JP2017041599A - Ultra high frequency ferromagnetic thin film and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic thin film suitable for an electromagnetic induction electronic device of an electronic device.SOLUTION: The composition (atomic ratio) of a ferromagnetic thin film having in-plane uniaxial magnetic anisotropy is represented by the general formula LMF. L is Fe, Co and/or Ni and M is Li, Mg, Al, Ca, Sr, Ba, Gd and/or Y. F is fluorine, the composition ratio a is 3% or more and less than 7%, b is 6% or more and less than 18%. The sum of a+b is 10% or more and 24% or less, that is, L is 76% or more and 90% or less. A saturation magnetization having a structure in which a metal consisting of L and a fluoride of M and F are mixed is 3.5 kG or more and 21.5 kG or less and an anisotropic magnetic field is 300Oe or more. The ferromagnetic resonance frequency of the high frequency magnetic permeability is 7 GHz or more. The resistivity is 1.0×10μohm cm or more.SELECTED DRAWING: None

Description

The present invention relates to an ultra-high-frequency ferromagnetic thin film, and more specifically, relates to an ultra-high-frequency magnetic thin film having uniaxial magnetic anisotropy in the film plane, which is used for electromagnetic inductive electronic devices of electronic equipment. It is. In recent years, the speed of information processing and transmission in electronic devices has been rapidly increasing, and their operating frequency has been reduced from the conventional high-frequency band (1 GHz or less) to, for example, the wireless LAN standard 2.4 GHz band. It has increased to microwave (~ 3 GHz). In the future, in order to increase the communication speed, a higher SHF band (from 3 GHz) will be the mainstream, for example, a 5.2 GHz standard wireless LAN. In addition, since electronic devices in recent years have become multifunctional and downsized, electronic devices that occupy most of the internal volume, such as electromagnetic induction high-frequency magnetic devices such as inductors, couplers, baluns, and noise filters, have been downsized and integrated. There is a strong demand for conversion. For this purpose, it is very effective to reduce the reluctance of the magnetic circuit by introducing a magnetic material into a conventional air-core magnetic device. For this reason, a magnetic material whose magnetic permeability remains constant up to at least 7 GHz, in other words, a material with an extremely high magnetic resonance frequency is desired. Furthermore, as a recent trend of electronic devices, active consideration is being given to thin film devices and integration with semiconductor ICs, and magnetic materials are expected as thin film materials.
Furthermore, the present invention relates to a novel manufacturing process that can further improve material properties. That is, as described in detail below, the ultrahigh-frequency ferromagnetic thin film of the present invention can be formed by a normal thin film manufacturing process, but the anisotropic dispersion of the nanogranular film can be reduced by changing the process conditions. Can do.

      The advantages and disadvantages of existing typical magnetic materials will be clarified below, but conventional magnetic materials cannot maintain sufficient characteristics up to the high frequency band.

Crystalline metal magnetic material
Fe, Co, Ni alone or an alloy containing them is a typical crystalline magnetic material. Some metal materials have very good magnetic properties, and the magnetic resonance ferromagnetic resonance frequency extends to the GHz band. However, since the specific resistance is as small as 1 × 10 ¹ μΩ · cm, even if the resistivity is high, eddy currents are generally generated inside the magnetic material in the high frequency band of 1 MHz or more, causing serious loss. In order to reduce this eddy current loss, these must be made into an extremely thin thin film, and the effective magnetic permeability at the time of device application is small due to the high reluctance of the magnetic circuit and the demagnetizing field.

Ferrite, which is a ferrite material ceramic, is an oxide, and even if its specific resistance is low, it is as high as 10 ⁴ μΩ · cm of magnetite, and as many as 1 × 10 ¹² μΩ · cm as represented by Ni-based spinel ferrite. The loss due to eddy current is small. Since the feature of ferrite having a high specific resistance enables it to be used as a thick film or a bulk, most of the current electromagnetic inductive electronic devices using a magnetic material are discrete devices using ferrite. Further, some hexagonal ferrites having high crystal magnetic anisotropy have a magnetic resonance frequency of permeability reaching the GHz band. However, since ferrite has essentially small saturation magnetization and a large damping constant (dissipative friction coefficient of magnetic moment) for ferromagnetic resonance, permeability resonance (in this case, natural resonance) having a large half-value width occurs. In other words, even if the resonance frequency is high, the imaginary part of the magnetic permeability is large even below the desired operating frequency, so there is a limit to low loss utilization in the GHz band. In addition, in the composition system in which the specific resistance is increased in order to extend the high frequency usage limit, the magnetic permeability is extremely small due to the small saturation magnetization as described above. Above all, the problem of increased reluctance is striking. Therefore, when responding to the demand for thin film as described above, the performance cannot be exhibited enough to be indistinguishable from the paramagnetic material, so it must be said that ferrite is poor in future development.

Amorphous metal magnetic material Amorphous metal magnetic material has high specific resistance by containing a metalloid or a metal with high specific resistance, but the high magnetic properties of the metal material itself are not greatly impaired. Research on high frequency applications has been actively conducted as a material that combines the features of materials and ferrite. Some magnetic resonance frequencies exceed 1 GHz and the specific resistance reaches the first half of the 1 × 10 ² μΩ · cm range, but this specific resistance is not sufficient for application in the GHz band. There is no ferromagnetic resonance frequency that extends to the SHF band because of its low isotropic property, and it has the same problem as the above crystalline metal material.

Thin-film electronic devices using conventional materials By the way, in terms of non-material aspects, eddy current loss must be minimized first so that magnetic materials can be applied to devices operating at low loss in the frequency band targeted by the present invention. In order to limit the film thickness, the film thickness is reduced to one-third or less of the skin depth; there is a means to cut the eddy current path by slitting or the like. However, since the skin depth of the magnetic thin film having a small specific resistance is very shallow, the thickness of the magnetic material has to be extremely reduced in order to reduce the eddy current loss. In addition, the slit processing also has problems such as a decrease in volume of the magnetic material and magnetic saturation due to local concentration of magnetic flux due to an unintended shape effect. However, these processes bring about a higher effective magnetic permeability due to shape anisotropy and a demagnetizing field, but there is a trade-off relationship between the absolute value of the magnetic permeability and the higher frequency of the magnetic permeability characteristics. In other words, even if the frequency characteristics of the effective permeability are increased from the original material, the volume reduction makes the effective permeability in the magnetic circuit of the device extremely small. Therefore, the impedance of an electronic component with a magnetic material introduced into a conventional coil structure cannot sufficiently show a significant difference from an air core component of the same structure that does not use a magnetic material. It becomes. Therefore, it is desirable that a magnetic circuit can be configured by using a relatively thick film without processing. For this purpose, a material having a high specific resistance and a high ferromagnetic resonance frequency is required.

Nano-granular material As described above, in the prior art, a high-frequency device using a magnetic thin film has not yet been put to practical use in applications in a high-frequency band (particularly in the GHz band). By the way, Non-Patent Document 1: “Materia” Vol. 41, 2002 (No. 6), pages 402 to 409, “Trends and Prospects of Nanogranular Magnetic Thin Films” (published by the Japan Institute of Metals), in order to obtain high-frequency soft magnetic properties superior to the above three types of magnetic materials. In addition, it was explained that a large anisotropic magnetic field, saturation magnetization and high specific resistance had to be realized at the same time, and nanogranular structural materials in which ferromagnetic metals such as Fe and Co were dispersed in oxide ceramics were introduced. Yes. Nano-granular materials have a structure in which ferromagnetic granules made of nano-sized particles of Fe, Co or their alloys are dispersed in a base material made of ceramics, and have a high saturation magnetization and anisotropic magnetic field due to magnetic granules, and It also has high specific resistance due to insulating ceramics.
Next, the prior art of high-frequency soft magnetic materials published in patent documents and the like will be described.

      Patent Document 1: Japanese Patent Application Laid-Open No. 2014-175617 relates to a nano-granular material using a fluoride as a base material and a ferromagnetic material containing a noble metal as a granule, and has been proposed by the present inventors. Although the total atomic ratio of L as referred to in the invention is less than 75% and the specific resistance is higher than that of the present invention, the magnetic resonance frequency is the magnetization characteristic (magnetization 8.5 kG; anisotropic) of sample number 25 of this document About 6 GHz estimated from the magnetic field 502 Oe) is the highest. None of the patent documents cited below shows a magnetic resonance frequency higher than that of Patent Document 1.

      Patent Document 2: Japanese Patent Application Laid-Open No. 2013-008767 relates to a high-frequency nanogranular thin film material containing Pd, but the base material is an oxide and the ferromagnetic resonance frequency of magnetic permeability does not exceed 3 GHz (see FIG. 2, 5-10).

Patent Document 3: Japanese Patent Laid-Open No. 7-86035 relates to a uniaxial magnetic anisotropic thin film which is a soft magnetic thin film having both high electric resistance and saturation magnetization and excellent in high frequency characteristics. The composition of this thin film is represented by the general formula Fe _100-xyz M _x N _y L _z (atomic%), where M is Be, B, Mg, Al, Si, Ca, Ti, Y, Zr, Mo, In, Sn, Cs, Ba, La, Hf, Ta, Bi, Pb and / or W, L is O and / or F, and each atomic ratio is 5 ≦ x ≦ 25, 0 ≦ y ≦ 15, 15 ≦ z ≦ 35 and 28 ≦ x + y + z ≦ 50. The crystal structure of the thin film is mainly composed of a magnetic metal phase having a bcc-Fe structure and an oxide or fluoride phase of M. However, the anisotropic magnetic field (H _k ) of the uniaxial magnetic anisotropic nanogranular thin film proposed by Patent Document 3 has a maximum value of 830 Oe, and the magnetic resonance frequency is a maximum of 500 MHz (FIG. 4). .

Patent Document 4: Japanese Patent Application Laid-Open No. 9-82522 discloses a magnetic film having a uniaxial magnetic anisotropy of an appropriate size, a large electric resistance and a high saturation magnetization, and an excellent permeability and high frequency characteristics. As proposed. The composition of the magnetic film is an oxide-based material represented by the general formula (Co _1-a Fe _a ) _100-xy M _x O _y . M is Al, Dy, Er, Gd, Hf, Li, Mg, Nd, Sc, Sr, Tm, Y, Yb, and / or Zr, and the composition ratio a is a <0.3, x and y are atomic% 8 <x <12, 27 <y <37, and 36 <x + y <48, and a small amount of impurities. The anisotropic magnetic field is 50 Oe or more and 100 Oe or less, the saturation magnetic flux density is 8 kG or more, and the specific resistance is 300 μΩ · cm or more and 1500 μΩ · cm or less.

Patent Document 4 describes the magnetic characteristics as follows. (B) Even if the magnetic particles have a large anisotropic energy, the size is nano-sized, and the magnetization direction of each particle has different orientations due to the anisotropic energy of each particle. As a result, the entire energy of the magnetic material approaches zero and becomes soft magnetic. That is, excellent soft magnetism can be obtained by a decrease in effective magnetocrystalline anisotropy accompanying a decrease in particle size. (B) Soft magnetism is lost when the particle size of the granule exceeds 100 Å (10 nm). (C) When the grain boundary is thick, the magnetic interaction between the grains is lost, and the soft magnetism is also lost.
In the above (a) to (c), in order for the nano-granular material to exhibit such soft magnetism, (a) the magnetic granules approach each other at an interval that causes a magnetic interaction, and (b) This shows that the grain size of the granules needs to be smaller than the critical diameter that leads to a reduction in effective magnetocrystalline anisotropy. On the other hand, Patent Document 4 shows that when the particle size of magnetic Co particles exceeds 100 angstroms (10 nm), perpendicular magnetic anisotropy appears and soft magnetism is lost. In the example of Patent Document 4, the maximum value of the frequency at which the magnetic permeability of the thin film is measured is 500 MHz.

      Patent Document 5: Japanese Patent Application Laid-Open No. 2007-173863 is also a uniaxial magnetic anisotropic film using an oxide as a base material.

Patent Document 6: Japanese Patent Application Laid-Open No. 2012-69428 relates to a thin film dielectric having a nano-granular structure. The composition of the thin film dielectric is represented by the general formula _{Fe a Co b Ni c M w} N x O y F z, M components Mg, Al, Si, Ti, Y, Zr, Nb, Hf, and / or Ta, composition ratios a, b, c, w, x, y, z are atomic ratios (%), 0 ≦ a ≦ 60, 0 ≦ b ≦ 60, 0 ≦ c ≦ 60, 10 <a + b + c <60, 10 ≦ w ≦ 50, 0 ≦ x ≦ 50, 0 ≦ y ≦ 50, 0 ≦ z ≦ 50, 20 ≦ x + y + z ≦ 70, a + b + c + w + x + y A metal granule represented by + z = 100 and made of Fe, Co and / or Ni and having a size of nm is dispersed in an insulator matrix made of M component and N, O and / or F. In addition to dielectric properties such as dielectric constant and dielectric loss, it is also described that the specific resistance is 1 × 10 ⁴ to 1 × 10 ¹⁵ μΩ · cm. However, the soft magnetic thin film does not exhibit a high magnetic resonance frequency.

Non-Patent Document 2: “IEEE Magnetics Letters” Vol. 5, 2014, Document No. 3740404, “Control of In-Plane Uniaxial Anisotropy of CoPd-CaF ₂ Nanogranular Films by Tandem-Sputtering Deposition” (published by the Institute of Electrical and Electronics Engineers of Japan) the about 15% of the replaced with Pd, increased H _k film by increasing the magnetocrystalline anisotropy, a high frequency limit performance showed extremely increased that. Also, Non-Patent Document 3: “Journal of Magnetism and Magnetic Materials” Vol. 391, 2015, pp. 213-222, “Ultra-high resistive and anisotropic CoPd-CaF ₂ nanogranular soft magnetic films prepared by tandem-sputtering deposition” (published by Elsevier), the specific resistance can be reduced by using fluoride as a base material. It has been shown to be very large. However, with regard to higher frequencies, the composition ratio of the atomic ratio of L was less than 75%, and the maximum magnetic resonance frequency remained at about 7 GHz. Furthermore, nano-granular materials are inherently large in anisotropic dispersion, and even if the magnetic resonance frequency is increased, an imaginary part of complex permeability that directly corresponds to the AC resistance component of electrical loss from a low frequency occurs. Therefore, in order to avoid this, the practical frequency as a device application has to be lowered.

Patent Document 1: Japanese Patent Application Laid-Open No. 2014-175617 Patent Document 2: Japanese Patent Application Laid-Open No. 2013-008767 Patent Document 3: Japanese Patent Application Laid-Open No. 7-86035 Patent Document 4: Japanese Patent Application Laid-Open No. 9-82522 Patent Document 5: Japanese Patent Application Laid-Open No. 9-82522 JP 2007-173863 A Patent Document 6: JP 2012-69428 A

Non-Patent Document 1: “Materia” Vol. 41, 2002 (No. 6), pp. 402-409, “Trends and Prospects of Nanogranular Magnetic Thin Films”
Non-Patent Document 2: “IEEE Magnetics Letters” Vol. 5, 2014, literature number # 3 700404, "Control of In-Plane Uniaxial Anisotropy of CoPd-CaF ₂ Nan ogranular Films by Tandem-Sputtering Deposition"
Non-Patent Document 3: “Journal of Magnetism and Magnetic Materials” Vol. 391, 2015, pp. 213-222, “Ultra-highresistive and anisotropic Co PdCaF ₂ nanogranular soft magnetic films prepared by tandem-sputtering deposition”
Non-Patent Document 4: “Magnetic Materials (Metal Engineering Series)”, Hideo Kaneko and Motofumi Honma, Japan Institute of Metals, 1977

The present inventors considered the physical properties of nano-granular materials that are stable in the GHz band and related to low-loss permeability as follows.
Ferromagnetism : The conventional nano-granular thin film such as Patent Document 4 uses the fact that the particle size of the magnetic metal granule having a nano-granular structure is nano-sized, and that ferromagnetism is expressed by the magnetic interaction between the magnetic metal granules. Thus, stable magnetic permeability is achieved in the high frequency band. According to the study by the present inventors, the magnetic permeability of the superparamagnetic nanogranular material with few magnetic metal granules is extremely small, and it is impossible to obtain a magnetic permeability large enough for practical use in the quasi-micro band. Therefore, in the present invention, “ferromagnetism” does not include “superparamagnetism” which means that the granular density of the nano-granular film is reduced and is no longer ferromagnetism. Need to be packed densely. Even in Patent Document 1, when the granule concentration is 75% (atomic ratio), which is the upper limit of the claim range, the magnetic metal granules become dense. However, the ferromagnetic resonance frequency of 7 GHz or more intended by the present invention is achieved. In order to obtain it, it is important to further increase the ferromagnetism by a composition with a higher density, that is, a granule concentration of 76% or more.
Anisotropic magnetic field and saturation magnetization : As discussed in Non-Patent Document 1, etc., in order to increase the ferromagnetic resonance frequency of the magnetic permeability, it is necessary that the anisotropic magnetic field is high. However, since only a high anisotropic magnetic field cannot achieve a ferromagnetic resonance frequency of 7 GHz or higher, saturation magnetization as high as possible is also necessary. On the contrary, for example, in order to satisfy a ferromagnetic resonance frequency of 7 GHz or more even for a material having a high saturation magnetic field such as 12.1 kG shown in Patent Document 4 (Table 1, Alloy No. 3), It is necessary to make the anisotropic magnetic field higher than the value in the above table (78 Oe).
Ferromagnetic resonance frequency of magnetic permeability : When a ferromagnetic material undergoes ferromagnetic resonance by frequency sweep, the imaginary part (loss term) of the magnetic permeability becomes maximum at this resonance frequency, but page 122 of Non-Patent Document 4 As shown in FIG. 9-30, since the Gaussian distribution frequency dispersion with the maximum value as the median is shown, a certain value is also shown around the resonance frequency. The quality factor Q of the material is expressed as μ ′ / μ ”by the real part μ ′ and the imaginary part μ ″ of the complex permeability, and it is said that at least 5 to 10 is necessary for device application. Therefore, Q is larger as μ ″ is smaller, and in order to avoid high μ ″, it is said that the magnetic resonance ferromagnetic resonance frequency is generally required to be at least twice as high as the frequency to be used with low loss. . That is, for example, in order to drive a 2.4 GHz band device with low loss, it is important that the ferromagnetic resonance frequency of the magnetic permeability exceeds 4.8 GHz or more.
Uniaxial anisotropy : Basically, such a high ferromagnetic resonance frequency is achieved by obtaining a high anisotropic magnetic field with a uniaxial anisotropic material, as in Patent Documents 1 and 4.
Anisotropic dispersion : Nano-granular materials, like the Co ₇₀ Y ₇ O ₂₃ thin film proposed in Patent Document 4, have a very clear uniaxial magnetic anisotropy (FIG. 5, paragraph number 0023). However, because it has the structure mentioned in paragraph (0012) of paragraph (0012), the measured value (Δ) of the imaginary part of the permeability is larger than the calculated value (▲) as shown in FIG. As can be seen, the anisotropic dispersion (angular dispersion) is inherently large. As described above, the imaginary part of the magnetic permeability shows a certain value even around the resonance frequency, so it is stated that the ferromagnetic resonance frequency is required to be at least twice the operating frequency. This means that the half-value width of the dynamic frequency dispersion is wide, and considering the relatively large anisotropic dispersion of nano-granular materials, it is considered that the ferromagnetic resonance frequency is required to be at least three times the operating frequency in order to reduce loss. . In other words, this is the reason why a ferromagnetic resonance frequency of about 7 GHz or more is necessary. The ferromagnetic resonance frequency of permeability is roughly calculated by multiplying the square root of the value obtained by multiplying the saturation magnetization and the anisotropic magnetic field by the gyromagnetic constant (2.21 × 10 ⁵ m / A · sec) and dividing this by 2π. The For example, if the saturation magnetization is 3.5 kG, the anisotropic magnetic field is 1310 Oe or more, and if the magnetization is 21.5 kG, the anisotropic magnetic field is 7 GHz or more in combination of 300 Oe or more. Conventional materials do not reach levels above 7 GHz even at such approximate ferromagnetic resonance frequencies. Here, if the anisotropic dispersion of the nanogranular material having a ferromagnetic resonance frequency of 7 GHz or more is reduced, the material can be used up to a higher frequency. However, as will be described in detail in the embodiments of the present invention, in the nanogranular material, the estimated value and the actual measurement value of the ferromagnetic resonance frequency are slightly different, and the actual measurement value is rather high.
Specific resistance : The eddy current loss is proportional to the frequency and inversely proportional to the specific resistance, as also described from page 119, line 15 of Non-Patent Document 4. In order to reduce eddy current loss in the quasi-microwave region or higher, a specific resistance with a higher dimension than before is required. Conventionally, the specific resistance of an amorphous metal thin film known as a high resistance soft magnetic material is at most about 1.0 × 10 ² μΩ · cm, and it is preferable that the specific resistance is higher than this. In Patent Document 1, a higher specific resistance of 1.5 × 10 ³ μΩ · cm or more is achieved with a magnetic metal concentration lower than that of the present invention, but as described above, the ferromagnetic resonance frequency cannot achieve 7 GHz. The present invention provides a thin film that achieves a high ferromagnetic resonance frequency at the expense of specific resistance.
Manufacturing method : The ferromagnetic thin film according to the present invention satisfying the above six physical properties is manufactured by forming a thin film having a predetermined composition by a known nano-granular material manufacturing method. In this manufacturing method, a uniaxial anisotropy is imparted by applying a magnetic field to a film during sputtering film formation (Patent Document 1, Paragraph Number 0032; Patent Document 2, Paragraph Number 0020; Patent Document) 3, Examples 1 and 2; Patent Document 4, Examples 1 to 4; Patent Document 5, Reference Example 1, Examples 1 and 2). A heat treatment in a magnetic field is also performed after performing known sputtering. However, surprisingly, as disclosed in Non-Patent Document 2 by the present inventors, uniaxial magnetic anisotropy accompanied by a large anisotropic magnetic field even when a substrate is simply placed on a rotating anode plate without applying a magnetic field. Is granted. Based on this knowledge, a manufacturing method for reducing anisotropic dispersion was studied and tested.

      As described above, the above-described studies of the prior art and the researches of the present inventors are summarized. A magnetic material thin film having a conventional nano-granular structure has a stable magnetic permeability and a low loss in the GHz band. The present invention aims to provide a thin film suitable for the electronic device described in the industrial application field because it is not suitable for the near future electronic device required as a basic characteristic. Furthermore, another object of the present invention is to provide a method for reducing the anisotropic dispersion due to the angular dispersion of the nanogranular material constituting the thin film having this characteristic.

      The present invention solves the above problems by providing a nanogranular magnetic thin film having both a very high magnetic resonance frequency and a certain high resistivity. The basic physical principle of such a magnetic thin film will be described.

The above-mentioned (a) (paragraph number 0012) in which magnetic metal granules (hereinafter referred to as “granules”) interact magnetically with each other in a specific resistance nano-granular structure is such that the distance between the granules causes an exchange interaction. Require closeness or contact. When the granules come into contact with each other, they are magnetically coupled, but the specific resistance is greatly reduced because the relatively large proportions of the granules come into direct contact with each other. Therefore, it is necessary that the current path passing through the nano granular film in a macro manner is electrically separated to some extent by an insulator. At a distance between granules smaller than about 1 nm, both the magnetic interaction between the granules and the tunneling of electrons through the insulator due to the quantum effect occur simultaneously. The specific resistance of a substance exhibiting electric conduction by tunnel conduction is larger than that of metal conduction. However, since the insulating property inherent to the insulator is greatly impaired, it is important to select a material that is particularly excellent in the inherent insulating property. Fluoride insulators achieve high specific resistance to limit the current path even under conditions of tunneling conduction or metal conduction by contact at distances of about 1 nm or less that cause magnetic coupling for reasons described later. can do.

Density of granules Next, nano- granular materials, which are a kind of nano-magnetic material, cause soft magnetic properties due to a decrease in effective magnetocrystalline anisotropy (paragraph number 0012 (b)), but the granules are magnetic. (B) (paragraph number 0012). In order to satisfy this requirement (b) (the total volume of granules, in other words, it is necessary to increase the packing density of the granules, so that the amount of metal in the thin film increases. In this case, the ferromagnetism increases and is high. Although the ferromagnetic resonance frequency can be achieved, since the amount of the insulator is relatively reduced, the number of locations where the metal granules are in contact with increases as compared to Patent Document 1 and the specific resistance decreases. In order to prevent the decrease in the resistance from being lower than that of the conventional metal-based material, it can be eliminated by using the fluoride insulator discussed below as the matrix material of the granule.

Crystal orientation As described above, in the mechanism (random anisotropy) in which the nanostructured magnetic material causes a decrease in the effective magnetocrystalline anisotropy and generates soft magnetism (random anisotropy), the anisotropic magnetic field exhibits soft magnetism. (Paragraph number 0012 (b)). However, as shown in Non-Patent Document 2 and FIG. 7 to be described later, the nano granular material can have a certain crystal orientation unlike a general nano-structured soft magnetic material. That is, it is effective to use a magnetic metal having high crystal magnetic anisotropy for the granule.

Fluoride A nano-granular structure including a fluoride crystal has a high specific resistance. This is because fluorides such as MgF ₂ and CaF ₂ have a larger energy band gap than oxides such as Al ₂ O ₃ (CaF ₂ : 12.1 eV, MgF ₂ : 11.8 eV, Al ₂ O ₃ : 9 eV, all of which are single crystal values), and the specific resistance is high. A feature of the nano-granular structure film using fluoride is that, unlike the case of using nitride or oxide, the fluoride has a crystal structure. The crystal structure means that the composition is stable near the stoichiometric composition, there is no decrease in the band gap unlike the material of the amorphous structure, and the metal constituting the granule at the time of manufacturing the material. Since mixing of fluorides is suppressed, it is possible to achieve high electrical resistance at a very high level compared to the conventional case. In addition, when such an insulator is used, a conventional oxide or nitride is used as a matrix material even in a material having a metal amount in a region where the contact between granules increases and the specific resistance decreases. The specific resistance is relatively higher than that of the conventional nanogranular ferromagnetic film.

Relationship between granule composition and anisotropic magnetic field
Co alone is a material having a high magnetocrystalline anisotropy constant of 10 ⁶ erg / cm ³ . Fe and Ni are also weaker than Co, but have 10 ⁵ erg / cm ³ crystal anisotropy. However, it is a well-known fact that when Fe or Ni is dissolved in Co, the anisotropy is not simply weakened, but rather there is a combination that becomes stronger. It is also known that when a noble metal such as Pt or Pd is dissolved in the above magnetic metal, anisotropy of 10 ⁷ erg / cm ^3, which has been dramatically increased, can be obtained. Thus, the anisotropic magnetic field of the nanogranular film having crystal orientation can be increased by selecting the metal composition of the highly anisotropic granule.

The features of the present invention completed based on the above physical considerations are as follows.
The first invention is represented by the general formula _{L 100-ab M a F b} , L is Fe, 1 or more elements selected from Co and Ni - However, sole Ni except - and, M is Li One or more elements selected from Mg, Al, Ca, Sr, Ba, Gd and Y, F is fluorine, and the composition ratios a and b are atomic ratios, and a is 3% or more and 7%. And b is 6% or more and less than 18%, and the total atomic ratio of a + b is 10% or more and 24% or less, that is, L is 76% or more and 90% or less, and The saturation magnetization is 3.5 kG or more and 21.5 kG or less, the anisotropic magnetic field is 300 Oe or more, and the high frequency permeability has a ferromagnetic resonance frequency of 7 The present invention relates to a ferromagnetic thin film having in-film uniaxial magnetic anisotropy, characterized in that it has a specific resistance of 1.0 × 10 ² μΩ · cm or more.

The second invention is represented by the general formula _{L 100-ab M a F b} , L is Fe, and one or more ferromagnetic elements selected from Co and Ni, one or more selected from Pd or Pt It is an alloy made of a noble metal element, the content of Pd and Pt in the alloy is 50% or less in atomic ratio, and M is selected from Li, Mg, Al, Ca, Sr, Ba, Gd and Y One or more elements, F is fluorine, and the composition ratios a and b are atomic ratios, a is 3% or more and less than 7%, b is 6% or more and less than 18%, and a + b It has a composition in which the total atomic ratio is 10% or more and 24% or less, that is, L is 76% or more and 90% or less, and has a structure in which the alloy of L and the fluoride of M and F are mixed and saturated Magnetization is 3.5 kG or more and 21.5 kG or less, anisotropic magnetic field is 300 Oe or more, ferromagnetic resonance frequency of high frequency permeability is 7 GHz or more, and specific resistance is 1.0 × 10 ² μΩ ・ cm or more Be It relates ferromagnetic thin film having a film plane uniaxial magnetic anisotropy, characterized.

      The third invention is characterized in that the magnetic fine particles composed of L and having an average particle diameter of 1 to 20 nm have a nano-granular structure uniformly distributed in an insulator matrix composed of the fluorides of M and F. 3. A ferromagnetic thin film having uniaxial magnetic anisotropy according to item 1 or 2.

      The uniaxial shaft according to any one of claims 1 to 3, wherein the fourth invention is used as an electromagnetic inductive electronic component incorporated in an electronic device such as an inductor, a coupler, a balun, or a noise filter used in the GHz band. The present invention relates to a ferromagnetic thin film having magnetic anisotropy.

5th invention is 1st cathode which consists of L which is 1 or more types of elements selected from Fe, Ni, and Co, and 1 selected from Li, Mg, Al, Ca, Sr, Ba, Gd, and Y A second cathode made of fluorides of M and F, which are more than seed elements, is fixed in the sputtering apparatus, and power in the range of 10 to 1000 W is independently controlled and applied to the first cathode and the second cathode, respectively. The substrate supported by the anode is rotated at a rotation speed of 1 to 200 rpm in the absence of a magnetic field so that the sputtered particles emitted from the first cathode and the second cathode are periodically passed through the substrate. Sputtering conditions (A) for imparting in-plane uniaxial magnetic anisotropy to the LMF-based ferromagnetic thin film formed on the substrate, and sputtering conditions (B) for applying a magnetic field in the direction of easy magnetization of the LMF-based ferromagnetic thin film Of the thin film by simultaneously performing The flame direction of the coercive force is less than 100 Oe, a method of manufacturing a ferromagnetic thin film having a uniaxial magnetic anisotropy of claim 3, characterized in that to reduce the anisotropy dispersion of the nano-granular structure I following.
The present invention will be described in detail below.

Of the components L of the ferromagnetic thin film of the present invention (first invention), Ni has a low saturation magnetization, so these metals alone are excluded from L. Therefore, as L, Co alone, Fe alone, Co—Fe, Co—Ni, Co—Ni—Fe or the like can be used. In the general formula L _100-ab M _a F _b representing the composition of the ferromagnetic thin film, if a and b are less than 3% and less than 6%, respectively, the specific resistance is 1.0 × 10 ² μΩ · cm or less, while a , b is 7% or more and 18% or more, respectively, the saturation magnetization and the anisotropic magnetic field both decrease, and it becomes difficult to obtain a ferromagnetic resonance frequency of 7 GHz or more.
Specifically, in LMF, when the total atomic ratio of M and F is 25% or more, the contact of granule made of metal L decreases, and the specific resistance reaches 1 × 10 ³ μΩ · cm or more. The magnetic coupling between the granules decreases, and the long-range permeability of the magnetocrystalline anisotropy decreases, so the anisotropic magnetic field also decreases. Also, the magnetization is diluted simply by reducing the space occupancy of the magnetic material. Furthermore, in the composition region where the total atomic ratio of M and F increases and exceeds 60%, the distance between the granules made of metal L increases, so that there is almost no magnetically coupled granules and the film ferromagnetism is reduced. Lost (superparamagnetism).

Therefore, a material having a particularly high anisotropic magnetic field and saturation magnetization can be obtained in a composition range in which the total atomic ratio of M and F is 24% or less, in other words, L is 76% or more. However, if L exceeds 90% or the total atomic ratio of M and F becomes less than 10%, the magnetic properties will improve, but (a) the specific resistance will no longer be less than 1.0 × 10 ² μΩ · cm. There is no difference in terms of metal material and eddy current loss. (B) When the magnetization is 3.5 kG or less and only the anisotropic magnetic field is made extremely high (for example, in the example described later, Table 1, the sample having a larger Pd substitution amount than sample number 29), the static permeability interrupts 3 In device applications, it becomes difficult to distinguish from air. (C) When the magnetization exceeds 21.5 kG, the specific resistance of the film falls below 1.0 × 10 ² μΩ · cm. Furthermore, for the reason described in the paragraph “Anisotropic magnetic field and saturation magnetization” in paragraph 0018, it is necessary that both the saturation magnetization of 3.5 kG or more and 21.5 kG or less and the anisotropic magnetic field of 300 Oe or more are satisfied. is there. In the present invention, in addition to the above (b) and (c), (d) the ferromagnetic resonance frequency needs to exceed 7 GHz. As a result of producing samples such as examples described later, when the saturation magnetization is 3.5 kG, the anisotropic magnetic field is 1310 Oe or more and the ferromagnetic resonance frequency exceeds 7 GHz. Alternatively, when the saturation magnetization is as high as 21.5 kG, a ferromagnetic resonance frequency with an anisotropic magnetic field of 300 Oe or more and a permeability of 7 GHz or more can be obtained.
In the present invention, the approximate value of the ferromagnetic resonance frequency of the magnetic permeability does not require a frequency sweep, so that the evaluation of the manufactured film is relatively simple and quick, and the measured value of the ferromagnetic resonance frequency of the magnetic permeability. Both of these values are required because each has the characteristic of ensuring the characteristics when using a nano-granular film having a large anisotropic dispersion in an electronic device.

As an example of the above experimental results, FIG. 1 shows M in the film for a thin film formed by the method performed in the examples described later, wherein L is composed of Co alone, Fe and Co, and M is Ca. And the relationship between the total of F and the specific resistance is shown. It can be seen that the specific resistance of 1.0 × 10 ² μΩ · cm 2 or more is satisfied in the composition range of 10% or more where the sum of M and F matches the lower limit of claim 1. FIG. 2 shows the relationship between the saturation magnetization at this time and the sum of M and F in the film. As described above, the higher the saturation magnetization, the better. However, the saturation magnetization of the magnetic material is theoretically the highest at 24 kG of permendur (Co ₆₅ Fe ₃₅ alloy). However, in the present invention, since the non-magnetic insulator and the magnetic material are mixed, the magnetization is diluted and lowered. In FIG. 2, it can be seen that the saturation magnetization of about 21.5 kG or more cannot be satisfied in the composition range of 10% or more where the sum of M and F matches the lower limit of claim 1. This is the basis for the upper limit of magnetization of 21.5 kG. On the other hand, when trying to obtain a ferromagnetic resonance frequency of 7 GHz or more by making the magnetization only 3.5 kG or less and making the anisotropic magnetic field extremely high, the static permeability of the film (the real part of the permeability is the low frequency). In the case where a constant value is interrupted by 3 and an attempt is made to make this into a device, it becomes difficult to distinguish it from air, so the lower limit of magnetization is set to 3.5 kG.
In-film uniaxial magnetic anisotropy of the present invention (first invention) will be described later with reference to FIGS.

      In the present invention (second invention), the magnetic metal granule composed of L is made of an alloy containing a chemically very stable Pd or Pt noble metal, thereby increasing the anti-fluorination property of the magnetic metal granule and Facilitates phase separation with the fluoride matrix. If the L element constituting the magnetic metal granule is combined with F, the saturation magnetization of the film decreases, but Pd and Pt have the effect of minimizing this. Further, since Pd and Pt have the effect of remarkably increasing the anisotropic magnetic field, Ni which is excluded from L can be used in the first invention. However, since Pd and Pt are nonmagnetic metals, if their atomic ratio exceeds 50%, the anisotropy increases, but the saturation magnetization decreases, and as a result the anisotropic magnetic field also decreases. In addition to not being able to maintain high performance exceeding 7 GHz, the magnetostriction constant is also significantly increased. Except that L described above is an alloy, the other configurations of the second invention are the same as those of the first invention.

The nano-granular structure of the present invention (third invention) can be obtained by producing a network-like microstructured thin film made of magnetic metal and fluoride by sputtering. These nano-granular films are made of a sputtering method, for example, an RF sputtering film forming apparatus, and a target disk made of a magnetic metal alloy raw material disk and a separately prepared sintered disk such as MgF ₂ and CaF _2. Are simultaneously sputtered, and the substrate disposed so as to face each disk is alternately passed. Film formation is performed in a static magnetic field or in the absence of a magnetic field. The substrate may be heated in the range of 100 ° C to 800 ° C. The heat treatment after the film formation is, for example, held at each temperature in the range of 100 ° C. to 800 ° C. for an appropriate time, for example, 5 minutes to 5 hours, in a static magnetic field, a rotating magnetic field, or no magnetic field. The film is formed in a static magnetic field, or the film after film formation is heat-treated in a static magnetic field. In-film uniaxial anisotropy can be imparted by any of these film forming methods and heat treatments.

The present invention (fourth invention) makes it possible to reduce the size of magnetic components of electronic devices by forming a ferromagnetic thin film having a thickness of submicron to several μm on a substrate of various materials and shapes.
Next, a method for forming a ferromagnetic thin film according to the present invention will be described.

The ferromagnetic thin film of the present invention can be formed by a conventional sputtering apparatus, which is a great advantage industrially. Using an RF sputter deposition system or the like, the above method, or an alloy disk containing pure Co or any one of Fe, Co and Ni and one or more of Pd and Pt contains M element. Even when a composite target in which tips of fluoride insulators are uniformly arranged is used, a nano-granular structure film in which magnetic granules and insulators are dispersed can be obtained by sputtering film formation on a substrate.
In addition, magnetic anisotropy is induced by applying a static magnetic field during film formation, such as placing an electromagnet or permanent magnet in the vicinity of the substrate, and uniaxial anisotropy is strengthened by rotating the substrate. Thus, a thin film having desired magnetic properties can be obtained.

The film forming method used in this experiment will be described more specifically. Using an RF magnetron / conventional type sputtering device, an RF magnetron / conventional type carousel sputtering device, or a DC facing target sputtering device, the diameter is 50 to 112 mm. One or more alloy disk targets (ie, the first cathode) containing at least two of pure Fe, pure Co, pure Ni or Fe, Co, Ni and at least one of Pd and Pt, and M element By holding the fluoride target (that is, the second cathode) containing the substrate downward, upward, or laterally in the sputtering apparatus and simultaneously performing sputtering, the materials constituting the first and second cathodes are sputtered and partially free. Radicalized sputtered particles jump out of the cathode. A substrate is disposed in a region where these particles are efficiently incident. By supporting the substrate on the anode, sputtered particles having negative charges are electrically attracted to the anode, and a thin film is formed on the substrate surface. In general, when the cathode is disposed downward, the anode is disposed upward. When the cathode is disposed upward, the anode is disposed downward. When the cathode is disposed laterally, the anode is also disposed sideways. The cathode / anode facing arrangement is performed. The following arrangement is also performed as a non-opposing arrangement of the cathode / anode. The first cathode is a pair of divided opposing cathodes, and the second cathode is arranged on the side of the first cathode so that the cathode surface is parallel to the opposing direction. Alternatively, the second cathode is also a pair of split opposed cathodes, and the first and second targets are opposed in the same direction. These first and second cathodes are arranged with an anode having a shape similar to a rotating cylinder around an axis. Each cathode of the divided cathode may have the same composition or a different composition.
The electric power supplied to the first cathode and the second cathode is independently controlled so as to correspond to the ratio of each cathode material constituting the membrane. At this time, the sputtered particles simultaneously sputtered from the first and second cathodes are formed on a substrate supported on the anode. A film having a desired composition is formed by periodically passing the substrate in the vicinity of the first and second cathodes. In order to control the incident angle of sputtered particles, the cathode or the substrate can be set at an arbitrary angle within the range where the magnetic anisotropy derived from the film structure is maintained, and the relationship of the cathode / anode facing arrangement can be controlled. is there. Similarly, in the non-opposing arrangement, a film having a desired composition is formed by periodically passing through the position where the substrate contacts the sputtered particles.
The above description basically applies to carousel sputtering. In the case of carousel sputtering, the first cathode and the second cathode are in different directions. The substrate supported on the cylindrical side surface is periodically passed through a position facing the first cathode and the second cathode. In the DC facing target sputtering apparatus, as described above, the divided first cathode is the facing target, the second cathode is on the opposite side across the substrate, and the anode (substrate) is alternately approaching both targets. Rotate.
In sputtering film formation, pure Ar gas is used as the sputtering gas. The film thickness is controlled by adjusting the film formation time, and is formed to a thickness of about 0.1 to 3 μm. The substrate is heated by indirect water cooling or an arbitrary temperature of 100 to 800 ° C., the Ar gas pressure during film formation is 1 to 20 mTorr, and the sputtering power is 10 to 1000 W. Further, a pair of permanent magnets can be arranged on the substrate holder, and a static magnetic field of 100 to 500 Oe can be applied to the substrate surface. Of course, it can be easily estimated that the same result can be obtained even if the shape and area of the target, the strength of the applied magnetic field, etc. exceed the above range.

      In order to increase the volume ratio of the granule touched in paragraph 0021 or the like, it is necessary to individually control the amount of particles popping out from each of the metal target and the fluoride target. That is, assuming a thin film in which the particle size of the metal granules and polycrystalline fluoride is constant in the thin film, the power of the metal target is relatively set so that many granule components jump out of the target and deposit on the substrate. When it is increased, it becomes a ferromagnetic thin film, while when the input power to the fluoride target is relatively increased, it becomes a superparamagnetic thin film.

Here, in the present invention (fifth invention), power in the range of 10 to 1000 W is independently controlled and applied to the first and second cathodes described in paragraph 0037. When the substrate disposed on the anode is passed over the cathode, below, or lateral position, the anode is rotated at a constant or variable speed within a range of 1 to 200 rpm, and the number of rotations in accordance with the number of rotations in the plane of the substrate. By applying a peripheral speed (rotational force), uniaxial orientation occurs without applying a magnetic field during the sputtering film forming process (sputtering condition (A)). 3 to 5 are shown in Table 1 with respect to Sample No. 2 of the film of the present invention to be described later (Co _0.84 Pd _{0.16) 81} - represented by (Ca _0.33 F _{0.67) 19,} a CoPd alloy as a granule, CaF _This is the result of film formation so that ₂ is a matrix and separate phase components. The substrate is water-cooled and no heat treatment is performed after the film formation.
3 to 5 adopt the conditions that the total input power to the target is 100 W and the anode rotation speed is 10 rpm in the RF magnetron / conventional type sputtering apparatus. Of the input power of 100 W, 75% (75 W) is input to the first cathode (target) (CoPd alloy) and the remaining 25% (25 W) is input to the second cathode (target) (CaF ₂ ). In addition, the power input circuit to each cathode was controlled independently. Since CoPd and CaF ₂ have different sputtering rates, the input power ratio does not directly become the composition of the film (ratio of granule to matrix), so the input power to the granule (first cathode) in the above example. There is a slight difference between 75% and 81% composition.
FIG. 3 shows a magnetization curve formed without applying a static magnetic field. The magnetization curve was measured with a vibrating sample magnetometer as will be described later. In FIG. 3, the film is formed while rotating the anode plate which is a substrate holder, and the centrifugal-centric direction of this rotation becomes the magnetic field easy direction. As will be described later with reference to FIGS. 7 and 8 in paragraph 0043, crystallographically, the direction perpendicular to the film surface tends to be the easy axis of magnetization, but the direction perpendicular to the film surface is difficult to magnetize due to the demagnetizing field. Therefore, the “in-film uniaxial magnetic anisotropy” of the present invention is formed.
Subsequently, FIG. 4 shows a result of film formation performed in a general magnet arrangement in the sputtering apparatus. In this case, since the static magnetic field is applied in the direction orthogonal to the film plane from the direction in which anisotropy is imparted by the rotation of the anode, the easy magnetization direction of the film is slightly rotated in that direction. This rotation angle depends on the composition of the film (atomic ratio of L), the number of rotations, and the strength of the static magnetic field, making it impossible to form a stable film, but `` uniaxial magnetic anisotropy in the film plane '' is added. ing.
Finally, as a new method (fifth invention), FIG. 5 shows the result of film formation by applying a static magnetic field in the centrifugal-centric direction of the anode rotation using a jig. In this case, uniaxial magnetic anisotropy is imparted as shown by the magnetization curve in FIG. 3 (that is, “in-film uniaxial magnetic anisotropy” of the present invention is imparted), but it varies depending on the rotation of the anode. Since a magnetic field in the range of 100 to 500 Oe is applied in the direction in which the directionality is imparted (sputtering condition (B)), the anisotropy of the film is strengthened. For the cylindrical anode described in paragraph 0038, N and S magnets are arranged in the rotation direction of the cylindrical body. In FIG. 3, the coercivity of the hard axis is greater than 100 Oe and as large as 200 Oe, and the squareness ratio in the easy magnetization direction is low, but in FIG. 5, the coercivity of the hard axis is less than 100 Oe. Based on this result, in the fifth aspect of the invention, the coercive force of less than 100 Oe in the hard axis direction is used as an index for reducing anisotropic dispersion.
The control of the magnetic field application direction hardly depends on the magnetic field polarity (N / S pole).

      Further, the magnetic properties can be adjusted by heat treatment at 100 to 800 ° C. after film formation or during film formation. Further, the anisotropic magnetic field can be controlled by heat treatment in a static magnetic field of 300 Oe to 10 kOe or a rotating magnetic field. However, if the heat treatment temperature is less than 100 ° C, there is almost no difference from the heat generated during film formation, so there is no effect.If the heat treatment temperature exceeds 800 ° C, the entire thin film component is completely dissolved and the structure becomes uniform. A nano granular structure which is a heterostructure cannot be obtained.

      Further, when the film formation and heat treatment conditions are adjusted within the range of the above sputtering conditions, (1) the particle size and dispersion state of the metal granules, (2) the structure and state of the fluoride insulator, and (3) the fluoride Atomic level, such as crystal structure of insulator, (4) junction interface between granule and fluoride insulator, (5) about several impurities in insulator and granule, and arrangement and movement of atoms at interface It has a slight effect on structural changes in

(A) Since the ferromagnetic thin film of the present invention (first invention) has a phase composed of L and a fluoride phase of M and F, the former is a metal nano granule having ferromagnetism, and the latter is A magnetic metal having a strong crystal anisotropy, which exists as a fluoride insulator grain boundary phase, achieves both a high saturation magnetization and an anisotropic magnetic field, and realizes a ferromagnetic resonance frequency with a high magnetic permeability. Further, it will be explained that the fluoride matrix material corresponding to the grain boundary phase is present around the magnetic granules, so that the specific resistance is increased and a stable magnetic permeability is realized in the microwave band.
(B) In order to increase the ferromagnetic resonance frequency in order to obtain stable permeability characteristics in the GHz band, a large saturation magnetization is required simultaneously with a large anisotropic magnetic field. Compared to the characteristics shown in Table 2 for the film of FIG. 5 of Patent Document 4 and the film of Sample No. 3 of the present invention described later, the saturation magnetization is equivalent to 10.5 kG for the former and 10 kG for the latter. The isotropic magnetic field is 80 Oe in the former, and 1505 Oe in the latter, which is about 19 times higher. Reflecting this, the ferromagnetic resonance frequency of the magnetic permeability was 2.6 GHz for the former, and 17.2 GHz for the latter.
(C) Since fluoride insulators have a larger band gap than oxide insulators, the tunneling probability of conduction electrons is the nitride of conventional materials even if the granules are close enough to have a magnetic interaction. -Since it is very low compared with oxide insulators, the conductance of tunnel conduction electrons is reduced, and a large specific resistance is exhibited. Furthermore, since the fluoride matrix has a crystal structure, the band gap does not decrease unlike conventional materials that become amorphous. The specific resistance of sample number 5 shown in FIG. 6 is 3.5 × 10 ² μΩ · cm. FIG. 5 of Patent Document 4 shows a magnetization curve of a Co ₇₀ Y ₇ O ₂₃ thin film in which the insulator is yttrium oxide and the metal granule is Co. In the thin film of FIG. 5, the loop of the magnetization curve in the easy magnetization direction rises vertically, while the coercive force in the difficult magnetization direction is almost zero, so it is ferromagnetic and has uniaxial anisotropy. However, the specific resistance is 3 × 10 ² μΩ · cm. In this film, the atomic ratio of L as referred to in the present invention is 70%, but in the films of Sample No. 2 (FIGS. 3 to 5) and Sample No. 5 (FIG. 6) having higher specific resistance, L It is the effect of using fluoride as the matrix material that can exhibit a sufficiently high specific resistance even in the composition of the present invention having a larger amount of L than that of the conventional material.
(D) When the L component was further increased, such as sample number 13, although the specific resistance decreased, it still maintained a high value of 1.2 × 10 ² μΩ · cm, and the magnetization increased to 21.2 kG rather. . Therefore, a practical material showing a stable magnetic permeability in the GHz region can be obtained.
(E) FIG. 6 shows the complex of the film (second invention) having the composition of (Co _0.74 Pd _0.26 ) _80- (Ca _0.33 F _0.67 ) ₂₀ shown in Table 1 for the film of sample number 5 of the present invention described later. It is a frequency characteristic of magnetic permeability. This characteristic was measured by the short-circuit microstrip line method as described later. This film has a saturation magnetization of 9.4 kG and an anisotropic magnetic field of 1380 Oe, and the ferromagnetic resonance frequency reaches 17.9 GHz. This frequency is an extremely high value as compared with a known conventional material (for example, the material of Patent Document 4) as a soft magnetic material. The static permeability (see paragraph No. 0033) is about 5, and can withstand practical use. The specific resistance is about 3.5 × 10 ² μΩ · cm, which is 2 to 4 times the value of conventional metal materials. These are attributed to the high magnetocrystalline anisotropy of the CoPd alloy granules and the high insulating properties of the CaF ₂ matrix.
At the end of paragraph 0015, it was mentioned that the electrical loss occurs due to the high imaginary part of the complex permeability as a problem of the conventional nanogranular material. On the other hand, the imaginary part of the complex permeability shown in FIG. 6 is stable down to about 4 GHz and the real part is stable up to the same frequency, so Q does not fall below 10. Therefore, the thin film of the present invention hardly causes electrical loss when used as an inductor in the 2.4 GHz band, for example.
(F) The nanostructures of these ultra-high frequency nano-granular materials are different from general nanomagnets in which ferromagnetic nanocrystals are randomly oriented crystallographically, and cross-sectional TEM images (Fig. 7) and X-ray pole figures ( As shown in FIG. 8), it has a crystal orientation. The TEM image in Fig. 7 is a magnetic granule made of Co ₈₅ Pd ₁₅ alloy that is dark in color and surrounded by an ellipse with a broken line, and has a face-centered cubic lattice. Therefore, it can be seen that the spacing is the (111) plane spacing, which is the crystallographic easy magnetization direction of this alloy. That is, it is shown that the <111> crystal orientation is uniformly aligned in a direction slightly oblique to the film thickness direction. The pole figure of FIG. 8 shows the crystal orientation of the Co ₈₅ Pd ₁₅ (111) plane of the entire film. Although not observed by local observation such as a TEM image, this indicates that this crystal orientation is concentrated in the same direction as the easy magnetization direction of the film. In this case, the anisotropy of the film is enhanced as compared with the conventional case due to the magnetocrystalline anisotropy of the granules, and a high anisotropic magnetic field is developed. FIG. 7 shows that the granule size is 7 to 10 nm in the long side direction of the ellipse and 5 to 7 nm in the short side direction.
(G) As shown by the changes from FIGS. 3 to 5, the anisotropic dispersion of the film can be reduced by controlling the magnetic field application direction during film formation. As shown in each figure, the saturation magnetization does not change and the specific resistance does not change depending on the magnetic field application direction. When a method outside the scope of the present invention (fifth invention), in which a magnetic field is applied in a direction orthogonal to the anisotropy imparted by the anode rotation, the anisotropic magnetic field appears to have dropped as shown in FIG. This is because the easy magnetization direction of the film is rotating from the measurement direction of the magnetization curve (vertical direction on the paper surface of FIG. 4), and the original anisotropic magnetic field is accurately measured in accordance with the difficult magnetization direction of the film. If you do, there is almost no change. The nanostructure and crystal orientation are also in accordance with FIGS.

      As described above, in the present invention, the magnetic resonance frequencies of saturation magnetization, anisotropic magnetic field, specific resistance, and high-frequency magnetic permeability are satisfied. Conventional nanogranular materials were also intended to improve some or all of these, but are not sufficient from the perspective of the present invention as shown in Table 1 below.

The meanings of the symbols used in Table 1 are as follows. “Magnetic Resonance Frequency (A)” — estimated value; “Magnetic Resonance Frequency (B)” — actually measured value; “◯” —respective characteristic values specified by the present invention; “×”: characteristic value specified by the present invention "-"-Unknown because it is not described in the relevant literature.
From Table 1, it can be seen that in the present invention, a magnetic metal having high magnetocrystalline anisotropy or magnetization is used, and in addition to obtaining a high resonance frequency, high resistivity is maintained with high insulation by fluoride.

Hereinafter, with respect to the present invention (first, second and third inventions), referring to Example 1, a thin film satisfying the saturation magnetization, anisotropic magnetic field and specific resistance defined by the present invention is a magnetic resonance ferromagnetic resonance frequency. The fact that (actually measured value) is satisfied will be described. In connection with this, it is also noted that the approximate value of the ferromagnetic resonance frequency of the magnetic permeability does not necessarily show the tendency of the actual measurement value, and when the composition of the granule component L of the present invention changes within the scope of the present invention, How the magnetic properties such as saturation magnetization are affected (second invention) will be described, and the nanostructure of the third invention will also be described. The present invention (fifth invention) will be described with reference to the second embodiment.
[Example 1]
The preliminary test substrate is approximately 0.5 mm thick Corning Eagle XG (Corning brand name) glass, about 0.5 mm thick Corning Eagle 2000 (Corning brand name) glass, 0.5 mm thick surface. Thermally oxidized Si wafer, 0.5 mm thick quartz glass, or similarly about 0.5 mm thick MgO and sapphire, and a thin film having the composition of sample number 2 with the film thickness changed in the range of 0.2 to 3 μm Was deposited. At this time, a first target having a composition of Co ₈₄ Pd ₁₆ and a second target having a composition of CaF ₂ were used for the cathode. As a result of chemical analysis of the formed film, the atomic ratio of the magnetic material of the second cathode (target) was 79%, and the atomic ratio of the insulating material of the first cathode (target) was 21%. From this, it was confirmed that the film composition was derived from the target composition and could be controlled. When the magnetic properties of the film were measured, the magnetic properties did not change significantly regardless of the substrate type, film thickness, deposition rate (absolute value of sputtering power), and sputtering pressure. Various sample preparations were performed.

Ferromagnetic thin film production method and conditions in the examples Film deposition device: RF magnetron sputtering device Anode: Diameter 250 mm
Substrate: Eagle XG
Film thickness: 1 μm (Pt containing sample is 0.2 μm)
Substrate temperature: Water cooling Sputtering pressure: 0.5 mTorr
Total sputter power: 90 to 300 W (for adjusting the ratio of power input to magnetic metal and fluoride target)
Magnetic field applied to substrate during film formation: No magnetic field Heat treatment: No treatment

Method for evaluating ferromagnetic thin film The thin film sample produced as described above was measured for its magnetization curve in the range of an applied magnetic field ± 15 kOe using a sample vibration type magnetometer, and the high-frequency permeability was measured by the short-circuit microstrip line method. Measured up to GHz. The specific resistance was measured using a direct current four-terminal method, and the film composition was analyzed by wavelength dispersion spectroscopy (WDS). The crystal structure and nanostructure of the film were analyzed by powder X-ray diffraction (XRD) using a Cu-Kα radiation source, X-ray pole figure analysis using the radiation source, and transmission electron microscope (TEM). The applied voltage in TEM observation was 200 kV, and the observation sample was prepared with a precision ion polishing apparatus. The composition of each thin film sample is shown in Table 2, and various properties are shown in Table 3.

In Table 3, all samples achieved a resonance frequency (measured value) of permeability of 7 GHz or more. The resonance frequency of the magnetic permeability was highest in the sample number 5 and the sample group of the sample numbers 22 to 26 having the same composition and concentration of the granule but different in the composition of the matrix material. The frequency characteristic of the complex permeability of sample number 5 is as shown in FIG. In sample numbers 1 to 9, the amount of Pd is increased in the atomic ratio of Co and Pd in the granule composition. Sample No. 4 has the highest anisotropic magnetic field, and its magnetization is higher than Sample No. 5 having a large amount of Pd. That is, the resonance frequency estimated by calculation from the magnetization and the anisotropic magnetic field is higher for the sample 5, but the measured values are different. Strictly speaking, the composition of each magnetic granule is not uniform, as can be seen from the fact that another resonance is seen near 11 GHz apart from the main peak at 17.9 GHz in Fig. 6. Correspondingly, several anisotropic components with different strengths are expressed. This is because these indicate the superimposed magnetic permeability characteristics. This is due to the strength dispersion among the anisotropic dispersions.
Looking at the trends of sample numbers 1 to 9, when the Pd content in the CoPd alloy exceeds 30%, the tendency that “the resonance frequency does not increase even if the anisotropic magnetic field and the magnetization are high” becomes prominent. When the Pd content of the magnetic granules increases, if it exceeds 10%, the crystal structure changes from a hexagonal close-packed structure to a face-centered cubic structure, and the crystal anisotropy of the CoPd alloy temporarily weakens from pure Co. However, in the CoPd alloy having a face-centered cubic structure, the anisotropy becomes stronger again when the Pd content increases (sample numbers 3 and 4). However, when the amount of Pd, which is a nonmagnetic element, increases (first invention), the magnetization rapidly decreases (sample numbers 7, 8, 9). The anisotropic magnetic field is determined by the saturation magnetization of the film and the strength of the anisotropy. However, since the anisotropic magnetic field is reduced by the decrease in magnetization (corresponding to the composition change seen in the order of sample numbers 3 to 9), Pd The higher the number, the better the high frequency characteristics.

      Sample numbers 10 and 11 are obtained by changing the atomic ratio of granule (L) and matrix (M + F) with respect to sample number 1. It can be seen that even though the granule composition is the same, the magnetization and the anisotropic magnetic field increase and decrease in accordance with the increase and decrease of L, and the resonance frequency changes. The change in magnetization is caused by the volume occupancy (concentration) of the magnetic material, and the change in anisotropy corresponds to the change in the long-range permeability of the magnetocrystalline anisotropy.

      Samples Nos. 12 to 14 are anisotropic because CoFe, which is a sample group in which CoFe alloys with the highest saturation magnetization among magnetic metals are applied to granules, has a lower magnetocrystalline anisotropy than compositions containing Pd and Pt. Although the magnetic field is small, it does not contain Pd, which is a nonmagnetic element, so the saturation magnetization is extremely high enough to compensate for the decrease in the anisotropic magnetic field, and the actual measured resonance frequency actually exceeds 7 GHz. However, simply because the saturation magnetization is high, the resonance frequency does not increase, and the CoFe composition (sample number 12) with less Fe than the permendule composition (sample number 14) has a higher magnetocrystalline anisotropy. It can be seen that a higher resonance frequency can be obtained. Sample numbers 15 to 17 are obtained by alloying these CoFe granules and Pd. When Pd is introduced, the saturation magnetization is decreased, but the anisotropic magnetic field is further increased, and as a result, the resonance frequency is increased.

      Sample numbers 18 to 20 are the results of alloying with pure Co or a CoFe alloy and Pt instead of Pd. Since Pt has a very high effect of increasing the magnetocrystalline anisotropy, a perpendicular magnetization component is generated even with a film thickness of about 1 μm. Therefore, the film thickness of these samples was set to 0.2 μm, and the demagnetizing factor in the film thickness direction was increased to lay the easy magnetization direction in the film surface, but the same effect as Pd was obtained.

      Sample Nos. 21 to 28 are obtained by changing the composition of the magnetic alloy to be alloyed with Pd and the composition of the matrix material that forms the magnetic granules and the nano-granular structure. In particular, when the composition of the matrix material is changed, the specific resistance slightly increases or decreases due to the essential change in insulation due to the difference in the energy band gap, and it is understood that both are within the scope of the present invention. The same applies to the magnetic characteristics.

      Sample numbers 29 and 30 are obtained by applying only Ni, which is a magnetic element having the lowest saturation magnetization, to a granule as an alloy with Pd. Although the saturation magnetization is extremely low compared to other samples, it is shown that a resonance frequency of 7 GHz can be obtained by adjusting the atomic ratio between the composition of the NiPd alloy and fluoride.

All samples have a nano-granular structure in which several nanometers of magnetic granules are dispersed in a fluoride matrix in accordance with Fig. 7. It was found by calculating the crystal grain size of the steel or by TEM observation.
Therefore, all the samples satisfied the claims of the present application.

[Comparative Example 1]
Using a reactive RF magnetron sputtering apparatus based on stationary facing sputtering, a target having a diameter of 4 inches was sputtered to produce a thin film having a thickness of about 1 μm. The target composition at this time was Co ₈₅ Al ₁₅ and Corning Eagle XG glass having a thickness of about 0.5 mm was used for the substrate. The sputtering pressure during film formation was 0.5 mTorr, and the oxygen flow ratio of the reactive gas to the argon gas was 3%. Further, a magnetic field of about 130 Oe is applied by a pair of permanent magnets so that uniaxial magnetic anisotropy is imparted to the substrate during film formation. Note that the sputtering power was constant at 200 W.
The resulting sample has a composition of (Co ₉₀ Al ₁₀ ) _78- (Al _0.20 O _0.80 ) ₂₂ , and its structure is determined from the main CoAl alloy phase with a particle size of 10 nm or less by X-ray diffraction or TEM observation. It was a network-like structure consisting of fine particles and Al-O ceramic phase or grain boundaries with a thickness of about 1 nm or less. The sample had uniaxial magnetic anisotropy that facilitated magnetization in the direction parallel to the applied magnetic field during film formation, and the magnitude of the anisotropic magnetic field was 83 Oe. The coercive force in the direction of hard magnetization is 2.2 Oe, the saturation magnetization is 11 kG, and the specific resistance is 9.8 × 10 ¹ μΩ · cm, so it must be a uniaxial anisotropic nanogranular soft magnetic film. I understand. However, although the saturation magnetization is equivalent to the example group of the present invention, the anisotropic magnetic field is 1 to 2 orders of magnitude lower and the specific resistance L is 78%, but the result is 1.0 × 10 ² μΩ · cm or less. Obtained. This is attributed to the film-forming method without substrate rotation, the low crystal magnetic anisotropy of the CoAl alloy, and the matrix Al oxide being amorphous.

[Comparative Example 2]
In order to improve the anisotropic magnetic field, the sample in which the flow rate ratio of oxygen to argon gas is lower than that of Comparative Example 1 has a composition of (Co ₈₈ Al ₁₂ ) _82- (Al _0.20 O _0.80 ) ₁₈ , and as a result Although the saturation magnetization increased to 12 kG, the specific resistance was still lower than 1.0 × 10 ² μΩ · cm, no dramatic increase in anisotropic magnetic field was obtained, and the resonance frequency remained below 3 GHz. In the conventional film formation method, the amount of Al used to bind to oxygen from the CoAl alloy target and become the matrix phase of the Al oxide differs depending on the oxygen gas flow rate, so that the granule composition is kept constant. I can't. Therefore, the saturation magnetization and the anisotropic magnetic field are not constant.
On the other hand, in the embodiment of the present invention, the alloy target to be granulated in advance and the fluoride target to be the matrix are separated. For example, when Co is used as the magnetic material and AlF ₃ is used as the fluoride, AlF ₃ Al, which is a constituent element, is incorporated into Co, and the composition of the granule is not changed, and the magnetization and magnetocrystalline anisotropy are kept within the scope of the present invention.

[Example 2]
The experimental method is in accordance with Example 1 (see paragraph 0048). However, as shown in FIGS. 4 to 5, there is a sample in which a magnetic field is applied to the substrate by a magnet. The strength of the applied magnetic field was 270 Oe at the center of the substrate.
FIG. 9 shows a static magnetization curve of a film having the composition of sample number 2, which is a reference example of Example 2. Sample No. 2 was formed in the absence of a magnetic field as in Paragraph No. 0048, but after that, a magnetic field of 2 kOe was applied in the direction of easy magnetization in a vacuum and heat treatment was held at 140 ° C. for 10 minutes. The two magnetization loops in FIG. 9 are measured in the easy magnetization direction and the hard magnetization direction of the film, and indicate that the film has uniaxial magnetic anisotropy in the film plane. The anisotropic magnetic field determined from the inclination of the magnetization curve in the hard axis direction is 779 Oe. In addition, the maximum magnetization appears to be about 10.0 kG in the applied magnetic field range in the figure, but when the applied magnetic field strength is further increased, a saturation magnetization value of 10.5 kG or more is exhibited. The resonance frequency of permeability was 8.7 GHz. When the specific resistance of this sample was measured by the direct current four-terminal method, it was 4.5 × 10 ² μΩ · cm, which was 2 to 4 times or more that of a conventional metal material. The most characteristic feature of this film is that the magnetic metal contains Pd, and therefore the anisotropic magnetic field is extremely large, which greatly contributes to the increase in the frequency limit of the magnetic permeability. Similarly, in sample numbers 18 to 20 containing Pt, an increase in the anisotropic magnetic field can be confirmed as compared with samples using other magnetic metals.
The results of investigating the influence of magnetic field application during film formation on sample number 2 are as shown in FIGS. 3 corresponds to the sputtering condition (A) of the fifth invention, FIG. 4 is a reference example of Example 2, and FIG. 5 corresponds to the fifth invention in which the sputtering conditions (A) and (B) are performed simultaneously, It is a central part of Example 2. Comparing Fig. 3 and Fig. 5, the saturation magnetization and the anisotropic magnetic field hardly change, but Fig. 5 shows an improvement in coercive force and squareness ratio. Looking at the frequency characteristics of this complex permeability, it is clearly strong. It was found that the magnetic ring half-width was reduced, and that even higher frequencies could be used.
In FIGS. 4 and 5, since the magnetic field application method is special, FIG. 3 (film formation without magnetic field and no heat treatment) is suitable for comparison with FIG. 9 (magnetic field heat treatment). By contrast, the magnetization curve in the easy magnetization direction and the magnetization curve in the difficult magnetization direction are separated by the centrifugal / centripetal force generated by the rotation of the anode plate and the oblique incidence of sputtered particles, as in the case of heat treatment in a magnetic field, and uniaxial magnetic It can be seen that anisotropy is imparted.
Note that the anisotropic dispersion reduction described in FIGS. 3 to 5 is related to “angular dispersion”, which is different from “strength dispersion” (paragraph number 0052). "Is rather increasing the ferromagnetic resonance of the film.

      As described above, the high electrical resistance ferromagnetic thin film according to the present invention can cope with a high frequency band covering the GHz band even if it is relatively thick, and has a characteristic having a clear significant difference from an air core component with low loss. This greatly contributes to the practical application of the high-frequency magnetic device to be realized. Although the application in the GHz band has been mainly described above, as can be seen from FIG. 6 and the like, the high electrical resistance ferromagnetic film according to the present invention corresponding to the GHz band has a magnetic loss and an eddy current loss in a lower frequency band. Therefore, it is also effective as a device material used in, for example, the VHF band (30 to 300 MHz) or HF band (3 to 30 MHz). Although the present invention focuses on the use of the real part of the stable complex permeability, paradoxically, it uses an imaginary part that becomes larger at 10 GHz or more, and in a frequency region much higher than that of the conventional material. It can be easily analogized that it is also useful for noise absorbing devices (EMC countermeasure devices).

6 is a graph showing an example of a change in specific resistance with respect to the total atomic% of the M component and the F component of the L-MF system thin film of the present invention. It is a graph which shows an example of the change of the saturation magnetization with respect to the total atomic% of the M component and F component of the L-MF system thin film of this invention. The sample No. 2 of the embodiment of the present invention shows a static magnetization curve and a substrate arrangement when no magnetic field is applied during film formation. The sample number 2 of the embodiment of the present invention is a static magnetization curve when a static magnetic field is applied in the direction parallel to the substrate rotation during film formation, and the arrangement of the substrate and magnet. The sample number 2 of the embodiment of the present invention is the substrate rotation during film formation, the static magnetization curve when a static magnetic field is applied in the orthogonal direction within the substrate surface, and the arrangement of the substrate and magnet. It is a frequency characteristic of the complex magnetic permeability of the sample number 5 of an Example of this invention. It is a TEM image showing the typical nano structure of the nano granular film of the present invention. FIG. 2 is a typical X-ray pole figure of the nanogranular film of the present invention. It is a static magnetization curve when the sample number 2 of an Example of this invention is vacuum-heat-treated at 140 degreeC in the static magnetic field of 2 kOe.

Claims (5)

Represented by the general formula _{L 100-ab M a F b} , L is Fe, 1 or more elements selected from Co and Ni - although Ni alone except - and, M is Li, Mg, Al, Ca Is one or more elements selected from Sr, Ba, Gd and Y, F is fluorine, and the composition ratios a and b are atomic ratios, a is 3% or more and less than 7%, and b is 6% And a composition in which the total atomic ratio of a + b is 10% or more and 24% or less, that is, L is 76% or more and 90% or less, and the metal comprising L and M and F The saturation magnetization is 3.5 kG or more and 21.5 kG or less, the anisotropic magnetic field is 300 Oe or more, and the high frequency magnetic resonance frequency is 7 GHz or more. Is a ferromagnetic thin film having in-plane uniaxial magnetic anisotropy characterized by a specific resistance of 1.0 × 10 ² μΩ · cm or more. Represented by the general formula _{L 100-ab M a F b} , L is Fe, and one or more ferromagnetic elements that will be selected from Co and Ni, alloys of one or more noble metal elements selected from Pd or Pt The Pd and Pt contents in the alloy are 50% or less in atomic ratio, and M is one or more elements selected from Li, Mg, Al, Ca, Sr, Ba, Gd and Y F is fluorine, and the composition ratios a and b are atomic ratios, a is 3% or more and less than 7%, b is 6% or more and less than 18%, and the total atomic ratio of a + b is 10% or more and 24% or less, that is, L has a composition of 76% or more and 90% or less, and has a structure in which the alloy of L and the fluoride of M and F are mixed, and the saturation magnetization is 3.5 kG or more 21.5 kG or less, anisotropic magnetic field is 300 Oe or more, ferromagnetic resonance frequency of high-frequency permeability is 7 GHz or more, and specific resistance is 1.0 × 10 ² μΩ · cm or more Toss Ferromagnetic thin film having a film plane uniaxial magnetic anisotropy. 3. The magnetic fine particle comprising L and having an average particle diameter of 1 to 20 nm has a nanogranular structure uniformly distributed in an insulator matrix made of the fluoride of M and F. 3. A ferromagnetic thin film having uniaxial magnetic anisotropy. The uniaxial magnetic anisotropy according to any one of claims 1 to 3, wherein the uniaxial magnetic anisotropy is used as an electromagnetic inductive electronic component incorporated in an electronic device such as an inductor, a coupler, a balun, or a noise filter used in a GHz band. A ferromagnetic thin film. A first cathode composed of L which is one or more elements selected from Fe, Ni and Co, and one or more elements selected from Li, Mg, Al, Ca, Sr, Ba, Gd and Y A second cathode made of fluoride of M and F is fixed in the sputtering apparatus, and power in the range of 10 to 1000 W is independently controlled and applied to the first cathode and the second cathode, and supported by the anode. The anode is rotated at a rotational speed of 1 to 200 rpm in the absence of a magnetic field so that the sputtered particles emitted from the first cathode and the second cathode are periodically passed through the substrate. A sputtering condition (A) for imparting in-plane uniaxial magnetic anisotropy to the LMF ferromagnetic thin film to be deposited and a sputtering condition (B) for applying a magnetic field in the easy magnetization direction of the LMF ferromagnetic thin film are simultaneously performed. It is difficult to magnetize the thin film The direction of the coercive force is less than 100 Oe, a manufacturing method of a ferromagnetic thin film having a uniaxial magnetic anisotropy of claim 3, characterized in that to reduce the anisotropy dispersion of the nano-granular structure I following.

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