JP2581232B2 - Manufacturing method of magnetic recording medium - Google Patents

Description

The present invention relates to a method for manufacturing a magnetic recording medium that is a storage element of a fixed magnetic recording device used as an external recording device such as a computer.

[Conventional technology]

In recent years, with the development of computers, word processors, and the like, fixed magnetic recording devices—particularly, small fixed magnetic recording devices—have become widespread as external storage devices.

In a fixed magnetic recording apparatus, CSS (Co-ntact S) is generally used.
tart Stop) method is adopted. A magnetic recording medium (hereinafter, also simply referred to as a medium) is incorporated in a device in combination with a magnetic head. The magnetic head comes into contact with the surface of the stopped medium when the device is stopped, and stops when the device is driven (information During recording / reproduction), the device slightly floats on the surface of the medium rotating at high speed and travels. Therefore, the media surface must be appropriately rough so that the magnetic head has low friction so that the magnetic head can slide smoothly, and that the magnetic head does not stick when stopped. It is important to ensure durability and reliability. In addition, since the amount of processing information is increasing, the market demand for a large storage capacity of the device is strong, and the high recording density of the media used as the storage element is strongly demanded. Therefore, by increasing the coercive force, Has been requested.

As a medium, generally, a nonmagnetic metal underlayer made of Cr, a nonmagnetic metal base layer made of Co, is formed on a nonmagnetic substrate in which a Ni--P alloy layer is formed by electroless plating on the surface of a donut-shaped Al alloy plate.
There is known a configuration in which a ferromagnetic metal magnetic layer made of an alloy and a protective layer made of C are sequentially formed and laminated by a sputtering method.

In such a medium, the surface roughness depends on the surface roughness of a substrate serving as a support for each layer constituting the medium, but further largely depends on the substrate temperature at which the respective layers are formed. It is known that the higher the temperature, the smoother the surface of the medium after film formation and the higher the frictional force.

Further, in order to increase the coercive force of the medium, (a) the crystal magnetic anisotropy of the magnetic layer is increased by appropriately selecting the Co alloy and the composition forming the magnetic layer.

(B) Increase the crystallinity (orientation growth) of the magnetic layer by increasing the thickness of the Cr layer, which is the underlayer of the magnetic layer.

(C) The crystallinity (orientation growth) of the Cr underlayer and the Co alloy magnetic layer is increased by increasing the substrate temperature during film formation.

(D) Forming a magnetic layer by increasing the substrate temperature during film formation
It promotes intragranular segregation of impurities and component elements in microcrystal grains of a Co alloy.

Such methods are known.

[Problems to be solved by the invention]

As described above, the surface of the medium becomes smoother and friction increases as the substrate temperature increases when the layers constituting the medium are deposited, and becomes rougher and lower as the substrate temperature decreases. At present, it is necessary to keep the substrate temperature at 200 ° C. or lower in order to obtain a low-friction medium that can withstand practical use.

On the other hand, the coercive force of the media can be increased by the above-described methods, but at present, it is not possible to stably mass-produce media having a coercive force exceeding 1300 Oe required from the market at a substrate temperature of 200 ° C. or less. . For example,
At a substrate temperature of 200 ° C., about 1000 Oe for a magnetic layer made of a Co--Ni--Cr alloy, and 1 for a magnetic layer made of a Co--Cr--Ta alloy.
It is about 200 Oe, and the coercive force decreases as the substrate temperature decreases.

As described above, it is necessary to lower the substrate temperature to 200 ° C. or lower in order to reduce the friction of the media surface, and it is necessary to increase the substrate temperature to 200 ° C. or higher to increase the coercive force of the media. With the above-described conventional method, a medium having low friction and high coercive force at the level required from the market cannot be obtained.

The present invention has been made in view of the above-described problems, and has as its object to provide a manufacturing method capable of stably mass-producing media having low friction and high coercive force.

[Means for solving the problem]

According to the present invention, a surface including a step of depositing and laminating a Cr underlayer, a Co alloy magnetic layer, and a hard protective layer in this order on a textured nonmagnetic substrate by a sputtering method. In the method for manufacturing an internal magnetic recording medium, the temperature of the non-magnetic substrate is maintained at a temperature in a range of 150 ° C. or more and 200 ° C. or less, and a Cr underlayer and a Co alloy are applied while a bias voltage is applied to the non-magnetic substrate. The magnetic layer is formed by sputtering, and the relative load length of the relative load curve of the surface shape is 10%.
The value obtained by subtracting the cutting depth at a relative load length of 1% from the cutting depth at 150% has a surface roughness of 150 ° or more.

[Action]

The bias applied to the substrate during the formation of the Cr underlayer and the Co alloy magnetic layer has the effect of improving the crystallinity of both layers and promoting the segregation within the microcrystal grains of the ferromagnetic metal magnetic layer. The effect of increasing the coercive force can be obtained, and the effect increases as the bias voltage increases. Therefore, by holding the substrate temperature at a relatively low temperature of 200 ° C. or less, by forming the two layers while applying a bias to the substrate,
A medium having low friction and high coercive force can be obtained.

The lower the substrate temperature, the lower the friction of the media surface, but the lower the coercive force. Therefore, it is necessary to increase the coercive force by setting the bias voltage higher than the bias voltage. However, as the bias voltage is increased, the sputtering voltage becomes unstable, and film formation cannot be performed satisfactorily. There is a limit to increasing the coercive force by applying a bias, so that the substrate temperature cannot be lowered too much.

By holding the substrate temperature at a temperature in the range of 150 ° C. or more and 200 ° C. or less, and by forming the two layers while applying an appropriate bias voltage to the substrate, a medium having low friction and high coercive force can be obtained. Mass production can be performed stably.

〔Example〕

The inner and outer diameters of an Al alloy disk are machined into a donut shape, and the surface is machined flat by grinding and polishing. A Ni-P alloy layer with a thickness of about 20 μm is formed on this surface by electroless plating,
polished to a thickness of m, and the surface roughness is center line average roughness Ra of 20
Mirror-polished to about Å, and further textured to make the surface roughness about 70 ° in Ra, which is used as the substrate of the media.

After the substrate obtained in this way is ultra-precisely cleaned, it is mounted on a holder, and a Cr underlayer, a Co alloy magnetic layer, and a C protection layer are formed on the substrate surface by an inline sputtering apparatus as shown in the conceptual diagram of FIG. The layers are sequentially formed by a DC magnetron sputtering method.

FIG. 2 is a conceptual diagram showing a holder and a state in which the holder is conveyed in the apparatus. FIG. 2 (a) is a view of the holder as viewed from the front, and FIG. 2 (b) is a view of the holder as viewed from the side. The figure is shown. In FIG. 2, a holder 6 is a wheel provided at a lower end.
103 moves on a rail 102 laid in the apparatus. A plurality of (in the figure, nine cases) substrates 101 can be mounted on the holder 6, and the portion of the holder 6 where the substrates 101 are mounted is insulated from the ground by an insulator 104. A bias is applied to the substrate 101 from a DC bias power supply (not shown) provided outside the device, from an electrode introduction port 106 attached to the side wall 1 of the device.
And applying a voltage to a mounting portion of the holder 6 on the substrate 101 via a bias applying shoe 12 connected thereto and having elastic contact with the surface of the holder 6 and sliding on the surface as the holder 6 moves. It is performed by

The loading chamber 2 shown in FIG.
Set on a rail (not shown) in the 5x
The substrate is heated by a substrate heater 7 with a high vacuum of 10 ⁻⁵ Torr. After the board reaches the specified temperature, the loading door 5a
Is opened and closed to transfer the holder 6 into the film forming chamber 3. Deposition chamber 3
The inside is set to an Ar atmosphere of 10 mTorr, and a Cr target 8, a Co alloy target 9, and a C target 10 are sequentially sputtered while transporting the holder 6, and a Cr underlayer (film thickness 1500) is formed on the substrate.
Å), Co alloy magnetic layer (thickness 450,), C protective layer (thickness 400)
Å) are sequentially formed and laminated. When forming the Cr underlayer and the Co alloy magnetic layer, an electrode introduction port (not shown) attached to the side wall 1 and a bias connected to the electrode are provided by a DC bias power supply 11 provided outside the side wall 1. A bias is applied to the holder 6 via the application shoe 12. A plurality of electrode introduction ports and bias application shoes 12 are shown (four are shown in the figure). These bias application shoes 12 come into contact with each other as the holder 6 is conveyed, so that the film is formed throughout the film formation. Make sure that the bias is not interrupted. After the film is formed up to the C protective layer, the holder 6 is conveyed to the extraction chamber 4 by opening and closing the partition door 5b. Remove it.

As described above, the composition of the magnetic layer Co- ₃₀ Ni- _7.5 Cr
(Numerical values indicate atomic%) and Co- ₁₂ Cr-
Two kinds of media and ₂ Ta media were produced. Further, at the time of film formation, media having different conditions for each type were manufactured by changing the substrate temperature and the bias voltage. At that time, the substrate temperature was suppressed to a maximum of 300 ° C in consideration of the thermal deformation of the substrate and the magnetization of the Ni-P alloy on the substrate surface,
Since the sputter discharge becomes unstable when the bias voltage exceeds -600 V, the upper limit is -500 V.

With respect to the media thus manufactured, the relationship between the substrate temperature during film formation, the bias voltage, the media surface roughness, and the coercive force was examined.

The media surface roughness is a value tp10− obtained by subtracting the cutting depth at a relative load length of 1% from the cutting depth at a relative load length of 10% in the relative load curve of the surface shape.
Indicated by 1.

As a result of the investigation, the media surface roughness did not depend on the composition of the magnetic layer. FIG. 3 shows the relationship between the substrate temperature and the media surface roughness using the bias voltage as a parameter. Also,
FIG. 4 shows the relationship between the bias voltage and the media surface roughness using the substrate temperature as a parameter. From FIGS. 3 and 4, it can be seen that the media surface roughness increases as the substrate temperature decreases, irrespective of the presence or absence of bias application, but the degree of the increase decreases as the bias voltage increases.

It is known that there is a relationship shown in FIG. 7 between the media surface roughness and the dynamic friction coefficient. In FIG. 7, the abscissa indicates the media surface roughness tp10-1, and the ordinate indicates when the media is rotated at such a low speed that the magnetic head does not float and the magnetic head is slid over the media surface for one hour. The dynamic friction coefficient _μ60min is shown, and the relationship that the dynamic friction coefficient _μ60min decreases as the media surface roughness increases is shown. To a low friction media surface to such an extent to satisfy the market demand is required that mu _60min is about 0.5 or less, Tp10-1 from Figure 7 it can be seen that shall be not less than about 150 Å. Therefore, it can be seen from FIG. 3 that the substrate temperature needs to be 200 ° C. or less.

Next, the media composition of the magnetic layer is Co- ₃₀ Ni- _7.5 Cr, showing the relationship between the substrate temperature and the coercive force Hc in Fig. 5 a bias voltage as a parameter. As can be seen from FIG. 5, the coercive force increases as the substrate temperature increases. Further, by applying a bias, the coercive force can be increased at the same substrate temperature, and the higher the bias voltage, the greater the increase. For example, at a substrate temperature of 200 ° C., the coercive force is about 1050 Oe when the bias voltage is 0 V, but the coercive force increases as the bias is applied and the voltage is increased, and is increased to about 1650 Oe by applying the bias voltage −500 V. Can be enhanced. Moreover, in this case, the change in the media surface roughness is small as seen in FIG. When the substrate temperature is 150 ° C, the bias voltage is 0V
In this case, the coercive force is about 900 Oe, but by applying an appropriate bias voltage, the coercive force can be increased to about 1400 Oe while maintaining the minimum required media surface roughness.

FIG. 6 shows the relationship between the substrate temperature and the coercive force of a medium having a magnetic layer composition of Co- ₁₂ Cr- ₂ Ta using the bias voltage as a parameter. Yes, a high coercive force can be realized at a relatively low substrate temperature by applying a bias during film formation.

Thus, by maintaining the substrate temperature at the time of film formation in the range of 150 ° C. or more and 200 ° C. or less, and applying an appropriate bias voltage to the substrate during the formation of the Cr lower layer and the Co alloy magnetic layer, It is possible to stably mass-produce media having low friction and high coercive force.

In the above embodiment, the film is formed by the DC magnetron sputtering method, but the bias application is similarly effective in the RF magnetron sputtering method. The method of applying a bias to the substrate is not limited to the method of the embodiment. Further, it goes without saying that the material of the protective layer is not limited to C.

〔The invention's effect〕

According to the present invention, when forming a Cr underlayer and a Co alloy magnetic layer on a non-magnetic substrate having a textured surface by sputtering, the substrate temperature is maintained at a temperature within a range of 150 ° C. or more and 200 ° C. or less. The film is formed while applying a bias to the substrate, and the value obtained by subtracting the cutting depth at a relative load length of 1% from the cutting depth at a relative load length of 10% in the relative load curve of the surface shape is 150 ° or more. It has surface roughness. By applying a bias in this manner, a high coercive force can be realized even when a film is formed at a relatively low substrate temperature as described above, and a magnetic recording medium having a low friction and a high coercive force can be stabilized. It is possible to mass-produce the fixed magnetic recording device, and to cope with an increase in the capacity and reliability of the fixed magnetic recording device.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an in-line sputtering apparatus used in one embodiment of the present invention, FIG. 2 is a conceptual diagram showing a holder of a substrate and a transfer state of the holder in one embodiment of the present invention, and FIG. FIG. 4 is a diagram showing the relationship between the temperature and the media surface roughness using the bias voltage as a parameter, FIG. 4 is a diagram showing the relationship between the bias voltage and the media surface roughness using the substrate temperature as a parameter, and FIG. 5 is Co- ₃₀ Ni- FIG. 6 is a diagram showing the relationship between substrate temperature and coercive force using a bias voltage as a parameter for a medium provided with a magnetic layer made of a _7.5 Cr alloy, and FIG. 6 shows a medium provided with a magnetic layer made of a Co- ₁₂ Cr- ₂ Ta alloy. 7 is a diagram showing the relationship between the substrate temperature and the coercive force using the bias voltage as a parameter, and FIG. 7 is a diagram showing the relationship between the media surface roughness and the dynamic friction coefficient. 6 Holder, 7 Substrate heater, 8 Cr target, 9 Co alloy target, 11 DC bias power supply, 12 Bias power supply, 101 Substrate, 104
Insulator, 106 ... Electrode introduction port.

Claims (1)

(57) [Claims] 1. A method of manufacturing a longitudinal magnetic recording medium, comprising the steps of forming a Cr underlayer, a Co alloy magnetic layer, and a hard protective layer on a non-magnetic substrate having a textured surface in this order by sputtering and laminating the layers. In the method, the temperature of the non-magnetic substrate is increased by 15
A Cr underlayer and a Co alloy magnetic layer were formed by sputtering while maintaining a temperature in the range of 0 ° C or more and 200 ° C or less, and a bias voltage was applied to the non-magnetic substrate. A longitudinal magnetic recording medium characterized in that a value obtained by subtracting a cutting depth at a relative load length of 1% from a cutting depth at a relative load length of 10% of the curve has a surface roughness of 150 ° or more. Production method.