JPH0329304A - Soft magnetic thin film and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a soft magnetic film whose soft magnetic characteristic and thermal stability are excellent by a method wherein the film is formed of an alloy which is composed mainly of cobalt and to which at least one kind of metal element selected from a group of titanium end tantalum has been added and an element of nitrogen is mixed with the alloy. CONSTITUTION:When an addition ratio of Ti or Ta is about 15 atomic % or higher, a Co-Ti alloy film, a Co-Ta alloy film or the like normally becomes amorphous and becomes a good soft magnetic film. When nitrogen is mixed with these alloys, thermal stability can be enhanced while an excellent soft magnetic characteristic is being maintained. That is to say, even when the Co-Ti alloy film, the Co-Ta alloy film, a Co-Ti-Ta alloy film, a Co-Ti-third element alloy film, a Co-Ta-third element alloy film or a Co-Ti-Ta-third element alloy film is exposed to a high-temperature atmosphere, its crystallization progresses slowly; even when one part is crystallized, its soft magnetic characteristic is deteriorated little. Thereby, both the soft magnetic characteristic and the thermal stability can be enhanced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a soft magnetic thin film used, for example, in a magnetic head, and in particular to a soft magnetic thin film made of a mostly amorphous alloy mainly composed of cobalt, and its production. It concerns the method. [Prior Art] Bermalloy, cobalt-based amorphous alloys, and sendust are being mainly studied as soft magnetic thin film materials for use in magnetic heads, high-frequency reactor cores, magnetic shielding materials, etc. Especially CO-Tf alloy film or Co-
When a Ta alloy film is formed by a sputtering method or the like, it becomes an amorphous state, has a high saturation magnetic flux density, and has good soft magnetic properties, so it is considered promising. but,
This soft magnetic material is not without practical problems, and there are various constraints on the manufacturing process of various magnetic elements, especially in terms of thermal stability. For example, when manufacturing a magnetic head, there is a process in which glass is interposed between the magnetic cores and the glass is melted by heating to join the magnetic cores together, or the magnetic cores are heat-treated in a magnetic field to improve their magnetic properties. This process is carried out at a relatively high temperature of, for example, 600°C. Therefore, there is a problem in that these heat treatments advance the crystallization of the soft magnetic thin film, resulting in a significant deterioration of the soft magnetic properties. As a countermeasure to this problem, when manufacturing the magnetic head, a method has been adopted in which low melting point glass is used to lower the process temperature. However, low-melting glass has poor abrasion resistance compared to the magnetic core, and the glass layer wears out first due to sliding contact with the magnetic recording medium, resulting in a step difference between the glass layer surface and the magnetic core surface. Can be done. The formation of this step damages the magnetic layer of the magnetic recording medium, thereby degrading the magnetic recording characteristics. Furthermore, this Go-Ti alloy film or Co
- Like other Co-based amorphous alloys, when the Ta alloy film is made Go-rich to increase the saturation magnetic flux density, the crystallization temperature of the soft magnetic thin film drops significantly, which limits the heat treatment temperature. The problem is that the process margin is narrowed. Therefore, there are strong expectations for the development of materials that maintain high saturation magnetic flux density and have high crystallization temperatures, both from the perspective of process margins and magnetic properties. As one method to meet these expectations, a nitride film of Go-Nb-Zr-Ta amorphous alloy has already been proposed (IEICE technical research report MR86-4, P25~32rN, in mixed gas). "Magnetism of sputtered amorphous alloy film"). As a result, nitriding increases the crystallization temperature and increases the film hardness.
Another characteristic phenomenon. M. Takahashi
(T.K. kima et al. found this in iron nitride films)
ndM. Applied Ph
ysics Letters, vol. 20, PP4
92, 1972>, it was found that the saturation magnetic flux density increased by nitriding also in Go-Nb-Z r-Ta amorphous alloy. [Problems to be Solved by the Invention] However, on the other hand, the soft magnetic properties of this film deteriorate significantly when the film thickness exceeds 300, making it difficult to apply it to the field of application. As a countermeasure to this problem, an attempt was made to alternately stack extremely thin nitride films and non-nitride films to prevent deterioration of the magnetic properties. Although this method prevented deterioration of the soft magnetic properties, it was necessary to form extremely thin films into multiple layers to achieve a desired film thickness. The thickness of the nitride film and non-nitride film is 200 mm.
In the case of humans, for example, in order to form a soft magnetic thin film of 10 μm, it is necessary to repeat the formation of nitride and non-nitride films 500 times. As a result, the manufacturing process is extremely complicated, leading to problems in terms of productivity and cost. The object of the present invention is to eliminate such drawbacks and provide a soft magnetic film having excellent soft magnetic properties and thermal stability, as well as a method for manufacturing the same. [Means for Solving the Problems] In order to achieve the above object, the present invention consists of an alloy mainly composed of cobalt and to which at least one metal element selected from the group of titanium and tantalum is added, and nitrogen is added to it. It is characterized by the fact that it contains elements. In order to achieve the above-mentioned objective, the present invention further includes:
An alloy consisting mainly of cobalt and at least one metal element selected from the group of titanium and tantalum added thereto, and by sputtering the alloy in the presence of nitrogen gas, the nitrogen element is mixed onto the substrate. It is characterized by the formation of an alloy thin film. In order to achieve the above object, the present invention further uses a target mainly composed of cobalt and to which at least one metal element selected from the group of titanium and tankles and nitrogen element is added. It is characterized by forming an alloy thin film containing nitrogen element on the substrate by sputtering. [Function] Normally, a Co-Ti alloy film or a Co-Ta alloy film becomes amorphous and becomes a good soft magnetic film when the addition rate of Ti or Ta is about 15 atomic % or more. We have discovered that by incorporating nitrogen into the alloy, it is possible to improve thermal stability while maintaining excellent soft magnetic properties. That is, Go-Ti alloy film or C
When an amorphous alloy film such as an o-Ta alloy film is exposed to a temperature higher than its crystallization temperature, crystallization progresses rapidly and its soft magnetic properties are significantly degraded. In contrast, the Co of the present invention
-Ti, Co-Ta, Go-Ti-Ta, Co-Ti-third element (described later), Go -Ta-third element, Co
-The Ti-Ta-third element nitride alloy film progresses slowly in crystallization even when exposed to a high temperature atmosphere, and even if a portion of it crystallizes, the deterioration of the soft magnetic properties is very small. Although the theoretical basis for this improvement in thermal stability due to nitridation is not clear, it is thought that nitrogen strongly bonds with the parent metal element and suppresses the progress of crystallization. As a method for producing a nitride alloy film such as Co-Ti or Go-Ta according to the present invention, an alloy such as Co-Ti or Co-Ta may be sputtered in a nitrogen-containing gas atmosphere, or
A nitride alloy target such as Co-Ti or Co-Ta may be sputtered as is. In addition, as sputtering methods, ion beam sputtering, radio frequency sputtering, DC sputtering, etc. are used. In particular, soft magnetic films manufactured by ion beam sputtering have excellent magnetic properties and are therefore useful. [Example] The soft magnetic material used in the present invention is mainly composed of Co. CO containing a predetermined amount of Ta or (and) Ti
Nitrogen is further mixed into the base alloy. The crystal structure of this soft magnetic thin film is almost completely amorphous before heat treatment, and after heat treatment it is mostly amorphous, although some parts become microcrystalline. In addition, in order to adjust the magnetostriction constant in the soft magnetic thin film of the present invention, for example, Zr, Hf, Y, Nb
It is also possible to add small amounts of other third elements such as , Mo, and W. The addition rate of Ta or (and) Ti to CO is:
A suitable value is 15 to 307 F atoms (18 atomic % in the example). FIG. 1 is a schematic diagram of an ion beam sputtering apparatus used in an embodiment of the present invention. In the figure, 1 is an exhaust pipe, 2 is a 21 dollar valve, 3 is an ion gun, 4 is a target, 5 is a substrate, and 6 is a vacuum chamber. After the inside of the vacuum chamber 6 was brought to a high vacuum state of less than I x 10 torr, a mixed gas of argon and nitrogen was introduced from the twenty-one dollar valve 2 so that the pressure inside the chamber was 3 x 10 torr. Next, argon ions accelerated to 0.7 KV from ion #li!3 are irradiated onto a target 4 made of, for example, a Co@2Ti1m alloy, and the resulting sputtered fine particles are spread onto a substrate 5 made of heat-resistant glass in a film thickness of 7000 mm. The argon ion irradiation current during thin film formation was 20 mA, the film deposition rate was 20 to 30 persons/min, and a bias voltage of -40 V was applied to the thin film form or to the substrate 5. The film formed in this way was then heat treated in a magnetic field (4000 s) at 500°C for about 30 minutes. (Coercive force) was measured by VSM, and the results are shown in the table below.In addition, as a result of examining the crystal structure of each sample by X-ray diffraction (CuKα), it was found that all of the samples before heat treatment were almost completely It was in an amorphous state.The nitride film after heat treatment was partially microcrystalline, but most of it was in an amorphous state, whereas the non-nitride film had progressed considerably in crystallization. As is clear from the above table, in the case of a non-nitride film, crystallization starts at about 400°C, so the coercive force increases rapidly (550 times) with heat treatment at 500°C. On the other hand, although the nitride film of the present invention is partially crystallized according to X-ray diffraction, the progress of crystallization is slow, so even after high-temperature heat treatment, it has good soft magnetic properties (coercive force is 60 times larger, The heat treatment was performed in a magnetic field, but the same excellent softness can be achieved even if the heat treatment is performed without applying a magnetic field. It has been confirmed through experiments that magnetic properties can be obtained.Although Co-Ti alloy was used in the above example, Co-Ta alloy, Go-
Ti-Ta alloy, Co-Ti-third element alloy, Go-T
Good soft magnetic properties can also be obtained in a-third element alloy, Co-Ti-Ta-third element alloy, etc. In the above example, a Co-Ti alloy was used as a target and sputtering was performed in the presence of nitrogen gas.
Using a composite with a Co plate as a target (the alloy composition in the formed thin film varies depending on the number of pellets on the Co plate)
Even if this is sputtered as it is, a Co-based alloy thin film containing nitrogen can be obtained. In the above embodiment, the soft magnetic thin film was formed by wide ion beam sputtering, but the soft magnetic thin film can also be formed by other methods such as high frequency sputtering.
Among these thin film formation techniques, soft magnetic thin films produced by ion beam sputtering have excellent magnetic properties. The theoretical basis for this is not clear, but
The following can be considered. In other words, if nitrogen exists in the sputtering atmosphere, it will be ionized in the argon plasma, but if the ion beam sputtering method is used, the plasma is inside the ion gun and the formed film will be ionized. It is predicted that this is due to the fact that something like a columnar structure does not form in the membrane because it is not exposed to nitrogen ions. [Effects of the Invention] The present invention is configured as described above, and can improve both soft magnetic properties and thermal stability. Furthermore, according to the present invention, it is possible to obtain a good soft magnetic film even in a relatively thick single layer film of about 5,000 to 8,000 layers. There is no need to stack the layers. Therefore, it is possible to improve productivity and reduce costs.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the ion beam sputtering apparatus used in the present invention. Fig. 1 1...Exhaust pipe, 2...21 dollar valve, 3...Ion gun, 4...Target, 5... Substrate, 6... Vacuum chamber.

Claims (5)

[Claims] (1) A soft magnetic thin film characterized in that it is made of an alloy mainly composed of cobalt and to which at least one metal element selected from the group of titanium and tantalum is added, and a nitrogen element is mixed therein. (2) The soft magnetic thin film according to claim (1), wherein most of the crystal structure of the alloy is in an amorphous state. (3) An alloy consisting of cobalt as a main ingredient and at least one metal element selected from the group of titanium and tantalum added thereto, and by sputtering the alloy in the presence of nitrogen gas, nitrogen elements are deposited on the substrate. 1. A method for producing a soft magnetic thin film, characterized by forming an alloy thin film mixed with. (4) Using a target mainly composed of cobalt and to which at least one metal element selected from the group of titanium and tantalum and a nitrogen element are added,
A method for producing a soft magnetic thin film, characterized in that an alloy thin film containing nitrogen element is formed on a substrate by sputtering the alloy. (5) In claim (3) or claim (4),
A method for producing a soft magnetic thin film, characterized in that the sputtering is ion beam sputtering in which a target is irradiated with an accelerated ion beam to generate fine particles.