JPH10241938A - High-frequency soft magnetic film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form two or more kinds of microstructures having different nano- scale compositions by adding Ni or Pt at the time of forming a film of an alloy composed of Co, an oxide, etc., by sputtering in an oxygen atmosphere or a nitrogen atmosphere. SOLUTION: In the composition expressed by a formula, Co100- X- Y- Z- WMXRYLZQW (atomic %), M, R, L, and Q respectively represent one or tow kinds of element selected out of Ni and Pt, one or two kinds of elements selected out of Fe and Ru, one or two or more kinds of elements selected from among Be, B, Mg, A, Si, Ca, Y, Dy, Gd, Hf, Ti, and Zr, and one or two kinds of elements selected out of N and Q and X, Y, Z, and W are respectively set at 10<X<50, 0<=Y<20, 10<Z<20, 10<W<30, and 30<X+Y+Z+W<70. Therefore, a high-frequency soft magnetic film composed of two or more kinds of microstructures and having an anisotropic magnetic field of >=100 Oe and an electric specific resistance of >=400μΩ.cm is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic film exhibiting excellent soft magnetism in a high frequency range and having a large electric resistivity, a large saturation magnetization and a large anisotropic magnetic field.

[0002]

2. Description of the Related Art In recent years, as electronic devices have become smaller, the operating frequency tends to increase. However, there is no known magnetic material used for a transformer, an inductor, a magnetic head, or the like that can sufficiently maintain characteristics up to a high frequency range, and the use of these components in a high frequency range is often limited. Generally, when the frequency is higher than 1 MHz, a large loss occurs due to eddy current flowing through the magnetic material itself. Since the magnetic resistance of the metal-based magnetic material is low, the eddy current increases, and it has been difficult to use the magnetic material in a high frequency range.
On the other hand, oxide-based magnetic materials such as ferrite and garnet have very high electrical resistance, so that little loss due to eddy currents occurs. However, it is difficult to obtain a material having a high magnetic permeability, and its saturation magnetization is small, so that its natural resonance frequency is low, and its use in a high frequency range is often limited.

There is great expectation for magnetic materials having high saturation magnetization and good high-frequency characteristics, and several methods have been proposed to increase the electrical resistance of metallic magnetic materials. For example, a method of obtaining an amorphous alloy film in which ceramics are dispersed by simultaneous sputtering of a metal and ceramics has been proposed in Japanese Patent Application Laid-Open No. 60-152651. Appl. Phys. 63
(8), Fe-BC-based dispersion film is disclosed in Appl. Phys. 67 (9), 1 May
In 1990, Co. 4Fe. 4B. 2-SiO ₂ dispersion film is shown as having both high electrical resistivity and the soft magnetic properties. In addition, Co., which does not show good soft magnetic characteristics with a thick single-layer film, is used. 95 Fe. Soft magnetic characteristics can be obtained by making the 05-BN-based dispersion film a magnetic layer of 0.1 μm or less, and soft magnetic characteristics can be obtained even with a thick film by laminating this thin film with a non-magnetic intermediate layer interposed therebetween. This is disclosed in
-142710 public information.

[0004]

The high frequency loss of the magnetic material is roughly classified into eddy current loss and natural resonance loss. Since the eddy current loss is caused by the induction of a current inside the magnetic material by excitation, the electric resistivity of the magnetic material may be increased,
This can be suppressed by reducing the thickness of the magnetic material so that current does not easily flow. The resonance loss is caused by the precession of electrons (spins) of a magnetic material resonating with an excitation magnetic field, and the resonance frequency is proportional to the saturation magnetic flux density and the anisotropic magnetic field. In an actual magnetic material, the magnitude and direction of the anisotropic magnetic field are distributed in a certain range. If this is widely distributed from a low value to a high value, a loss occurs from a low frequency region. This anisotropic distribution is called anisotropic dispersion,
It is known that high magnetostrictive materials and the like increase due to the distribution of residual stress during processing. From these facts, it is necessary to consider the following in order to design a magnetic material used in a high frequency range.

(1) A high saturation magnetic flux density. (2) The electrical resistivity is large. (3) Large magnetic anisotropy and small dispersion. (4) Magnetostriction is small.

In recent years, for the purpose of increasing the electric resistivity of a magnetic material, an amorphous dispersion film obtained by simultaneously sputtering metal and ceramic has been actively studied. Many Fe-based and CoFe-based alloys have been studied as alloys. When these films become amorphous, they have a large magnetostriction of 10 ⁻⁵ or more and a small anisotropic magnetic field, and thus cannot be said to be necessarily suitable as high-frequency soft magnetic materials. Co-based films have characteristics such as low magnetostriction and easy application of an anisotropic magnetic field, but have the problem that magnetic anisotropy perpendicular to the film surface is likely to occur. Was extremely small.

More recently, in a Co-based film, a Co-Al-O film containing N, which has a large heat of forming an oxide, has a thickness of 500 μΩc.
m or more, electric resistivity of 10 kG or more and 7
It has been found that the film is a soft magnetic film having an anisotropic magnetic field of 0 Oe.
d Compounds 222 (1995) 167-1
72. However, there are several points to be improved, such as the coercive force of the obtained film is slightly large and the dispersion of the anisotropic magnetic field is considerably large. It is also reported in Japanese Patent Application No. 5-224438 that adding Pd to a Co-based alloy thin film having a granular structure composed of two or more crystal phases increases Hk and improves soft magnetic properties. . That is, the obtained film is shown to have high electric resistance as well as soft magnetism, and that one of them has a large Hk of 200 Oe or more. But,
The additive element for obtaining such properties is limited to only Pd, and an economical viewpoint demands an inexpensive alloy thin film.

The present invention has been made in view of the above points, and has as its object to provide a magnetic thin film having excellent soft magnetic characteristics in a high frequency range and a large electric resistivity.

[0010]

The present inventors have made intensive efforts in view of the above circumstances, and as a result, have found that an alloy composed of an element having a large heat of formation of Co and an oxide or a nitride can be obtained in an oxygen and nitrogen atmosphere. When forming a film by sputtering,
When i or Pt is added, it has two or more types of microstructures having different nanoscale compositions and an anisotropic magnetic field of 1
The present inventors have found that a film having an electric resistivity of not less than 00 Oe and an electric resistivity of not less than 400 μΩcm and exhibiting excellent soft magnetic properties in a high frequency range can be obtained. The magnetic film of the present invention,
Excellent as a high frequency soft magnetic material, such as a large anisotropic magnetic field of 100 Oe or more can be obtained without addition of inexpensive elements such as Ni without impairing the high electric resistance and soft magnetism of the Co-Al-O film. Show characteristics.

The features of the present invention are as follows. The first invention has a general formula Co100-XYZW
In a composition represented by MXRYLZQW (atomic%),
M is one or two elements selected from Ni and Pt, R is one or two elements selected from Fe and Ru, and L is Be, B, Mg, Al, Si, Ca,
One or two or more elements selected from Y, Dy, Gd, Hf, Ti, and Zr, Q is one or two elements selected from N and O, and the atomic ratio thereof is 10 <X <500 < Y <2010 <Z <2010 <W <3030 <X + Y + Z + W <70, consisting of two or more types of microstructures, an anisotropic magnetic field of 100 Oe or more, and an electrical resistivity of A high-frequency soft magnetic film having a thickness of 400 μΩcm or more.

The second invention is based on the general formula Co100-XY
In the composition represented by -Z-WNiXRYLZQW (atomic%), R is one or two selected from Fe and Ru.
L is Be, B, Mg, Al, S
i is one or more elements selected from i, Ca, Y, Dy, Gd, Hf, Ti, and Zr, and Q is one or two elements selected from N and O. The atomic ratio is 10 <X <500 < Y <2010 <Z <2010 <W <3030 <X + Y + Z + W <70, is composed of two or more kinds of fine structures, and has an anisotropic magnetic field of 100 Oe or more. 2. The high frequency soft magnetic film according to claim 1, wherein the electrical resistivity is 400 [mu] [Omega] cm or more.

A third aspect of the present invention relates to the general formula Co100-XY
In the composition represented by -Z-WPtXRYLZQW (atomic%), R is one or two selected from Fe and Ru.
L is Be, B, Mg, Al, S
i is one or more elements selected from i, Ca, Y, Dy, Gd, Hf, Ti, and Zr, and Q is one or two elements selected from N and O. an atomic ratio of 5 <X <20 0 <Y <20 10 <Z <20 10 <W <30 30 <X + Y + Z + W <60, at 2 consists or more microstructures, and anisotropic magnetic field than 100 Oe, 2. The high-frequency soft magnetic film according to claim 1, wherein the electrical resistivity is 400 μΩcm or more.

According to a fourth aspect of the present invention, there is provided a high-frequency soft magnetic film according to any one of the first to third aspects, wherein Pd of less than 8%.
High frequency soft magnetic film characterized by containing

A fifth invention is a magnetic device using the high-frequency soft magnetic film according to any one of claims 1 to 4.

[0016]

In order for the magnetic film of the present invention to have both high electric resistance and soft magnetic characteristics, the film must be composed of two or more types of microstructures consisting of nano-sized magnetic fine particles and a grain boundary of a thin ceramic film surrounding it. It is necessary to have a structure. However, if the grain boundaries are too thick, the particles become isolated and become superparamagnetic, and as a result, the film becomes a non-magnetic film. On the other hand, if the grain boundaries are too thin, they will be ferromagnetic, but their electrical resistance will be small. In order to simultaneously exhibit high electric resistance and soft magnetic properties, it is necessary to use ceramic forming L
The concentrations of the element and the Q element are respectively 10 <Z <20, 10
<W <30 (atomic%).

Actually, it is assumed that the film thickness required when manufacturing a magnetic device is 1 to 2 μm, and the operating frequency is a high frequency band of 100 MHz or more. In this case, if the electric resistivity of the film is 400 μΩcm or less, the existence of eddy current loss in a high frequency band becomes so large that it cannot be ignored.

The film of the present invention is characterized by having an anisotropic magnetic field of 100 Oe or more in addition to high electric resistance and soft magnetic characteristics. This is realized when the structure of the film is fcc and the particle size is 50-70 °. Such a structure is N
If i does not contain 10% or more and Pt does not contain 5% or more, it cannot be obtained. However, in a film containing 40% or more of Pt, the Pt element concentration is preferably 40% or less because not only the saturation magnetic flux density is remarkably reduced but also Hk is reduced. In the case of a film containing Ni, which is a magnetic element, relatively large magnetization can be obtained up to 50%, but if it exceeds 50%, the magnetization becomes considerably small. Similar effects can be obtained by replacing Ni or Pt with another element that promotes fcc conversion. In particular, Fe and Ru have a concentration of 20.
%, Bs without deteriorating other characteristics.
And further excellent soft magnetism is shown.

[0019]

Embodiments of the present invention will be described below with reference to comparison with a conventional nano-granular structure film.

The present invention will be described in more detail with reference to specific examples.

To prepare a Co-Ni-Al-O thin film Example -1] RF magnetron sputtering apparatus using a (Co.7Ni.3) 85Al15 (atomic%) reaction sputtering of a target in Ar + _{O 2} mixed gas atmosphere . The film forming conditions were set as follows.

Sputtering pressure 5 × 10 ⁻³ Torr Input power 200 W Substrate temperature 20 ° C. Substrate Corning # 7059 (thickness 0.5 mm) Film thickness 2.0-3.0 μm Oxygen flow rate 0.0-2.0% Applied magnetic field 130 Oe (A pair of permanent magnets)

The tissue of the obtained sample was identified by an X-ray diffractometer. The results are shown in FIG. A sharp peak which is considered to correspond to (111) of the fcc structure is observed in the film formed only with Ar. When oxygen is introduced into the sputtering gas, the peak becomes extremely broad, indicating that the crystal grains constituting the film are extremely small. The soft magnetism obtained from the half width of this peak by using Scherrer's equation is 25 to 30 at. The% O film has a particle size of about 40 °. As a result of observing the film with an electron microscope, it was confirmed that the film had a network-like structure composed of clusters having an average particle size of about 40 ° and grain boundaries having a thickness of about 10 ° or less, that is, a granular structure.

Next, the DC magnetic properties of the obtained film were measured by a sample vibration magnetometer. The results are shown in FIG. The two data in the figure represent the results obtained by exciting (parallel (‖)) and perpendicular (⊥) the excitation direction of the magnetic field during film formation. The sample has a uniaxial magnetic anisotropy parallel to the direction of the magnetic field applied at the time of film formation.
It was very large at 40 Oe. Further, as is apparent from the results of the vertical hysteresis curve (BH hysteresis loop), it is inferred that the straightness of the loop is good and the anisotropic dispersion of the film is not so large. The coercive force (Hc) of this film is small both vertically and in parallel, indicating that the obtained film is a soft magnetic film. The saturation magnetic flux density (Bs) was also 9.2 kG, which was sufficiently large. The electrical resistivity (ρ) of this film measured by the DC four-terminal method showed a large value of 553 μΩcm.

[0024]

[Embodiment 2] Under the same conditions as in Embodiment 1, Co-
A Ni-Al-O film was produced. FIG. 3 shows the results of Hk and Hc obtained from the DC magnetic characteristics. Hk increases with an increase in Ni, and 50 at. Hk = 160Oe in% Ni
Is realized. On the other hand, Hc hardly changes even if the amount of Ni changes. In addition, the magnitude of ρ does not change with respect to the amount of Ni. As described above, since the film of the present invention has a large Bs and Hk and also has a large ρ, it can be inferred that the film exhibits good frequency characteristics of magnetic permeability.

Next, the saturation magnetostriction constants of these films were measured under a magnetic field of 100 Oe by an optical lever type saturation magnetostriction measuring device. Since it was very difficult to actually measure the Young's modulus of the film, its value was 9 × 10
^The calculation was performed by adopting ³ kg / mm ² . As a result, it was confirmed that the saturation magnetostriction of each film was within −2 × 10 ⁻⁶ and was sufficiently small.

[0026]

Example 3 On a Co85Al15 (atomic%) disk,
5 composite target × 5 mm Pt plate coverage is established to be about 14%, to prepare a Co-Al-Pt-O film by RF sputtering in (Ar + _{O 2).} Other film forming conditions were the same as in Example 1. X-ray diffraction confirmed that the obtained sample contained a very fine fccCo phase oriented to the (111) plane. FIG. 3 shows the DC magnetic characteristics. The sample had uniaxial magnetic anisotropy parallel to the direction of the magnetic field applied during film formation, and the anisotropic magnetic field was as large as about 270 Oe. Further, it can be seen that the anisotropic dispersion is not so large because the straightness of the BH loop is good. In particular, the coercive force (Hc) of this film is such that Hc in the vertical direction is 0.3 O
e, the saturation magnetic flux density (Bs) was 8.5 kG, which was sufficiently large, and ρ was also a large value, 436 μΩcm.

In order to clarify film forming conditions for obtaining such a film having a large Hk, detailed film forming conditions were examined. FIG. 5 shows the relationship between the sputtering gas pressure, the oxygen flow rate ratio, and Hk, which are the most influential deposition conditions. The conditions for forming a film exhibiting a large Hk are 5 mTorr, 1.2% O
₂ and its value is Hk> 250 Oe. This value could be found on the lower oxygen flow rate side as the gas pressure was higher, and on the higher oxygen concentration side when the gas pressure was low.

In order to clarify the effect of replacing Ni and Pt, a Co—Al— (Ni or Ft) —O film was prepared using a target in which the amounts of Ni and Pt were systematically changed. Co-Al- (Pd or Pt) -O film is Co8
A composite target in which a 5 × 5 mm Pt plate or a Pd plate was placed on a 5Al15 (atomic%) disk was produced by high-frequency sputtering in (Ar + O ₂ ). The Co-Al-Ni-O film is (Co-Ni) 85Al15
The alloy target was produced by high frequency sputtering in (Ar + O ₂ ). Other film forming conditions are the same as those in Example-1. By X-ray diffraction, each of the obtained samples had a very fine fcc-
It was confirmed that the particles consisted of Co phase particles. FIG.
Is a result of arranging Hk obtained from the DC magnetic characteristics of the obtained film by Ni and pt concentrations. Co as a comparative example
The results for the -Pd-Al-O film are also shown in the figure. Hk tends to increase monotonically with an increase in the concentration of Ni-base atoms such as Ni and Pt, and then show a broad maximum at a certain concentration and then decrease. The increasing tendency is greatest for Pt, and decreases in the order of Pd and Ni.

The structure of the film obtained for the purpose of clarifying the cause of the large Hk was examined by an X-ray diffraction method (FIG. 7).
Basic Co-Al-O film and CoPd as a comparative example
The measurement results of -Al-O are also shown. In the Co-Al-O film, a broad peak in which fcc-Co and hcp-Co were mixed was observed around 2θ = 45 °, and the film was found to have fcc-Co.
This suggests that the particles consist of fine particles mainly composed of Co and hcp-Co. As the Ni substitution amount increases, the peak of the fcc phase starts to become remarkable, and most of the 50% Ni film becomes the fcc phase. The structure of the film containing Pt and Pd is also f
It shows that it is a cc phase. Also, C with large Hk
In o-Pt-Al-O and Co-Pd-Al-O, Co
As apparent from comparison with -Al-O, the half width of the peak is narrow, that is, the particle size is large (50 to 70 °). From this, the high electric resistance soft magnetic film showing large Hk is
This is achieved by adding i or Pt. One of the factors is that the particle size of the crystal grains constituting the film is 50 to 70.
And that the structure is fcc.

[0030]

[Table 1]

Table 1 shows the measurement results of typical examples of the thin film according to the present invention, which were produced by a method substantially similar to that described above.
It is arranged by s, ρ, Hk, Hc. As a comparative example, a result of a film containing no Ni element is shown. Hk of the film containing no Ni group element is at most 80 Oe, whereas Hk of the film containing the Ni group element shows a large value of 100 Oe or more. As described above, it has been confirmed that the addition of the Ni group element is very effective in promoting soft magnetism and increasing the anisotropic magnetic field.

FIG. 8 shows the results obtained by rearranging the high electric resistance soft magnetic films having a large anisotropic magnetic field obtained by the present invention including the films shown in Table 1 by anisotropic magnetic field and electric resistivity. Shown in As a comparative example, Co-Fe-Al-O is a typical example of a Co-based amorphous soft magnetic film and a Co-O-based high electric resistance soft magnetic film.
The results of the Fe— (Hf, Y, Dy) —O film are also shown as typical examples of the film and the Fe—O high electric resistance soft magnetic film. As is clear from the figure, the Co-based amorphous soft magnetic film
It shows an anisotropic magnetic field around 0 Oe and an electrical resistivity of about 120 μΩcm. On the other hand, the Fe—O high electric resistance soft magnetic film shows a large electric resistivity, but has a small anisotropic magnetic field. Further, even in a conventional high-frequency soft magnetic film, the magnitude of the anisotropic magnetic field is at most 80 even in a Co—O-based high electric resistance soft magnetic film exhibiting the best characteristics.
Oe. In contrast, the films of the present invention were all 400
The film has both a high electrical resistivity of μΩcm or more and a large anisotropic magnetic field of 100 Oe or more, suggesting that the film of the present invention exhibits extremely excellent high-frequency soft magnetic characteristics.

As described above, the natural resonance frequency (fr) that causes the deterioration of the magnetic permeability in the high frequency band is HK and Bs
Is proportional to the product of FIG. 9 shows the relationship between Hk, Bs, and the resonance frequency of the film of the present invention. As comparative examples, results of a conventional Co-based amorphous film and a Co—O-based soft magnetic film having a granular structure are also shown. The fr of a Co-based amorphous film well known as an excellent high-frequency soft magnetic material is 1.2
It exists near GHz. On the other hand, that of the Co—O-based granular soft magnetic film not substituted with the Ni group element is 2.0%.
It exists at ~ 3.0 GHz. On the other hand, the fr of the film of the present invention is higher than that, especially, Co-Al
The -Pt-O film includes a film whose fr exceeds 4 GHz.

[0034]

As described above, according to the present invention, a soft magnetic thin film material having good uniaxial magnetic anisotropy, high electric resistance, small saturation magnetostriction constant, and excellent high frequency characteristics is provided. I can do it. By subjecting the thin film of the present invention to heat treatment in a magnetic field, its anisotropic magnetic field can be controlled widely from 100 Oe or more to almost 0 Oe. Furthermore, since the saturation magnetostriction constant is as small as 10 ⁻⁶ or less, a small element can be manufactured without giving much consideration to the influence of processing strain and the like. Further, the magnitude of the anisotropic magnetic field of the thin film of the present invention can be controlled by heat treatment in a magnetic field, which has been widely performed in the past, and also by controlling the size of the permanent magnet near the substrate during sputtering. You can control. Therefore, in the magnetic thin film of the present invention, when used in a high frequency range, an anisotropic magnetic field having a necessary magnitude can be obtained with little dispersion. Further, since there is no need to form a multilayer film, no special process or device is required, and therefore, its industrial significance is great.

[Brief description of the drawings]

FIG. 1 shows Co—Ni—Al— fabricated by changing the oxygen concentration.
X-ray diffraction pattern of O film.

FIG. 2 shows a Co-Ni-A having a granular structure manufactured using a target in which 30% of co is replaced with Ni.
B-H hysteresis loop of the l-O film.

FIG. 3 shows the relationship between the Ni concentration of the Co—Ni—Al—O film, the anisotropic magnetic field, and the magnitude of the coercive force.

FIG. 4 is a BH hysteresis loop of a Co—Pt—Al—O film having a granular structure manufactured by a composite target method.

FIG. 5 is a characteristic diagram showing a relationship between the magnitude of Hk of the Co—Pt—Al—O film and film forming conditions (sputter gas pressure and oxygen gas flow ratio).

FIG. 6 shows a Co-TM-Al-O film (TM: Ni, Pt,
FIG. 4 is a characteristic diagram showing the relationship between TM concentration and Hk in Pd).

FIG. 7: Co—Al—O, Co—Ni—Al—O, Co
-X-ray diffraction pattern of -Pt-Al-O, Co-Pd-Al-O film.

FIG. 8 is a characteristic diagram showing a relationship between an anisotropic magnetic field and electric resistivity of the film of the present invention and a comparative example.

FIG. 9 is a characteristic diagram showing a relationship between a natural resonance frequency, Hk, and Bs of a typical film of the present invention and a comparative example.

Claims (5)

[Claims] 1. A compound of the general formula Co100-XYZ-WMXR
In the composition represented by YUQW (atomic%), M is N
one or two elements selected from i and Pt;
R is one or two elements selected from Fe and Ru, and L is Be, B, Mg, Al, Si, Ca, Y, D
one or two or more elements selected from y, Gd, Hf, Ti, and Zr, and Q is one or two elements selected from N and O, and the atomic ratio thereof is 10 <X <50 0 < Y <20 10 <Z <20 10 <W <30 30 <X + Y + Z + W <70, consisting of two or more kinds of microstructures, an anisotropic magnetic field of 100 Oe or more, and an electric resistivity of 400 μΩcm or more A high frequency soft magnetic film characterized by the following. 2. A compound of the general formula Co100-XYZ-WNiX
In the composition represented by RYLZQW (atomic%), R is one or more elements selected from Fc and Ru, and L is Be, B, Mg, Al, Si, Ca, Y, D
one or two or more elements selected from y, Gd, Hf, Ti, and Zr, and Q is one or two elements selected from N and O, and the atomic ratio thereof is 10 <X <50 0 < Y <20 10 <Z <20 10 <W <30 30 <X + Y + Z + W <70, consisting of two or more kinds of microstructures, an anisotropic magnetic field of 100 Oe or more, and an electric resistivity of 400 μΩcm or more The high-frequency soft magnetic film according to claim 1, wherein 3. The general formula Co100-XYZ-WPtX
In the composition represented by RYLZQW (atomic%), R is one or more elements selected from Fe and Ru, and L is Be, B, Mg, Al, Si, Ca, Y, D
y is one or more elements selected from Gd, Hf, Ti, and Zr, and Q is one or two elements selected from N and O, and the atomic ratio is 5 <X <20 0 < Y <20 10 <Z <20 10 <W <30 30 <X + Y + Z + W <60, consisting of two or more kinds of microstructures, an anisotropic magnetic field of 100 Oe or more, and an electric resistivity of 400 μΩcm or more The high-frequency soft magnetic film according to claim 1, wherein 4. The high-frequency soft magnetic film according to claim 1, wherein the high-frequency soft magnetic film contains less than 8% of Pd. 5. A magnetic device using the high-frequency soft magnetic film according to claim 1.