JPH0664735B2 - Method for manufacturing perpendicular magnetic recording medium having permalloy thin film soft magnetic layer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a double-layered perpendicular magnetic recording medium, and more particularly, the present invention relates to a method for producing a soft magnetic permalloy layer.

(Prior Art) In recent years, the perpendicular magnetic recording system has been attracting attention as a recording system suitable for high-density magnetic recording. As a recording medium suitable for this recording system, a two-layer film medium including a soft magnetic layer such as Permalloy and a perpendicular magnetization film layer such as Co—Cr is known. The smaller the coercive force of the soft magnetic layer and the higher the magnetic permeability, the better the recording sensitivity and the larger the reproduction output. However,
It is known that if the soft magnetism becomes too good, spike noise is generated, which is not preferable, and the coercive force is 2 to 3 oersteds or more as a rough guideline for suppressing the noise generation.

Permalloy and a Co-based amorphous magnetic film are known as the soft magnetic layer, but permalloy is often used from the viewpoint of economy.

(Problems to be solved by the invention) However, in the case of a permalloy thin film, magnetic anisotropy perpendicular to the substrate surface is likely to occur, and the coercive force becomes 10 oersteds or more. Was bad.

The present invention provides a method for producing a soft magnetic layer for a perpendicular magnetic recording medium having excellent soft magnetic characteristics with a small coercive force by suppressing the perpendicular magnetic anisotropy of the permalloy soft magnetic layer of the conventional perpendicular magnetic recording medium. Is intended to be provided,
By providing a method according to the claims,
The above object can be achieved.

(Means for Solving Problems) The present invention relates to a method for manufacturing a perpendicular magnetic recording medium having a permalloy thin film soft magnetic layer in which a permalloy layer and a Co—Cr perpendicular magnetization film layer are sequentially formed on a nonmagnetic substrate by a sputtering method. In: A method of manufacturing a perpendicular magnetic recording medium having a permalloy thin film soft magnetic layer, which comprises the following sequence of steps (a), (b) and (c): (a) a non-magnetic substrate in a vacuum chamber A step of heat-treating; (b) a step of introducing air into the vacuum chamber to expose the substrate after the heat treatment to the atmosphere; and (c) an evacuation of the vacuum vessel and then introducing an argon gas, and a permalloy by a sputtering method. Forming layers.

It is about.

The present inventors, since the perpendicular magnetic anisotropy of the permalloy thin film layer is likely to appear when the vacuum state of the back ground of the sputter chamber is improved, the polymer film substrate is heat treated in the vacuum chamber, and then the inside of the vacuum chamber is changed. The present invention was newly found that the appearance of perpendicular magnetic anisotropy can be suppressed by opening to the atmosphere and then again evacuating the vacuum chamber and introducing argon gas, and starting the spatula. completed.

In the present invention, the heat treatment step (a) is performed for the purpose of cleaning the surface of the non-magnetic substrate and heat shrinking. That is, a polymer film substrate such as polyimide or polyester is heat-shrinked in advance in order to degas and remove water and impurities attached to the film, and to prevent heat shrinkage (curling) during film formation of the magnetic film. This is done to stabilize it. The temperature of this heat treatment is preferably lower than the heat resistant temperature of the film used as the substrate, and is preferably higher than the substrate surface temperature at the time of film formation.

The reason why the inside of the vacuum chamber is opened to the atmosphere after the non-magnetic substrate is heat-treated in the vacuum chamber is not clear,
One of the atmospheric components (N ₂ , O ₂ , H _2, etc.) adheres to the surface of the substrate, and then this atmospheric component is re-emitted during the sputtering of the magnetic film, which is favorable for film growth. It is considered that this is because it exerts an influence and suppresses the appearance of perpendicular magnetic anisotropy.

Next, the present invention will be described in detail with reference to experimental data.

A conventional method for producing a soft magnetic permalloy layer is described in Comparative Examples 1 to 1 below.
3 will be described.

Comparative Example 1 A polyimide substrate was set in a batch type sputtering device,
10 ^- heat-treated for 30 minutes at 200 ° C. for about ^{6 Torr, 3 × 10 - 7} T
After evacuation to orr, argon gas was introduced, and a molybdenum permalloy film was formed under the following conditions.

Sputtering method: RF magnetron target: Mo on 8 inch 78Ni-Fe target
Peretsuto arrangement (4% by area) argon pressure: 0.6~1 × 10 ^{- 3} Torr substrate temperature: 20 to 90 ° C. sputter power: 0.7 W / cm ² Supatsutareito: Characteristics of 0.017 micrometer / min thickness of about 0.50μm membrane Is shown in Table 1. Hc is coercive force, △ θ _{5 0} in the membrane surface is a half-value width of the orientation angle from the film surface normal direction of the (111) crystallographic axis by X-ray diffraction Rotsukingu curve. The coercive force Hc was measured with a vibrating sample magnetometer (VSM).

In all the cases shown in the table, the shape of the MH loop is as shown in FIG. 1 (A), which shows that the perpendicular magnetic anisotropy exists. Therefore, as shown in Table 1, the coercive force Hc often shows a large value of 10 oersteds or more.

Comparative Example 2 A permalloy film was formed using the winding type sputter device shown in FIG.

FIG. 2 is an explanatory view showing the outline of the apparatus, 1 is a vacuum chamber,
2 is a connection port to the exhaust system, 3a and 3b are cathodes respectively, permalloy is attached to 3a, and Co-Cr target is attached to 3b. The anode is omitted. 4a and 4b are substrate film winders and unwinders, 5a, 5b,
6a and 6b are guide rollers, 7a and 7b are dancer rollers, 8
Reference numerals a and 8b are cooling rollers, 9 is a mask, 10 is a mask, 11 is a spatula gas outlet, 12 is a substrate film, and 13 is a substrate heating heater. The vacuum chamber 1 10 ^- After evacuated to ⁶ Torr base, a polyimide film 12 is heated at 100 to 190 ° C. by Quillan 9 or substrate heating heater 13 and transferred to wind the film from the unwinder 4b winder 4a. Cool the can 9 or the substrate heater 13 used for heating to 0.75 ~
1 × 10 ^- After evacuation to ⁶ Torr, argon gas was introduced from Supatsutagasu outlet 11, cathode 3a are kept to a predetermined gas pressure
A molybdenum permalloy target attached to was used to continuously form thin films on a moving polyimide substrate. Sputter conditions are as follows: sputter method: DC magnetron sputtering Tagetsuto composition: 5 wt% molybdenum permalloy argon gas pressure: 0.5~3 × 10 ^{- 3} Torr sputter power: about 8.5 W / cm ² Supatsutareito: about 0.4 .mu.m / min The results obtained with a film thickness of 0.45 to 0.5 μm
Shown in the figure. Curve a coercive force Hc, the curve b, measured in the longitudinal direction of the substrate film is shown for each argon pressure orientation angle △ theta _{5 0} (111) crystal axis. The change due to the heat treatment temperature of the substrate was small. In all cases, the MH loop has a loop shape as shown in FIG.
Perpendicular magnetic anisotropy was present. The coercive force Hc also showed a large value of 10 Oe or more.

[Comparative Example 3] A molybdenum permalloy film was formed using a polyester film under the same apparatus and the same sputtering conditions as in Comparative Example 2. Figure 4 is 80 ° C. The sputter when the substrate temperature, the argon pressure to 0.5 × 10 ^- orientation angle of ³ Torr and film length direction of the coercive force Hc for the heat treatment temperature of the substrate when (curve c) crystal axis △ theta _{5 0} (curve d) is shown. Also in these cases, a large coercive force is exhibited due to the appearance of perpendicular magnetic anisotropy.

Fig. 5 shows the coercive force Hc (curve e) and the crystal orientation angle Δ with respect to the gas pressure of the sputtering gas when the substrate temperature during sputtering is 6 ° C or less.
theta ₅ is a graph showing changes in ₀ (curve f). In each case, perpendicular magnetic anisotropy appears, and the argon pressure is 2 ×.
10 ^- shows a large coercive force at ³ Torr or less. Argon pressure is 2 × 10 ^- but ³ Torr coercive force Hc in the larger area is summer quite small, smaller perpendicular magnetic anisotropy in this case was confirmed. Further, in this region, as shown in FIG. 5, forming a small orientation angle [Delta] [theta] _{5 0} has become quite large as 15 ° or more. When the crystal orientation angle [Delta] [theta] _{5 0} of the so-called permalloy film increases, Co-Cr to form on the film surface
The crystallinity of the film is impaired and the perpendicular magnetic anisotropy is adversely affected.

Next, the present invention will be described with reference to examples.

Example 1 Using the same sputtering device as in Comparative Example 2, a molybdenum permalloy film was formed in the next step. That the polyester substrate 10 and excisional in the vacuum chamber ^- was evacuated to ⁶ Torr base was heat-treated polyester substrate at 100 ° C.. The vacuum chamber is opened to the atmosphere and thereafter, again 1 × 10 ^- up to ⁶ Torr was evacuated argon gas was introduced with KoTsuta the Supatsuta.

Table 2 shows the results obtained with a film thickness of about 0.45 μm when the substrate temperature at the time of sputtering was set to 60 ° C. or lower. In all cases, the shape of the AH loop shows the loop as shown in FIG. 1 (B), which indicates that there is no perpendicular magnetic anisotropy. Therefore, as is apparent from Table 2, the coercive force Hc in the film length direction shows a small value.

Figure 6 is argon pressure of 0.5 × 10 ^{- 3} Torr, Supatsuta at substrate temperature of coercive force Hc when the sputtered power was 8.5 W / cm ² (curve g) and the crystal orientation angle △ θ _{5 0 (curve} h) Shows the changes to. The perpendicular magnetic anisotropy does not appear when the substrate temperature is 70 ° C or lower, and the coercive force is 10 oersteds or less, but when the temperature is higher than 70 ° C, the perpendicular magnetic anisotropy appears and the coercive force increases. Shows.

Example 2 Using the same sputtering device as in Comparative Example 2, a molybdenum permalloy film was sputtered in the same steps as in Example 1 using a polyimide substrate. However, the heat treatment temperature of the substrate is 19
The temperature was 0 ° C. Table 3 shows the results when the substrate temperature during sputtering was 60 ° C or lower and the sputtering power was 8.5 W / cm ² .
In this case, the existence of extremely small perpendicular magnetic anisotropy was recognized, but the coercive force Hc was a smaller value than in the cases of Comparative Examples 1 to 3.

From the examples described in detail above, in the two-layer film perpendicular magnetic recording suppressed to state crystal orientation angle [Delta] [theta] _{5 0} is less the appearance of the perpendicular magnetic anisotropy of Permalloy soft magnetic layer of the medium, the coercive force Hc
In order to reduce the size, it is very necessary to perform a manufacturing process according to the present invention, that is, to heat the substrate film in a vacuum chamber and then to open the inside of the vacuum chamber to the atmosphere. Clearly effective.

As described above, according to the present invention, a soft magnetic permalloy thin film layer having extremely small perpendicular magnetic anisotropy or substantially no perpendicular magnetic anisotropy can be obtained and used as a soft magnetic layer for a two-layer perpendicular magnetic recording medium. An excellent permalloy thin film can be produced.

[Brief description of drawings]

FIG. 1 is a diagram showing an MH loop of a permalloy thin film. FIG. 1A shows a loop when perpendicular magnetic anisotropy exists, and FIG. 1B shows a loop when perpendicular magnetic anisotropy does not exist. FIG. 2 is a diagram showing the shape, FIG. 2 is an explanatory diagram showing the outline of the sputter device, FIG. 3 is a diagram showing coercive force and crystal orientation angle with respect to argon pressure, and FIG. 4 is coercive force and crystal orientation with respect to the heat treatment temperature of the substrate. FIG. 5 is a diagram showing changes in angle, FIG. 5 is a diagram showing dependence of coercive force and crystal orientation angle on argon pressure, and FIG. 6 is a diagram showing dependence of coercive force and crystal orientation angle on substrate temperature at the time of sputtering. . 1 ... Vacuum chamber, 3a, 3b ... Cathode, 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b ... Roller, 9 ... Kyan, 12 ... Substrate film, 13 ... Substrate heating heater.

Claims (2)

[Claims] 1. A permalloy layer and Co—Cr on a non-magnetic substrate.
In a method of manufacturing a perpendicular magnetic recording medium having a permalloy thin film soft magnetic layer in which perpendicularly magnetized film layers are sequentially formed by a sputtering method: permalloy comprising the following sequence of steps (a), (b) and (c): Method of manufacturing perpendicular magnetic recording medium having thin film soft magnetic layer. (A) a step of heat-treating the non-magnetic substrate in a vacuum chamber; (b) a step of introducing air into the vacuum chamber to expose the substrate after the heat treatment to the atmosphere; and (c) after evacuation of the vacuum chamber. A step of forming a permalloy bath on the substrate at 60 ° C. or lower by introducing an argon gas and performing a sputtering method. 2. The method for producing a perpendicular magnetic recording medium according to claim 1, wherein the non-magnetic substrate is a polymer film of polyimide, polyethylene terephthalate or the like.