JPH03278510A - Manufacture of high-permeability magnetic thin film - Google Patents

Abstract

PURPOSE:To enable improving magnetic properties by obtaining a uniform structure at the time of film-forming thorugh making a sputter input power at the time of film-forming larger in the early stage of film-forming and thereafter through conducting a gradient power input while decreasing the power gradually. CONSTITUTION:When a high permeability magnetic thin film 22 is manufactured by a sputtering process, a sputter input power at the time of film-forming is made larger in the early stage of film-forming and thereafter a gradient power input is conducted while the sputter input power is deceased gradually. For example, (Co0.94Nb0.06)90B10 is used as target and RF spurtering apparatus is used as film-forming apparatus to conduct film-forming on a cooling substrate 21. Further, the sputter input power at that time is 5.2W/cm<2> in the early stage of film-forming, which is gradually decreased thereafter and is 2.6W/cm<2> in the last stage thereof; other conditions than the sputter input power are made constant; and after a thick film 2mum is formed, the film is subjected to the processing at 300 deg.C of rotating field. Thus, it is possible to obtain a uniform film structure from the early stage of film-forming to obtain a thin film having excellent specific initial permeability mui and frequency characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a high permeability magnetic thin film used as a magnetic core material for inductors, transformers, etc. used in high frequency regions.

[Prior art] One of the problems associated with miniaturization of magnetic elements is that when the excitation frequency is increased, the condition that the frequency characteristics do not deteriorate is that the thickness must be extremely uniform, and the material and magnetic characteristics must be uniform. That is important. Generally, when forming a film by sputtering,
The method used is to reach a predetermined degree of vacuum in the chamber, and after steps such as substrate etching and press sputtering, the main sputtering is started. Generally, once plasma is generated, conditions are selected to maintain a plasma state as stable as possible until the end of sputtering. That is, as sputtering conditions, monitoring and control are mainly performed to minimize fluctuations in sputtering power, set gas pressure, flow rate, and the like. Furthermore, new and improved sputtering equipment continues to be developed and research is being carried out to add various improvements and new functions in order to automatically eliminate these fluctuation factors in film forming conditions. In any case, the conventional and common method is to form a film by keeping the sputtering power constant once sputtering is started until it ends.

[Issue 1i to be solved by the invention] The thin film obtained by such a general method is shown in Fig. 1 (b
), as the deposition of the thin film 12 progresses from the surface of the substrate 11, the structure of the thin film 12 closer to the surface of the substrate 11 and the thin film 12 in the later stages of deposition may become non-uniform. It's quite predictable. That is, it is predicted that an extremely fine structure will be formed in the initial stage of film formation, and that it will become a coarse structure as the film is deposited. After the thin film 12 is formed, distortions during film formation are usually alleviated by heat treatment.
Even with this heat treatment, the nonuniform structure remains without being sufficiently eliminated, and as a result, the improvement in the magnetic properties of the thin film is small.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a high permeability magnetic thin film that can improve magnetic properties by obtaining a uniform structure during film formation.

[Means and effects for solving the problem] The present invention focuses on making the structure uniform, and the conventional structure non-uniformity is caused by ultrafine fineness of the film deposited on the substrate in the initial stage of film formation. In view of the structure, the present invention
We particularly focused on sputtering power as a source of heat generation during film formation, and based on the fact that as sputtering power increases, the substrate temperature rises.In particular, when a large amount of sputtering power is input in the early stage of film formation, and as the deposition progresses, this phenomenon occurs. A magnetic thin film with higher magnetic permeability than the conventional one was obtained by adopting a method of ramping power input in which the power input is reduced in consideration of temperature rise.

[Example] Examples of the present invention will be described in detail below.

The high permeability magnetic thin film of the present invention is a material that has excellent soft magnetism in a high frequency region, and if the material is suitable for this, it can be amorphous,
It does not matter whether the structure is crystalline or a mixture of amorphous and crystalline materials. However, important material properties as a condition for creating these magnetic thin films are that the change in coercive force Hc due to sputtering power P is small, as shown in material A shown in Figure 2, or that the coercive force Hc is sensitive to temperature changes. It is necessary to have low sensitivity. Typical composition examples of magnetic thin films suitable for this purpose include CoNbZr type and CoNbB type.

A film is formed on a cooled substrate by sputtering using such an alloy material as a target, and the sputtering input power at the initial stage of film formation is set to be the maximum during film formation. Practically speaking, approximately 5 W/elf is desirable. If the sputtering power is smaller than this, the desired effect cannot be obtained.

The effect also decreases if the initial sputtering input power is too high, but this is probably due to deviation from the appropriate size of the initially deposited film structure. In addition, the initial sputtering power was 5 W.
/c12, when a film is formed to a desired thickness with this constant input power for sputtering, the magnetic properties deteriorate, but this is considered to be the result of coarsening of the deposited upper structure. In any case, the appropriate amount of sputter input power is set at the start of sputtering to be the highest during film formation, and from then on,
A feature of the present invention is to perform ramped power input in which the sputtering power is gradually reduced.

FIG. 1(a) is a structural model of a magnetic thin film expected to be formed by the gradient power input sputtering method according to the present invention, and the magnetic thin film 22 deposited on the substrate 21 has a uniform structure.

Specific examples of the present invention are shown below.

◎ Specific Examples A (CO0,94N b O,06) 90B IQ was used as a test target, and a film was formed using an RF sputtering apparatus under the following conditions.

1) Conventional method Sputtering power 5.2W/c22)
〃 3.9W/am"3) Present invention method"5.2W/cs'→2.6W/e
(2) Conditions other than the sputtering input power were kept constant, and the thickness of the film was 2 μm. After film formation, a rotating magnetic field treatment at 300° C. was performed. The results are shown in Figure 3 as a relationship between specific initial magnetic permeability μi (applied magnetic field 5m0e) and frequency f (kHz).

It is clear from FIG. 3 that a thin film having excellent specific initial permeability μi and frequency characteristics can be obtained by the gradient power input method which is the process of the present invention.

[Effects of the Invention] As described above, according to the present invention, when creating a magnetic alloy thin film by sputtering, the sputtering input power is made the highest at the initial stage of film formation and is gradually decreased during film formation. It has been found that a magnetic alloy thin film with high magnetic permeability can be obtained by the injection method, and this has great industrial significance and effects on the industrial world.

[Brief explanation of the drawing]

FIG. 1(a) is a schematic diagram showing an example of the magnetic thin film structure predicted by the gradient power input sputtering method based on the present invention, and FIG. 1(b) is a schematic diagram showing the magnetic thin film structure predicted by the conventional sputtering method. A schematic diagram, FIG. 2 is a characteristic diagram showing an example of the difference in sputtering power dependence of coercive force Hc for each magnetic thin film material, and FIG. FIG. 2 is a characteristic diagram showing the magnetic permeability of a magnetic thin film and its frequency dependence. 21...Substrate, 22...Magnetic thin film.

Claims (1)

[Claims] In manufacturing a high magnetic permeability magnetic thin film by sputtering, the sputtering power input during film formation is increased at the initial stage of film formation, and thereafter, the sputtering power is gradually reduced while ramping power input is performed. Method for manufacturing magnetic thin film.