JP3127070B2 - Method for producing soft magnetic thin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a soft magnetic thin film used for a magnetic head such as a VTR and a magnetic disk.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for higher density of magnetic recording, and a higher coercive force of a recording medium and a narrower track of a magnetic head have been advanced. Accordingly, a high saturation magnetic flux density for magnetizing a recording medium with a high coercive force and a magnetic head core material having good soft magnetic properties have been required,
A magnetic head using a soft magnetic thin film such as Sendust / Permalloy / Co amorphous material as a core material has been put to practical use. However, the saturation magnetic flux density of these materials is 1.1 T for Sendust, and 0.1 T for Permalloy and Co-based amorphous materials.
8T, higher than ferrite, but coercive force is 120k
Sufficient writing cannot be performed on a high coercive force medium exceeding A / m.

[0003] In order to cope with such a situation, research has been conducted on a high saturation magnetic flux density material containing iron as a main component, and a material reaching a practical level has been developed. Specifically, by reducing the particle size of iron particles, the apparent crystal magnetic anisotropy is reduced, and a magnetic material having both high saturation magnetic flux density and good soft magnetic properties is obtained. As typical examples, those obtained by adding a transition metal and nitrogen to iron and those obtained by adding a transition metal and carbon to iron are known. 5 for these materials
After heat treatment at 00 ° C to 550 ° C, the saturation magnetic flux density is about 1.
At 6T, the coercive force is 40 A / m or less. Also,
In addition to these, Journal of the Japan Society of Applied Magnetics 14,301-
304 (1990), as disclosed in JP-A-4-65805 and JP-A-4-142721.
A system in which silicon and nitrogen are added to iron is also being studied. JP-A-4-65805 discloses that after heat treatment at 450 ° C.
No. 142721 shows good magnetic properties of a saturation magnetic flux density of 1.5 T or more and 40 A / m or less immediately after film formation. This system has been studied by the present inventors (Japanese Patent Publication No. 92-4812,
According to Japanese Patent Application No. 4-33065, a thin film having magnetic properties of a saturation magnetic flux density of 1.7 T or more and a coercive force of 100 A / m or less is obtained after heat treatment at 500 ° C.

[0004]

When a soft magnetic thin film is used as a core material of a magnetic head, the temperature experienced by the core material differs depending on the form of the head. That is, in the manufacturing process of the magnetic head, the temperature experienced by the soft magnetic thin film is different, for example, up to about 200 ° C. for a so-called fixed type thin film head, and about 500 ° C. for a rotary type head such as a VTR due to the glass welding step. .

[0005] Japanese Patent Application Laid-Open No. 4-65805 and Japanese Patent Application No. 4-33
In the example of No. 065, good soft magnetic properties cannot be obtained unless heat treatment is performed at 450 ° C. or 500 ° C., respectively, and a high-temperature heat treatment process is required. The same applies to the case where a transition metal and nitrogen are added to iron and the case where a transition metal and carbon are added to iron.

As disclosed in Japanese Journal of Applied Magnetics, 15, 357-360 (1991), those exhibiting good soft magnetic properties immediately after film formation as disclosed in JP-A-4-142721 are disclosed.
After the heat treatment at 00 ° C., the characteristics are rapidly deteriorated. If the amount of silicon in the film is increased in order to improve the heat resistance, the saturation magnetic flux density is reduced and the soft magnetic characteristics are also deteriorated.

As described above, in the case of these thin films or thin film forming methods obtained by the prior art, the heat treatment process capable of obtaining good soft magnetic characteristics is limited to a relatively narrow range. Therefore, there is a problem that the form and manufacturing process of the magnetic head that can be used are limited by the selected material system and the film forming method.

The present invention adjusts the substrate temperature and the amount of N ₂ gas under the conditions for forming the Fe—Si—N thin film, so that even if a heat treatment process at any temperature from immediately after the film formation to 500 ° C. is added, good softness can be obtained. A soft magnetic thin film having both magnetic properties and a high saturation magnetic flux density is obtained, and a method for forming a soft magnetic thin film without limiting the form and manufacturing process of a usable magnetic head is provided.

[0009]

According to the method of manufacturing a soft magnetic thin film of the present invention, when a Fe—Si—N thin film is formed by sputtering in a mixed gas atmosphere of Ar and N ₂ , N ₂
The ratio of the gas and the substrate temperature are set to the following conditions. _{(0.12-0.00026T SUB) (T a -500} ) +58
_{≦ {V N / (V Ar} + V N)} × 100 ≦ (0.10-0.00
_{034T SUB) (T a -500)} +62 However, T _SUB [℃]: the substrate temperature, T _a [℃]: heat treatment temperature V _N [m ^3] after deposition: 0 ℃, N ₂ gas at 1 atm V _Ar [m ³ ] : 0 ° C., volume of Ar gas at 1 atm. 150 ° C. ≦ T _SUB ≦ 250 ° C. T _SUB <T _a ≦ 500 ° C. 0.44 ≦ V _N / (V _Ar + V _N ) ≦ so as to satisfy 0.62, it is to set the substrate temperature T _SUB and N ₂ ratio of the gas _{V N / (V Ar + V} N) with respect to the heat treatment temperature T _a desired post film formation. Here, a high coercive force medium (for example, H _c
> 120 KA / m), with reference to film characteristics of saturation magnetic flux density of 1.6 T or more and coercive force of 100 A / m or less as a standard for obtaining a conventional or higher recording / reproducing efficiency, the substrate temperature, The heat treatment temperature and the range of the N ₂ gas ratio were set.

[0010]

In general, it is said that in iron-based materials which have been studied to obtain a high saturation magnetic flux density, iron particles are refined by an additive and good soft magnetic characteristics can be obtained. That is, in the case of the Fe-Si-N system, by adding N to Fe-Si, the iron particles become finer, and the apparent magnetic anisotropy is reduced. As a result, a high saturation magnetic flux density and good soft magnetic characteristics are obtained. The result is that a combined thin film can be obtained.

In forming the Fe—Si—N film in the present invention, a normal RF sputtering method, a DC sputtering method, an ion beam sputtering method, or the like can be used. A composite target in which Si pellets are arranged on a Si alloy target or an Fe target can be used. The Si composition in the film is not particularly limited, but is preferably 1 to 3 wt% from the viewpoint of obtaining a high saturation magnetic flux density. As a sputtering gas, Ar gas and N ₂ gas are mixed and introduced at a desired volume ratio. Substrate temperature T _SUB and ratio of N ₂ gas {V _N / (V _Ar + V _N )} × 10
For the range of 0 , 150 ° C. to 250 ° C. and 4
4% to 62%. Thereby, 150 ° C. to 250
500 ° C from substrate temperature for all substrate temperatures in ° C
It is possible to obtain an Fe-Si-N thin film having a high saturation magnetic flux density of 1.6 T or more and excellent coercive force of 100 A / m or less in the heat treatment temperature range up to.

Therefore, according to the present invention, the temperature experienced by the soft magnetic thin film in the head manufacturing process is from 150 ° C.
If the temperature is 500 ° C., a magnetic head having excellent recording / reproducing characteristics can be obtained by selecting an appropriate substrate temperature T _sub and a ratio V _N / (V _Ar + V _N ) of N ₂ gas.

[0013]

EXAMPLES Examples of the film forming method according to the present invention will be described below in detail. The present invention is not limited to the following examples. In this embodiment, an ion beam sputtering apparatus was used for film formation. The target is 3 wt% Si-ba
l. Using an alloy target of Fe, the amount of Si in the film is about 2
~ 3 wt% was obtained.

[0014] Sputtering Conditions ultimate vacuum 6.7 × 10 ^{- 7} Pa accelerating voltage 800V accelerating current 120mA nitrogen in a volume ratio of 44 to 62% total gas pressure 3.2~4.3 × 10 ^{- 2} Pa substrate temperature 0.99 ° C. ~ 250 ° C substrate rotation speed 2 rpm substrate glass (coefficient of thermal expansion α = 80 × 10 ^−
7) crystallized glass ^{(α = 110~135 × 10 - 7} ) non-magnetic ferrite ^{(α = 85 × 10 - 7} ) substrate angle target and 3 hours parallel thickness 1μm heat treatment in vacuum, the above conditions to 500 ° C. As shown, the substrate temperature was between 150 ° C and 25 ° C.
0 ° C., the N ₂ gas volume ratio is 44 to 62%, and the coefficient of thermal expansion α =
A film was formed on a substrate of 80 to 135 × 10 ⁻⁷ . Thereafter, a heat treatment in 50 ° C. intervals from the substrate temperature to 500 ° C., was measured saturation magnetic flux density B _s and the coercive force H _c. For measurement of H _c and B _s, a BH loop tracer and VSM were used, respectively.

The present inventors first formed a film by changing the N ₂ gas volume ratio while keeping the substrate temperature constant, and examined the dependence of the magnetic properties of the obtained thin film on the heat treatment temperature. Other conditions were the same as the above sputtering conditions. The results are as shown in Examples 1 to 4 shown in Table 1. According to the combination of the substrate temperature and the N ₂ gas volume ratio, good soft magnetic characteristics satisfying the condition of H _c <100 A / m can be obtained. It can be seen that the range of the heat treatment temperature has changed. As for the B _s of each embodiment, it is understood that it is determined by the most varied to not without, N ₂ gas volume by a heat treatment temperature.

[0016]

[Table 1]

As described above, the dependence of the magnetic properties of the Fe—Si—N thin film on the substrate temperature, the N ₂ gas volume ratio, and the heat treatment temperature were examined in detail within the above-mentioned sputtering conditions. Experimental results were obtained as shown. FIG. 1 shows the change of B _s with respect to the volume ratio. From this result, it can be seen that all the claims of the volume ratio of the present invention described below have a saturation magnetic flux density of 1.6 T. 2, 3, respectively the substrate temperature 0.99 ° C. in FIG. 4, 200 ° C., shows the dependence of H _c for the heat treatment temperature and the N ₂ volume ratio of at 250 ° C.. In these figures, ○ indicates a point satisfying H _c <100 A / m, and no significant change was observed in the magnetic characteristics even when the substrate used was changed.

From these experimental results, the range of the N ₂ gas volume ratio at which soft magnetic characteristics can be obtained in a certain heat treatment temperature process varies depending on the substrate temperature. _c <100A
It can be seen that there is a combination of the substrate temperature and the N ₂ gas volume ratio satisfying the condition of / m.

Based on these results, the upper and lower limits of the N ₂ gas volume ratio are defined as a function of the substrate temperature and the heat treatment temperature.
When approximated by a straight line, (0.12-0.00026T _SUB ) (T _a −500) +58
_{≦ {V N / (V Ar} + V N)} × 100 ≦ (0.10-0.00
_{034T SUB) (T a -500)} +62 However, T _SUB [℃]: the substrate temperature, T _a [℃]: heat treatment temperature V _N [m ^3] after deposition: 0 ℃, N ₂ gas at 1 atm V _Ar [m ³ ] : 0 ° C., volume of Ar gas at 1 atm. 150 ° C. ≦ T _SUB ≦ 250 ° C. T _SUB <T _a ≦ 500 ° C. 0.44 ≦ V _N / (V _Ar + V _N ) ≦ 0.62 is obtained, and in this range, H _c <100 A / m and B _s
A soft magnetic thin film satisfying the magnetic property of> 1.6T is obtained.
The conditions to be combined may be appropriately selected for a desired heat treatment temperature process. For example, if the maximum temperature during the head fabrication process is about 300 ° C., the volume ratio of N ₂ gas is reduced to 1.9T. It is also possible to obtain a high saturation magnetic flux density.

[0020]

According to the present invention, has both _{H c <100A / m, B} s> in a wide temperature range of 0.99 ° C. to 500 ° C. good soft magnetic characteristics and high saturation magnetic flux density of 1.6 T F
An e-Si-N thin film can be obtained.

That is, since desired characteristics can be obtained immediately after film formation at a substrate temperature of 150 ° C., use in combination with a material whose characteristics are degraded at a high temperature, or film formation on a substrate having a significantly different coefficient of thermal expansion. Etc. become possible. In addition, 500 ° C
Since the desired characteristics can be obtained even after the heat treatment, it can be used for those requiring a high-temperature process such as glass welding. Therefore, when the application to a magnetic head is considered, the film forming method according to the present invention provides a practical magnetic material that is independent of other materials to be combined and a heat treatment temperature process, and obtains a magnetic head having excellent recording / reproducing characteristics. Can be.

[Brief description of the drawings]

FIG. 1 is a drawing showing a relationship between a saturation magnetic flux density and a N ₂ gas volume ratio by a method of manufacturing a magnetic film according to the present invention.

FIG. 2 is a diagram showing soft magnetic characteristics with respect to a combination of a N ₂ gas volume ratio at a substrate temperature of 150 ° C. and a heat treatment temperature according to a method of manufacturing a magnetic film according to the present invention.

FIG. 3 is a diagram showing soft magnetic characteristics with respect to a combination of a N ₂ gas volume ratio at a substrate temperature of 200 ° C. and a heat treatment temperature according to the method of manufacturing a magnetic film according to the present invention.

FIG. 4 is a diagram showing soft magnetic characteristics with respect to a combination of a nitrogen volume ratio at a substrate temperature of 250 ° C. and a heat treatment temperature according to the method of manufacturing a magnetic film according to the present invention.

[Explanation of symbols]

Claims (1)

(57) [Claims] When a Fe—Si—N thin film is formed by sputtering in a mixed gas atmosphere of Ar and N ₂ , the substrate temperature is set to T _SUB [° C.] , and the heat treatment temperature after the film _{formation is set} to T _SUB [° C.] . _a [° C] , 0
Assuming that the volume of N ₂ gas at 1 ° C. is V _N [m ³ ] and the volume of Ar gas at 0 ° C. 1 atm is V _Ar [m ³ ] , the temperature range of the substrate temperature is 150 ° C. ≦ T _SUB ≦ 250 ° C., the relationship between the substrate temperature and the heat treatment temperature after film _formation is T _SUB <T _a
When a ≦ 500 ℃, N ₂ gas relationship proportions and the substrate temperature in the gas mixture _{(0.12-0.00026T SUB) (T a -500} ) +58
_{≦ {V N / (V Ar} + V N)} × 100 ≦ (0.10-0.00
_{034T SUB) (T a -500)} +62 manufacturing method of the soft magnetic thin film characterized in that a.