JPH0974016A - Magnetic thin film with reduced high-frequency loss - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-loss magnetic thin film which is a multilayer film of a high saturation magnetic flux density constituted of magnetic thin films and insulating thin films and which has a small loss at a high-frequency region. SOLUTION: A low-loss magnetic film is a multilayer magnetic thin film which is made by stacking magnetic thin films and insulating thin films alternately and a high-frequency device is the one which uses this thin film. In such a low-loss magnetic thin film, an effective value of a real part of a complex magnetic permeability is 450 or above and the ratio of the real part to an imaginary part is 50 or above at 100MHz and 20 or above at 200MHz.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has an effective value of the real part of high frequency complex permeability of 450 or more and a ratio of the real part to the imaginary part of 100.
The present invention relates to a high frequency low loss magnetic thin film showing 50 or more at MHz or 20 or more at 200 MHz, a thin film inductor for high frequency of the thin film, a magnetic core material of a transformer, a magnetic sensor and the like.

[0002]

2. Description of the Related Art In recent years, with the spread of portable electronic devices, there is a tendency toward higher frequencies and smaller sizes, especially in the field of mobile communications. Along with this, the components used are required to be thinner and have higher frequencies. However, an air-core inductor that does not use a magnetic core has been used for an inductor or the like that has been conventionally used in a high frequency region of 100 MHz or more. However, in order to obtain a high inductance by using such an air-core coil, it is necessary to increase the volume of the coil and a large mounting area is required due to the routing of the coil. In order to reduce this mounting area, it is necessary to increase the inductance value per unit volume by using a magnetic core. However, when the conventional magnetic film is used as the magnetic core of the inductor, the figure of merit is much lower than that of the air-core inductor due to the increase of the loss of the magnetic core in the high frequency region.

On the other hand, for thin film transformers, higher frequencies have been studied, but since the development of magnetic materials exhibiting low loss in the high frequency region has not been sufficiently developed, higher frequencies for thin film transformers cannot be achieved. Conventionally, the frequency that can be used is several MHz even when using ferrite, which is said to have low loss at high frequencies.
It is the following.

[0004]

As one of the methods for reducing the loss of the magnetic core, it has been widely studied to alternately stack magnetic thin films and insulating thin films. However, in these studies, there was a problem in the method of evaluating the magnetic thin film. That is, it was performed on a sample having a large size such as 10 mm × 20 mm, which is not actually used in the high frequency region because of its measurement sensitivity and simplicity. However, when actually used in a high frequency region, for example, (1) small dimensions such as several hundreds of μm × several millimeters, high frequency characteristics deteriorate, and (2) large dimensions exhibit low loss. It has become clear that the thin film does not necessarily exhibit low loss when it is formed into a very small size. The present invention aims to provide a high-frequency magnetic thin film that exhibits low loss in a minute size and shape by examining using a single body and an aggregate thereof that are actually molded to a size used at high frequencies.

[0005]

The present invention is the result of earnest efforts in view of the above circumstances. Considering the magnetization reversal mechanism of the magnetic film, the domain wall movement is the main factor in the low frequency region of 1 MHz or less, and the magnetization rotation is the main factor in the high frequency region of 100 MHz or more. In this intermediate region, both domain wall movement and magnetization rotation can be considered. The loss reduction of the conventional soft magnetic film has been studied in order to reduce the loss due to the domain wall motion. In the present invention, in order to reduce the loss at a high frequency of 100 MHz or more, the use of the magnetic film having a minute size is a means for reducing the resonance loss at a high frequency.
In order to reduce the resonance loss, a large saturation magnetic flux density is necessary, but generally, when trying to obtain a large saturation magnetic flux density, the magnetostriction becomes large, so it has not been noticed as a conventional practical soft magnetic film. . In the present invention, by clarifying the relationship between the magnetostriction, the saturation magnetic flux density and the loss in the region where the magnetization rotation is mainly 100 MHz or more, it becomes clear that the influence of the magnetostriction on the high frequency loss is small, and the high saturation magnetic flux is high. It has made it possible to develop a high-frequency low-loss soft magnetic film with high density.

Therefore, the high frequency low loss magnetic thin film of the present invention is as follows. That is, the first invention is that, in a multilayer magnetic thin film in which magnetic thin films and insulating thin films are alternately laminated, the effective value of the real part of the complex permeability is 450 or more, and the ratio of the real part and the imaginary part is 50 or more at 100 MHz or 200 MHz
And a high frequency low loss magnetic thin film.

Alternatively, the second invention is a high-frequency low-loss magnetic thin film characterized by using a soft magnetic thin film having a saturation magnetic flux density of 12 kG or more.

Alternatively, in the third invention, the magnetic thin film is
(Co _1-x Fe _x ) _100-z (Si at atomic concentration
_1-y B _{y) z} (where, 0.06 <x <0.16,0.
3 <y <0.7, 25 <z <16), and the insulating thin film is SiO ₂ , Al ₂ O ₃ , ZrO ₂ , AlN and BN.
A high-frequency low-loss magnetic thin film comprising a composition containing one or more of the above.

Alternatively, the fourth invention is characterized in that the magnetic thin film is formed in argon gas and the insulating thin film is formed in argon gas or a mixed gas of two or more kinds of argon, oxygen and nitrogen. And a high-frequency low-loss magnetic thin film.

Alternatively, the fifth aspect of the present invention is to form a single body or an aggregate having a rectangular magnetic thin film having a short side of 50 μm or more and 1 mm or less and a long side of more than 1.5 times the short side. And a high-frequency low-loss magnetic thin film.

Alternatively, the sixth invention is a high-frequency low-loss magnetic thin film, characterized in that the film is formed in a magnetic field such that the long side direction of the rectangular shape is in the direction of hard magnetization.

Alternatively, the seventh invention has a structure of a thin film inductor made of a high frequency low loss magnetic thin film.

Alternatively, the eighth invention has a structure of a thin film transformer formed of a high frequency and low loss magnetic thin film.

Alternatively, the ninth invention has a structure of a magnetic sensor comprising a high frequency and low loss magnetic thin film.

[0015]

In the past, the evaluation of the characteristics of the magnetic thin film in the high frequency region has been carried out without sufficiently considering the relationship between the size and shape of the thin film actually used as the magnetic core and the high frequency characteristics.
However, the magnetic characteristics in the high frequency region are very sensitive to the shape and size thereof, and when used in the high frequency region, they are very small, for example, 1/10 to 1/20, compared to the normally measured size. Since it is used in dimensions, it is a problem in high frequency circuit design, unlike the measured value and the value in the actual high frequency region. For the measurement of the present invention, a magnetic thin film simple substance or an aggregate having a minute dimension similar to that when actually used in a high frequency region was produced, and a low loss magnetic thin film was found from the frequency dependence of its complex permeability.

[0016]

Embodiments of the present invention will now be described with reference to the drawings.

Example 1 A method for producing and evaluating a high frequency low loss thin film having a high saturation magnetic flux density will be described. Cobalt (C
o), iron (Fe), silicon (Si), silicon (B) or C
An alloy composed of o, Fe, niobium (Nb), and zirconium (Zr) was melted in a high-frequency induction electric furnace in an argon atmosphere, then stirred well to form a homogeneous molten alloy, which was cast into a columnar shape. Then, in an arc melting furnace, this is 100m in diameter.
m, molded into a disk shape with a thickness of 10 mm, cut this,
It was molded into a diameter of about 75 mm and a thickness of 1 mm.

The substrate used for film formation has a thickness of about 0.5 mm,
Corning # 7059 with a width of 50 mm and a length of 50 mm
Hoechst Japan resist # 421 on the glass
0 is used to form a rectangular pattern with a space of 100 μm as shown in FIG. Figure 1 is 1m in minor axis
m and the major axis is 2 mm. The film formation is about 60 Oe in the direction perpendicular to the longitudinal direction of the minute magnetic film arranged on this substrate.
Was applied with a permanent magnet. The magnetic film aggregate having a minute size was formed by the lift-off method after being formed. The substrate was water-cooled to such an extent that the resist patterned into a minute size did not solidify.

The CoFeSiB and CoNbZr magnetic thin films have an applied power of 200 W and an argon gas flow rate of 30 cc.
/ Min, the gas pressure was 3 mT. The insulating thin film uses, for example, a target such as SiO ₂ , Al ₂ O ₃ , AiN, ZrO ₂ , and B, an applied power of 200 W, a mixed gas of oxygen or argon having a nitrogen concentration of 5 to 30%, and a flow rate of 30.
A film was formed at cc / min and a gas pressure of 6 mT. The multilayer film was produced by alternately forming magnetic thin films and insulating thin films with a desired film thickness under the above conditions.

The thus-prepared assembly of magnetic thin films of minute dimensions was cut into a strip of 10 mm × 50 mm, and the frequency characteristic of complex magnetic permeability up to 500 MHz was measured using a parallel line and a network analyzer. The high frequency characteristics were evaluated from the ratio of the real part (μ ') and the imaginary part (μ ") of the complex magnetic permeability.

[0020]

[Table 1]

[0021]

Example 2 (Co _1-x Fe _x ) ₈₄ (S
i _0.48 B _0.52 ) ₁₆ and a magnetic thin film composed of S
For a multilayer film in which insulating thin films are alternately stacked using an iO ₂ target, the saturation magnetization and the real part (μ ′) and imaginary part (μ ″) of the complex permeability at 200 MHz when the iron concentration is changed. 2 shows that the multilayer film has a structure in which a magnetic thin film of 0.1 μm and an insulating thin film of 0.05 μm are laminated in ten layers, and the horizontal axis x is the atomic concentration (Co _1-x F
The Fe concentration in the case of being _{expressed as} e _x ) ₈₄ ( _Si0.48B0.52 ) ₁₆ is shown. From the figure, it can be seen that the value of the real part of the complex permeability is almost constant with respect to the iron concentration, but the imaginary part becomes smaller as the Fe concentration increases, that is, as the saturation magnetic flux density increases. Therefore, the ratio of the real part (μ ') to the imaginary part (μ ") of complex permeability and the value of μ' / μ" (figure of merit) are increased, that is, the saturation magnetic flux density is large in order to reduce the loss. Is required.

[0022]

Third Embodiment The relationship between the ratio of the real part and the imaginary part of the complex permeability to the magnetic film thickness and the insulating film thickness when the magnetic thin film and the insulating thin film are laminated as in the second embodiment will be described. As an example, a saturated magnetic flux density of 13 kG (Co _0.95 Fe
_0.05 ) ₈₂ (Si _0.6 B _0.5 ) ₁₈ Soft magnetic film and complex magnetic permeability with respect to film thickness of insulating film when laminated with an insulating thin film formed by targeting SiO ₂ The relationship between the real part and the imaginary part of is shown in FIG. The number of laminated layers is 10 and the size of the unit magnetic film is 1 mm × 2 mm. The vertical axis represents the film thickness of the magnetic film, the horizontal axis represents the film thickness of the insulating film, and the numbers in the figure are values of the ratio of the real part and the imaginary part at 100 MHz. The number of stacked layers is changed so that the total magnetic film thickness is 2 μm. In this case, the magnetic film thickness is 0.1 μm and the insulating film is 0.05.
In the vicinity of μm, the ratio of the real part and the imaginary part is the largest, that is, the combination of the film thicknesses gives the magnetic thin film having the smallest high frequency loss.

[0023]

[Embodiment 4] Conventionally, when a soft magnetic film is used in a device or the like, a material having a magnetostriction close to zero has been studied so that the soft magnetic characteristics are not deteriorated by molding or the like. FIG. 4 shows the atomic concentration of (Co _1-x Fe _x ) ₈₂ (Si _0.48 B _0.52 ).
_The magnetostriction constant with respect to the Fe concentration when indicated as ₁₈ is shown. Despite the fact that there is a large difference in thermal expansion between the substrate and the magnetic film during film formation cooling, large strain, and that the magnetic thin film is laminated with the insulating thin film, there is considerable internal stress in the magnetic thin film. It can be seen that a magnetic film having a small imaginary part of complex magnetic permeability can be obtained in a region where the magnetostriction is relatively large. From this, it can be seen that the high frequency loss in the multilayer film is less affected by magnetostriction than in the case of the single layer film.

[0024]

Example 5 A composition showing low loss at high frequencies (Co _0.9 F
e _0.1 ) ₈₂ (Si _0.55 B _0.45 ) ₁₈ magnetic thin film and an insulating thin film formed by using a SiO ₂ target are alternately laminated in 30 layers with a thickness of 0.1 μm and 0.05 μm, respectively. Then, it was used as a magnetic core of a wire-wound inductor as shown in FIG. The size of the magnetic core is 200 μm wide and 2 mm long
It is. The thickness of the coil is 3 μm, the line (L) / space (S) is 80 μm / 20 μm, and the number of turns is 20 turns. In this case, the film thickness of the insulating layer between the coil and the magnetic core is set to 3 μm by curing the resist.

The frequency characteristics of the inductance and resistance of the thin film inductor are shown in FIG. For comparison, the results are shown in the case where a magnetic material for high frequencies, Co ₈₁ Nb ₁₆ Zr ₃ magnetic film having almost zero magnetostriction is used and a magnetic film multilayered with ZrO ₂ is used as a magnetic core. Loss resistance is C in the high frequency range.
When the ₈₁ Nb ₁₆ Zr ₃ thin film is used as a magnetic core, the frequency increases from a low frequency. It is predicted that the internal stress of the magnetic core is increased due to the insulation of the coil and the magnetic thin film during the manufacturing process of the inductor, but nevertheless, CoFeSiB / S having a relatively large magnetostriction is produced.
It shows that the loss of the iO ₂ multilayer film is small. Therefore, as described in Example 3, it is considered that the effect of magnetostriction on the high frequency loss of the magnetic film is small.

[0026]

Example 6 (Co _1-x Fe _x ) ₈₂ (Si _0.48 )
B _0.52 ) ₁₈ single layer film, and the result of comparing the real part and the imaginary part of the complex magnetic permeability of the magnetic thin film in which this magnetic film and the insulating film produced by targeting SiO ₂ are multilayered are shown in FIG. 7. . The value of the imaginary part becomes small due to the multi-layering, and when the total magnetic film has the same thickness, the value of the imaginary part can be made small without changing the value of the real part of the complex magnetic permeability by the multi-layering.

[0027]

Seventh Embodiment The frequency characteristics of the insertion loss of the inductor of the fifth embodiment will be described. In FIG. 8, the magnetic core width is 300 μm,
The insertion loss when the number of turns is changed with the same coil pitch and the magnetic core length is changed is shown with respect to frequency. Even if the length of the magnetic core is reduced and the inductance value is reduced, the resonance frequency cannot be increased due to an increase in loss resistance of the magnetic core.

On the other hand, FIG. 9 shows frequency characteristics of insertion loss when an inductor having a magnetic core width of 250 μm or less is used, the number of turns is changed, the length of the magnetic core is changed, and the inductance value is changed. Since the loss resistance of the magnetic core does not increase, the inductance decreases, that is, the number of turns decreases,
The resonance frequency is increasing. This result shows that when a rectangular magnetic core is used, it must be sufficiently long with respect to the radiation of the magnetic core.

[0029]

As described above, the multilayer film showing low loss in the high frequency region of the present invention improves the performance index of the thin film inductor in the high frequency region, and increases the attenuation of the insertion loss when used in a filter or the like. I will let you. Further, since the loss resistance at high frequencies can be reduced by using the high frequency low loss magnetic thin film, the performance of the high frequency device can be improved, and its industrial significance is great.

[Brief description of drawings]

FIG. 1 Small dimensional shape and planar shape of its aggregate

FIG. 2 is (Co _1-x Fe _x ) ₈₂ (Si _0.48 B
_0.52 ) ₁₈ / SiO ₂ multilayer magnetization characteristic graph showing the relationship between the saturation magnetization, the real and imaginary parts of the complex permeability and the iron concentration.

FIG. 3 is (Co _0.95 Fe _0.05 ) ₈₂ (Si
_0.6 B _0.4 ) ₁₈ / SiO ₂ multilayer film characteristic diagram showing the relationship between the film thickness of the magnetic film and the insulating film and the ratio of the real part and the imaginary part of the complex permeability.

FIG. 4 is (Co _1-x Fe _x ) ₈₂ (Si _0.48 B
_0.52 ) ₁₈ / SiO ₂ single layer and multi-layered film showing characteristic relationship between magnetostriction and iron concentration

[Figure 5] External view of thin film inductor

FIG. 6 is (Co _0.9 Fe _0.1 ) ₈₂ (Si _0.48
B _0.52 ) ₁₈ and Co ₈₁ Nb ₁₆ Zr ₃ thin-film inductors showing the relationship between resistance and inductance

FIG. 7: (Co _1-x Fe _x ) ₈₂ (Si _0.55 B
_0.45 ) ₁₈ Characteristic diagram showing the relationship between the real part and the imaginary part of the complex permeability in a single-layer film and a multilayer film

FIG. 8 is a characteristic diagram showing the relationship between the insertion loss of a filter and the frequency when an inductor using a multilayer thin film with a width of 300 μm as a magnetic core is used.

FIG. 9 is a characteristic diagram showing the relationship between the insertion loss of a filter and the frequency when an inductor using a multilayer thin film having a width of 200 μm as a magnetic core is used.

Claims (9)

[Claims] 1. In a multilayer magnetic thin film in which magnetic thin films and insulating thin films are alternately laminated, the effective value of the real part of complex permeability is 45.
0 or more and the ratio of the real part and the imaginary part is 5 at 100MHz
A high frequency low loss magnetic thin film having 0 or more or 20 or more at 200 MHz. 2. The high frequency low loss magnetic thin film according to claim 1, wherein the magnetic thin film has a saturation magnetic flux density of 12 kG or more. 3. The magnetic thin film has an atomic concentration of (Co _1-x Fe
_x ) _100-z (Si _{1- y By} ) _z (however, 0.02
<X <0.16, 0.3 <y <0.7, 25 <z <1
4) alloy or Co (the balance), 8 to 20 at.
% Nb, 2-5 at. % Zr alloy, and the insulating thin film is composed of a composition containing one or more of SiO ₂ , Al ₂ O ₃ , ZrO ₂ , AlN and BN. The high-frequency low-loss magnetic thin film described in (4). 4. A magnetic thin film is formed in an argon gas, and an insulating thin film is formed in an argon gas or a mixed gas of two or more kinds of argon, oxygen and nitrogen. The high frequency low loss magnetic thin film according to any one of 1. 5. A rectangular magnetic thin film having a short side of 50 μm or more and 1 mm or less and a long side of more than 1.5 times the short side is formed, or a single body or an aggregate is formed. 5. A high-frequency low-loss magnetic thin film according to any one of items 1 to 4. 6. The film formation in a magnetic field so that the direction of the longer side of the rectangular shape is the direction of hard magnetization.
The high frequency low loss magnetic thin film according to any one of 1. 7. A thin film inductor comprising the high frequency low loss magnetic thin film according to claim 1. Description: 8. A thin film transformer comprising the high frequency low loss magnetic thin film according to any one of claims 1 to 6. 9. A magnetic sensor comprising the high frequency low loss magnetic thin film according to claim 1. Description: