JPH04117622A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve contact start stop (CSS) durability by specifying the relation between the flow rate of gaseous O2 and a sputtering rate per 1 sheet of targets at the time of executing reactive sputtering to form a film essentially consisting of Fe3O4 on a rigid substrate. CONSTITUTION:A magnet 11 is disposed on the rear surface side of the target 10 and a substrate is disposed to face the front surface of the target 10. The film essentially consisting of the Fe3O4 is formed on the rigid substrate by the reactive sputtering in an atmosphere contg. gaseous O2 and this film is oxidized to form the magnetic layer of a continuous thin film type essentially consisting of the gamma-Fe2O3. The relation between the flow rate of the gaseous O2 OGF (SCCM) and the sputtering rate SR (mum/min) per 1 sheet of the targets is specified to OGF=(55+ or -10)SR. The CSS durability of the resulted magnetic layer essentially consisting of the gamma-Fe2O3 is enhanced in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for manufacturing a magnetic recording medium having a continuous thin film type magnetic layer containing γ-FaxOa as a main component.

<Prior Art> A hard type magnetic disk in which a magnetic layer is formed on a rigid substrate and a floating magnetic head are used in magnetic disk drives used in computers and the like.

Conventionally, coated magnetic disks have been used in such magnetic disk drive devices, but as the capacity of magnetic disks has increased, sputtering methods have been used because they are advantageous in terms of magnetic properties, recording density, etc. 2. Description of the Related Art Thin-film magnetic disks having a continuous thin-film magnetic layer formed by a vapor deposition method or the like have come into use.

Thin-film magnetic disks are made by plating a N1-P underlayer on a helium-based disk-shaped metal plate, or by oxidizing the surface of this metal plate to form alumite. It is generally constructed by sequentially depositing a Cr layer, a metal magnetic layer such as Co--Ni, and a protective lubricant film such as C by sputtering.

However, a metal magnetic layer such as Co--Ni has low corrosion resistance and low hardness, causing problems in reliability. On the other hand, Japanese Patent Application Laid-Open Nos. 62-43819 and 63-17521
The magnetic thin film mainly composed of iron oxide as described in Japanese Patent No. 9 is chemically stable, so there is no fear of corrosion, and it also has sufficient hardness.

In a contact start/stop (C3S) type hard disk drive, the surface of the magnetic layer of the disk comes into contact with the floating magnetic head when the disk is started and stopped, which tends to cause damage to the surface of the magnetic layer. The lower the flying bite of the floating magnetic head, the more likely this damage will occur.

The continuous thin film type magnetic layer whose main component is γ-Fezes is
Due to its high hardness, C8S durability is good, but in order to further increase recording density, it is necessary to further reduce the flying bite, so further improvement of C8S durability is required.

<Problem to be solved by the invention> The present invention has been made in view of the above circumstances.
An object of the present invention is to improve the C8S durability of a magnetic recording medium having a continuous thin film type magnetic layer containing -Fezes as a main component on a rigid substrate.

<Means for Solving the Problems> Such objects are achieved by the following inventions (1) to (3).

(1) Forming a film mainly composed of Fe504 on a rigid substrate by performing reactive sputtering in an atmosphere containing gas using a target mainly composed of Fe,
Next, in a method for manufacturing a magnetic recording medium, which includes a step of forming a continuous thin film type magnetic layer containing γ-Fetus as a main component by oxidizing this film, when performing the reactive sputtering, 02 A method for manufacturing a magnetic recording medium, characterized in that the relationship between gas flow rate OGF (SCCM) and sputter rate SR (μm/min) is OGF=(55±10)SR.

(2) A magnetron sputtering method is used for the reactive sputtering, and the maximum value of the component of the magnetic flux density on the target surface in a direction parallel to the target surface is set to 200 to 600G.
The method for manufacturing a magnetic recording medium according to the above (1), wherein the method is set as follows.

(3) The reactive sputtering is performed at 5.0X10-”~3.0
The above (1) or (2) carried out under a pressure of X10-1Pa
) The method for manufacturing a magnetic recording medium according to .

Direct neutralization method, direct reduction method, direct oxidation method, or indirect method is usually used to form a continuous thin film type magnetic layer mainly composed of γ-Fetus, but sputtering control is easy. The direct oxidation method is preferably used because of its high film formation rate and high film formation rate.

In the direct oxidation method, reactive sputtering is performed using an Fe target in an Ar gas atmosphere containing 0□ gas to form a Fe5Oa film, which is then oxidized to form γ-Fears.
This is a method for obtaining membranes.

In the present invention, in such a direct oxidation method, the relationship between the 0□ gas flow rate OGF (SCCM) per target and the sputtering rate S R (u/win) is expressed as OGF = (55 ± 10 )SR.

If reactive sputtering is performed with OGF and SR in this relationship, and a film containing Fe*0+ as the main component is formed,
The C8S durability of the finally obtained magnetic layer containing γ-Fears as a main component is extremely high.

<Specific configuration> Hereinafter, a specific configuration of the present invention will be explained in detail.

In the present invention, the above-described direct oxidation method is used when forming a continuous thin film type magnetic layer containing γ-Fe2es as a main component on a rigid substrate.

That is, in the present invention, a film mainly composed of Fe5O4 is formed on a rigid substrate by performing reactive sputtering in an atmosphere containing 0□ gas using a target mainly composed of Fe, and then this By oxidizing the film, a continuous thin film type magnetic layer containing γ-Fears as a main component is formed.

In the present invention, in order to improve the durability of the magnetic layer during the above-mentioned reactive sputtering, the
□Gas flow rate OG F (SCCM) and sputter rate S
The relationship with R (μm/min) is OGF=(55±10)SR, preferably OGF=(55±5)SR.

By performing reactive sputtering under such conditions, the durability of the magnetic layer, especially the C8S durability, becomes extremely high.

There is no particular limit to the range of sputter rate SR, but usually,
It is set to about 0.1 to 0.5 um/min.

The sputtering rate SR can be set to a desired value by appropriately selecting the input power, atmospheric pressure, the distance between the target and the substrate, the shape of the mask placed between the target and the substrate, etc. When magnetron sputtering is used, the intensity can also be adjusted by adjusting the strength of the magnetic field leaking from the target.

Note that in the present invention, it is preferable that the 02 gas be introduced near the substrate.

Details of Fear4 thin film formation by direct oxidation method can be found in the Transactions of the Institute of Electronics and Communication Engineers '80/9 VOl, J63-CN [L
9p, 609-616, and in the present invention, it is preferable to form the magnetic layer according to this.
At this time, the 02 gas flow rate OGF and the sputtering rate SR are set to the above relationship.

In addition, in the present invention, it is preferable to use a reactive DC sputtering method as the above-mentioned reactive sputtering. By using the DC sputtering method, non-uniformity of magnetic properties within the plane of the magnetic layer can be reduced.

This is considered to be due to the following reasons.

In the above-described reactive sputtering, atoms and molecules flying from the target are oxidized to Fe504 before they adhere to the substrate surface.

In the DC sputtering method, the spread of plasma is smaller than in the RF (radio frequency) sputtering method, and it is thought that the atmosphere near the substrate is less affected by the plasma. Therefore, fluctuations in the 02 gas concentration near the substrate are suppressed, and the oxidation degree distribution within the plane of the sputtered film becomes more uniform.

The Fe50< film formed by reactive sputtering is further oxidized to become γ-Fears, but the degree of oxidation of the finally obtained γ-Fezes is higher than that of Fe produced at an intermediate stage.
It depends on the degree of oxidation of 504. For this reason, the γ obtained from the Fe5O4 film formed by reactive DC sputtering
-The Fears film has little non-uniformity in the degree of oxidation within the plane, and as a result, uniform magnetic properties can be obtained within the plane.

In addition, the DC sputtering method uses Fe5O4 on both sides of the substrate at the same time.
It is particularly effective when forming a film.

When sputtering films are simultaneously formed on both sides of a substrate using the RF sputtering method, sputter targets are placed facing each other on both sides of the substrate, and a high frequency electric field is applied to each target independently. In this case, plasma corresponding to each high frequency electric field is generated on both sides of the substrate.

However, since there is usually a central hole penetrating the substrate at the center of the substrate, these electric fields interfere with each other near the substrate, making plasma discharge unstable. Therefore, the oxygen concentration near the substrate becomes unstable. Moreover, the instability of plasma discharge exhibits different aspects on both sides of the substrate, resulting in a difference in oxygen concentration on both sides of the substrate.

In reactive sputtering in the direct oxidation method, when the oxygen concentration fluctuates, the degree of oxidation of the sputtered film varies locally, resulting in non-uniform magnetic properties within the plane.

To alleviate this problem, a plug is inserted into the center hole of the board to prevent mutual interference between the electric fields on both sides of the board, but fitting the plug takes time and reduces productivity. Furthermore, interference between the electric fields on both sides of the substrate occurs not only in the center hole of the substrate (but also in the gap between the holder or tray that holds the substrate during sputtering and the substrate).

However, by using the DC sputtering method, it is possible to prevent non-uniformity of magnetic properties caused by mutual interference of high frequency electric fields.

However, in the present invention, not only the DC sputtering method but also the RF sputtering method may be used.

Furthermore, in the present invention, it is preferable to use magnetron sputtering because it has high productivity.

FIG. 1 shows an example of the configuration of the main parts of a magnetron sputtering apparatus.

In the configuration shown in FIG. 1, a target 10 is provided in a vacuum chamber (not shown) into which an atmospheric gas such as an inert gas or a reactive gas is introduced, and a magnet 1 is placed on the back side of the target 10.
1 is placed, and a substrate (not shown) is placed facing the surface of the target 10. Then, the target 10 is used as a cathode, and an anode is further provided, or the substrate or the vacuum chamber is used as an anode.

Generally, in sputtering, the target is eroded as sputtering progresses, but in magnetron sputtering, the target is locally eroded. That is, target l
O is eroded as shown in FIG.

The eroded region at this time corresponds to the region where the direction of the leakage magnetic field is approximately parallel to the target surface, but in conventional magnetron sputtering, this region is narrow and the efficiency of using expensive target material is low.

Also, depending on the atmosphere during sputtering, areas other than the eroded parts of the target surface may undergo changes due to oxidation, etc.
Sputtered particles may re-deposit, resulting in a surface-altered layer. As sputtering progresses, the depth of the eroded portion increases and its area increases.
The surface-altered layer emits bullets, and the foreign matter ejected from the bullets may mix into or adhere to the sputtered film.

For example, when forming a Feas4 film by the above-mentioned reactive sputtering, black discoloration appears due to redeposition of lithobatter particles whose surfaces other than the eroded areas of the target surface are oxidized, and as sputtering is repeated, the eroded areas As the depth increases, the area of the eroded region also increases, and this blackened part is also sputtered.Since the blackened part is lumpy and the bullets come out, the bullets do not reach the Fe5O4 film deposited on the substrate. Foreign matter may be mixed in or adhered to the surface of the Fe504 film, or these deposits may be peeled off from the surface of the Fe504 film after sputtering, resulting in film defects in these areas.

In the present invention, in order to prevent such film defects, it is preferable to set the leakage magnetic flux density from the target to 200 to 600 G, particularly 200 to 500 G.

Here, the leakage magnetic flux density is the maximum value of the component of the leakage magnetic flux density in a direction parallel to the target surface, and is a value measured on the target surface. Note that by repeating sputtering, the target is eroded and recesses are formed on the surface, and in such a case, the magnetic flux density is measured on the surface of the recess. Further, the magnetic flux density can be measured using a Gaussmeter using a Hall element or the like.

If the leakage magnetic flux density is within the above range, the area where magnetron discharge occurs will be expanded. Therefore, the eroded area of the target is expanded, and the target utilization efficiency is increased.

Since the erosion area expands in this way, the formation of a black variant layer on the target is prevented, and the incorporation of foreign substances into the Fe5O4 film is reduced, ultimately resulting in a γ-Fears magnetic layer with extremely few film defects. It will be done.

Note that if the leakage magnetic flux density is less than the above range, magnetron discharge will not occur, and if it exceeds the above range, the eroded area of the target will be critically reduced.

Furthermore, although the strength of the leakage magnetic field during sputtering is preferably constant, it may vary within the above range.

As the target is eroded by repeated sputtering, the leakage magnetic flux density changes. In this case, in order to keep the leakage magnetic flux density within the above range, the power applied to the target, the usage time, etc. are monitored, and the leakage magnetic flux density is changed. It is preferable to have a configuration in which the magnetic field strength can be changed.

In order to change the magnetic field strength on the back surface of the target, it is preferable to use an electromagnet as the magnet because it is easy to control, but there is also a configuration in which a permanent magnet is used as the magnet and the distance between the magnet and the target is controlled. You can also use it as

Further, the strength of the leakage magnetic field is set to the above range, and the pressure of the gas in the vacuum chamber, that is, the sputtering pressure is set to 5. Ox 1
0-'' to 3.Ox 10 days Pa is preferable.

When the sputtering pressure is reduced in this way, the erosion area on the target surface is further expanded, and the contamination of foreign matter into the Fe5O4 film is significantly reduced.

When the sputtering pressure is less than this range, magnetron discharge is difficult to occur, and when it exceeds this range, further expansion of the eroded region cannot be expected.

Fem0<, which was formed by reactive sputtering, is γ-
It is oxidized to Fe2O3.

This oxidation occurs at a 2O3 gas partial pressure of about 0.05 to 0.8 atm.
The heat treatment may be carried out in an atmosphere with a total pressure of about 0.5 to 2 atmospheres, and it is usually preferable to carry out the heat treatment in the atmosphere.

The holding temperature during heat treatment is 200 to 400°C, especially 25°C.
The temperature is preferably 0 to 350°C, and the temperature holding time is
It is preferably 100 to 10 hours, particularly 1 to 5 hours.

Note that it is preferable that α-Fears be contained in the magnetic layer containing γ-Fe*Os as a main component in order to improve durability. In order to maintain the content of α-Fears at an effective level for improving durability, the heating rate should be set at 0.5 to 20"C/min, especially 1 to 10"C/min during the above heat treatment.
It is preferable to set it as min.

Note that the temperature increase rate may be constant, gradually increased or decreased, or a plurality of temperature increase rates may be combined to increase the temperature to the holding temperature.

If necessary, C01Ti%Cu or the like may be added to the magnetic layer, and Ar or the like contained in the film forming atmosphere may be contained.

Co is an effective element for adjusting coercive force. The content of Co in the magnetic layer is preferably such that it replaces Fe by 10 wt% or less. Further, in order to make the magnetic layer contain Co, a Fe target containing Co may be used.

The layer thickness of the magnetic layer is determined by considering productivity, magnetic properties, etc.
The number of participants is preferably about 0 to 2,000.

For a rigid substrate on which a magnetic layer is formed on the surface, the manufacturing process is simplified as there is no need to provide an underlayer, and it is also easy to polish and control the surface roughness. It is preferable to use glass because it can withstand heat treatment during the formation of the magnetic layer and to control its surface roughness.

As the glass, it is preferable to use tempered glass, particularly surface-strengthened glass obtained by chemical strengthening.

Furthermore, a lubricating film containing an organic compound, an inorganic protective film, or the like may be provided on the magnetic layer.

<Example> Hereinafter, the present invention will be explained in further detail by giving specific examples of the present invention.

[Formation of Fe5O4 film] Outer diameter 130m+n, inner diameter 40mm, thickness 1.27111
An ff+ aluminosilicate glass substrate was polished and further subjected to chemical strengthening treatment. The chemical strengthening treatment was performed by immersing it in molten potassium nitrate at 450°C for 10 hours.

Next, the surface of this glass substrate was smoothed by mechanochemical polishing. A polishing liquid containing colloidal silica was used for mechanochemical polishing.

The surface roughness Rwax of the glass substrate after polishing was 50.

A magnetic layer containing γ-Fezes as a main component was formed on the surface of the cleaned glass substrate by a direct oxidation method.

First, preliminary sputtering is performed in an Ar gas atmosphere, and F
e The fluoride film on the target surface was removed. Then 0.
A gas was introduced and reactive sputtering was performed to form a Fe5O4 film. Note that 02 gas was introduced near the substrate.

This reactive sputtering was performed by DC sputtering using a magnetron sputtering apparatus having the configuration shown in FIG. And 0. A plurality of Fe1O< films were formed by changing the relationship between the gas flow rate OGF and the sputtering rate SR. Note that the sputter rate SR is determined by input power of 2 to 5 W.
Adjustment was made by changing the value within the range of 1/cm".

The thickness of these Fe504 films was 2000.

The thickness of the target is 3 mm, the leakage magnetic field strength on the target surface during sputtering (the maximum value of the component of the magnetic flux density measured on the target surface in the direction parallel to the target surface) is 350 G, and the pressure during sputtering is 1.5X10- 1
It was set as Pa.

Note that as sputtering progresses, the leakage magnetic flux density changes due to erosion of the target surface, but in this example, an electromagnet is used as the magnetic field generation source, and the leakage magnetic flux density is kept constant by changing the generated magnetic field strength. I kept it.

The surface of each FemO4 film formed in this way was examined at a magnification of 5
Observation was made using a 0x optical microscope, and the number of foreign particles existing within a 1 cm x 1 cm area was measured at four arbitrary locations on the film surface, and the total was calculated.
It was less than one.

[Formation of γ-Fears magnetic layer J] Each Fe5Oa film produced in this way was
Oxidized at 10°C for 1 hour to form a γ-Fe*Os magnetic layer,
I got a magnetic disk.

For these magnetic disks, use the following magnetic head,
C8S durability was evaluated based on the following criteria.

A42z O with Vickers hardness of 2200 kgf/■
After forming a thin film magnetic head element on the s-T i C substrate, it is processed into the shape of the magnetic head, and a support spring (gimbal) is formed.
An air-bearing type floating magnetic head was created by attaching it to the The RIIlax of the magnetic head floating surface was set to 130 people.

Adjust the slider width and gimbal load to get the flying height to 0°0.
It was set to 8μ.

A C8S test was conducted at 25° C. and 50% relative humidity using the magnetic head described above.

C8S was performed by repeating the cycle shown in FIG. 2, and the number of times until the recording/reproducing output decreased to less than half of the initial level was measured, and the following 5-level evaluation was performed.

o: 100,000 times or more ○: 50,000 times or more and less than 100,000 times △: 20,000 times or more and less than 50,000 times ×: 10,000 times or more and less than 20,000 times × . In FIG. 3, the results of C8S durability are plotted with the horizontal axis representing the sputtering rate SR when forming the Fe504 film of each magnetic disk, and the vertical axis representing 0 and the gas flow rate OGF per target.

From the results shown in FIG. 3, the effects of the present invention are clear.

<Effects of the Invention> According to the present invention, it is possible to improve the C8S durability of a magnetic recording medium having a continuous thin film type magnetic layer containing γ-Fezes as a main component, and further to reduce defects in the magnetic layer. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the configuration of the main parts of the magnetron swivel device. FIG. 2 is a graph showing one cycle of C8S. Figure 3 shows the sputtering rate SR when forming the Fe5Oa film.
and 02 gas flow rate OGF and a graph showing the relationship between C8S durability. Explanation of symbols 10...Target 11...Magnet■G. Engineering G. 8 temples (f′j)

Claims (3)

[Claims] (1) A film mainly composed of Fe_3O_4 is formed on a rigid substrate by reactive sputtering using a target mainly composed of Fe in an atmosphere containing O_2 gas, and then this film is oxidized. By this, γ-Fe_
In a method for manufacturing a magnetic recording medium that includes a step of forming a continuous thin magnetic layer containing 2O_3 as a main component, when performing the reactive sputtering, the O_2 gas flow rate OGF (SCCM) per target and the sputtering rate SR are determined. (μm/min) OGF=(55±10)SR. (2) A magnetron sputtering method is used for the reactive sputtering, and the maximum value of the component of the magnetic flux density on the target surface in a direction parallel to the target surface is set to 200 to 600G.
2. The method of manufacturing a magnetic recording medium according to claim 1, wherein: (3) Sputter the reactive sputter at 5.0×10^-^2~3
．． 3. The method for manufacturing a magnetic recording medium according to claim 1, wherein the manufacturing method is carried out under a pressure of 0x10^-^1 Pa.