JPH0677055A - Plane magnetic element - Google Patents

Abstract

PURPOSE:To obtain a plane magnetic element such as a plane inductor or a plane transformer high in quality factor Q by a method wherein a soft magnetic material is lessened in high frequency iron loss by restraining an eddy current induced in the surface of the soft magnetic material. CONSTITUTION:A spiral plane coil 1, an insulator 2, and a soft magnetic body 3 are laminated to form a plane magnetic element, where a high resistance region 4 is formed on the same plane with the soft magnetic body 3 to fractionize an eddy current generated in the surface of the soft magnetic body 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plane magnetic element such as a plane inductor or a plane transformer.

[0002]

2. Description of the Related Art Recently, various electronic devices have been actively reduced in size and weight. This is largely due to the LSI implementation of various circuits by semiconductor process technology. But,
Integration of power supply parts for supplying power to various circuits has been delayed, and the ratio of the volume to the entire electronic device is increasing. The biggest factor that hinders the miniaturization of the power supply part is the magnetic parts such as inductors and transformers.
Due to its unique winding structure, it is difficult to make it small and thin.

Against this background, technological developments for flattening or thinning magnetic components have become active (for example, Shirakawa et al .; Institute of Electrical Engineers of Japan, Magnetics Research Material MA).
G-92-14).

In a planar magnetic element, a planar inductor structure in which a spiral planar coil is sandwiched by a soft magnetic material is well known as an element structure having excellent magnetic shield characteristics and a large inductance per unit occupied area of the element (for example, Kawabe et al .; IEEE Tran
actions on Magnetics, MA
G-20, p. 1804 (1984)). In order to put such a planar magnetic element into practical use, it is necessary to have a sufficiently low loss in the frequency band used, and it is necessary to use a soft magnetic material with little high frequency iron loss. However, even if the high-frequency iron loss measured by the soft magnetic material alone is sufficiently small, when it is actually applied to a planar magnetic element, the element characteristics are far inferior to the expected characteristics. Often. Therefore, the conventional planar magnetic element is inferior in high frequency characteristics, has a low quality factor Q, and is far from being practically used.

The reason will be described in more detail below. FIG. 9 shows the magnetic flux distribution of the planar inductance of the sandwich structure of soft magnetic material 3 / insulator 2 / spiral plane coil 1 / insulator 2 / soft magnetic material 3. In the figure, B ₁ represents an in-plane magnetic flux component of the soft magnetic material, and B ₂ represents a magnetic flux component perpendicular to the soft magnetic material surface. Here, the characteristic length λ expressed by the following equation (1) is introduced. λ = (μ ₀ · μ _s · g · t / 2) ^1/2 (1)

In equation (1), μ ₀ is the vacuum permeability, μ
_s is the relative magnetic permeability of the soft magnetic material, g is the gap length between the upper and lower soft magnetic materials, and t is the thickness of the soft magnetic material. The characteristic length λ has a dimension of length, and B ₁ and B ₂ are e ⁻¹ from a certain reference position.
It means the distance to the position where it decays to. Actually, the number of turns of the spiral coil is 28, and the relative permeability μ _s of the soft magnetic material is 1.
B ₁ for a planar inductor with a thickness t of the soft magnetic material of 2 μm and a gap length g of the upper and lower soft magnetic materials of 20 μm.
And B ₂ were examined. In this case, the characteristic length λ is 173.2.
μm.

FIGS. 10 (a) and 10 (b) show a line width = 30 μm for a conductor forming a spiral coil,
Space width = 75 μm, space width s is characteristic length λ
The change in B ₁ and B ₂ when about 2/5 is shown.
11A and 11B show line width = 100 μm, space width = 5 μm, and space width s is about 1/35 of the characteristic length λ for the conductors forming the spiral coil.
The change of B ₁ and B ₂ in the case of As can be easily seen from these figures, in order to reduce B ₂ , s <
<Λ is required.

FIG. 12 shows the dependence of the soft magnetic loss component R _{MAG. Of} the planar inductor on the coil parameter d / p. p is a conductor pitch and is represented by p = d + s where d is the line width and s is the space width. That is, s
When → 0, p → 1. As is clear from this figure, it is understood that R _MAG. Can be reduced by reducing s. This is because B ₂
Because it can be made smaller. However, even if s is in the extreme state (s → 0), R _MAG. Still exists. s →
In R _{MAG. At} 0, in addition to the _{one due} to the in-plane magnetic flux component B ₁ of the soft magnetic material, the _one due to B ₂ is still included. This is because, as can be seen from FIG. 10 (b) and FIG. 11 (b), B ₂ cannot theoretically be zero near the center and the end of the spiral planar coil.

FIG. 13 schematically shows an in-plane eddy current generated by a magnetic flux component perpendicular to the surface of the soft magnetic material. FIG. 14 shows the spatial distribution of the in-plane eddy current of the soft magnetic material calculated based on FIG. 11 (b). From this figure, it can be seen that the in-plane eddy current is generated over a wide range of the soft magnetic material. As described above, the high frequency eddy current generated by B ₂ flows over a wide area in the plane of the soft magnetic material, so that the loss becomes much larger than that by B ₁ .

As described above, the reason why it is difficult to obtain good characteristics in an actual planar magnetic element even when a soft magnetic material having good characteristics is used is that eddy current loss accompanying B ₂ is added. It depends.

Generally, as a method of reducing the eddy current loss, (i) increasing the resistivity of the soft magnetic material, (ii) thinning the soft magnetic material thin film or thin plate, and laminating it with an insulator. , (Iii) It is effective to subdivide the magnetic domain.
In order to improve the high frequency characteristics of the planar magnetic element, it is considered that a material satisfying these requirements should be used. However, with respect to (i), high resistivity materials typically have the drawback of low saturation flux density. With respect to (ii) and (iii), almost no expectation can be made for reducing the eddy current due to the magnetic flux component perpendicular to the surface of the soft magnetic body in the planar magnetic element.

[0012]

An object of the present invention is to reduce the high frequency iron loss of the soft magnetic material by suppressing the eddy current generated in the surface of the soft magnetic material, and to provide a planar inductor having a high quality factor Q. It is to provide a planar magnetic element such as a planar transformer.

[0013]

A planar magnetic element of the present invention is a planar magnetic element constituted by laminating a spiral planar coil, an insulator and a soft magnetic material, and has a high resistance region on the same plane as the soft magnetic material. Is formed. Hereinafter, the present invention will be described in more detail.

In the present invention, the shape of the spiral coil forming the planar magnetic element is not particularly limited. That is, if the structure in which the coil conductor is wound on the same plane is partially included, such as a circular shape, a square shape, a rectangular shape, an elliptical shape, and other composite types, all planar coils are included.

Examples of the soft magnetic material used in the planar magnetic element of the present invention include Fe-based, Co-based, and FeCo-based alloys. The crystal structure of these soft magnetic materials is not particularly limited, and may be single crystal, polycrystal (including microcrystal), or amorphous. It is desirable that the saturation magnetic flux density be 1 tesla or more and the coercive force be 1 oersted or less.

In the planar magnetic element of the present invention, a high resistance region is formed on the same plane as a soft magnetic material having a high saturation magnetic flux density having a low resistivity to forcibly interrupt the in-plane eddy current path. It is intended to reduce high frequency loss. That is, the magnitude of the eddy current is proportional to the square of the magnetic flux density and inversely proportional to the resistivity. Therefore, when the high resistance region is formed in the passage of the eddy current flowing in the surface of the soft magnetic body, the passage of the eddy current is subdivided, whereby the high frequency loss can be reduced.

In the present invention, the high resistance region formed on the same plane as the soft magnetic material is arranged so as not to impede the flowability of the in-plane magnetic flux of the soft magnetic material. The most effective method is to make the boundary between the soft magnetic material and the high resistance region parallel to the magnetic flux flowing direction. 1 (a) and (b),
An example of a planar inductor in which the soft magnetic material 3 and the high resistance region 4 are formed on the same plane via the insulator 2 on both surfaces of the circular spiral coil 1 is shown. FIG. 2 schematically shows that the high resistance region 4 is formed on the same plane as the soft magnetic body 3 so that the path of the eddy current due to the magnetic flux component perpendicular to the surface of the soft magnetic body is subdivided. . With such a configuration, the passage of the in-plane eddy current of the soft magnetic material can be forcibly cut off, so that the high frequency loss can be reduced.

As the material forming the high resistance region,
Examples include (A) high-resistivity soft magnetic material, (B) soft magnetic material constituent oxides, nitrides, borides, and (C) insulators. From the viewpoint of preventing leakage of magnetic flux, it is preferable that the high resistance region is also made of a soft magnetic material.

The high-resistivity soft magnetic material is an oxide soft magnetic material such as manganese-zinc based ferrite or nickel-zinc based ferrite, or a soft magnetic material dispersion type insulation in which soft magnetic fine particles are dispersed in an insulating resin. The body. Also, 1
A multilayer structure material in which a metal soft magnetic material having a layer thickness of 2000 angstroms or less and an insulator are laminated may be used.
Such a multilayer structure material has a high resistance because the probability of surface scattering of conduction electrons is increased by thinning the metal soft magnetic material (Kanehara; Basic technology of thin film, p. 159 to 166,
The University of Tokyo Press, 1987 first edition). In this case, for example, by combining a thin strip of a high saturation magnetic flux density metal soft magnetic material formed in a predetermined shape and a high resistivity soft magnetic material,
A high resistance region is formed.

As a method of forming the high resistance region made of oxide, nitride, boride, etc. of soft magnetic material, (a) oxygen,
A method of implanting ions such as nitrogen and boron, a method of (b) heat treatment in an atmosphere of oxygen or nitrogen, and a method (c) of treatment in oxygen or nitrogen plasma are conceivable, but not limited to these methods. Figure 3 illustrates these methods.
Will be described with reference to. In this case, the soft magnetic material 3 is formed on the underlayer 11, and a suitable mask 12 made of an oxide film or the like is formed on the soft magnetic material 3, and ion implantation, heat treatment in an atmosphere,
Plasma treatment. The mask 12 is patterned so that the opened processing window is parallel to the direction in which the in-plane magnetic flux of the soft magnetic material flows. Among these methods, the ion implantation method forms oxides, nitrides, borides, etc., and partially transforms them into amorphous when crystalline metal is used as the soft magnetic material. Can be expected.

A method of forming a high resistance region made of an insulator will be described with reference to FIGS. 4 (a) and 4 (b). Figure 4 (a)
As shown in FIG. 3, the soft magnetic material 3 is formed on the underlayer 11, and the soft magnetic material 3 is grooved by wet etching, dry etching, or the resist lift-off method. This groove is patterned so as to be parallel to the direction in which the in-plane magnetic flux of the soft magnetic material flows. As shown in FIG. 4A, a high-resistance insulator 5 is deposited on the entire surface, the insulator 5 is embedded in the groove of the soft magnetic body 3, and further planarization processing is performed. This embedded portion becomes the high resistance region 4.

However, in the case of the thin film process, when the oxide magnetic material (and the insulating resin in which the oxide magnetic material particles are dispersed) is partially formed as the soft magnetic material, the material of the element is The forming temperature is determined in consideration of the heat resistant temperature.

Next, FIG. 5 shows the relationship between the number of divisions of the soft magnetic material by the high resistance region and the loss due to the in-plane eddy current of the soft magnetic material. The horizontal axis indicates the number of divisions, for example, n = 0 means no division and n = 2 means two divisions. From this figure, it is understood that the loss due to the in-plane eddy current can be reduced to half or less by setting n ≧ 4.

Further, as described above, the shape of the spiral plane coil is not particularly limited. The pattern of the high resistance region formed on the same plane as the soft magnetic material is determined so as to be parallel to the direction of the magnetic flux flowing in the surface of the soft magnetic material according to the shape of the spiral coil. 6 to 8 show examples of patterns of the high resistance region in the case where spiral flat coils having various shapes are used. 6 shows a case of a square spiral coil, FIG. 7 shows a case of a rectangular spiral coil, and FIG. 8 shows a case of a rectangular double spiral coil.

Even if the configuration of the present invention is adopted,
As described above, the eddy current loss due to the in-plane magnetic flux component still remains. The means (i), (ii), and (iii) described above are effective in suppressing this, and by combining with the present invention, total eddy current loss can be reduced. Although the planar inductor has been described above, the high frequency characteristics of the planar transformer can be expected to be improved in the same manner.

[0026]

EXAMPLES Examples of the present invention will be described below. Example 1

A copper foil was adhered to a substrate made of a polyimide film, and the copper foil was processed by wet etching to form a circular spiral coil. A polyimide film was also adhered to the other surface of this circular spiral coil. As a high saturation magnetic flux density soft magnetic material, a Co-based amorphous ribbon with a thickness of 15 μm produced by the melt quenching method was used for 5 m.
Cut into m squares. As a high resistivity soft magnetic material, thickness 15μ
A nickel-zinc based ferrite piece having m, a width of 1 mm and a length of 5 mm was prepared. The Co-based amorphous ribbon and the nickel-zinc-based ferrite piece were combined to form a soft magnetic material and a high resistance region. That is, this soft magnetic layer is divided into four parts, and a hole of 1 mm × 1 mm is formed at the center. This hole is used as a terminal lead-out portion of the spiral coil. The laminated adhesive type planar inductor thus manufactured has a size of 11 mm square and a thickness of 0.5 mm.

For this planar inductor, 500 k
The quality factor Q value in Hz was 15. On the other hand, Co
The quality factor Q value was about 8 when only the system amorphous ribbon was used (when not divided). Example 2

A 2 μm thick CoFeSiB amorphous film was formed as a lower soft magnetic thin film on the substrate by a thin film process. By the registry lift-off method, CoFeSi
Four grooves having a width of 5 μm were formed in the radial direction from the center of the B amorphous film. On top of this, manganese with a particle size of 0.5 μm
A paste in which zinc-based soft magnetic ferrite particles were dispersed in an insulating resin was applied by a spin coating method, and heat-cured at a temperature of 200 ° C. Since the viscosity of this ferrite paste is as low as 1000 cp or less, the surface is flattened when applied to the underlayer. In this case, the unevenness of the surface after coating and heating became 1/50 or less of the step difference of the base. A Cu circular spiral coil was formed on this ferrite dispersed resin layer by a thin film process. Further, in the same manner as described above, the ferrite-dispersed resin layer, the width of which is 5
An upper soft magnetic thin film having four μm grooves formed thereon and a ferrite-dispersed resin layer were sequentially formed to manufacture a planar inductor.

In this planar inductor, the ferrite dispersed resin layer is also used as an interlayer insulating layer between the lower soft magnetic thin film and the Cu spiral coil and between the Cu spiral coil and the upper soft magnetic thin film, and as a final protective layer for the upper soft magnetic thin film. Has been.

In the planar inductor of this embodiment, not only the high frequency quality coefficient is improved, but also the ferrite dispersed resin layer can be easily embedded and flattened, so that the process can be simplified. Example 3

Fe ₈₀ Co _{20 with a} thickness of 1 μm was formed as a high saturation magnetic flux density soft magnetic thin film on the substrate by ion beam sputtering.
A film was formed. Si serving as a mask on the Fe ₈₀ Co ₂₀ film
An O ₂ film was formed. By photolithography and reactive ion etching, an ion implantation window having a width of 2 μm was formed in this SiO ₂ film in parallel with the direction in which the magnetic flux passes, as shown in FIG. Using this SiO ₂ film pattern as a mask, 10
²⁰ / cm ² Oxygen was ion-implanted at a dose of 2 to form a high resistance region made of oxide of the soft magnetic thin film. The electrical resistivity was 10 μΩ · cm in the non-implanted region and 1000 μΩ · cm in the ion-implanted region. On top of this, RF
SiO _{2 having a} thickness of ₂ μm is formed as an interlayer insulating film by the sputtering method.
A film was formed. On this, a 10 μm thick primary side Cu square spiral coil was formed. Furthermore, as an interlayer insulating film, a SiO ₂ film, a secondary side Cu square spiral coil,
An SiO ₂ film is formed as an interlayer insulating film and a Fe ₈₀ Co ₂₀ film is formed as a high saturation magnetic flux density soft magnetic thin film, and oxygen is selectively ion-implanted in the same manner as described above to form a high resistance region made of an oxide of the soft magnetic thin film. Formed. A flat transformer was manufactured by these steps.

For the flat transformer of this embodiment, 10
The quality factor Q value in MHz was 15. This value was twice as large as that of the plane transformer produced without implanting ions into the Fe ₈₀ Co ₂₀ film. Example 4

The same 2 μm thick CoFeSiB amorphous film as in Example 2 was formed as the lower soft magnetic thin film on the substrate by a thin film process. A mask made of a SiO ₂ film pattern was formed on this. An RF power of 200 W was supplied in oxygen gas at a pressure of 40 Pa to generate RF plasma, and the exposed region of the soft magnetic thin film was plasma-treated.
As a result, the electrical resistivity of the plasma-treated region was 5 times that of the untreated region. Further, a Cu spiral coil, an SiO ₂ film as an interlayer insulating film, and an upper soft magnetic thin film were formed, and plasma treatment was performed as described above to form a high resistance region. A planar inductor was manufactured by these steps.

Regarding the planar inductor of this embodiment, 1
The quality factor Q value at 0 MHz was 11. This value was 1.5 times the value of a flat transformer produced on the CoFeSiB amorphous film without plasma treatment.

[0036]

As described in detail above, according to the planar magnetic element of the present invention, the eddy current generated in the surface of the soft magnetic layer can be suppressed by partially increasing the resistance of the soft magnetic layer. ,
The effect of improving the high frequency characteristics is extremely large.

[Brief description of drawings]

FIG. 1A is a plan view of a planar magnetic element according to the present invention,
(B) is a sectional view.

FIG. 2 is a schematic diagram showing an eddy current generated in a plane of a soft magnetic body of the planar magnetic element of the present invention.

FIG. 3 is a sectional view showing a method of forming a high resistance region on the same plane as the soft magnetic body of the planar magnetic element of the present invention.

4A and 4B are cross-sectional views showing a method of forming a high resistance region on the same plane of a soft magnetic material of a planar magnetic element of the present invention.

FIG. 5 is a characteristic diagram showing the relationship between the number of divisions of the soft magnetic body by the high resistance region and the loss due to the in-plane eddy current in the planar magnetic element of the present invention.

FIG. 6A is a plan view of a planar magnetic element using a square spiral coil according to the present invention, and FIG. 6B is a sectional view.

7A is a plan view of a planar magnetic element using a rectangular spiral coil according to the present invention, and FIG. 7B is a sectional view.

8A is a plan view of a planar magnetic element using a rectangular double spiral coil according to the present invention, and FIG. 8B is a sectional view.

FIG. 9 is a sectional view showing a magnetic flux density distribution in a conventional planar magnetic element.

10 (a) and 10 (b) respectively show a conductor forming a spiral coil of a conventional planar magnetic element,
FIG. 4 is a characteristic diagram showing changes in B ₁ and B ₂ when the space width s is about 2/5 of the characteristic length λ.

11 (a) and 11 (b) respectively show a conductor forming a spiral coil of a conventional planar magnetic element,
B ₁ when the space width s is about 1/35 of the characteristic length λ
And a characteristic diagram showing changes in B ₂ .

FIG. 12 is a characteristic diagram showing a relationship between a coil parameter and a loss resistance of a conventional planar magnetic element.

FIG. 13 is a schematic diagram showing an eddy current generated in a plane of a soft magnetic body of a conventional planar magnetic element.

FIG. 14 is a diagram showing a spatial distribution of an eddy current generated in a surface of a soft magnetic body of a conventional planar magnetic element.

[Explanation of symbols]

1 ... Spiral coil, 2 ... Insulator, 3 ... Soft magnetic material, 4
... High resistance region, 11 ... Substrate, 12 ... Mask.

Claims (1)

[Claims] 1. A planar magnetic element formed by laminating a spiral planar coil, an insulator and a soft magnetic material, wherein a high resistance region is formed on the same plane as the soft magnetic material.