JP2001155923A - Inductor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inductor element which can use effectively the whole section of a magnetic film, maintain magnetic flux shield effect of the magnetic film to be high, and hold a figure of merit Q value to be high, in a high-frequency range of at least 1 GHz, by a necessary and minimum thickness of the magnetic film. SOLUTION: An inductor line 12 is formed on a substrate 11, and constituted of a conductor film 14, magnetic films 15, 16 formed on both surfaces of the conductor film 14, and insulating films 17 and 18 formed on the surfaces of the magnetic films 17 and 18, respectively. The thickness t2 of the magnetic films 15, 16 is made smaller than or equal to two times the skin depth at the frequency to be used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inductor element used as an electric circuit element, and more particularly to an inductor element in which an inductor line is provided on a mother board such as a printed wiring board or a ceramic board.

[0002]

2. Description of the Related Art Hitherto, meander type and spiral type have been known as inductor elements. The meander type has a structure like a river with meandering inductor lines.
The currents flowing in adjacent lines are in opposite directions to each other, and such a meander type is easy to manufacture and has a feature that a medium inductance can be obtained.

On the other hand, in the spiral type, an inductor line has a spiral structure, and currents flowing in adjacent conductors are in the same direction as each other. Such a spiral type has a relatively large inductance. There is a feature that can be obtained.

A conventional inductor element is disclosed in
The one disclosed in JP-A-121237 is known. As shown in FIG. 6, the inductor element disclosed in this publication is a spiral planar stacked type,
An insulating film is formed on a base substrate such as silicon, and an inductor line 1 is formed thereon. In the inductor line 1, the planar coil conductor portion 3 is surrounded by a magnetic film 5, which is surrounded by an insulating film 7, and a magnetic film 8 is provided above and below the insulating film 7.
9 is formed.

That is, the inductor element disclosed in this publication is buried in the insulating film 7 with the planar coil conductor 3 covered with the magnetic film 5, and the magnetic films 8 are formed on the upper and lower surfaces of the insulating film 7. , 9 are formed.

The thickness of the planar coil conductor 3 in the stacking direction is 27 μm, the thickness of the magnetic film 5 covering the planar coil conductor 3 is 3 μm, and the magnetic films 8 and 9 formed on the upper and lower surfaces of the insulating film 7. Is 3 mm, and the thickness of the insulating film 7 formed between the magnetic films 8 and 9 and the magnetic film 5 is 10 μm each.
m.

In such an inductor element, since the planar coil conductor portion 3 is covered with the magnetic film 5, the magnetic film 5 avoids a crossing magnetic flux that vertically interlinks the planar coil conductor 3. That is, since the amount of magnetic flux passing therethrough is reduced, copper loss (eddy current loss) is reduced. Assuming that the coil resistance is R, the inductance is L, and the driving angular frequency is ω, the coefficient of performance Q is expressed as Q = ωL / R. Therefore, in the inductor element disclosed in the above publication, copper loss is reduced, Coil resistance R
Is reduced, the performance coefficient Q value can be increased.

[0008]

However, in the inductor element disclosed in Japanese Patent Application Laid-Open No. H11-112237, the thickness of the magnetic film 5 formed on the surface of the planar coil conductor 3 is as large as 3 μm. In the low frequency range, the magnetic film 5 has an effect of reducing copper loss.
In the above high frequency range, the eddy current loss of the magnetic film 5 becomes large, the effect of shielding magnetic flux becomes insufficient, the effect of reducing copper loss is weakened, and the performance coefficient Q value is reduced.

In the above publication, specifically, Ni is used for the magnetic film 5, and its specific resistivity is 7.2 × 10 ^-6.
Ωcm and relative permeability was 500. The skin depth δ at 1 GHz of the magnetic film 5 is expressed by the formula δ = (10ρ / fμ) ^1/2 × 10 ⁴ / 2π (ρ: specific resistance of the magnetic film, f: operating frequency, μ: magnetic film) Is 0.2 μm, and that which functions as a magnetic flux shielding effect is 0.4 μm, which is about twice the skin depth. That is, at the operating frequency of 1 GHz, only a part of the magnetic film thickness of 3 μm functions effectively, and the remaining portion does not function. However, there is a problem that the time is lengthened.

Further, since the thickness of the insulating film 7 interposed between the magnetic films 8 and 9 and the magnetic film 5 is as large as 10 μm, the distance between the planar coil conductor portion 3 and the magnetic film 5 increases. Since the magnetic resistance is increased, there is a problem that the magnetic film 8 and 9 have a low magnetic flux shielding effect.

According to the present invention, it is possible to effectively utilize the entire cross section of the magnetic film, to maintain a high magnetic flux shielding effect of the magnetic film with a minimum necessary thickness of the magnetic film even in a high frequency range of 1 GHz or more. It is an object of the present invention to provide an inductor element capable of maintaining a high performance coefficient Q value.

[0012]

The inductor element according to the present invention comprises an inductor line provided on a substrate, and the inductor line includes a conductor film, magnetic films formed on both surfaces of the conductor film, and An insulating film formed on the surface of the magnetic film, wherein the thickness of the magnetic film is twice or less the skin depth at the operating frequency.

As described above, by setting the thickness of the magnetic film to twice or less the skin depth at the operating frequency, it is possible to effectively utilize the entire cross section of the magnetic film with the minimum necessary thickness of the magnetic film. For example, even in a high frequency range of 1 GHz or more, the magnetic flux shielding effect of the magnetic film can be maintained at a high level, the coefficient of performance Q can be kept high, and the magnetic film can be thinned, so that the film formation time is short. Cost can be reduced.

Further, in the inductor element of the present invention, it is desirable that the inductor line is formed by alternately laminating a magnetic film and an insulating film on both surfaces of the conductor film, and the thickness of the insulating film is 5 μm or less.

As described above, the shield made of a plurality of magnetic films is formed on both surfaces of the conductor film, and the magnetic flux shielding effect can be maintained at a higher level. Further, since a plurality of magnetic films are formed, leakage of magnetic flux is small. Thus, the performance coefficient Q value can be increased. When a plurality of magnetic films are provided on both surfaces of the conductive film, the thickness of the insulating film between the magnetic films is set to 5 μm or less, so that the magnetic flux shielding effect and the performance coefficient Q value can be maintained high. Even when a plurality of annular magnetic films are formed so as to surround the films, insulation between these annular magnetic films can be reliably maintained.

Further, it is desirable that an insulating film above the conductor film is thicker than a thickness of the insulating film below the conductor film. The conductor film, the magnetic film, and the insulating film are generally formed by a film forming technique such as sputtering, CVD, or vapor deposition. In this case, in order to enhance the magnetic flux shielding effect of the magnetic film, the conductor film is surrounded around the conductor film. Thus, a plurality of annular magnetic films are formed. At this time, by increasing the thickness of the upper insulating film, the connection between the inner and outer annular magnetic films can be prevented, and the shielding effect due to the multilayered magnetic film can be reliably obtained. By increasing the thickness of the insulating film above the conductor film as it goes upward, the inner and outer annular magnetic films can be more reliably insulated.

The thickness of the magnetic film is desirably 1 μm or less. As a result, the entire cross section of the magnetic film can be effectively used at a use frequency of 1 GHz or more,
Even in a high frequency range of 1 GHz or more, the magnetic flux shielding effect of the magnetic film can be kept high, and the performance coefficient Q value can be kept high.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An inductor element according to the present invention is shown in FIG.
As shown in FIG. 2, a spiral inductor line 12 is provided on an insulating substrate 11, and the inductor line 12 includes a conductor film 14 and a conductor film 1 as shown in FIG.
4 and the magnetic films 15 and 16 formed on both surfaces of the magnetic film 1
And insulating films 17 and 18 formed on the surfaces of the insulating films 5 and 16, respectively. FIG. 2 shows a cross section taken along line AA in FIG.

That is, the inductor line 12 is connected to the insulating substrate 1.
1, an insulating film 17 is formed, and a magnetic film 15, a conductor film 14, a magnetic film 16, and an insulating film 18 are sequentially laminated thereon. The periphery of the conductor film 14 is surrounded by magnetic films 15 and 16, and the periphery of the magnetic films 15 and 16 is
It is surrounded by 7 and 18.

As described above, the conductor film 14 becomes the magnetic film 15, 1
6 and the inductor line 12 having a structure surrounded by the insulating films 17 and 18 are formed by photolithography, sputtering,
It is formed on the substrate 11 by a film forming technique such as CVD or vapor deposition.

For example, first, an insulating film 17 is formed on an insulating substrate 11 by sputtering, and a magnetic film 15 is formed thereon.
The conductor films 14 are sequentially laminated. At this time, the magnetic film 15 is formed such that the outer periphery of the insulating film 17 slightly remains, and the conductor film 14 is formed such that the outer periphery of the magnetic film 15 slightly remains.

Thereafter, a magnetic film 16 is formed on the conductor film 14 so as to cover the outer periphery of the magnetic film 15, and the upper surface of the magnetic film 16 is also covered on the outer periphery of the insulating film 17. By forming the insulating film 18 as described above, the inductor element of the present invention is manufactured.

The inductor element has its inductor line 1
There are various types depending on the shape of (2). Although FIG. 1 shows a spiral type, the present invention can also be applied to a meander type and other types of inductors.

In the present invention, the inductor line 12
The thickness t ₂ of the magnetic films 15 and 16 is less than 2 times the skin depth at the operating frequency of the widthwise central portion.

That is, at high frequencies, the skin effect becomes remarkable,
Even if a single-layer thick film is used, the entire cross section of the film cannot be used effectively. For example, in the case of FeSiAl, the skin depth in a high frequency range of 1 GHz is 0.5 μm when calculated based on the above-described formula. Therefore, for effective use, it is necessary to reduce the thickness to about twice the skin depth or less. In particular, in the case of a magnetic material made of FeSiAl, the thickness t ₂ of the magnetic films 15 and 16 is It is desirable that the thickness be 1 μm or less.

As the insulating substrate 11, any material having an insulating property may be used, but Al ₂ O ₃ is particularly preferable, and glass, silicon, and the like can be applied.

The conductor film 14 is formed by a photolithography technique, a film forming technique such as sputtering, and may be patterned by a mask in addition to the photolithography technique. As a film formation method, a vacuum evaporation and plating method can be applied other than the sputtering. As the conductor material, Au or Cu is preferable, but Al, Ag, or the like can also be applied.

The surface of the insulating substrate 11 is covered with a protective film (not shown). Such a protective film is
It is made of SiO ₂ , Si ₃ N ₄ , Al ₂ O ₃ , polyimide, benzomichlorobutene (BCB), or the like, and is manufactured by a photoengraving technique, a film forming technique such as sputtering, CVD, or spin coating. That is, the inductor line 12 is formed on the protective film of the insulating substrate 11.

The insulating films 17 and 18 are made of SiO ₂ , Si ₃ N
_4. A material such as Al ₂ O ₃ is preferable, and is produced by a film-making technique such as photolithography, sputtering, CVD, or vapor deposition.

The material of the magnetic films 15 and 16 is FeN
i, FeSiAl, Co-based amorphous alloy can be applied. Further, high resistivity materials such as FeAlO and soft magnetic ferrite are suitable.

In the inductor element configured as described above, by setting the thickness t ₂ of the magnetic films 15 and 16 to twice or less the skin depth at the operating frequency, the magnetic film cross section can be used effectively, With the minimum thickness, the magnetic flux shielding effect of the magnetic films 15 and 16 can be maintained, and the Q factor can be kept high. Further, since the thickness of the magnetic films 15 and 16 can be reduced, the film formation time is short and the cost can be reduced.

FIG. 3 shows another inductance element according to the present invention, which is constituted by providing a spiral inductor line 32 on an insulating substrate 31.
2 are magnetic films 35, 36, 45,
46 and insulating films 37, 38, 47 and 48 are alternately stacked.

That is, the inductor line 32 is connected to the insulating substrate 3
1, an insulating film 47, a magnetic film 45, an insulating film 37, a magnetic film 3
5, conductor film 34, magnetic film 36, insulating film 38, magnetic film 4
6, the insulating film 48 is sequentially laminated.

In this inductance element, the conductor film 34
Although two magnetic films are formed on one side of the above, three or more magnetic films may be formed. In this case, the magnetic films 35, 36,
The thickness t ₂ of the central portion in the width direction of the inductor line 32 of 45 and 46 are more than 2 times the skin depth at the operating frequency.

The thicknesses t ₃ and t _{4 of the} insulating films 37, 38, 47 and 48 are set to 5 μm or less, and the thickness t ₃ of the insulating films 38 and 48 above the conductor film 34 is The thickness is larger than the thickness t ₄ of the insulating films 37 and 47 below the film 34.

The reason why the thicknesses t ₃ and t ₄ of the insulating films 37, 38, 47 and 48 are set to 5 μm or less is that the insulating films 37 and
If the thicknesses t ₃ and t ₄ of 8, 47 and 48 are greater than 5 μm, the magnetic flux shielding effect is reduced and the inductance is reduced. On the other hand, if the thickness is less than 0.05 μm, the insulation tends to be poor due to the influence of the surface irregularities of the base, so that the thickness t of the insulating films 37, 38, 47, 48 is
₃ and t ₄ are desirably 0.05 μm or more. In order to maintain high inductance and prevent insulation failure, the thicknesses t ₃ , t _{4 of the} insulating films 37, 38, 47, 48 are set.
Is desirably 0.2 to 2 μm.

In such an inductor element, the same effect as in the above example can be obtained, and the inductor line 32 is provided on both surfaces of the conductor film 34 by the magnetic films 35, 36, 4
5, 46 and the insulating films 37, 38, 47, 48 are alternately laminated to form a shield around the conductor film 34 by a multi-layer magnetic film 35, 36, 45, 46, Since the magnetic flux shielding effect can be maintained at a higher level and two annular magnetic films 35, 36, 45, and 46 are formed, the leakage of magnetic flux is reduced and the Q factor can be increased. .

The insulating film 3 above the conductor film 34
The thickness t ₃ of the insulating film 3 below the conductor film 34
Due to the greater than the thickness t ₄ of 7 and 47, it is possible to prevent the connection of the magnetic film between the annular inner and outer layers on the side of the inductor line 32 (stepped portion 49), the magnetic films 35 and 36 , 45, 46 can be prevented from reducing the shielding effect.

Further, since the thicknesses t ₃ and t ₄ of the insulating films 37, 38, 47 and 48 are set to 0.05 to 5.0 μm, the magnetic flux shielding effect can be further maintained and the performance coefficient Q value is further increased. be able to. FIG. 4 shows the inductor element shown in FIG.
6,45,46 The thickness t ₂ as 1μm of the insulating film 3
The inductance was determined when the thicknesses of the insulating films 37, 38, 47, and 48 were changed, with the thicknesses of 7, 38, 47, and 48 being the same, and a graph thereof was described.

FIG. 5 shows that the insulating films 37, 38, 47,
It can be seen that increasing the thickness of 48 reduces the inductance at 1 GHz. In order to maintain a high inductance, it is necessary to reduce the thickness of the insulating film, and it is understood from FIG. 5 that the thickness needs to be 5 μm or less.

On the other hand, the conductor film 34, the magnetic films 35, 36, 4
The surface roughness of the surfaces 5 and 46 is superimposed, the surface irregularities increase on the outermost surface, and the base is exposed when the thicknesses t ₃ and t ₄ of the insulating films 37, 38, 47 and 48 are smaller than 0.05 μm, This is because the annular magnetic films of the inner layer and the outer layer are electrically connected to each other, so that the insulating property cannot be secured and the shielding effect of the lamination is lost. That is, the thickness of the insulating films 37, 38, 47, and 48 is set to 0.1.
By setting the thickness to 0.05 to 5 μm, a high magnetic flux shielding effect can be maintained and the performance coefficient Q value can be increased.

FIG. 5 shows still another inductor element.
Are an insulating film 53, a magnetic film 54, an insulating film 55, a magnetic film 56, an insulating film 57, a magnetic film 58, and a conductor film 5 on an insulating substrate 51.
9, magnetic film 60, insulating film 61, magnetic film 62, insulating film 6
3, a magnetic film 64 and an insulating film 65 are sequentially laminated.

Magnetic films 54, 56, 58, 60, 62, 6
The thickness t ₂ of No. 4 is not more than twice the skin depth at the used frequency.

The insulating films 53, 55, 57, 61, 63, 6
5 has a thickness of 5 μm or less, and has a thickness t of the insulating films 61, 63, 65 above the conductor film 59.
₅ , t ₆ , t ₇ are the insulating films 53, 5 below the conductor film 59.
The insulating film 6 is thicker than the thickness t _{8 of}
The thicknesses t ₅ , t ₆ , and t _{7 of 1} , 63, and 65 are thicker (t ₅ <t ₆ <t ₇ ) as they go upward.

In this inductor element, since the thicknesses of the insulating films 61, 63, and 65 above the conductor film 59 are thicker as going upward, the thickness of the insulating layer between the inner and outer annular magnetic films is large. 4, the connection between the inner and outer annular magnetic films on the side surface (stepped portion 69) of the inductor line can be further suppressed, and the shielding effect of the annular magnetic film can be surely exerted.

[0046]

According to the inductor element of the present invention, the thickness of the magnetic film is set to twice or less the skin depth at the operating frequency.
With the minimum necessary thickness of the magnetic film, the entire cross section of the magnetic film can be effectively used. For example, even in a high frequency region of 1 GHz or more, the magnetic flux shielding effect of the magnetic film can be maintained high, and the performance coefficient Q value can be reduced. Can be kept high.

[Brief description of the drawings]

FIG. 1 is a plan view showing a spiral inductor element of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

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

FIG. 4 is a graph showing the relationship between the thickness of an insulating film of an inductor element and inductance.

FIG. 5 is a sectional view showing still another inductor element of the present invention.

FIG. 6 is a sectional view showing a conventional spiral inductor element.

[Explanation of symbols]

11, 31, 51: Substrate 12, 32, 52: Inductor line 14, 34, 59: Conductive film 15, 16, 35, 36, 45, 46, 54, 56, 5
8, 60, 62, 64 ... magnetic films 17, 18, 37, 38, 47, 48, 53, 55, 5
7,61,63,65 ... insulating film _{t 1, t 3, t 4} , t 5, t 6, t 7, t 8 ··· insulating film thicknesses of t ₂ ... magnetic film

Claims (5)

[Claims] An inductor line is provided on a substrate. The inductor line includes a conductor film, magnetic films formed on both surfaces of the conductor film, and insulating films respectively formed on the surface of the magnetic film. Wherein the thickness of the magnetic film is not more than twice the skin depth at the operating frequency. 2. The inductor according to claim 1, wherein the inductor line is formed by alternately laminating a magnetic film and an insulating film on both surfaces of the conductor film, and the thickness of the insulating film is 5 μm or less. element. 3. The inductor element according to claim 2, wherein the insulating film above the conductive film is thicker than the insulating film below the conductive film. 4. The inductor element according to claim 2, wherein the insulating film above the conductor film is thicker upward. 5. The inductor element according to claim 1, wherein the thickness of the magnetic film is 1 μm or less.