JP2002093624A - Minute element of type such as minute inductor, and minute transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a minute element capable of increasing a maximum operation frequency. SOLUTION: A minute element (1) is a minute inductor or a minute inductive transformer. A metal winding (2) with a form of solenoid, a magnetic core (4) located at the center of the solenoid (2) and having strips (12 and 13) made of ferromagnetic material are provided. A magnetic core (4) is located, in parallel with the strips (12 and 13), and at least one additional layer (14) for generating a magnetic field in a direction vertical to the axis (20) of the solenoid (2) is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to the field of microelectronics, and more particularly to the manufacture of microelements, particularly intended for use in radio frequency applications. is there. More specifically, the present invention relates to a micro device such as a micro inductor or a micro transformer having a magnetic core capable of operating at a particularly high frequency.

[0002]

BACKGROUND OF THE INVENTION As is known, electronic circuits used, particularly in radio frequency applications, such as mobile telephone technology, include an oscillating circuit comprising capacitors and inductors. I have.

Due to the trend of miniaturization, it is necessary to maintain a sufficiently large inductance value and a sufficiently large quality factor while gradually reducing the occupied volume of a small element such as a small inductor. Is required.

[0004] Furthermore, the general trend is towards higher operating frequencies. In this case, the new UMT in mobile telephony is compared to the 900-1800 MHz frequency band used in the GSM standard.
The frequency used in the S standard is 2.4 GHz
It can be mentioned that it is a belt.

[0005] The increase in operating frequency introduces problems associated with the behavior of the magnetic core of the microinductor.

This is because in order to obtain a good quality factor,
In general, it is required to increase the inductance of the minute inductor. For this purpose, a magnetic material is selected, the shape and dimensions of the magnetic material being such that the highest possible magnetic permeability is obtained.

However, in view of the phenomenon of rotating magnetism, magnetic permeability changes with frequency, more specifically, there is a resonance frequency, and beyond this resonance frequency, the inductor exhibits capacitive behavior. It is known. In other words, the micro inductor must be used at a frequency that is absolutely lower than the resonance frequency.

However, when the operating frequency is increased, a phenomenon called rotational magnetic resonance is encountered, and therefore, for a given shape, the frequency range in which the inductor can be optimally used is limited.

The problem to be solved by the present invention is the problem of the limitation of the working frequency which is inherent due to the existence of the rotating magnetic phenomenon.

[0010]

SUMMARY OF THE INVENTION Accordingly, the present invention provides
An inductive microelement, such as a microinductor or microtransformer, that has a metal winding in the form of a solenoid and a strip located at the center of the solenoid and formed from ferromagnetic material And a magnetic element.

In the present invention, the microelement comprises at least one additional element in which the magnetic core is arranged parallel to the strip and can generate a magnetic field oriented perpendicular to the axis of the solenoid. It is characterized by having a layer.

In other words, the additional layer provided in connection with the ferromagnetic strip is an active member for generating a magnetic field which is closed by passing through the strip. This applies a magnetic field in a direction perpendicular to the axis of the solenoid to the solenoid, that is, a magnetic field generally perpendicular to the large dimensions of the magnetic core is applied to the solenoid.

An auxiliary magnetic field is present in the strip, oriented parallel to the easy axis of the ferromagnetic strip, and serves as a countermeasure against rotation of the magnetization in a direction other than the easy axis. This reduces the permeability of the strip and reduces the inductance of the microelement. Note that this shortcoming is compensated for by increasing the resonant frequency with respect to the rotating magnetic effect corresponding to the maximum frequency at which the microelement can maintain inductive behavior.

The resonance frequency due to the rotating magnetism is as follows:
Determined by the Landau-Lifschitz equation.

(Equation 1) Here, M is a magnetic moment, H is a magnetic field holding the magnetic moment, γ is a rotating magnetic constant, and α is a damping coefficient.

To determine the permeability along the hard axis of the ferromagnetic material, which corresponds to the direction of the main axis of the solenoid, it is necessary to determine the various magnetic fields that the ferromagnetic material receives. Here, the material of the given shape is a magnetic field (H _ext )
When held within, the magnetization tends to align along the magnetic field.

Thus, the neutrality of the material is lost and a charge appears, creating a magnetic field that opposes the external magnetic field. This reduces the resulting internal magnetic field (H _int ). A magnetic field that opposes an external magnetic field is generally called a "magnetization canceling magnetic field".
(H _d ) and is highly dependent on shape. More specifically, the magnetization canceling magnetic field coefficient is expressed as N, and the following equation is obtained.

(Equation 2)

This coefficient N depends only on the shape. This magnetization canceling magnetic field generated by the magnetic member in the direction of the hard axis reduces the resulting internal magnetic field and thus opposes the passage of the magnetic field lines. In other words, this magnetization canceling magnetic field has the consequence of decreasing the permeability.

Therefore, taking this model into account, the Landau-type can be determined so that the value of the magnetic permeability along the hard axis can be determined.
You can solve Lifschitz's equation. As is known,
The permeability is a complex number such that the real part represents the effective permeability and the imaginary part represents the loss. Therefore, by solving these equations, a real part (μ ′) and an imaginary part (μ ″) can be obtained as a function of the frequency, N, and the intrinsic property of the material.

The resonance frequency at which the value of μ ″ becomes maximum is obtained by the following equation.

(Equation 3) Here, N is the magnetization canceling magnetic field coefficient, γ is the rotational magnetic constant, H _k is the value of the anisotropic magnetic field, and M _s
Is the value of the magnetic moment at saturation.

Accordingly, it has been found that the resonance frequency increases with the value of the anisotropic magnetic field for orienting the magnetic domain along the easy axis. Thus, by applying an auxiliary magnetic field based on the additional special layer to the ferromagnetic core, an auxiliary magnetic field is added to the intrinsic anisotropic magnetic field,
This increases the effect of anisotropy on the magnetic domain.

As a result, the auxiliary magnetic field counteracts such phenomena, thereby reducing the magnetic permeability, which is indicative of the ability to rotate the magnetization of the material. Instead, the resonance frequency for the rotating magnetic effect, whose value increases with the anisotropic magnetic field, increases. This makes it possible to use a micro inductor or a micro transformer at a higher frequency.

In practice, the additional magnetic field may be provided by an additional layer of a so-called hard ferromagnetic material (magnet) or by an additional layer of a conductive metal layer configured to allow current to flow through the layer. Can be formed by an appropriate layer.

In the first case, the magnetization of the hard additional layer is selected to be perpendicular to the axis of the solenoid.

In practice, an isolation layer can be inserted between the hard additional layer and the ferromagnetic core, whereby
In particular, the effect of magnetic coupling can be limited.

It is practically advantageous to provide two hard additional layers which are arranged on both sides of the ferromagnetic strip. Thereby, the value of the additional magnetic field (auxiliary magnetic field) superimposed on the intrinsic anisotropic magnetic field can be further increased. As a result, it is possible to increase the resonance frequency that defines the upper limit of use of the inductor.

Advantageously, the hard ferromagnetic material forming the additional layer can be a cobalt-platinum alloy or hexaferrite.

Depending on the thickness of the additional layer and the remanent magnetization of the additional layer, the magnitude of the magnetic field superimposed on the intrinsic anisotropic magnetic field can be selected, and therefore the permeability of the magnetic core Magnetic susceptibility can be selected.

If the additional layer is a conductive metal layer, this layer can be used to control the intensity of the current flowing therethrough and / or
Or it is advantageously connected to means that can adjust the shape. Thus, the value of the magnetic field at the time of saturation can be adjusted dramatically, and thus the permeability can be changed dramatically, and thus the inductance can be changed dramatically. This configuration makes it possible, for example, to dramatically change the resonance frequency of the oscillation circuit in a very simple manner.

In practice, the ferromagnetic strip and the additional conductive layer can be electrically insulated from each other or can be electrically connected to each other. In high frequency applications, it is advantageous for the strip and the additional layer to be insulated from each other.

The shape of the magnetic core is not limited to a simple combination of the two layers, but rather a ferromagnetic strip or an additional layer (hard or conductive) between two adjacent ferromagnetic strips. A plurality of hard ferromagnetic layers can be used, such as those with a layer interposed.

Although not a preferred embodiment, if the ferromagnetic strip is conductive, current can flow through the strip such that a magnetic field is created within the strip itself. The magnetic field in this case has the same effect as the magnetic field generated by the additional isolated layer.

[0032]

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the present invention and the advantages based thereon will become apparent from reading the following description of embodiments with reference to the accompanying drawings.

As described above, the present invention relates to a microelement such as a microinductor or a microtransformer. The magnetic core of the microelement includes a ferromagnetic strip and an intrinsic anisotropic magnetic field of the ferromagnetic strip. A special layer forming an auxiliary magnetic field source superimposed on the special layer.

The additional layer can be formed from a so-called hard ferromagnetic material, or from a conductive material such that by passing a current through the layer, the layer becomes an active member for the magnetic field.

In the following description, the second embodiment will be described in detail.

As shown in FIG. 1, the micro inductor (1) according to the present invention includes a metal winding (2) having a plurality of turns wound around a magnetic core. More specifically, each turn (3) forming a solenoid has a lower part (5) embedded in the surface of the base (6) and a lower part (5,
Multiple arches (7) connecting the ends of 5 ')
And

In this case, in order to obtain such an inductor, a plurality of parallel channels (10) are provided on the upper surface of the insulating substrate or of the insulating layer on the conductive or semiconductive substrate (6). Etched on the top surface. The lower part (5) of each turn is obtained by electrolytically growing copper and then flattening the surface of the substrate (6) to obtain an optimal surface condition.

Next, a silica layer (11) is formed on the upper surface of the substrate (6). This insulates the lower part (5) of each turn from the material used for the magnetic core.

Thereafter, the magnetic core (4) is formed. As described above, a plurality of aspects can be employed. In the following description, one embodiment which does not limit the present invention will be described in detail. Thus, the core (4) in FIG. 3 comprises two ferromagnetic strips (12, 13).
And a conductive layer (14) interposed between these strips
And

More specifically, several techniques can be used to form the ferromagnetic layer (12), such as sputtering and electrolytic deposition. Here, in the second technique, a magnetic material is electrolytically deposited over a growth region located on a plurality of segments forming a lower portion (5) of each turn. The thickness of the ferromagnetic layer (12) is
The range is 0.1 to 10 μm so that a sufficiently large inductance can be obtained while limiting the induced current phenomenon.

After forming the lower layer (12) made of a ferromagnetic material, an insulating layer (15) is formed on the lower layer (12) by a sputtering method. Next, a conductive layer (14) is formed. This conductive layer can be formed, for example, from gold. This film formation can be performed by either an electrolytic method or a sputtering method. This conductive layer (14) is covered with an insulating layer (16).

Next, a second ferroelectric layer (13) is formed on the layer (1).
As in the case of 2), a film is formed on the insulating layer (16).

The two ferroelectric layers (12, 13) are preferably of the same thickness to provide symmetry around the conductive layer (14).

After forming the magnetic core assembly (4), a silica layer (22) for electrically insulating the magnetic core (4) from the upper part (7) of each turn (2) is formed. . Thereafter, an electrolytic copper film is formed, thereby forming an arch (7) connecting the opposite ends of the lower portions (5, 5 ') adjacent to each other. Thus, FIG.
Are formed as shown in FIG. Thereafter, a step of forming connection pads (23, 24) is performed.

The magnetic material used for the core can be various materials as long as it has a large magnetization and a controlled anisotropy. In this case, for example, CoZ
Crystalline or amorphous materials, such as rNb or other alloys based on cobalt, nickel or iron, can be used. The conductive layer can be formed from a low-resistance material such as copper or gold.

Here, the conductive layer (14) extends between the pads (26, 27) along the direction of the axis (20) of the solenoid.
When a current flows through the inside of the conductive layer (14)
A magnetic field is generated perpendicular to the axis (20) of the solenoid. This magnetic field (illustrated by arrows) passes through the ferromagnetic layers (12, 13) surrounding the conductive layer (14). This auxiliary magnetic field is superimposed on the intrinsic anisotropic magnetic field characteristic of the ferromagnetic material. Thus, this auxiliary magnetic field opposes the gyromagnetic rotation of the various magnetic domains that are inherently aligned along the easy axis of the ferromagnetic material. That is, it opposes the magnetic rotation of the various magnetic domains that are inherently aligned in a direction perpendicular to the axis of the solenoid. Such opposition to gyromagnetic rotation increases the value of the magnetic field required to achieve saturation. Therefore, the magnetic permeability of the magnetic core decreases.

In addition, as described above, an increase in the saturation magnetic field increases the resonance frequency of the rotating magnetic effect. Thus, such an increase in the resonance frequency allows the use of microelements at higher frequencies than existing elements.

By adjusting the current flowing in the conductive layer (14), the magnetic permeability of the magnetic core can be changed,
Therefore, the inductance coefficient of the element can be changed.

It will be appreciated that the invention is not limited to the above embodiments, such as obtaining an auxiliary magnetic field by using an auxiliary conductive layer. This is because the auxiliary magnetic field is also obtained by an auxiliary hard ferromagnetic layer arranged such that the magnetization is perpendicular to the axis of the solenoid. That is, as shown in FIG. 4, the magnetic core includes two ferromagnetic strips (30, 3).
It has an additional hard ferromagnetic layer (32) interposed between 1). The auxiliary magnetic field (indicated by the arrow) generated by the ferromagnetic layer (32) is occluded by the two strips (30, 31), thereby increasing the intrinsic anisotropic magnetic field. .

The present invention is not limited to the embodiment in which the magnetic core includes two ferromagnetic layers and an additional layer interposed between these layers. Other arrangements comprising one ferromagnetic layer and an auxiliary hard ferromagnetic layer can also be envisaged. That is,
As shown in FIG. 5, the magnetic core comprises a ferromagnetic strip (35) and an additional hard ferromagnetic layer (36). The auxiliary magnetic field (indicated by the arrow) generated by the ferromagnetic layer (36) is occluded by the strip (35), thereby increasing the intrinsic anisotropic magnetic field of the ferromagnetic layer (35). Let me. The additional ferromagnetic layer (36) may be replaced by a conductive layer that generates a magnetic field in the ferromagnetic layer (35) by passing a current. Additional layers can be located above or below the ferromagnetic strip, depending on the thickness and the manufacturing process selected.

In the present invention, other structures can be adopted. For example, a structure including a plurality of ferromagnetic layers and a plurality of additional ferromagnetic layers or a plurality of additional conductive layers may be employed. That is, as shown in FIG. 6, the magnetic core can include two high ferromagnetic layers (41, 42) and a ferromagnetic strip (40) interposed between these layers. . The auxiliary magnetic field (indicated by the arrows) generated by the additional layers (41, 42) is occluded by the strip (40), which has the desired effect. In FIG. 7, the magnetic core comprises two high ferromagnetic layers (41, 42) and two conductive sheets (45, 46).
Has been replaced by In this case, the two conductive sheets (45, 46) are subjected to currents of the same strength and opposite directions, whereby the auxiliary magnetic field (indicated by the arrow) generated by the two conductive sheets is reduced. , Each in the same orientation, closed by a strip (40).

Further, although the present invention has been described in detail by taking a small inductor as an example, the present invention is not limited to the case in which a small inductor is disposed around a common core.
It goes without saying that a micro-transformer in which one winding is wound is also within the scope of the present invention.

From the above, it is clear that the microelement according to the invention has many advantages. In particular,
The microelement according to the present invention can increase the maximum operating frequency and can drastically change the magnetic permeability as compared with microelements of the same size and of the same material, and thus can greatly reduce the inductance. Can be changed.

Such a microelement can be particularly suitably applied to radio frequency applications such as mobile radio telecommunications.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing a micro inductor manufactured according to the present invention.

FIG. 2 is a longitudinal sectional view along the II-II ′ plane in FIG. 1;

FIG. 3 is a transverse cross-sectional view along a III-III ′ plane in FIG. 1;

FIG. 4 is a cross-sectional view similar to FIG. 3 in another embodiment.

FIG. 5 is a cross-sectional view similar to FIG. 3 in still another embodiment.

FIG. 6 is a cross sectional view similar to FIG. 3 in still another embodiment.

FIG. 7 is a cross-sectional view similar to FIG. 3 in another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Micro inductor (micro element) 2 Metal winding, solenoid 4 Magnetic core 12 Ferroelectric strip, ferroelectric layer (strip) 13 Ferroelectric strip, ferroelectric layer (strip) 14 Conductive layer (additional layer) 15 Insulation layer (isolation layer) 16 Insulation layer (isolation layer) 20 axis 36 Ferromagnetic layer (additional layer)

Claims (10)

[Claims] An inductive microelement (1), such as a microinductor or microtransformer, comprising: a metal winding (2) in the form of a solenoid; and a metal winding (2) arranged at the center of the solenoid (2). And a magnetic core (4) having strips (12, 13) formed of a ferromagnetic material, wherein the magnetic core (4) comprises the strips (12, 13).
And at least one additional layer (14) capable of generating a magnetic field oriented parallel to and oriented perpendicular to the axis (20) of said solenoid (2). Characteristic microelement. 2. The microelement according to claim 1, wherein the additional layer is formed of a ferromagnetic material. 3. The microelement according to claim 2, wherein said strips (12, 13) and said additional layers (1) are provided.
A microelement comprising an isolation layer (15, 16) between the microelement and (4). 4. The microelement according to claim 1, comprising two additional layers arranged on both sides of the strip. 5. The microelement according to claim 2, wherein the ferromagnetic material forming the additional layer is a cobalt-platinum alloy or hexaferrite. 6. The microelement according to claim 1, wherein the additional layer is a conductive metal layer intended to carry a current. 7. The microelement according to claim 6, wherein the additional layer is connected to means for adjusting the intensity and / or shape of the current flowing therethrough. Microelements. 8. The microelement according to claim 6, wherein the strip and the additional layer are electrically insulated from each other. 9. The microelement according to claim 6, wherein the strip (12, 13) and the additional layer (1) are arranged.
And 4) are electrically connected to each other. 10. The microelement according to claim 6, comprising a plurality of strips (12, 13) and a conductive metal layer (14) interposed between the plurality of strips. Characteristic microelement.