JP2001220656A - Ion-zirconium-boron-silver soft magnetic material and method for deposition of thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soft magnetic material as a magnetic core material combining characteristics of high magnetic permeability, low loss and high saturation magnetization in the MHz region and a method for deposition of a soft magnetic thin film. SOLUTION: An Fe86.7Zr3.3B4Ag6 amorphous thin film, in which Ag is added to an Fe-Zr-B composition constituting a crystal phase, is deposited by the DC magnetron sputtering method using an Fe-Zr-B alloy target and a small piece of Ag. Then vacuum heat treatment is carried out in a uniaxial magnetic field at about 400 deg.C for 1 h, followed by cooking using a fan.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an iron-zirconium-boron-silver (FeZrBAg) -based soft magnetic material as a magnetic core material applicable in a high frequency band of MHz and a method of manufacturing a soft magnetic thin film.

[0002]

2. Description of the Related Art Generally, soft magnetic materials are manufactured in the form of bulk, thin wire, thin ribbon, or thin film depending on the purpose of use. Soft magnetic materials having an amorphous structure are mainly made of thin wires, thin ribbons,
It has a thin film structure. All of them are manufactured and used in an amorphous phase in a composition region where an amorphous phase is formed, or are used after being heat-treated at a temperature higher than a crystallization temperature.

The amorphous soft magnetic thin films studied so far are:
They are roughly classified into Fe-based and Co-based. In general, Fe-based alloys have the advantage of high saturation magnetization, but have the disadvantages of low magnetic permeability at high frequencies, large magnetic deformation, poor high-frequency characteristics, thermal safety, and large loss. In the case of Co-system,
It has the advantage of high magnetic permeability and low coercive force in the high frequency range, but has the disadvantage of low saturation magnetization. Further, these materials are in the form of a ribbon having a thickness of 10 μm or more, and the application is a magnetic core material in the kHz range.

On the other hand, FeZrBCu and F
In the case of a soft magnetic material having an eZrBAg composition, first, Cu or Ag is added to 1a based on the FeZrB composition forming an amorphous phase.
about 10% by using the liquid quenching method.
Make a ribbon of m or more. Thereafter, at a temperature of 600 ° C. or higher for FeZrBCu, 400 ° C. for FeZrBAg.
It was reported that soft magnetic properties were improved by precipitating fine crystal grains by heat treatment at ℃. However, the purpose of these soft magnetic ribbons is to apply in the kHz range.
The characteristics in the z frequency domain are very poor.

A soft magnetic thin film intended for application in the MHz region is Fe-MX (M = Zr, Hf, Nb, Tb).
a, Al, X = N, O, C), Co-MX (M = N
b, Hf, Ta, Al, X = O, N, Zr, Pd) An ultra-fine crystal grain thin film in which fine crystal grains are formed and a high-resistance thin film are heat-treated at a high temperature of 500 ° C. or more. No thin film that simultaneously satisfies the characteristics of high permeability, low loss, and high saturation magnetization has been reported.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a high permeability, low loss, and high saturation magnetization in the MHz range. It is an object of the present invention to provide a soft magnetic material as a magnetic core material and a method for producing a soft magnetic thin film, which simultaneously satisfy the above characteristics.

[0007]

In order to achieve the above object, a soft magnetic material for a high-frequency device according to the present invention comprises:
e _α Zr _β B _γ Ag _δ (α = 80 to 95 at%, β = 2
〜１０10 at%, γ = 2 to 10 at%, δ = 5 to 10 at
%).

Further, according to the present invention, FeZrB
A softening step including a first step of forming a film using an alloy target and Ag pieces, a second step of heat-treating the formed FeZrBAg film, and a third step of cooling the heat-treated FeZrBAg film to room temperature. A method for manufacturing a magnetic thin film is provided.

The conditions at the time of film formation are as follows: the initial degree of vacuum is 10 ⁻⁶ to
rr or less, film forming current 50 to 300 mA, film forming pressure 1
-10 mtorr is desirable.
Cool below.

In the second step, the crystallization temperature is ± 50 ° C.
The condition is that the degree of vacuum is 10 ⁻⁶ torr.
r, the magnetic field is applied at 0.5 to 2.0 kOe, 10 ° C /
An isothermal heat treatment in a crystallization temperature range of ± 50 ° C. at a heating rate of min.

According to such a configuration, for example, Fe _86.7
The Zr _3.3 B ₄ Ag ₆ thin film can simultaneously satisfy high magnetic permeability, low loss, and high saturation magnetization characteristics.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
Preferred embodiments of the iron-zirconium-boron-silver soft magnetic material and the method for producing a thin film according to the present invention will be described in detail. In the specification and the drawings, components having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted.

In this embodiment, first, Fe-Zr
-B ternary system Fe ₉₂ Zr _3. Fe _86.7 Zr _3.3 B ₄ Ag was _{added to} the basic composition of ₈ B _4.2 composition by direct current (DC) magnetron sputtering using Ag pieces.
_6. Produce a thin film.

The basic composition Fe₉₂Zr_3.8B
_4.2The composition is a composition in which amorphous is not formed.
No studies on adulthood have been reported. In the present invention, Fe
₉₂Zr_{3 . 8}B_4.2Add Ag to the composition
To Fe_86.7Zr_3.3B₄Ag ₆Produce a thin film.

In order to obtain an amorphous phase at the time of producing a thin film, the substrate is water-cooled to, for example, 20 ° C., and a sputtering time is adjusted to produce a 0.5 μm thick film. After removing the residual stress of the manufactured thin film to precipitate fine crystal grains and evacuating the inside of the furnace in order to control the anisotropic magnetic field, an applied magnetic field of, for example, 1.5 kOe, in a temperature range of 300 to 700 ° C. , For example, for one hour in a uniaxial magnetic field.

The characteristics of the Fe _86.7 Zr _3.3 B ₄ Ag ₆ thin film were determined by using a vibrating sample magnetometer.
Using a ple magnetometer (VSM), the coercive force (H _c ) and the saturation magnetization (4πM _s ) were measured at an applied magnetic field of 50 Oe and 5 kOe, respectively. Anisotropy field _{(H k)} was determined from M-H magnetic hysteresis curve measured by VSM.

The electric resistivity was measured from the vacuum to 700 ° C. at a rate of 0.5 ° C./min from the vacuum by a four-terminal method. The magnetic permeability is measured by a one-turn coil type measuring jig (Iwadzu Co.) and a network analyzer (HP8752).
C) by applying a magnetic field of 0.2 mOe to 1 MHz to
It was measured in the frequency range of 1,000 MHz.

An X-ray diffraction analyzer (x-ray diff)
A crystal structure analysis and a lattice constant of the thin film are obtained by using a fractometer, and a change in crystal grain size depending on a heat treatment temperature is obtained by using a Scherrel equation.

In the present embodiment, the basic composition F
When e ₉₂ Zr _3.8 B _4.2 thin film is manufactured by DC magnetron sputtering, crystal grains having a size of 14.4 nm are deposited in the formed state, and the coercive force is 2.059 Oe. The saturation magnetization was 1.082 T and the magnetic permeability was 758, and did not show excellent soft magnetic characteristics.

However, when heat-treated at 400 ° C. for 1 hour,
The crystal grain size is 14.42 nm and the coercive force is 1.183
Oe, the saturation magnetization was 1.750 T, and the magnetic permeability was 2,072, and the soft magnetic characteristics were improved.

The basic composition of Fe₉₂Zr_3.8
B_4.2Fe with Ag added to the composition _86.7Zr_3.3
B₄Ag₆In the case of a thin film, the amorphous phase
However, this is because the addition of Ag improves the ability to form an amorphous phase.
It is. Fe_86.7Zr _3.3B₄Ag₆Production of thin film
In the film-formed state, the coercive force is 0.6 Oe and the saturation magnetization is 1.4.
T, permeability is 1000 (50MHz, 0.2mOe),
Loss is 9.218W / cc (1MHz), Ag is added
Not Fe₉₂Zr_3.8B_4.2More characteristic than thin film
Improved.

Film-formed amorphous Fe _86.7 Zr _3.3 B
_{When a 4} Ag ₆ thin film is heat-treated in a uniaxial magnetic field, 7.2 n having a lattice constant of 0.28775 nm near the crystallization temperature is used.
Crystal grains having a size of m are generated, so that the coercive force is 0.825 Oe, the saturation magnetization is 1.7 T, and the electric resistivity is 1
40 μΩcm, permeability 7800 (50 MHz, 0.2
mOe), and the loss was 1.4 W / cc. That is,
The magnetic permeability is 7.8 times higher and the saturation magnetization is 1.
It increased by a factor of 2 and the loss decreased by a factor of 6.6.

Therefore, the basic composition of Fe ₉₂ Zr
_3.8 B _4.2 Addition of 6 at% of Ag to the composition and heat treatment in a uniaxial magnetic field near the crystallization temperature (that is, crystallization temperature ± 50 ° C.) Fe _86.7 Zr _3.3 B ₄ Ag ₆ It acts to simultaneously satisfy the high permeability, low loss, and high saturation magnetization characteristics of the thin film.

Hereinafter, the sputtering according to the present embodiment will be described.
Fe produced by the plating method_86.7Zr _3.3B₄Ag₆Thin
The characteristics of the film will be described with an example. First, FeZrBA
g DC magnetron sputtering to produce amorphous thin films.
A tarling device was used.

Further, a small piece of Ag was mounted on the target, and a FeZrBAg thin film was formed on a silicon wafer (Si-wafer) facing back by a composite target method.
A film was formed to a thickness of μm.

The initial degree of vacuum is 3 × 10 ⁻⁶ torr or less, the Ar flow rate is 13 sccm, and the current during film formation is 50 m.
A thin film was manufactured under the conditions of 100 mA in this embodiment within the range of A to 300 mA, the pressure during film formation was fixed at 4 mtorr in the range of 1 to 10 mtorr.

In this embodiment, in order to obtain an FeZrBAg amorphous thin film, a substrate (Si-wafer) at the time of film formation is used.
r) should be kept below about 25 ° C.
Water cooled to 20 ° C. Table 1 shows the FeZrB used in the present invention.
The conditions for forming the Ag thin film are shown. The composition of the thin film formed in this embodiment was Fe _86.7 Zr _3.3 B ₄ Ag ₆ (hereinafter, referred to as FeZrBAg).

[0028]

[Table 1]

In order to apply the anisotropy of the formed FeZrBAg thin film, a heat treatment apparatus in a vacuum magnetic field is used. After reducing the degree of vacuum to 10 ⁻⁶ torr or less, the magnetic field is 0.5 kOe.
Apply at 1.5 kOe in the range of
heat treatment in a uniaxial magnetic field in a temperature range of 300 to 700 ° C. for 1 hour at a heating rate of 300 min. (uniaxial field)
nealing (UFA), and then the fan (f
An) was used to cool to room temperature.

The thickness of the formed thin film is measured by a surface step measuring device (α-step) and a scanning electron microscope (scanning).
electron microscope (SEM)
Was measured using The magnetic properties are determined by a vibrating sample magnetometer.
meter: VSM) and applied magnetic fields of 50 Oe and 5
The coercive force (H _c ) and the saturation magnetization (4πM _s ) were measured with kOe.

The anisotropic magnetic field (H _k ) was determined from an MH magnetic hysteresis curve measured by VSM. The electric resistivity is 700 by a four-terminal method at a heating rate of 0.5 ° C./min in vacuum.
Measured to ° C.

The magnetic permeability was measured in a frequency range of 1 MHz to 1,000 MHz by applying a magnetic field of 0.2 mOe using a one-turn coil type measuring jig and a network analyzer. The crystal structure of the thin film was analyzed using an X-ray diffraction analyzer (XRD) and the lattice constant was determined.
The change in the size of the crystal grains according to the heat treatment temperature was determined using the equation (rrr).

FIG. 1 is a graph showing a change in electrical resistivity with temperature of a formed FeZrBAg thin film. As shown in FIG. 1, it can be inferred that FeZrBAg has a typical amorphous structure with an electrical resistivity of about 150 μΩcm in a film-formed state. A value of about 140 μΩcm is maintained up to about 400 ° C., and at a temperature higher than about 140 μΩcm, the resistivity starts to decrease and becomes about
It shows a value of about 80 μΩcm at 00 ° C. It can be seen from this change in the electrical resistivity that crystallization starts to occur at about 400 ° C.

FIG. 2 is a graph obtained by XRD analysis to examine the crystal structure change of the FeZrBAg thin film depending on the heat treatment temperature.
It was shown to. As shown in FIG. 2, FeZrBAg is an amorphous phase in a film-formed state, and crystallization starts to occur at about 400 ° C. as the heat treatment temperature increases. This agrees well with the result that the electrical resistivity starts to decrease at about 400 ° C. as shown in FIG.

At about 500 ° C., a bcc α-Fe crystal phase was formed, and no other crystal phase other than the bcc α-Fe crystal phase was formed until about 600 ° C., but at 700 ° C., α-Fe, Fe ₃ It can be seen that the (Zr, B) -based compound and the FeSi crystal phase generated by the reaction with the substrate are mixed.

FIG. 3 shows the FeZrB according to the present embodiment.
It is the result of having calculated | required the magnitude | size of the crystal grain and lattice constant of (alpha) -Fe calculated | required using the Scherrell formula from the XRD peak of Ag thin film.

At 400 ° C., the formed bcc α-Fe
The size of the crystal grains is 7.2 nm and the lattice constant is 0.2
Pure bcc α-Fe at 8775 nm (0.2866
4 nm). This is the generated bcc
The α-Fe crystal phase means containing Zr and B atoms.

As the heat treatment temperature increases, the size of the crystal grains increases, and the lattice constant decreases. At 600 ° C., the crystal grain size is 14.2 nm and the lattice constant is 0.2
Less than the lattice constant of pure bcc α-Fe at 8550 nm. This indicates that at about 600 ° C., bcc α-Fe starts to decompose into other phases.

Suzuki et al., FeZrB
In the case of a Cu soft magnetic alloy, bcc α-Fe begins to be formed at 500 ° C., and a single-phase bcc α-Fe
Only reported to be produced. However, in the present embodiment, the crystallization of the FeZrBAg amorphous thin film is about 400 ° C.
Therefore, it can be seen that Ag, which is an Fe element and an insoluble element, promotes bcc α-Fe crystal precipitation.

In the case of the FeZrBCu alloy, 550 ° C.
The crystal grain size is 17 nm to 20 nm in the temperature range of 50 ° C.
In this embodiment, the size of the crystal grains is 14.2 nm at 600 ° C., which is smaller than that of the FeZrBCu thin film. This means that when Ag is added to FeZrB, the crystal formation of bcc α-Fe is promoted and the crystal grains become fine.

From the above results, the FeZrBAg thin film has a single-phase amorphous → amorphous + bcc α-Fe cluster (cluster) due to an increase in the heat treatment temperature.
→ bcc α-Fe nanocrystalline
(Nanocrystalline) → bcc α-Fe crystal
ine (crystalline) → bcc α-Fe + Fe ₃ (Zr,
B) It turns out that it changes into + FeSi.

FIG. 4 shows that FeZrBAg according to the heat treatment temperature.
FIG. 4 shows changes in saturation magnetization and coercive force of an amorphous thin film. In the case of saturation magnetization, the film shows a high value of 1.4 T or more in a thin film state, and the saturation magnetization increases with an increase in the heat treatment temperature, and has a value of 1.7 T at 400 ° C.
Maintain a constant value of 1.67 T up to ° C. F at about 600 ° C
The eZrBAg thin film starts to decompose the bcc α-Fe crystal phase from the result of FIG.
It has a value of 5T.

As a whole, the heat treatment increased the saturation magnetization from the state of film formation, but this was due to bcc α
This means that spin interaction occurs more strongly than single-phase amorphous due to -Fe crystal formation. The coercive force of the FeZrBAg thin film has a very low value of 0.6 Oe in the as-formed state, and the coercive force increases as the heat treatment temperature increases, and has a value of 0.825 Oe at 400 ° C.

The reason that the coercive force decreases again at 500 ° C. is α
-Fe nanocrystals (nanocrystallin)
This is considered to be due to the formation of e). At 600 ° C., the coercive force rapidly increases due to crystal grain growth and decomposition of the α-Fe crystal. From the above results, it is expected that the saturation magnetization is the highest at a heat treatment temperature of about 400 ° C., the coercive force is small, and excellent soft magnetic characteristics are exhibited.

FIG. 5 shows FeZrB measured at 50 MHz.
FIG. 5 is a diagram showing a change in magnetic permeability of an Ag thin film. As shown in FIG. 5, as the heat treatment temperature is increased, the magnetic permeability increases. From 300 to 500 ° C., the magnetic permeability has a high value of 4000 or more. In particular, when heat-treated in a uniaxial magnetic field at 400 ° C, the magnetic permeability is 7800, and FeZrB
Cu thin film (3200, 1 MHz), FeHfC thin film (5
250, 1 MHz), CoZrRe thin film (5000, 1
0 MHz).

Herzer states that in the case of an ultrafine grained alloy having a grain size of 35 nm or less,
He reported that the permeability was proportional to the square of the saturation magnetization and inversely proportional to the sixth power of the crystal grain size. Therefore, when the FeZrBAg thin film was heat-treated at 400 ° C. as in the present embodiment, it showed a very high magnetic permeability of 7800 at 50 MHz, which means that the crystal grain size was very fine to about 7.2 nm and the saturation magnetization was high. Is as high as 1.7 T, and amorphous phase + α
This is probably because the -Fe cluster structure has a small crystal magnetic anisotropy and a small coercive force.

FIG. 6 shows that Fe was heat-treated in a uniaxial magnetic field at 400 ° C. for 1 hour, which is a heat treatment condition having the best soft magnetic properties.
FIG. 4 is a diagram showing the magnetic permeability-frequency dependence of a ZrBAg thin film. As shown in FIG. 6, the magnetic permeability has a high value of 7500 or more and is kept constant up to 100 MHz.
Resonance occurs at 200 MHz and sharply decreases. This is thought to be because, as shown in the above results, the formation of fine α-Fe clusters of about 7.2 nm at 400 ° C. makes the magnetic domains finer and spin rotation often occurs at high frequencies.
Thereby, the magnetic permeability shows excellent high-frequency characteristics up to 100 MHz.

From the above results, Fe _86.7 Zr _3.3 B ₄
When the Ag ₆ amorphous thin film was heat-treated in a uniaxial magnetic field at 400 ° C., it exhibited the best soft magnetic properties. Therefore, FIG. 7 shows that FeZrBAg heat-treated in a uniaxial magnetic field at 400 ° C.
Frequency dependence of the loss of the thin film is shown. For comparison, the loss values of a high-resistance soft magnetic FeAlO thin film and Mn-Zn ferrite, which were recently reported to have excellent high-frequency characteristics, are shown.

The FeZrBAg soft magnetic thin film produced by the present invention has a very low loss as a whole, and at 1 MHz, the loss is 1.4 W / cc, which is about 1/10 of the loss of the high-resistance FeAlO thin film. It is very low and shows lower characteristics than Mn-Zn ferrite.

As described above, according to the iron-zirconium-boron-silver-based soft magnetic material and the method for producing a thin film according to the present invention, the characteristics of high permeability, low loss and high saturation magnetization in the MHz band are simultaneously satisfied. A hard magnetic material can be provided.

The preferred embodiments of the iron-zirconium-boron-silver-based soft magnetic material and the method for producing a thin film according to the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive various changes or modifications within the scope of the technical idea described in the claims, and those modifications naturally fall within the technical scope of the present invention. It is understood to belong.

[0052]

As described above in detail, according to the method of manufacturing a soft magnetic material for a high frequency device and the method of manufacturing a soft magnetic thin film according to the present invention, the Fe ₉₂ Zr _3.8 B _4.2 thin film having the basic composition has a crystalline phase. However, an amorphous phase can be manufactured by adding 6 at% of Ag, and Fe _86.7 Zr formed on a substrate is formed.
_{When a 3.3} B ₄ Ag ₆ amorphous thin film is heat-treated in a uniaxial magnetic field, crystal grains having a lattice constant of 0.28775 nm and a size of 7.2 nm are generated at 400 ° C.

Thus, the coercive force is 0.825 Oe, the saturation magnetization is 1.7 T, the electric resistivity is 140 μΩcm, the magnetic permeability is 7800 (50 MHz, 0.2 mOe), and the loss is 1.4 W / cc (1 MHz, 0.1 T). ), The magnetic permeability increased 7.8 times, the saturation magnetization increased 1.2 times, and the loss decreased 6.6 times from the state immediately after the film formation.

Since these characteristics are superior to those of existing soft magnetic thin films, they can be applied to the magnetic core of a high-frequency (MHz) thin-film magnetic element. Thus, there is an effect that an inductance higher than that of the existing soft magnetic thin film can be obtained.

[Brief description of the drawings]

FIG. 1 shows Fe _86.7 Zr _3.3 B _{4 depending on the} heat treatment temperature.
4 is a graph showing a change in electric resistivity of an Ag ₆ soft magnetic thin film.

FIG. 2 shows Fe _86.7 Zr _3.3 B _{4 depending on the} heat treatment temperature.
4 is a graph showing a change in an XRD diffraction pattern of an Ag ₆ soft magnetic thin film.

FIG. 3 shows Fe _86.7 Zr _3.3 B _{4 depending on the} heat treatment temperature.
4 is a graph showing changes in lattice constant and crystal grain size of an Ag ₆ soft magnetic thin film.

FIG. 4 shows Fe _86.7 Zr _3.3 B _{4 depending on the} heat treatment temperature.
4 is a graph showing changes in saturation magnetization and coercive force of an Ag ₆ soft magnetic thin film.

FIG. 5 shows Fe _86.7 Zr _3.3 B _{4 depending on the} heat treatment temperature.
4 is a graph showing a change in magnetic permeability of an Ag ₆ soft magnetic thin film.

FIG. 6 shows Fe _86.7 Z subjected to uniaxial magnetic field heat treatment at 400 ° C.
It is a graph showing a change in the magnetic permeability according to the frequency of the r _3.3 B ₄ Ag ₆ soft magnetic thin film.

FIG. 7 shows Fe _86.7 Z heat-treated at 400 ° C. in a uniaxial magnetic field.
is a graph showing the loss variation due to the frequency of the r _3.3 B ₄ Ag ₆ soft magnetic thin film.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01F 10/14 H01F 10/14

Claims (6)

[Claims] 1. The method of claim 1, wherein Fe _α Zr _β B _γ Ag _δ (α = 80-9
5 at%, β = 2 to 10 at%, γ = 2 to 10 at%,
δ = 5 to 10 at%) iron-zirconium-
Boron-silver soft magnetic material. 2. A first step of forming a film on a substrate by using a FeZrB alloy target and a small piece of Ag using a direct current magnetron sputtering method;
A second step of heat-treating the Ag film;
a third step of cooling the eZrBAg film to room temperature. 3. The conditions for the film formation are as follows:
^The method for producing a soft magnetic thin film according to claim 2, wherein the film forming current is 50 to 300 mA, and the film forming pressure is 1 to 10 mtorr. 4. The method according to claim 2, wherein the substrate is cooled to 25 ° C. or less during the film formation. 5. The method according to claim 1, wherein the second step is performed at a crystallization temperature of ± 50 ° C.
3. The method for producing a soft magnetic thin film according to claim 2, wherein the heat treatment is performed in a magnetic field in the range described above. 6. The condition for heat treatment in a magnetic field is as follows:
6. An isothermal heat treatment in a crystallization temperature range of ± 50 ° C. at a heating rate of 10 ° C./min with a magnetic field of 0.5 to 2.0 kOe applied at ⁻⁶ torr or less. 3. The method for producing a soft magnetic thin film according to item 1.