JPH0629131A - Thin film magnetic core for magnetic element - Google Patents

Abstract

PURPOSE:To obtain a magnetic device thin film core which is capable of minimizing an anti-magnetic field factor in a film formation process of a magnetic thin film, providing an uniaxial magnetic anisotropy effectively, reducing the size of a triangular magnetic domain and providing excellent high frequency magnetic properties. CONSTITUTION:On a substrate having strip-shaped stepped portions 11a, 11b and 11c comprising a plurality of nonmagnetic substances formed in parallel at a specified width and span on the top, there are formed magnetic thin films each of which is continued under the application of similar magnetic fields (marked with the arrow Hf) in a direction which intersects the stepped portions 11a, 11b and 11ca, thereby forming a plurality of strip-shaped magnetic cores 12a to 12e.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film magnetic core structure of a magnetic element used as an electric circuit element such as a micro inductor, a transformer or various sensors.

[0002]

2. Description of the Related Art FIG. 4 shows, for example, the MAG90-125 and MAG90-4 materials of the Institute of Electrical Engineers and Magnetics Research Group.
4 is a perspective view of the conventional winding structure type thin film inductor shown in FIG. In the figure, 1 is a non-magnetic substrate, and 2a is a lower layer coil made of a copper thin film formed on the non-magnetic substrate 1 by using a photolithography technique and a film forming technique such as sputtering and plating, and corresponds to the first layer of the element. . The second layer is an insulating layer made of an organic material such as a resist or an inorganic material such as SiO ₂ , but is omitted in the figure for simplicity. The strip-shaped magnetic cores 4a, 4b and 4c are made of alloy or amorphous thin film formed by sputtering or plating, and correspond to the third layer of the device. The fourth layer is an insulating layer like the second layer, but is omitted in the drawing. Similarly to the first layer, 2b is an upper coil made of a copper thin film to form the fifth layer of the device. 3a and 3b are coil terminal portions.

Next, the operation will be described. FIG. 5 is a sectional view taken along the line AA 'of the conventional strip-shaped magnetic cores 4a, 4b, 4c of FIG. FIG. 6 also shows a conventional strip-shaped magnetic core 4
It is a top view of a, 4b, 4c.

The signal magnetic field induced by the high frequency signal current Is applied from the terminal portions 3a and 3b is indicated by arrows Hs ₁ and Hs ₂ alternating at high frequencies. In order to improve the high frequency magnetic characteristics of the strip-shaped magnetic core, the signal magnetic field (arrow Hs
₁ , Hs ₂ ) to regulate the easy axis of magnetization, the strip-shaped magnetic cores 4a, 4b, 4c are formed while applying a DC magnetic field from the outside in the direction of arrow Hf as shown in FIG. . The magnetic flux in the vicinity of the magnetic cores 4a, 4b, 4c formed under a uniform externally applied magnetic field (arrow Hf) shows a magnetic flux distribution as shown by a dashed arrow 5, and a part of this magnetic flux is generated inside the magnetic core. As a result, the magnetic cores 4a, 4b, 4c have their axes of easy magnetization restricted in the direction of the applied magnetic field (arrow Hf).

As a result of the easy axis of magnetization being restricted in the direction of the externally applied magnetic field (arrow Hf), the strip-shaped magnetic cores 4a, 4b,
4c has a magnetic domain structure as shown in the plan view of FIG. Arrow 6 indicates the direction of magnetization of each magnetic domain, and 7 indicates a 90 degree domain wall,
8 shows a 180 degree domain wall. Reference numeral 9 indicates a triangular magnetic domain surrounded by the 90 degree domain wall 7, and a signal magnetic field alternating with a high frequency (arrow Hs
₁ , Hs ₂ ) does not respond effectively.
For the high frequency signal magnetic fields indicated by the arrows Hs ₁ and Hs ₂ , effective high frequency magnetic response is obtained by rotation of spins aligned in the directions indicated by the arrows 6a and 6b in the hexagonal magnetic domains.

The strip-shaped magnetic core has a length l _{1 of the} magnetic core.
4 and 5, the signal magnetic field direction (arrow H
s ₁ , Hs ₂ ), the ratio of the cross-sectional area S _{1 of the} magnetic core opposite to l ₁
The diamagnetic field coefficient N ₁ determined by / S ₁ is small, and there is an advantage that a magnetic core having a large effective high-frequency permeability μ can be obtained.
The demagnetizing factor N has the property of decreasing with an increase in the ratio 1 / S of the length 1 of the magnetic core in the magnetization direction of the magnetic core and the cross-sectional area S of the magnetic core in the magnetization direction.

[0007]

Since the conventional strip-shaped magnetic core is divided as shown in FIG. 5, an external magnetic field (arrow Hf) is applied in a film forming process under a uniform external magnetic field (arrow Hf). the length l ₂ of the direction of the magnetic core, which the ratio l ₂ / S ₂ is small and the side cross-sectional area S ₂ of the core shown in opposed 10b, demagnetizing factor N ₂ increases result, the magnetic core by an externally applied magnetic field The magnetic flux 5 traversing inside is reduced. As a result,
There is a problem that the effect of imparting uniaxial anisotropy by the external magnetic field (arrow Hf) is small.

As a result of the above, as shown in the magnetic domain structure of FIG. 6, the size of the triangular magnetic domain 9 which does not effectively act on the high frequency alternating magnetic field (arrows Hs ₁ and Hs ₂ ) becomes large, and this increases the volume occupied in the magnetic core. As a result, the effective magnetic core volume decreases, which is a problem.

In addition, the triangular magnetic domains are rarely arranged in order as shown in FIG. 6, and often have an irregular arrangement due to the presence of stress or the like. The presence of this irregular triangular magnetic domain causes discontinuous magnetization behavior under an alternating magnetic field,
There is a problem that magnetic noise is generated due to this.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to reduce the demagnetizing field coefficient in the film forming process of the magnetic thin film and effectively impart uniaxial anisotropy to the size of the triangular magnetic domain. It is intended to obtain a thin film magnetic core for a magnetic element which can reduce the thickness and has excellent high frequency magnetic characteristics.

[0011]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides an insulating member having a strip-shaped step portion formed of a plurality of non-magnetic members on the upper surface in parallel with a predetermined width and interval. In addition, a plurality of strip-shaped magnetic cores are constituted by mutually continuous magnetic thin films formed by applying a uniform DC magnetic field in a direction orthogonal to the step portion.

[0012]

Since the strip-shaped magnetic core according to the present invention has a step difference and the adjacent magnetic cores have a continuous magnetic thin film structure, the magnetic core corresponding to the magnetization direction by the high-frequency signal magnetic field is occupied as compared with the conventional strip-shaped magnetic core. Since the cross-sectional area can be increased, the magnetic resistance of the magnetic core can be reduced. In addition, by having a magnetic thin film structure in which adjacent magnetic cores are continuous with each other, it is possible to reduce the demagnetizing factor against the externally applied magnetic field in the magnetic thin film deposition process and the heat treatment process while applying the external magnetic field after deposition. The uniaxial anisotropy is strongly imparted, the size of the triangular magnetic domain can be controlled to be small, the effective volume of the magnetic core is large, and a strip-shaped magnetic core having excellent high-frequency magnetic characteristics can be obtained.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a cross-sectional view of a magnetic core according to an embodiment of the present invention, which is opposed to the direction of a high-frequency signal magnetic field, and FIG. 2 is a plan view thereof.

Reference numerals 11a, 11b and 11c denote strip-shaped step portions formed of a non-magnetic material such as SiO ₂ formed on a substrate (not shown), having a predetermined strip width l ₂ and a thickness t, and being spaced apart from each other. It is arranged with d. 12a to 12e
Is a plurality of strip-shaped magnetic cores connected to each other, and is an alloy or amorphous film formed by sputtering or plating on the substrate having the step portions 11a to 11c and the distance d under a uniform external magnetic field (arrow Hf). It is composed of one continuous magnetic thin film having a thickness T of, for example. In this embodiment, the thickness T of the magnetic thin film is 3 μm and the thickness t of the steps 11a to 11c is 1 μm. The strip-shaped magnetic cores 12a, 12c, 12e are formed on the strip-shaped stepped portions 11a, 11b, 11c having the width l ₂ , and the strip-shaped magnetic cores 12b, 12d are formed on the substrate and have a width d. In this embodiment, the width l ₂ = d = 100 μm. The strip-shaped magnetic cores 12a, 12c, 12e and the strip-shaped magnetic cores 12b, 12d have a step corresponding to the thickness t, and adjacent magnetic cores are magnetically connected to each other.

As described above, the strip-shaped magnetic cores 12a-1
Since 2e are magnetically connected to each other, the length of the magnetic thin film in the direction of the externally applied magnetic field (arrow Hf) during film formation is substantially 3l ₂ + 2d with respect to the conventional l ₂ (100 μm in the embodiment). (500 μm in the example), which is significantly long, and the demagnetizing factor is significantly reduced.
Most of the magnetic flux lines indicated by the broken line arrow 15 are magnetic cores 12a to 12e.
As a result of traversing the inside, a magnetic core provided with strong uniaxial anisotropy in the direction of the external magnetic field (arrow Hf) is obtained.

As a result, the width w of the magnetic domain is restricted to be extremely small as shown in the plan view of FIG. Amorphous (C
In the embodiment using the (o, Fe, SiB) sputtered film, the width w of the magnetic domain is regulated to 10 μm or less, and the volume occupied by the triangular magnetic domain is substantially negligibly small. As a result, a magnetic core having excellent magnetic characteristics can be obtained even with an alternating magnetic field (arrows Hs ₁ and Hs ₂ ) corresponding to a high frequency signal of several 100 MHz.

The high frequency signal magnetic field (arrows Hs ₁ , H
The cross-sectional area of the magnetic core corresponding to s ₂ ) is also increased by about 1.7 times in this embodiment as compared with the conventional example, and the magnetic resistance of the magnetic core can be reduced with the increase of the occupied area of the magnetic core.

In the above embodiment, the thickness T of the magnetic thin film is larger than the thickness t of the non-magnetic strip-shaped step portions 11a to 11c.
However, as shown in the other embodiment of FIG. 3, the non-magnetic strip-shaped step portions 111a to 111c are formed.
Even if the thickness T of the magnetic thin film is small by providing the taper portion 13 in the
2a to 12e are magnetically connected at a portion corresponding to the taper portion 13, and a demagnetizing field against an externally applied magnetic field (arrow Hf) can be significantly reduced, and the same effect as that of the above-described embodiment can be obtained.

In the above embodiment, the strip-shaped magnetic core is 1
It is composed of 5 lines 2a to 12e, and its width l ₂ = d = 10
Although it is set to 0 μm, the number of strip-shaped magnetic cores and the width thereof can be arbitrarily configured.

In the above embodiment, the strip-shaped step portion 1
Although 1a, 11b, and 11c are described as being formed on the substrate, the strip-shaped step portion is not always formed on the substrate in a magnetic element having a multilayer structure, and the strip-shaped step portion is not necessarily formed on the intermediate insulating layer of the magnetic element having a multilayer structure. Even if it is formed, the same effect as that of the above embodiment can be obtained.

[0021]

As described above, according to the present invention, a plurality of strip-shaped step portions that are parallel to the direction of the high-frequency signal magnetic field are provided, and a magnetic layer having a thickness greater than the step thickness is provided between and on each step portion. By forming a thin film, each strip-shaped magnetic core acts as one continuous magnetic thin film at the time of film formation, and the influence of the demagnetizing field can be significantly reduced, and a magnetic thin film with strong uniaxial anisotropy can be obtained. . On the other hand, when considering operation by a high-frequency signal magnetic field, adjacent strip-shaped magnetic cores are connected to each other with a predetermined step difference, and as a result, they act as strip-shaped magnetic cores that are independent from each other in terms of magnetic domain structure. It is a feature of the strip-shaped magnetic core according to the invention. As a result, there is an effect that the volume occupied by the triangular magnetic domains can be significantly reduced, the high frequency characteristics are excellent, and a strip-shaped magnetic core having a larger occupied cross-sectional area of the magnetic core can be obtained as compared with the conventional strip-shaped magnetic core.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a plan view showing an embodiment of the present invention.

FIG. 3 is a sectional view showing another embodiment of the present invention.

FIG. 4 is a perspective view showing an inductor using a conventional strip-shaped magnetic core.

FIG. 5 is a cross-sectional view showing a conventional strip-shaped magnetic core.

FIG. 6 is a plan view showing a conventional strip-shaped magnetic core.

[Explanation of symbols]

4a, 4b, 4c ... Conventional strip-shaped magnetic core, 9 ... Triangular domain, 11a, 11b, 11c ... Non-magnetic strip-shaped stepped portion, 12a-12e ... Strip-shaped magnetic core according to one embodiment of the present invention, 13 ... Non-magnetic strip Tapered portion of the stepped portion, Hf ... Arrows showing the direction of the externally applied magnetic field in the film forming process of the magnetic core, Hs ₁ , Hs ₂ ... Arrows showing the direction of the alternating magnetic field by the high frequency signal.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication location H01F 41/24 (72) Inventor Shoji Terasaka 3-3-14 Hachiman, Aoba-ku, Sendai-shi, Miyagi (72) ) Inventor Masao Sandera 1-24-39 Yoshinari Aoba-ku, Sendai City, Miyagi Prefecture

Claims (2)

[Claims] 1. A uniform DC magnetic field in a direction orthogonal to the stepped portion on an insulating member having a strip-shaped stepped portion made of a plurality of non-magnetic materials formed on the upper surface in parallel with a predetermined width and interval. A thin film magnetic core for a magnetic element, characterized in that a plurality of strip-shaped magnetic cores are constituted by magnetic thin films which are continuous with each other while being applied. 2. The thin film magnetic core for a magnetic element according to claim 1, wherein a side portion of the strip-shaped step portion has a taper portion.