rate is slow and the film becomes rough, so that separation and refinement of Ru crystal particles can be promoted, Co miniaturization is also possible. In addition, in the case of the laminated structure by the low gas pressure process and the high gas pressure process as in this embodiment, not only the same material but also different materials can be combined.

Furthermore, a small amount of oxygen may be contained in Ru of the base layer 118. As a result, the separation and refinement of the Ru crystal grains can be further promoted, and the magnetic recording layer 122 can be further isolated and refined. Note that oxygen may be contained by reactive sputtering, but it is preferable to use a target containing oxygen at the time of sputtering film formation.

In addition, in this embodiment, although the base layer was comprised from Ru, it is not limited to this. As the material for the underlayer, a simple substance or an alloy having a face-centered cubic (fcc) structure or a hexagonal close-packed (hcp) structure can be preferably used. Examples thereof include Pd, Pt, Ti, and alloys containing them. be able to.

The nonmagnetic granular layer 120 is a nonmagnetic layer having a granular structure. A non-magnetic granular layer is formed on the hcp crystal structure of the underlayer 118, and the granular layer of the first magnetic recording layer 122a (or magnetic recording layer 122) is grown thereon, whereby the magnetic granular layer is initially formed. It has the effect of separating from the growth stage (rise). Thereby, isolation of the magnetic particles of the magnetic recording layer 122 can be promoted. The composition of the nonmagnetic granular layer 120 can be a granular structure by forming a grain boundary by segregating a nonmagnetic substance between nonmagnetic crystal grains made of a Co-based alloy.

In this embodiment, CoCr—SiO ₂ is used for the nonmagnetic granular layer 120. As a result, SiO ₂ (nonmagnetic substance) segregates between Co-based alloys (nonmagnetic crystal grains) to form grain boundaries, and the nonmagnetic granular layer 120 has a granular structure. Note that CoCr—SiO ₂ is an example, and the present invention is not limited to this. In addition, CoCrRu—SiO ₂ can be preferably used, and Rh (rhodium), Pd (palladium), Ag (silver), Os (osmium), Ir (iridium), Au (gold) can be used instead of Ru. Can also be used. A nonmagnetic substance is a substance that can form a grain boundary around magnetic grains so that exchange interaction between magnetic grains (magnetic grains) is suppressed or blocked, and is cobalt (Co). Any non-magnetic substance that does not dissolve in solution can be used. Examples thereof include silicon oxide (SiOx), chromium oxide (Cr ₂ O ₃ ), titanium oxide (TiO ₂ ), zircon oxide (ZrO ₂ ), and tantalum oxide (Ta ₂ O ₅ ).

In this embodiment, the nonmagnetic granular layer 120 is provided on the underlayer 188 (second underlayer 188b). However, the present invention is not limited to this, and the nonmagnetic granular layer 120 is not provided. The recording medium 100 can also be configured.

The magnetic recording layer 122 has a columnar granular structure in which a nonmagnetic substance is segregated around magnetic grains of a hard magnetic material selected from a Co-based alloy, an Fe-based alloy, and a Ni-based alloy to form a grain boundary. It is a magnetic layer. By providing the nonmagnetic granular layer 120, the magnetic grains can be continuously epitaxially grown from the granular structure. In the present embodiment, the first magnetic recording layer 122a and the second magnetic recording layer 122b having different compositions and film thicknesses are used. The first magnetic recording layer 122a and the second magnetic recording layer 122b are all non-magnetic materials such as oxides such as SiO ₂ , Cr ₂ O ₃ , TiO ₂ , B ₂ O ₃ , Fe ₂ O ₃ , BN, etc. Nitride and carbides such as B ₄ C ₃ can be preferably used.

In this embodiment, CoCrPt—Cr ₂ O ₃ is used for the first magnetic recording layer 122a. In CoCrPt—Cr ₂ O ₃ , Cr and Cr ₂ O ₃ (oxide), which are nonmagnetic substances, segregate around magnetic grains (grains) made of CoCrPt to form grain boundaries, and the magnetic grains are columnar. A grown granular structure was formed. The magnetic grains were epitaxially grown continuously from the granular structure of the nonmagnetic granular layer.

In addition, CoCrPt—SiO ₂ —TiO ₂ is used for the second magnetic recording layer 122b. Also in the second magnetic recording layer 122b, Cr, SiO ₂ and TiO ₂ (composite oxide), which are nonmagnetic substances, segregate around the magnetic grains (grains) made of CoCrPt to form grain boundaries. A granular structure grown in a columnar shape was formed.

The materials used for the first magnetic recording layer 122a and the second magnetic recording layer 122b described above are merely examples, and the present invention is not limited thereto. In the present embodiment, the first magnetic recording layer 122a and the second magnetic recording layer 122b are made of different materials (targets). However, the present invention is not limited to this, and materials having the same composition and type may be used. Examples of the nonmagnetic material for forming the nonmagnetic region include elements such as Si, Ti, and Co, silicon oxide (SiO _x ), chromium oxide (Cr _X O _Y ), titanium oxide (TiO ₂ ), and oxidation. Examples of the oxide include zircon (ZrO ₂ ), tantalum oxide (Ta ₂ O ₅ ), cobalt oxide (CoO or Co ₃ O ₄ ), iron oxide (Fe ₂ O ₃ ), and boron oxide (B ₂ O ₃ ). . Further, nitrides such as _BN, a carbide such as B 4 _{C 3} can also be suitably used.

Furthermore, in this embodiment, one type of nonmagnetic material (oxide) is used in the first magnetic recording layer 122a and two types of nonmagnetic substances (oxides) in the second magnetic recording layer 122b. However, the present invention is not limited to this. It is also possible to use a composite of two or more kinds of nonmagnetic substances in either or both of the first magnetic recording layer 122a and the second magnetic recording layer 122b. Although there is no limitation on the kind of nonmagnetic substance contained at this time, it is particularly preferable to contain SiO ₂ and TiO ₂ as in this embodiment. Therefore, unlike the present embodiment, when the magnetic recording layer 122 is composed of only one layer, the magnetic recording layer 122 is preferably made of CoCrPt—SiO ₂ —TiO ₂ .

The film thickness of the magnetic recording layer 122 is preferably 20 nm or less, for example. The magnetic recording layer 122 is not necessarily composed of a plurality of layers, and may be a single layer.

The auxiliary recording layer 124 is a magnetic layer that is substantially magnetically continuous in the in-plane direction of the main surface of the substrate. The auxiliary recording layer 124 needs to be adjacent or close to the magnetic recording layer 122 so as to have a magnetic interaction. As a material of the auxiliary recording layer 124, for example, CoCrPt, CoCrPtB, or a small amount of oxides can be contained in these. The purpose of the auxiliary recording layer 124 is to adjust the reverse magnetic domain nucleation magnetic field Hn and the coercive force Hc, thereby improving the heat resistance fluctuation characteristic, the OW characteristic, and the SNR. In order to achieve this object, it is desirable that the auxiliary recording layer 124 has high perpendicular magnetic anisotropy Ku and saturation magnetization Ms.

In addition, “magnetically continuous” means that magnetism is continuous. “Substantially continuous” means that the magnetism may be discontinuous not by a single magnet but by grain boundaries of crystal grains when observed in the entire auxiliary recording layer 124. The grain boundaries are not limited to crystal discontinuities, and Cr may be segregated, and further, a minute amount of oxide may be contained and segregated. However, even when a grain boundary containing an oxide is formed in the auxiliary recording layer 124, it is preferable that the area is smaller than the grain boundary of the magnetic recording layer 122 (the content of the oxide is small). The function and action of the auxiliary recording layer 124 are not necessarily clear, but Hn and Hc can be adjusted by having magnetic interaction with the granular magnetic grains of the magnetic recording layer 122 (with exchange coupling), and heat resistance. It is thought that fluctuation characteristics and SNR are improved. In addition, since the crystal grains connected to the granular magnetic grains (crystal grains having a magnetic interaction) have a larger area than the cross section of the granular magnetic grains, the magnetization is easily reversed by receiving a large amount of magnetic flux from the magnetic head. It is thought to improve the characteristics.

The auxiliary recording layer 124 may be a CGC structure (CoupledupGranular 形成 Continuous) that forms a thin film having a high perpendicular magnetic anisotropy and a high saturation magnetization Ms, instead of a single layer. The CGC structure is an exchange energy control layer comprising a magnetic recording layer having a granular structure, a thin film coupling control layer made of a nonmagnetic material such as Pd or Pt, and an alternating laminated film in which thin films of CoB and Pd are laminated. It can consist of.

The protective layer 126 is formed by depositing carbon by a CVD method while maintaining a vacuum. In the present embodiment, the protective layer 126 is made of hydrogenated carbon. The protective layer 126 is a layer for protecting the perpendicular magnetic recording medium 100 from the impact of the magnetic head, and includes diamond-like carbon (DLC). Therefore, the protective layer 126 can be dense and durable.

Generally, carbon film formed by the CVD method has an improved film hardness as compared with that formed by the sputtering method, so that the perpendicular magnetic recording medium 100 can be more effectively protected against the impact from the magnetic head.

In the present embodiment, in the protective layer film forming step for forming the protective layer 126, the protective layer 126 is formed in the second pressure atmosphere after the first pressure atmosphere, and the first pressure is the second pressure. Above pressure.

The film is formed before the protective layer 126 is formed by a configuration in which the pressure (second pressure) when forming the upper part is lower than the pressure (first pressure) when forming the lower part of the protective layer 126. The protective layer 126 is formed on the upper layer (the auxiliary recording layer 124 in this embodiment) at a pressure that does not cause damage (first pressure), and a layer having higher hardness than the lower portion is formed on the upper portion. can do.

In the CVD method, the higher the atmospheric pressure, the shorter the mean free path and the higher the collision frequency between plasma ions. That is, the higher the atmospheric pressure, the more the gas that has become plasma loses energy by repeated collisions and reaches the surface of the disk substrate 110. Therefore, by increasing the atmospheric pressure, the protective layer 126 is formed at a pressure that does not damage the layer (the auxiliary recording layer 124 in this embodiment) formed before the protective layer 126 is formed. Can be membrane. The upper layer (surface) of the protective layer 126 can be formed with high density and hardness by a configuration in which the protective layer 126 is further formed by reducing the pressure.

FIG. 2 is an explanatory diagram for explaining a pressure change and a bias change in the CVD chamber in the protective layer forming step. In the protective layer film forming step of this embodiment, film formation is performed by changing the atmospheric pressure in the same CVD chamber without changing the CVD chamber.

As shown in FIG. 2, first, a gas (ethylene (C ₂ H ₄ ) in this embodiment) is introduced until the pressure in the chamber reaches the first pressure, and ignition (discharge between the electrodes to which high frequency is applied) is performed. To generate plasma. During this time, since the pressure of the atmosphere in the chamber is not stable, the process waits without performing film formation. Therefore, no bias voltage is applied to the substrate at this time.

Thereafter, when the atmospheric pressure in the chamber reaches the first pressure and becomes stable, the protective layer 126 is formed while applying a bias voltage (negative voltage) to the substrate on which the auxiliary recording layer 124 has been formed.

Then, after lowering the bias voltage applied to the substrate, the pressure in the chamber is lowered to the second pressure by lowering the amount of gas introduced, and the protective layer 126 is further formed. Here, when lowering the atmospheric pressure from the first pressure to the second pressure, the bias voltage applied to the substrate is lowered. This makes it possible to stop the film formation when the pressure is not stable. In addition, the film formation can be stably performed by the configuration in which the film formation of the protective layer 126 is restarted while the atmospheric pressure is maintained at the second pressure.

In this embodiment, after forming the protective layer 126, a nitriding process is further performed. The nitriding treatment step is performed by introducing nitrogen gas into the chamber, applying a high frequency bias to the magnetic recording medium, and doping nitrogen on the protective layer surface. Note that the carbon nitride film may be formed by a CVD method using carbon nitride or a sputtering method.

After the protective layer forming step, nitrogen can be contained in the upper portion of the protective layer 126, that is, the surface on which the lubricating layer 128 is formed, by a configuration including a nitriding step of nitriding the protective layer 126.

The lubricating layer 128 is formed of PFPE (perfluoropolyether) by dip coating. PFPE has a long chain molecular structure and has a hydroxyl group (OH ⁻ ) at the end. The hydroxyl group arranged at the end of PFPE has high affinity with nitrogen present on the surface of the protective layer 126. Therefore, by including the protective layer forming step and the nitriding treatment step according to this embodiment, it becomes possible to contain nitrogen on the surface of the protective layer 126, and the adhesion rate (BR) of the lubricating layer 128 to the protective layer 126 is improved. Can be made. Due to the action of the lubricating layer 128, even if the magnetic head comes into contact with the surface of the perpendicular magnetic recording medium 100, damage or loss of the protective layer 126 can be prevented.

(Examples and evaluation)
On the disk substrate 110, a film was formed in order from the adhesion layer 112 to the auxiliary recording layer 124 in an Ar atmosphere by a DC magnetron sputtering method using a film forming apparatus that was evacuated. The adhesion layer 112 was made of CrTi. In the soft magnetic layer 114, the composition of the first soft magnetic layer 114a and the second soft magnetic layer 114c was CoFeTaZr, and the composition of the spacer layer 114b was Ru. The composition of the pre-underlayer 116 was a NiW alloy having an fcc structure. For the underlayer 118, the first underlayer 118a was formed with Ru under low-pressure Ar, and the second underlayer 118b was formed with Ru under high-pressure Ar. The composition of the nonmagnetic granular layer 120 was nonmagnetic CoCr—SiO ₂ . The composition of the first magnetic recording layer 122a was CoCrPt—Cr ₂ O _3, and the composition of the second magnetic recording layer 122b was CoCrPt—SiO ₂ —TiO ₂ . The composition of the auxiliary recording layer 124 was CoCrPtB. The protective layer 126 was formed using C ₂ H ₄ by a CVD method, and nitriding was performed by introducing nitrogen in the same chamber. The lubricating layer 128 was formed to 1.3 nm using PFPE by dip coating.

Here, as Example 11, in the protective layer film forming step for forming the protective layer 126, the film was formed in a 2 Pa C ₂ H ₄ atmosphere and then formed in a 0.7 Pa C ₂ H ₄ atmosphere. A magnetic recording medium 100 was prepared. As a comparative example, a perpendicular magnetic recording medium (hereinafter referred to as Comparative Example 11) formed only in a 2 Pa C ₂ H ₄ atmosphere in the protective layer film forming step of forming the protective layer 126, and 0 A perpendicular magnetic recording medium (hereinafter referred to as Comparative Example 12) on which film formation was performed only in a 7 Pa C ₂ H ₄ atmosphere was prepared. In both the example and the comparative example, the bias applied to the disk substrate 110 is −400V.

FIG. 3 is a diagram comparing the example and the comparative example, in particular, FIG. 3 (a) shows the result of the scratch test, and FIG. 3 (b) shows the result of the corrosion resistance test. Here, the corrosion resistance test detects the number of Co spots deposited on the surface of the direct magnetic recording medium 100 when the perpendicular magnetic recording medium 100 is left for about one week in an environment of room temperature 85 ° C. and humidity 80%. A product of several or more was judged as a defective product (indicated by x in FIG. 3B), and a product of a predetermined number or less was judged as a non-defective product (indicated by ◯ in FIG. 3B).

As shown in FIG. 3A, as a result of the scratch test, the protective layer of Comparative Example 11 generates scratches unless the film thickness is at least about 4.0 nm (indicated by x in FIG. 3A). ) On the other hand, as in Comparative Example 12, the protective layer 126 of Example 11 does not generate a scratch if it is 3.5 nm or more (indicated by a circle in FIG. 3A).

As shown in FIG. 3B, as a result of the corrosion resistance test, the number of Co spots deposited exceeds the predetermined number in the protective layer of Comparative Example 12 unless the film thickness is at least about 5.0 nm. It was found that this is indicated by x in FIG. On the other hand, if the protective layer 126 of Example 11 is 3.5 nm or more, the number of deposited Co spots is not more than a predetermined number.

FIG. 4 is an explanatory diagram for explaining Dh / Gh and corrosion resistance of the protective layer. Here, Dh / Gh and the spectrum of 1350 cm ^-1, excluding the fluorescence from the Raman spectrum in a wave number 900 cm ^-1 ~ wavenumber 1800 cm ^-1 obtained by exciting the protective layer 126 by the argon ion laser beam having a wavelength of 514.5nm This is the peak ratio when the D peak Dh (peak due to DLC) appearing in the vicinity and the G peak Gh (peak due to amorphous graphite carbon) appearing near 1520 cm ⁻¹ are waveform-separated by a Gaussian function.

As shown in FIG. 4, in Example 11, Dh / Gh is 1.02 or less, which is lower than that of Comparative Example 12, but the number of Co spots deposited is less than a predetermined value. On the other hand, in Comparative Example 11, the number of Co spots deposited was not more than a predetermined value, but Dh / Gh was lower than Example 11. Therefore, it can be seen that Example 11 contains less DLC than Comparative Example 12 and more than Comparative Example 11. Therefore, Example 11 has a protective layer 126 that is lower in hardness than Comparative Example 12 but harder than Comparative Example 11.

FIG. 5 is an explanatory diagram for explaining the B / A and scratch test of the protective layer. Here, B / A means background intensity (B) including fluorescence of G peak due to graphite and peak intensity (A) excluding fluorescence when analyzing protective layer 126 using Raman spectroscopy. And the ratio. B / A indicates the ratio of the carbon-hydrogen bonding of the protective layer 126, and the larger the B / A, the higher the hydrogen content. That is, the lower the B / A, the more DLC is contained in the protective layer 126.

As shown in FIG. 5, in Example 11, the B / A is higher than that of Comparative Example 12, but the number of scratches is not more than a predetermined value. That is, Example 11 does not have the same hardness as Comparative Example 12, but has a hardness that is not problematic in the scratch test.

FIG. 6 is an explanatory diagram for explaining the relationship between the thickness of the protective layer and Dh / Gh, and the relationship between the thickness of the protective layer and B / A. As shown in FIG. 6A, in Example 11, Dh / Gh is 1.05 or less even when the protective layer 126 is thin, and has a high Dh / Gh equivalent to Comparative Example 12. I understand.

On the other hand, as shown in FIG. 6B, the B / A of the protective layer 126 of Example 11 is 1.5 or more, which is equivalent to that of Comparative Example 12 and Comparative Example 11, and therefore the amount of DLC in the protective layer 126 There is no difference.

FIG. 7 is a diagram for explaining the evaluation of the example and the comparative example. As shown in FIG. 7, in Example 11, it has the high corrosion resistance which the comparative example 11 has, and can have the sliding resistance (result of a scratch test) and high Dh / Gh which the comparative example 12 has.

As described above, according to the method of manufacturing a magnetic recording medium according to the present embodiment, the protective layer 126 having improved durability such as sliding resistance and corrosion resistance can be provided while maintaining a high coercive force. It becomes possible.

(Second Embodiment)
Next, an embodiment of a perpendicular magnetic recording medium and a method for manufacturing the same according to a second embodiment will be described. The difference between the first embodiment and the second embodiment is only the protective layer 126. Therefore, in the embodiment of the perpendicular magnetic recording medium and the manufacturing method thereof according to the second embodiment described below, only the protective layer 126 will be described in detail, and then the example will be described.

The protective layer 126 according to the second embodiment has a measurement result by Raman spectroscopy, Id / Ig is 2.20 to 2.45, B / A is 1.45 to 1.60, Id / Ig Is X and B / A is Y, Y / X is 0.7 to 0.8.

In the second embodiment, in the protective layer film forming step of forming the protective layer 126, the protective layer 126 is formed in the second pressure atmosphere after forming the protective layer 126 in the first pressure atmosphere. The pressure is 2 Pa or more higher than the second pressure. Furthermore, in the second embodiment, the thickness of the protective layer 126 is 5 nm or less, the thickness of the protective layer formed at the first pressure is M, and the thickness of the protective layer when the film is formed at the second pressure. When N, M / N is 0.25 to 1.

In the protective layer forming step, the pressure at the time of forming the upper part (second pressure) is lower than the pressure at the time of forming the lower part of the protective layer 126 (first pressure), so that the first pressure is vertical. By increasing the uniformity of the protective layer 126 in the in-plane direction of the magnetic recording medium 100 and forming the film at the second pressure, a layer having higher hardness than the lower part can be formed on the upper part.

As in the first embodiment, in the CVD method, the higher the atmospheric pressure, the shorter the mean free path, that is, the higher the collision frequency. That is, the higher the atmospheric pressure, the more the gas that has become plasma loses energy by repeated collisions and reaches the surface of the disk substrate 110. Therefore, by increasing the atmospheric pressure, the plasma gas uniformly covers the surface of the disk substrate 110 to the end, so that the coverage is improved and the corrosion resistance can be ensured. The upper layer (surface) of the protective layer 126 can be formed with high density and hardness by a configuration in which the protective layer 126 is further formed by reducing the pressure.

As a result of the above-described protective layer deposition step, the measurement results by Raman spectroscopy in the protective layer 126 are Id / Ig of 2.20 to 2.45, B / A of 1.45 to 1.60, Id / When Ig is X and B / A is Y, Y / X can be set to 0.7 to 0.8, while suppressing the occurrence of corrosion (improving corrosion resistance) and improving wear resistance. Thus, it is possible to reduce the thickness of the protective layer.

Here, means for changing the pressure in the CVD chamber include changing the flow rate of the gas introduced into the chamber and changing the exhaust amount from the chamber.

In this embodiment, about 3% nitric acid is dropped on the surface of the protective layer 126 and left at room temperature for about 1 hour, and then Co contained in the nitric acid is 0.1 ng / ml or less. When about 3% nitric acid is dropped on the surface of the protective layer 126, that is, the surface of the perpendicular magnetic recording medium 100 and left at room temperature for about 1 hour, Co contained in the magnetic recording layer 122 or the auxiliary recording layer 124 is eluted in the nitric acid. To do. Since the perpendicular magnetic recording medium 100 according to the present embodiment includes the protective layer 126, Co elution from the medium surface can be suppressed to 0.2 ng / ml or less. That is, the corrosion resistance can be improved.

In this embodiment, after forming the protective layer 126, a nitriding process is further performed. The nitriding treatment step is performed by changing the gas from ethylene to nitrogen in the same CVD chamber as that in the protective layer forming step. Specifically, nitrogen is introduced into the chamber to form plasma, and a high frequency bias is applied to the substrate to dope nitrogen into the protective layer surface. Note that the carbon nitride film may be formed by a CVD method using carbon nitride or a sputtering method.

(Examples and evaluation)
As Example 21, the protective layer forming step of forming a protective layer 126, after forming with _C 2 _{H 4} atmosphere of 4 Pa, a perpendicular magnetic recording medium 100 was deposited with _C 2 _{H 4} atmosphere 2Pa It was created. The bias applied to the disk substrate 110 is −400V. Note that the manufacturing process of the perpendicular magnetic recording medium 100 of Example 21 is the same as that of the first embodiment, and thus the description thereof is omitted.

FIG. 8 is an explanatory diagram for explaining an image of a Raman spectrum. Here, the surface of the protective layer 126 is irradiated with an Ar ion laser having a wavelength of 514.5 nm, Stokes components due to Raman scattering appearing in the wave number band of 900 cm-1 to 1800 cm-1 are observed, and the Stokes scattering frequency and incidence are observed. The Raman shift, which is the difference in laser frequency, is measured as a spectrum. The Raman spectrum analysis is usually performed before the lubrication layer 128 is applied (film formation), but may be measured after the lubrication layer 128 is applied. When the Raman spectrum analysis was performed before and after the lubrication layer 128 was applied, the Dh / Gh value showed exactly the same value both before and after, and the Raman spectrum analysis of the perfluoropolyether lubricant layer 128 having a hydroxyl group at the terminal group was performed. It became clear that there was no influence.

Among the wave number 900 cm ^-1 of the Raman spectrum in the range of 1800 cm ^-1, and corrects the background due to fluorescence in linear approximation, (abbreviated to. Less D peak and peak 1350cm around ^-1) lower wavenumber with high frequency side The ratio of the peak height of the D peak to the G peak (abbreviated as Dh and Gh, respectively) when the waveform is separated by a Gaussian function (peaks around 1520 cm ⁻¹ , hereinafter abbreviated as G peak) is Dh / Gh. And Dh is a Stokes component whose frequency is shifted by a dangling bond which is a dangling bond of carbon, and reflects the height of short-range order. Gh is a Stokes component whose frequency is shifted by GLC (Graphite like Carbon). It can be said that the higher the Dh / Gh, the higher the short-range order, the less the amorphous-graphite component, and the harder the diamond-like component.

In FIG. 8, the film quality can be evaluated by the ratio B / A of the background intensity (B) including the fluorescence of the G peak and the peak intensity (A) excluding the fluorescence. B / A shows the ratio of the polymer bond between carbon and hydrogen in the protective layer 126, and it can be said that the larger the B / A, the greater the hydrogen content.

Further, in FIG. 8, when the area intensity of the G peak is Ig and the area intensity of the D peak is Id, the film quality can be evaluated by the peak area intensity ratio Id / Ig. It can be said that the higher the peak area intensity ratio Id / Ig is, the harder the film is, the less the graphite / amorphous component and the more ordered diamond-like component (the better the wear resistance).

FIG. 9 is a diagram showing measurement results obtained by measuring the examples and comparative examples by Raman spectroscopy. FIG. 9A shows Id / Ig, and FIG. 9B shows B / A. Here, the perpendicular magnetic recording medium 100 that was formed only in a 2 Pa C ₂ H ₄ atmosphere in the protective layer film forming step for forming the protective layer 126 was used as Comparative Example 21.

As shown in FIG. 9A, in Example 21, Id / Ig was distributed between 2.20 and 2.45, whereas in Comparative Example 21, it was 2.30 or less. Further, as shown in FIG. 9B, in Example 21, B / A was distributed between 1.45 and 1.60, whereas in Comparative Example 21, it was 1.60 or more.

When the results of FIG. 9 are summarized, Example 21 has higher Id / Ig and lower B / A than Comparative Example 21. That is, it can be seen that Example 21 contains more DLC than Comparative Example 21. Therefore, it can be seen that Example 21 has a harder protective layer 126. Further, in Example 21, when Id / Ig is X and B / A is Y, it can be seen that the relationship Y / X is 0.7 to 0.8 is satisfied.

FIG. 10 is a diagram showing the results of performing a Co elution test on the example and the comparative example. In the protective layer film forming step for forming the protective layer 126, the film was formed in a 2 Pa C ₂ H ₄ atmosphere. The perpendicular magnetic recording medium 100 which was later formed into a film in a 1 Pa C ₂ H ₄ atmosphere was used as Comparative Example 22.

Here, about 100 μl of about 3% nitric acid was dropped on the surfaces of Example 21 and Comparative Example 22 and left at room temperature for about 1 hour, and then the nitric acid was measured with an ICP (Inductively Coupled Plasma) mass spectrometer. The amount of Co was detected by analysis.

As shown in FIG. 10, in Example 21, Co contained in nitric acid, that is, eluted Co is 0.2 ng / ml or less, whereas in Comparative Example 22, the thickness of the protective layer 126 is 5 nm or more. If not, Co was eluted at 0.2 ng / ml or more. Thus, it can be seen that Example 21 has higher corrosion resistance than Comparative Example 22.

FIG. 11 is an explanatory diagram for explaining the result of the sliding resistance test. In FIG. 11, the sliding resistance test was performed by changing the rate at which the protective layer 126 was formed at 2 Pa and the rate at which the protective layer 126 was formed at 4 Pa. In FIG. 11, the rate of deposition at 2 Pa is 0% means that the protective layer 126 is all deposited at 4 Pa, and the rate of deposition at 2 Pa is 100%. Is formed at 2 Pa.

As shown in FIG. 11, it can be seen that the sliding resistance is the best when the rate of film formation at 2 Pa is 75%. This corresponds to the case where the protective layer 126 has a total film thickness of 5 nm and is formed at 1.25 nm at 4 Pa and 3.75 nm at 2 Pa.

FIG. 12 is an explanatory diagram for explaining the results of performing the Co elution test while changing the rate of forming the protective layer at 2 Pa and the rate of forming the protective layer at 4 Pa. Here, as in FIG. 11, the rate of film formation at 2 Pa is 0% means that all the protective layers 126 are formed at 4 Pa, and the rate of film formation at 2 Pa is 100%. This means that all the protective layers 126 were formed at 2 Pa. As shown in FIG. 12, it can be seen that the amount of Co elution increases and the corrosion resistance deteriorates as the rate of film formation at 4 Pa decreases.

From the results of FIGS. 11 and 12, the protective layer having both impact resistance and corrosion resistance is obtained by setting the rate of film formation at 2 Pa to 50 to 75% and the rate of film formation at 4 Pa to 50 to 25%. 126 can be deposited. That is, when the film thickness of the protective layer 126 formed at 4 Pa as the first pressure is M, and the film thickness of the protective layer 126 when formed at 2 Pa as the second pressure is N, M / N is 0. .25 to 1 will be satisfied.

As described above, according to the protective layer 126 of the perpendicular magnetic recording medium 100 according to this embodiment, the uniformity of the protective layer 126 in the in-plane direction is increased by forming the protective layer 126 at the first pressure. Then, the corrosion resistance can be improved, and the protective layer 126 is further formed at the second pressure, which is lower than the first pressure, so that a layer having higher hardness than the lower portion is formed on the upper portion. Is possible. Therefore, it is possible to provide the perpendicular magnetic recording medium 100 having the protective layer 126 that can be thinned while having both wear resistance and corrosion resistance.

(Third embodiment)
Next, a method for manufacturing a perpendicular magnetic recording medium according to the third embodiment will be described. The main difference between the first embodiment and the third embodiment is the method for manufacturing the protective layer 126. Therefore, in the method for manufacturing a perpendicular magnetic recording medium according to the third embodiment described below, only the protective layer 126 will be described in detail, and then the example will be described.

FIG. 13 is a diagram for explaining the configuration of a perpendicular magnetic recording medium 200 as a magnetic recording medium according to the third embodiment. The perpendicular magnetic recording medium 200 shown in FIG. 13 includes a disk substrate 110, an adhesion layer 112, a first soft magnetic layer 114a, a spacer layer 114b, a second soft magnetic layer 114c, a pre-underlayer 116, a first underlayer 118a, and a second layer. The underlayer 118b, the first magnetic recording layer 122a, the second magnetic recording layer 122b, the dividing layer 123, the auxiliary recording layer 124, the protective layer 126, and the lubricating layer 128 are included. The first soft magnetic layer 114a, the spacer layer 114b, and the second soft magnetic layer 114c together constitute the soft magnetic layer 114. The first base layer 118a and the second base layer 118b together constitute the base layer 118. The first magnetic recording layer 122a and the second magnetic recording layer 122b together constitute the magnetic recording layer 122.

As described in detail in the first embodiment, the surface of the magnetic recording medium is protected from the magnetic head flying over the magnetic recording medium by providing the protective layer 126 (carbon-based protective layer) above the magnetic recording layer. Can do. In the method for manufacturing a perpendicular magnetic recording medium according to the third embodiment, the relationship between the gas flow rate and the gas pressure in the chamber when forming the protective layer 126 is such that the gas flow rate (unit: Pa) is relative to the gas pressure (unit: Pa). : Sccm) ratio (gas flow rate / gas pressure) is 75 (sccm / Pa) or more.

For example, when the pressure is changed only by the gas flow rate, the corrosion resistance, the metal ion elution resistance and the mechanical strength are not compatible, and if one of them improves, the other deteriorates. Therefore, in the present embodiment, the gas flow rate can be changed even at the same pressure by changing the exhaust conductance together with the gas flow rate. That is, in order to make the pressure constant, the exhaust speed is increased as the gas flow rate increases. According to this method, since the gas flow rate and the gas exhaust speed are high for a certain pressure, the source gas introduced into the film forming chamber is exhausted in a short time.

Further, since the ratio of the impurity gas existing in the film forming chamber is reduced, the influence of the impurities can be relatively reduced by being placed in a chamber atmosphere with relatively few impurities. This reduces the uptake of impurities and shortens the time that the source gas stays in the chamber after being decomposed in the plasma. In other words, the raw material decomposed by plasma that contributes to film formation is exhausted when it recombines over time and loses energy, and a film is formed mainly by high-energy plasma products that have just been decomposed. The

That is, as in the present embodiment, film formation is performed under the condition that the ratio of gas flow rate (unit: sccm) to gas pressure (unit: Pa) (gas flow rate / gas pressure) is 75 (sccm / Pa) or more. As a result, a denser film is formed by increasing the gas flow rate for a certain pressure. Even if the thickness is reduced, a protective film having sufficient mechanical strength as well as corrosion resistance and metal ion elution resistance can be formed.

In this embodiment, the gas pressure in the chamber when forming the protective layer 126 is preferably in the range of 1 to 3 Pa, for example. If the gas pressure is too high, even if the gas flow rate for that pressure is changed, recombination is likely to occur due to collisions between the source gas and the plasma product in the chamber, along with corrosion resistance and metal ion elution resistance. It becomes difficult to form a film having sufficient mechanical strength.

Furthermore, in the present embodiment, the protective layer 126 is preferably formed by a plasma CVD method. As the hydrocarbon gas used for film formation by the plasma CVD method, for example, a lower hydrocarbon gas represented by ethylene gas (having about 1 to 5 carbon atoms) is preferably used. Moreover, it is preferable that the film thickness of the protective layer 126 formed by the manufacturing method according to the present embodiment is 5 nm or less from the viewpoint of the demand for thinning. In particular, the range of 2 to 5 nm is preferable. If it is less than 2 nm, the performance as a protective layer may be deteriorated.

In this embodiment as well, it is preferable to perform nitriding treatment by a method such as irradiating the surface with nitrogen plasma after forming the protective layer 126. Thereby, the protective layer 126 can be a composition gradient layer containing nitrogen on the lubricating layer side and containing hydrogen on the magnetic recording layer 122 side, and the protective layer 126 is in close contact with the lubricating layer 128, for example. It becomes possible to improve the property suitably.

As described above, according to the method of manufacturing the perpendicular magnetic recording medium according to the third embodiment, the protective layer 126 having sufficient mechanical strength as well as corrosion resistance and metal ion elution resistance is formed even if the film thickness is reduced. be able to. Therefore, the magnetic spacing can be further reduced, and the magnetic head has an extremely low flying height (5 nm or less) due to the rapid increase in recording density in recent years. Thus, a magnetic recording medium having high durability and high reliability can be obtained even under the extremely severe environmental resistance.

The magnetic recording medium of the present embodiment is particularly suitable as a magnetic recording medium mounted on a LUL type magnetic disk device. Due to the further decrease in the flying height of the magnetic head accompanying the introduction of the LUL method, it has been demanded that the magnetic disk operates stably even at an ultra-low flying height of 5 nm or less, for example. Therefore, the magnetic recording medium of this embodiment having high durability and reliability is suitable.

Furthermore, in the third embodiment, a dividing layer 123 (also referred to as an exchange coupling control layer) is provided between the magnetic recording layer 122 and the auxiliary recording layer 124. As a result, the strength of exchange coupling between the magnetic recording layer 122 and the auxiliary recording layer 124 can be suitably controlled to optimize the recording / reproducing characteristics. For example, Ru is preferably used as the dividing layer 123.

In this embodiment, the nonmagnetic granular layer 120 provided in the perpendicular magnetic recording medium 100 of the first embodiment is not provided. This is because it is not always necessary to provide the nonmagnetic granular layer 120 in the perpendicular magnetic recording medium. However, the present invention is not limited to this example, and it is possible to provide a nonmagnetic granular layer as in the first embodiment. It is.

(Examples and evaluation)
Hereinafter, evaluation of Examples and Comparative Examples will be specifically described. First, the configuration of the example and the comparative example will be described, and then the evaluation will be described in detail. FIG. 14 is a diagram showing film forming conditions and evaluation of the protective layer in the example and the comparative example according to the third embodiment.

(Example 31)
Amorphous aluminosilicate glass was molded into a disk shape by direct pressing to produce a glass disk. The glass disk was subjected to grinding, polishing, and chemical strengthening in order, thereby obtaining a smooth non-magnetic disk substrate 110 made of a chemically strengthened glass disk. The disc diameter is 65 mm. When the surface roughness of the main surface of this glass substrate was measured with an AFM (atomic force microscope), it was a smooth surface shape with Rmax of 2.18 nm and Ra of 0.18 nm. Rmax and Ra are in accordance with Japanese Industrial Standard (JIS).

Next, the following layers were sequentially formed on the disk substrate 110 by a DC magnetron sputtering method using a single wafer static facing sputtering apparatus. In the following description, the numerical value in the description of each layer (each material) indicates the composition.

First, a 10 nm Cr-45Ti layer was deposited as the adhesion layer 112. Next, as the soft magnetic layer 114, a laminated film of two soft magnetic layers that are antiferromagnetic exchange coupled with the spacer layer 114b (nonmagnetic layer) interposed therebetween was formed. That is, a 25 nm (Co60Fe40) 92-Ta3-Zr5 layer is first formed as the first first soft magnetic layer 114a, and then a 0.5 nm Ru layer is formed as the spacer layer 114b. Further, as the second soft magnetic layer 114c of the second layer, the same (Co60Fe40) 92-Ta3-Zr5 layer as the first soft magnetic layer 114a of the first layer was formed to a thickness of 25 nm. Then, a 5 nm NiW5 layer was formed as the pre-underlayer 116 on the soft magnetic layer 114. Next, two Ru layers were formed as the base layer 118. That is, as the first underlayer 118a, Ru was formed to a thickness of 12 nm at an Ar gas pressure of 0.7 Pa, and as the second underlayer 118b, Ru was formed to a thickness of 12 nm at an Ar gas pressure of 4.5 Pa.

Then, a magnetic recording layer 122 was formed on the underlayer 118. First, as the first magnetic recording layer 122a, a layer made of (Co—Cr20—Pt18) 93—Cr ₂ O ₃ 7 having a thickness of 2 nm is formed thereon, and as the second magnetic recording layer 122b, the thickness is formed. A 9 nm (Co—Cr10—Pt18) 87-SiO ₂ 5-TiO ₂ 5-CoO3 film was formed. Thereafter, a 0.3 nm Ru layer was formed as the dividing layer 123 (exchange coupling control layer), and a 7 nm Co—Cr18—Pt13—B5 film was formed thereon as the auxiliary recording layer 124. Then, a protective layer 126 (carbon protective layer) was formed on the auxiliary recording layer 124 by a CVD method using ethylene gas. At this time, the pressure was set to 1 Pa in a state where ethylene gas was flowed into the chamber at 75 sccm, and a bias of −400 V was applied to the substrate. The thickness of the protective layer 126 was 4.5 nm. Subsequently, nitriding treatment was performed by exposing the formed protective layer 126 to nitrogen plasma.

After the perpendicular magnetic recording medium on which the protective layer 126 has been formed in this way is washed, a perfluoropolyether (PFPE) lubricant is then applied on the protective layer 126 by a dip method, thereby forming the lubricating layer 128. Formed. After the film formation, the perpendicular magnetic recording medium was heat-treated in a baking furnace at 110 ° C. for 60 minutes. As described above, the perpendicular magnetic recording medium 200 of Example 31 was obtained.

(Examples 32 to 39)
Example 32 to Example are the same as Example 31 except that the flow rate and gas pressure of ethylene gas introduced into the chamber when the protective layer 126 is formed are changed as shown in FIG. 39 perpendicular magnetic recording media were obtained.

(Comparative Examples 31-37)
Comparative Example 31 to Comparative Example were performed in the same manner as in Example 31 except that the flow rate and gas pressure of ethylene gas introduced into the chamber when the protective layer 126 was formed were changed as shown in FIG. 37 perpendicular magnetic recording media were obtained.

(Evaluation)
Next, the magnetic recording media of Examples 31 to 39 and Comparative Examples 31 to 37 were evaluated by the following test methods. FIG. 15 is a diagram showing a change in the Co elution amount test result depending on the film forming conditions of the example and the comparative example shown in FIG. FIG. 16 is a diagram showing changes in the pin-on test results depending on the film forming conditions of the example and the comparative example shown in FIG.

[Abrasion resistance evaluation]
In order to evaluate the wear resistance of the protective layer 126, a pin-on test was performed. In the pin-on test, a ball fixed to the tip of a rod with a load of 30 g is slid onto a position of a radius of 26 mm on a perpendicular magnetic recording medium rotated at 91.8 rpm until the protective layer 126 breaks. This was done by measuring the pass count. It can be said that the higher the pass count, the better the wear resistance of the protective layer 126.

[Evaluation of metal ion dissolution resistance (corrosion resistance)]
In order to evaluate the corrosion resistance of the protective layer 126, 100 μL of 3% nitric acid was dropped on the surface of the perpendicular magnetic recording medium for 8 points each and left at room temperature for about 1 hour. Measure the radius of and adjust to 1 mL. The metal components of these droplets were quantified with an ICP (Inductively Coupled Plasma) mass spectrometer, and the Co elution amount per 1 m ^{2 of the} perpendicular magnetic recording medium surface was calculated from the solution concentration and the dropping area. It can be said that the smaller the amount of Co eluted, the better the corrosion resistance of the protective layer.

As is apparent from the results of FIGS. 14, 15, and 16, the ratio of the gas flow rate to the gas pressure in the chamber (gas flow rate / gas pressure) when forming the protective layer 126 is 75 (sccm / Pa) or more. In the perpendicular magnetic recording media of Examples 31 to 39, as the gas flow rate / gas pressure ratio was increased, the pin-on test results were slightly improved, and the Co elution amount was significantly reduced. That is, it was confirmed that the perpendicular magnetic recording medium according to the present invention can form the protective layer 126 having both metal ion elution resistance, corrosion resistance thereby, and mechanical strength. Here, from Comparative Examples 33 and 34 and Examples 34, 35 and 36, Id / Ig in the case of having both corrosion resistance and mechanical strength was 2.4 or less.

On the other hand, in the perpendicular magnetic recording media of Comparative Examples 31 to 37 in which the ratio of the gas flow rate to the gas pressure in the chamber when forming the protective layer 126 (gas flow rate / gas pressure) is less than 75 (sccm / Pa), There was almost no change in the pin-on test and the Co elution amount, and the improvement effect could not be confirmed.

Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

For example, in the protective layer forming step of the above-described embodiment, the bias applied to the substrate is constant. However, the present invention is not limited to this, and the hardness of the protective layer may be changed by changing the bias. it can.

In the above-described embodiments, the perpendicular magnetic recording medium has been described as the magnetic recording medium. However, the present invention is also suitably used for patterned media such as discrete types and bit pattern types, and in-plane magnetic recording media. be able to.

The present invention can be used as a method for manufacturing a magnetic recording medium mounted on a perpendicular magnetic recording type HDD (hard disk drive) or the like and as a magnetic recording medium.

Claims (17)

A method of manufacturing a magnetic recording medium comprising a magnetic recording layer and a protective layer in this order on a substrate,
A magnetic recording layer forming step of forming the magnetic recording layer;
A protective layer forming step of forming the protective layer using a CVD (Chemical Vapor Deposition) method;
Including
In the protective layer film forming step, the protective layer is formed in an atmosphere at a second pressure after being formed in an atmosphere at a first pressure,
The method of manufacturing a magnetic recording medium, wherein the second pressure is less than the first pressure. The magnetic recording medium is a perpendicular magnetic recording medium,
2. The magnetic recording according to claim 1, further comprising an auxiliary recording layer film forming step of forming an auxiliary recording layer magnetically substantially continuous in a planar direction of the substrate before the protective layer film forming step. A method of manufacturing a medium After the protective layer forming step,
A nitriding step for nitriding the surface of the protective layer;
A lubricating layer forming step of forming the lubricating layer;
Including
3. The method of manufacturing a magnetic recording medium according to claim 1, wherein the nitriding step is performed by a method of doping nitrogen into the protective layer, a CVD method, or a sputtering method. 4. The method of manufacturing a magnetic recording medium according to claim 1, wherein the protective layer contains diamond-like carbon. A magnetic recording medium manufactured using the magnetic recording medium manufacturing method according to claim 1. A magnetic recording medium comprising at least a magnetic recording layer on a substrate and a protective layer containing diamond-like carbon in this order,
The height of the G peak due to graphite carbon in Raman spectroscopy is Gh, the height of the D peak due to D peak due to diamond-like carbon is Dh, and the background intensity including the fluorescence of the G peak. Assuming that the peak intensity excluding the fluorescence of B and the G peak is A, the measurement result by Raman spectroscopy of the protective layer is Dh / Gh of 1.05 or less, and B / A is 1.5 or less. A magnetic recording medium characterized by the above. On a substrate, a magnetic recording medium comprising a magnetic recording layer and a protective layer containing diamond-like carbon in this order,
The area intensity of the G peak due to graphite carbon in Raman spectroscopy is Ig, the area intensity of the D peak due to diamond-like carbon is Id, the background intensity including the fluorescence of the G peak is B, and the G Assuming that the peak intensity excluding the peak fluorescence is A, the measurement results of the protective layer by Raman spectroscopy are Id / Ig of 2.20 to 2.45 and B / A of 1.45 to 1. 60. A magnetic recording medium characterized in that Y / X is 0.7 to 0.8 where Id / Ig is X and B / A is Y. The magnetic recording medium according to claim 7, wherein the protective layer has a thickness of 5.0 nm or less. 8. The method according to claim 7, wherein about 3% nitric acid is dropped on the surface of the magnetic recording medium and left at room temperature for about 1 hour, and then Co contained in the nitric acid is 0.2 ng / ml or less. 9. A magnetic recording medium according to 8. A method of manufacturing a magnetic recording medium comprising a magnetic recording layer on a substrate and a protective layer containing diamond-like carbon in this order,
A magnetic recording layer forming step of forming the magnetic recording layer;
A protective layer forming step of forming the protective layer using a CVD (Chemical Vapor Deposition) method;
Including
In the protective layer forming step, after forming the film in an atmosphere of the first pressure, the protective layer is formed in an atmosphere of a second pressure that is a pressure lower than the first pressure,
When the film thickness of the protective layer formed at the first pressure is M and the film thickness of the protective layer when formed at the second pressure is N, M / N is 0.25 to 1. A method of manufacturing a magnetic recording medium. The method of manufacturing a magnetic recording medium according to claim 10, wherein the first pressure is a pressure higher by 2 Pa or more than the second pressure. A method of manufacturing a magnetic recording medium in which at least a magnetic recording layer and a carbon-based protective layer are sequentially provided on a substrate,
The relationship between the gas flow rate and the gas pressure in the chamber when forming the carbon-based protective layer is such that the ratio of the gas flow rate (unit: sccm) to the gas pressure (unit: Pa) (gas flow rate / gas pressure) is 75 ( sccm / Pa) or higher, a method for producing a magnetic recording medium, 13. The method of manufacturing a magnetic recording medium according to claim 12, wherein the gas pressure in the chamber when forming the carbon-based protective layer is in the range of 1 to 3 Pa. 14. The method of manufacturing a magnetic recording medium according to claim 12, wherein the carbon-based protective layer is formed by a plasma CVD method. 15. The method of manufacturing a magnetic recording medium according to claim 12, wherein the carbon-based protective layer has a thickness of 5 nm or less. 16. The magnetic recording medium according to claim 12, wherein the start / stop mechanism is mounted on a load / unload type magnetic disk device and used under a head flying height of 5 nm or less. The method for producing a magnetic recording medium according to any one of the above. The carbon-based protective layer has an Id / Ig ratio of 2.4 or less, which is a ratio of the area intensity Ig of the G peak attributed to graphite carbon in Raman spectroscopy to the area intensity Id of the D peak attributed to diamond-like carbon. The method of manufacturing a magnetic recording medium according to claim 12, wherein the method is a magnetic recording medium.

Images