JPH09266114A - Ferrite thin film method for manufacturing the same and thin film inductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high resistance ferrite thin film which exhibits excellent soft magnetic properties in high frequency region of giga hertz band by increasing oxidation degree of a ferrite thin film having a magnetoplambite crystal structure. SOLUTION: A substrate holder 4 holding a substrate 3 heated to a predetermined temperature is rotated in the upper part of a plasma discharge area 10 in which a reaction gas containing oxygen is made plasma discharge in a reduced pressure reaction chamber 1. A source gas is selectively supplied to a part of the area above the rotating substrate holder 4 from a source gas supplying means 8 whose supplying outlet is placed near the substrate holder 4. Ferrite thin film forming process and ferrite thin film oxidizing process are alternately repeated to make a ferrite thin film having magnetoplambite crystal structure grow.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferrite thin film used in a high frequency region of the gigahertz band, a manufacturing method thereof, and a thin film inductor element.

[0002]

2. Description of the Related Art Among soft magnetic materials, a ferrite material, which is an oxide of iron, has a higher resistance than a metal-based soft magnetic material, so that it has excellent soft magnetic characteristics in a high frequency region and a small magnetic loss. Therefore, ferrite materials are used as magnetic core materials for transformers and inductors.
Further, since the ferrite material has good wear resistance, it is also used as a head material for magnetic recording.

In recent years, with the trend toward smaller and lighter electronic devices, thin film transformers and thin film inductors having excellent characteristics in a high frequency region have been demanded. For example, a monolithic microwave integrated circuit (MMIC), which is in high demand mainly in the field of mobile communication, is used in a high frequency region of several hundred MHz or more, and therefore, as a magnetic core material of a thin film inductor integrated therein. It is required to have good magnetic properties in the gigahertz band. Further, as the soft magnetic material used in the high frequency region, a material having a large specific resistance is desired in order to reduce the eddy current loss. Since a soft magnetic ferrite material such as a Ni—Zn soft magnetic ferrite having a spinel type crystal structure has a large specific resistance as compared with a metal material, it is a promising material as a soft magnetic material used in a high frequency region. For this reason, in recent years, research on thinning of such soft magnetic ferrite materials has been actively carried out in various film forming methods such as vacuum vapor deposition, MOCVD, and plating (Nobuyuki Hiratsuka et al., Powder and powder metallurgy). 39 (1992) 152, Hideaki Ito and others,
Ceramic Industry Association Magazine 95 (1987) 60, Masanori Abe et al .: Metal Surface Technology 38 (1987) 416, etc.).

By the way, in general, when the frequency is increased in a soft magnetic material, natural resonance occurs at a certain frequency, and the magnetic permeability thereof is lowered to make it unusable. In this case, there is a Snoke limit line in which a material having a higher magnetic permeability causes natural resonance at a lower frequency, and a material having a lower magnetic permeability causes natural resonance at a higher frequency. Even in bulk Ni—Zn-based ferrites having a large specific resistance, most of them have low magnetic permeability at 100 MHz or less, and it is difficult to use them in the frequency region of several hundred MHz or more. Therefore, as a soft magnetic material suitable for a magnetic core material such as a thin film inductor or a thin film transformer used in a high frequency region of several hundred MHz or more, a soft magnetic material that exceeds the limit line of Snook is required. Soft magnetic ferrite material (iron oxide material) that exceeds the limit line of this snook
As such, there is an oxide having a magnetoplumbite type crystal structure called a ferox planer (hereinafter, also simply referred to as a magnetoplumbite type oxide).

[0005]

The magnetoplumbite type oxide is a Fe ³⁺ ion and a divalent metal ion M ^2+.
In addition to (M = Mn, Fe, Co, Ni, Cu, Zn, Mg), it is a ferrite containing ions having the same ionic radius as O ²⁻ such as Ba ²⁺ and Sr ²⁺ , and M ²⁺ And Fe ³⁺
A layer having a spinel structure consisting of and Ba ²⁺ or Sr ²⁺
It has a structure in which layers composed of and O ²⁻ are alternately combined, and belongs to the hexagonal system as a whole, and its (001)
It has strong uniaxial magnetic anisotropy in the direction. In this magnetoplumbite type oxide, the uniaxial anisotropy constant (Ku) is negative and the saturation magnetization (Ms) is stable in the c-plane. Since the magnetic anisotropy in the c-plane is relatively small and the saturation magnetization (Ms) can rotate freely in the c-plane, the magnetic permeability is relatively high. Then, during precession, when it deviates from the c-plane, a very strong anisotropy acts, so that the frequency at which natural resonance occurs also increases, and the snook limit line can be exceeded. However, it is difficult to increase the resistivity of this magnetoplumbite type oxide sufficiently, and the eddy current loss becomes large in the high frequency region, so it has not yet been put to practical use (Satoshi Chikano: Strong). Physics of magnetic materials (bottom), p326).

The present invention has been made in view of the above problems, and an object of the present invention is to provide a high resistance ferrite thin film exhibiting excellent soft magnetic characteristics in a high frequency region of the gigahertz band and a method of manufacturing the same. .

Another object of the present invention is to provide a thin film inductor element which exhibits excellent inductor characteristics in the high frequency region of the gigahertz band.

[0008]

In order to achieve the above object, the ferrite thin film of the present invention is a ferrite thin film having a magnetoplumbite type crystal structure and is substantially free of Fe ^2+. To do. By adopting such a structure, Fe ²⁺ and Fe ^{3+ in} the crystal, which have occurred in the conventional ferrite having the magnetoplumbite crystal structure,
There is no decrease in the specific resistance due to hopping conduction between the thin film and the thin film, and the thin film has a specific resistance of 1 × 10 ⁴ Ω · cm or more. Therefore, the eddy current loss does not increase even in the high frequency region of the gigahertz band, and excellent soft magnetic characteristics can be obtained.

Further, according to the method for producing a ferrite thin film of the present invention, a substrate held by a substrate holder and heated to a predetermined temperature in a plasma discharge region in which a reaction gas containing oxygen in a reduced pressure reaction chamber is plasma discharged. The substrate holder is rotated to rotate, and a ferrite source gas is supplied into the reduced pressure reaction chamber,
In a method for manufacturing a ferrite thin film, in which a ferrite thin film having a magnetoplumbite type crystal structure is grown on a rotating substrate, the raw material gas is selectively supplied to a partial region on the rotating substrate holder. ,
It is characterized in that the ferrite thin film having the magnetoplumbite crystal structure is grown while the formation of the ferrite thin film and the oxidation of the ferrite thin film are alternately repeated on the substrate. With such a structure, it is possible to grow a ferrite thin film having a magnetoplumbite-type crystal structure that has an extremely large degree of oxidation and that does not substantially contain Fe ²⁺ , and is 1 × 10 ⁴ Ω · cm.
It is possible to manufacture a ferrite thin film having a magnetoplumbite type crystal structure having the above specific resistance.

In the method for producing a ferrite thin film of the present invention, the raw material gas for ferrite is drawn from the outside of the reduced pressure reaction chamber into the reduced pressure reaction chamber, and its supply port is provided near the substrate holder. It is preferably supplied by means. With this configuration, the source gas can be reliably and selectively supplied to a partial region on the substrate holder, and the film growth process by alternately repeating the formation of the ferrite thin film and the oxidation of the ferrite thin film can be performed. It is stable.

The thin film inductor element of the present invention is a thin film inductor element using a ferrite thin film having a magnetoplumbite type crystal structure as a magnetic core material.
The ferrite thin film having the magnetoplumbite crystal structure has a specific resistance of 1 × 10 ⁴ Ω · cm or more. With such a configuration, the eddy current loss in the high frequency region of the gigahertz band of the ferrite thin film which is the magnetic core material is small, so that the inductor element exhibits excellent inductor characteristics.

In the thin film inductor element of the present invention, the first wiring layer is formed on one main surface of the ferrite thin film having the magnetoplumbite crystal structure, and the second layer including the spiral inductor is formed on the other main surface. A wiring layer is formed, and the first wiring layer and the spiral inductor are electrically connected to each other by a contact hole formed in the ferrite thin film having the magnetoplumbite crystal structure and a metal embedded therein. Is preferred. With such a configuration, it is not necessary to form an insulating layer between the ferrite thin film and the first wiring layer and between the ferrite thin film and the second wiring layer, and unnecessary stray capacitance does not occur. .

[0013]

1 is a sectional view showing a specific example of a manufacturing apparatus used for manufacturing a ferrite thin film having a magnetoplumbite type crystal structure according to the present invention. Less than,
The configuration of the present apparatus will be described. Both ends of the reaction chamber 1 made of a quartz tube having an inner diameter of 200 mm are supported and fixed by flanges 24 made of stainless steel. Substrate holder 4 (disk with a diameter of 150 mm) in the reaction chamber 1
Are provided rotatably. Here, the substrate holder 4 is rotated by the rotating mechanism 7. The substrate holder 4 has a built-in substrate heater 2 and is configured to hold the substrate 3 on its surface. The substrate holder 4 is grounded via the rotating mechanism 7. A high frequency coil 5 for generating plasma is provided around the reaction chamber 1, and the stainless steel flange 24 has the reaction chamber 1
Exhaust means 6 is provided to bring the inside into a low pressure state.
Plasma discharge region 10 formed by high frequency coil 5
A raw material gas supply nozzle 8 and a reaction gas supply nozzle 9 are provided therein. The reaction gas supply nozzle 9 is connected to the oxygen cylinder 21 via the valve 17. The raw material gas supply nozzle 8 includes a valve 25 and valves 13 and 14
It is connected to the vaporizers 11 and 12 via. Further, a nitrogen gas cylinder 20 is connected via the vaporizers 11 and 12. Starting materials 18 and 19 are contained in the vaporizers 11 and 12, and the material gas supply nozzle 8 and the reaction gas supply nozzle 9 are connected via a valve 26.

Next, a process of manufacturing a ferrite thin film having a magnetoplumbite type crystal structure using this apparatus will be described. First, the inside of the reaction chamber 1 is evacuated by the evacuation means 6, and the inside of the reaction chamber 1 is depressurized. The pressure here is generally 1 × 10 ⁻³ Torr or less, preferably 1 × 10 ⁻⁵ Torr or less. Next, the substrate 3 is heated by the substrate heating heater 2, and while the substrate holder 4 is rotated, oxygen, which is a reaction gas for generating plasma, is supplied from the reaction gas supply nozzle 9 into the reaction chamber 1, and the high frequency coil is supplied. High frequency to 5 (13.56 MH
z) A plasma discharge is generated by supplying electric power. Here, as the material of the substrate 3, for example, quartz, silicon, sapphire or the like is used. The temperature of the substrate varies depending on the material of the substrate used, but is generally 400 to 800 ° C.
It is preferably 450 to 600 ° C. Then, by supplying the raw material gas for forming the ferrite thin film from the raw material gas supply nozzle 8, the formation of the ferrite thin film and the oxidation of the ferrite thin film are alternately repeated on the rotating substrate 3, and the magnetoplumbite crystal structure is formed. Grows a ferrite thin film. The thickness of the growing ferrite thin film having a magnetoplumbite type crystal structure is generally 1 to 2.
The thickness is 0 μm, preferably 5 to 10 μm.

Next, the principle of obtaining a high-resistance ferrite thin film with little eddy current loss in the high frequency region by producing a ferrite thin film using the production apparatus of FIG. 1 will be described. FIG. 2 is a perspective view (however, the substrate 3 is omitted) showing the substrate holder 4 and its peripheral region in the manufacturing apparatus of FIG. The substrate holder 4 is located in the plasma discharge region 10 generated by oxygen as the reaction gas supplied from the reaction gas supply nozzle 9. From the source gas supply nozzle 8, a mixed vapor 50 of a vapor of a compound containing iron and a vapor of a compound containing barium, a compound containing strontium or a compound containing lead is supplied.
On the substrate holder 4, a film of magnetoplumbite type crystal structure ferrite is formed on the upper surface of the substrate 3 in contact with the mixed vapor, and in a region 23 not in contact with the mixed vapor, the film is oxidized. The substrate holder 4 is rotating in the direction of the arrow in the figure, and the film formation in the region 22 and the film oxidation in the region 23 are repeatedly performed, and the barium ferrite thin film (Ba) of the magnetoplumbite type crystal structure having a high degree of oxidation (Ba) is formed. A ferrite thin film), a strontium ferrite thin film (St ferrite thin film) or a lead ferrite thin film (Pb ferrite thin film) is formed. The substrate 3 held on the upper surface of the substrate holder 4
Alternatively, a single substrate or a plurality of substrates having an area smaller than the surface area of the substrate holder 4 may be held on the surface of the substrate holder 4. In short, the region where the source gas is supplied and the region where the source gas is not present are present on the substrate holder 4 at the same time, and the rotation of the substrate holder 4 causes the film forming process and the film to be formed on any region of the main surface of the substrate 3. Allow the oxidation process to alternate. Generally, electric conduction in a ferrite thin film having a magnetoplumbite type crystal structure is due to hopping conduction due to the presence of Fe ²⁺ and Fe ^{3+ in the} thin film. Since the ferrite thin film of the magnetoplumbite type crystal structure having a high degree of oxidation is sufficiently oxidized, Fe
²⁺ does not substantially exist (even if it exists, the ratio of the number of Fe ^{2+ to} the number of Fe ³⁺ per unit volume ((the number of Fe ²⁺ / the number of Fe ³⁺ ) × 100) is 1 % Or less.). Therefore, the ferrite thin film having the magnetoplumbite crystal structure has a larger specific resistance than the conventional one, and is generally 1 × 10 ⁴ Ω · cm or more, preferably 1 × 10 ⁴ Ω · cm or more.
X10 ⁶ Ω · cm or more, and the eddy current loss in the high frequency region is small.

FIGS. 3 and 4 are a sectional view and a top view showing one of the specific examples of the thin film inductor element using the Ba ferrite thin film of the magnetoplumbite type crystal structure manufactured as described above. The configuration of the thin film inductor element will be described below. On the upper surface of the semi-insulating GaAs substrate 101, the first
Si ₃ N ₄ insulating film 102 is formed. First Si
₃ N ₄ first layer wiring metal 104 made of Ti / Au in a predetermined area of the upper surface of the insulating film 102 is formed, a high resistance to the entire upper surface including a first layer wiring metal 104 the Si ₃ N ₄ insulating layer 102 ( For example, a Ba ferrite thin film 103 of magnetoplumbite type crystal structure having a specific resistance of 8 × 10 ⁵ Ω · cm is formed. A contact hole 107 for connecting the first layer wiring metal 104 and the second layer wiring metal 105 is formed in the Ba ferrite thin film 103, and Ti / Au is embedded in the contact hole 107. B
On the upper surface of the ferrite thin film 103, the first layer wiring metal 1
04 in the contact hole 107 connected to Ti / A
Second wiring metal 10 made of Ti / Au starting from u
5 is formed in a spiral shape (see FIG. 4). A high-resistance Ba ferrite thin film 106 is formed over the entire upper surface of the Ba ferrite thin film 103 so as to cover the second wiring metal 105. In the thin film inductor element having such a configuration, since the Ba ferrite thin film 103 having a high resistance magnetoplumbite crystal structure is used as the magnetic core material of the thin film inductor, the eddy current loss in the high frequency region is small and in the GHz band. Also shows good inductor characteristics. In addition, a magnetic core material (Ba ferrite thin film 103),
There is no need to form an insulating layer between the wiring metals 104 and 105, and unnecessary stray capacitance does not occur.

[0017]

【Example】

(Example 1) In this example, a magneto-plumbite type Ba ferrite thin film was manufactured using the manufacturing apparatus shown in FIG. Hereinafter, this will be described in detail.

Barium dipivaloyl methane (Ba (DPM) ₂ , DPM = C ₁₁ H ₁₉ O as starting materials 18 and 19)
₂ ), iron acetylacetonate (Fe (acac) ₃ ,
acac = C ₅ H ₇ O ₂ ) was used. Further, as the base substrate 3, two types of 3-inch size Si substrates (one having a SiO ₂ film formed on the surface, the other having a Ti film (200 nm) formed on the surface by a sputtering method, and further having a Pt film formed thereon (Having a thickness of 200 nm) was used. Vaporizer 1
Barium dipivaloyl methane and iron acetylacetonate were put in Nos. 1 and 12, and they were heated and maintained at 230 ° C. and 140 ° C., respectively. Then, the inside of the reaction chamber 1 is exhausted by the exhaust means 6.
The reaction chamber 1 is evacuated by means of a vacuum (0.
It was maintained at 1 Torr). Open the valve 17, introduce oxygen as a reaction gas from the oxygen cylinder 21 into the reaction chamber 1 at a flow rate of 50 sccm, and put 13.56 in the high-frequency coil 5.
400 W of rf power of MHz was supplied to generate plasma (region 10). Next, the base substrate heater 3 heats the base substrate 3 to 490 ° C.
It was spun at 50 rpm. Then the valves 15, 16,
13, 14, 25 are opened, and the vapor of barium dipivaloyl methane and the vapor of iron acetylacetonate are used as the carrier gas nitrogen (from the nitrogen gas cylinder 20 to the vaporizer 11 15
It was introduced at a flow rate of sccm and introduced from the nitrogen gas cylinder 20 to the vaporizer 12 side at a flow rate of 10 sccm) and was introduced into the reaction chamber 1. Then, as a result of reacting for 120 minutes, the underlying substrate 3 (SiO ₂ film / Si substrate, Pt film / T
A Ba ferrite thin film is formed on the (i film / Si substrate), and S
a sample film 1 (a) formed on an iO ₂ film / Si substrate,
Sample film 1 formed on Pt film / Ti film / Si substrate
(B) was obtained.

Next, for comparison, a conventional (Masaki Aoki
et al., United States Patent, Patent Number: 4,71
To prepare a Ba ferrite thin film over the base substrate 3 by the same method as the deposition method described in 7,584), SiO ₂
A sample film 2 (a) formed on the film / Si substrate and a sample film 2 (b) formed on the Pt film / Ti film / Si substrate were obtained. That is, in the manufacturing apparatus of FIG.
5 is closed and the valve 26 is opened so that the supply of the raw material gas is introduced not through the raw material gas nozzle 8 but through the reaction gas nozzle 9 into the reaction chamber 1 together with oxygen as the reaction gas, and barium dipivaloyl methane and iron. The vaporization temperature of acetylacetonate is 245 ° C and 160
℃, carrier gas (nitrogen) flow rate 40sccm and 28
sccm, oxygen flow rate 100 sccm, rf power 40
The film formation time was 0 W and the film formation time was 120 minutes. The substrate was fixed without rotating and the substrate temperature was set to 490 ° C.

The sample film 1 (a) thus obtained
With respect to (b) and sample films 2 (a) and (b), analysis by X-ray diffraction was performed to examine the crystal structure and orientation. As a result, it was found that all the films had a magnetoplumbite type crystal structure and showed high orientation in the (001) plane. From the scanning electron microscope (SEM) observation, the film thickness is 1
(a) was 8.3 μm and sample film 2 (a) was 7.5 μm. Also, the film composition was examined by chemical analysis. As a result, both of the sample films 1 and 2 were BaFe ₁₂ O ₁₉ . Next, a Pt electrode was formed on the surfaces of the sample films 1 (b) and 2 (b) by a sputtering method, and the electric resistance of the film at 1 kHz was measured. As a result, the specific resistance of the sample film 2 (b) was 3 × 10 ² Ω · cm, while the specific resistance of the sample film 1 (b) was 6 × 10 ⁶ Ω · cm. Therefore, when the Fe state of the sample film 1 (b) was examined by the Mossbauer effect, the ratio of the number of Fe ^{2+ to} the number of Fe ³⁺ per unit volume was 1% or less, and substantially all Fe was It was in the state of Fe ³⁺ .

Next, the magnetic properties (Q value) of the sample films 1 (a) and 2 (a) in the high frequency region were examined. The Q value is the ratio of the amount of magnetic field transmitted by the soft magnetic material to the amount of magnetic field absorbed by the soft magnetic material when the soft magnetic material is used in a high frequency region (the amount of magnetic field transmitted by the soft magnetic material / The amount of magnetic field absorbed). As a result, the sample film 1 (a) was 0.1 G
The Q value did not change from 18 Hz to 5 GHz from 18 GHz, but the sample film 1 (b) showed a large decrease in Q value of 14 to 1.8 with respect to the change from 0.1 GHz to 5 GHz. This example (comparative example) described above in the first and second rows of Table 1
Of the thin film, the composition of the thin film, the thickness of the thin film, the specific resistance of the thin film, and the Q value of the thin film.

As described above, according to the method of this embodiment, it is possible to easily increase the resistance of the Ba ferrite thin film, which was difficult with the conventional manufacturing method, and to obtain a high Q value even in the GHz band.
It was confirmed that a Ba ferrite thin film having a value was obtained.

(Example 2) In this example, a magneto-plumbite type crystal structure Sr ferrite thin film was manufactured using the manufacturing apparatus shown in FIG. Hereinafter, this will be described in detail.

Some of the manufacturing conditions in Example 1 were changed.
Further, a ferrite thin film was formed on the substrate 3. sand
That is, strontium dipivaloyl methane as a starting material.
(Sr (DPM)_Two) And iron acetylacetonate
The vaporization temperature to 220 ℃ and 140 ℃ respectively.
Agas (nitrogen) flow rate to 20sccm, 12sccm,
The oxygen flow rate of the reaction gas is 50 sccm and the rf power is 3
50W, vacuum degree 0.5 Torr, substrate 3 type
Silicon single crystal (111), substrate temperature 550 ℃,
Substrate 3 is changed by changing the substrate rotation speed to 1000 rotations.
(SiO_TwoFilm / Si substrate, Pt film / Ti film / Si substrate)
Sr ferrite thin film is prepared on the _TwoMembrane / Si
Sample film 3 (a) formed on the substrate and Pt film / Ti film /
A sample film 3 (b) produced on the Si substrate was obtained.

Next, for comparison, an Sr ferrite thin film was prepared by changing a part of the manufacturing conditions in the above-mentioned specific example 1 by the conventional film forming method, and the sample film formed on the SiO ₂ film / Si substrate. 4 (a) and a sample film 4 (b) formed on the Pt film / Ti film / Si substrate were obtained. That is, using strontium dipivaloyl methane and iron acetylacetonate as starting materials, vaporization temperatures of 230 ° C. and 146 ° C., carrier gas (nitrogen) flow rates of 50 sccm and 30 sccm, oxygen flow rate of 90 sccm, rf power of 400 W, film formation Time is 1
20 minutes. The substrate temperature was 550 ° C. and the substrate was not rotated.

For the sample films 3 (a) (b) and 4 (a) (b),
Analysis by X-ray diffraction was performed to examine the crystal structure and orientation. As a result, it was found that all the films had a magnetoplumbite type crystal structure and showed high orientation in the (001) plane. The film thickness was 6.9 μm for the sample film 1 (a) and 6.8 μm for the sample film 2 (a), as observed by scanning electron microscope (SEM). Also, the film composition was examined by chemical analysis. As a result, the sample films 3 and 4 were SrFe ₁₂ O ₁₉ . Next, a Pt electrode was formed on the surfaces of the sample films 3 (b) and 4 (b) by a sputtering method, and the electric resistance of the film at 1 kHz was measured.
As a result, the resistivity of the sample film 4 (b) was 5 × 10 ² Ω · cm.
On the other hand, the specific resistance of the sample film 3 (b) is 1 × 10 ⁷ Ω.
Cm. Then, when the state of Fe in the sample film 3 (b) was examined by the Mossbauer effect, the ratio of the number of Fe ^{2+ to} the number of Fe ³⁺ per unit volume was 1%.
Below, substantially all of the Fe was in the Fe ³⁺ state.

Next, the magnetic properties (Q value) of the sample films 3 (a) and 4 (a) were examined. As a result, the sample film 3 (a) was 0.1
The Q value did not change from GHz to 5 GHz and was 16 to 17, but the sample film 4 (b) was 0.1 GHz to 5 GHz.
The Q value significantly decreased to 12 to 1.4 with respect to the change to.
The third and fourth rows in Table 1 below are the thin film manufacturing conditions, the thin film composition, the thin film thickness, the thin film specific resistance, and the thin film Q value described above in this example (and comparative example).

As described above, according to the method of this embodiment, it is easy to increase the resistance of the Sr ferrite thin film, which was difficult with the conventional manufacturing method, and the high Q value is obtained even in the GHz band.
It was confirmed that an Sr ferrite thin film having a value was obtained.

(Embodiment 3) In this embodiment, a magneto-plumbite type crystal structure Sr ferrite thin film was manufactured using the manufacturing apparatus shown in FIG. Hereinafter, this will be described in detail.

A ferrite thin film was formed on the substrate 3 by changing some of the manufacturing conditions of the present invention in Example 1 above. That is, lead dipivaloyl methane (Pb
(DPM) ₂ ) and iron acetylacetonate, the vaporization temperature is 140 ° C. and 140 ° C., the carrier gas (nitrogen) flow rate is 20 sccm and 18 sccm, the oxygen flow rate of the reaction gas is 45 sccm, and the rf power is 300 W.
The vacuum degree to 1.0 Torr and the substrate temperature to 520 ° C.
In addition, the substrate rotation speed is changed to 50, and the substrate 3
To prepare a Pb ferrite thin film on a, SiO ₂ film / Si
Sample film 5 (a) formed on the substrate and Pt film / Ti film /
A sample film 5 (b) formed on the Si substrate was obtained.

Next, for comparison, a sample prepared on a SiO ₂ film / Si substrate by preparing a Pb ferrite thin film by changing some of the manufacturing conditions in Example 1 by the conventional film forming method as well. A film 6 (a) and a sample film 6 (b) formed on a Pt film / Ti film / Si substrate were obtained. That is, using lead dipivaloyl methane and iron acetylacetonate as starting materials,
Vaporization temperature 145 ℃ and 140 ℃, carrier gas (nitrogen)
Flow rates of 50 sccm and 30 sccm, oxygen flow rate of 100
The sccm and rf power were 400 W, and the film formation time was 120 minutes. The substrate temperature was 520 ° C. and the substrate was not rotated.

Regarding the sample films 5 (a) (b) and 6 (a) (b),
Analysis by X-ray diffraction was performed to examine the crystal structure and orientation. As a result, it was found that all the films had a magnetoplumbite type crystal structure and showed high orientation in the (001) plane. The film thickness was 9.8 μm for the sample film 5 (a) and 8.7 μm for the sample film 6 (a), as observed by scanning electron microscope (SEM). Also, the film composition was examined by chemical analysis. As a result, both of the sample films 5 and 6 were PbFe ₁₂ O ₁₉ . Next, a Pt electrode was formed on the surfaces of the sample films 5 (b) and 6 (b) by a sputtering method, and the electric resistance of the film at 1 kHz was measured.
As a result, the specific resistance of the sample film 6 (b) was 1 × 10 ² Ω · cm.
On the other hand, the specific resistance of the sample film 5 (b) is 9 × 10 ⁴ Ω
・ It was cm. Then, when the state of Fe in the sample film 5 (b) was examined by the Mossbauer effect, the ratio of the number of Fe ^{2+ to} the number of Fe ³⁺ per unit volume was 1
%, Substantially all Fe was in the state of Fe ³⁺ .

Next, the magnetic properties (Q value) of the sample films 5 (a) and 6 (a) were examined. As a result, the sample film 5 (a) was 0.1
The Q value did not change from GHz to 5 GHz and was 11 to 13, but the sample film 6 (a) was 0.1 GHz to 5 GHz.
The Q value significantly decreased from 9 to 1.2 in response to the change to.
The fifth and sixth rows in Table 1 below are the manufacturing conditions of the thin film of this example (comparative example), the composition of the thin film, the thickness of the thin film, the specific resistance of the thin film, and the Q value of the thin film described above.

As described above, according to the method of this embodiment, it is easy to increase the resistance of the Pb ferrite thin film, which was difficult with the conventional manufacturing method, and the high Q value is achieved even in the GHz band.
It was confirmed that a Pb ferrite thin film having a value was obtained.

[0035]

[Table 1]

(Embodiment 4) In this embodiment, a thin film inductor element having the structure shown in FIG. 3 will be described in detail.

First, a 0.5 μm thick Si ₃ N film is formed on the semi-insulating GaAs substrate 101 by using the plasma CVD method or the like.
_{4 The} insulating film 102 was formed on the entire surface. Then Si ₃ N ₄
A first layer wiring metal 104 made of Ti / Au and having a width of 6 μm and a thickness of 3 μm was formed on a predetermined region of the insulating film 102 by using an ion milling method or the like. Then, on the entire surface including the first-layer wiring metal 104 on the Si ₃ N ₄ insulating film 102, a high-resistance Ba ferrite thin film 103 (specific resistance: 4 × 10 4) having a thickness of 8.2 μm was manufactured by the manufacturing method described in the first embodiment. ⁶ Ω
cm) formed. Then, the Ba ferrite thin film 103
A contact hole 107 for connecting the first layer wiring metal 104 and the second layer wiring metal 105 was opened in a predetermined region of the above by using a dry etching method or the like. Then, Ti / is formed in the contact hole 107 by using a lift-off method or the like.
After embedding Au, Ti / Au having a thickness of 3 μm was formed on the entire surface of the high-resistance Ba ferrite thin film 103 by a vacuum evaporation method. Next, a spiral inductor of the second wiring metal 105 starting from Ti / Au in the contact hole 107 was manufactured by using the Ar ion milling method with the photoresist film as a mask, and subsequently, the description was made in the first embodiment. A 8.2 μm-thick high-resistance Ba ferrite thin film 106 (specific resistance: 4 × 10 ⁶ Ω · cm) was formed by the manufacturing method so as to cover the spiral inductor (thin-film inductor element A). For comparison, instead of the high-resistance Ba ferrite thin film 103, a low-resistance B having a thickness of 9.1 μm manufactured by a conventional manufacturing method as a comparative example in Example 1.
A ferrite thin film (specific resistance: 9 × 10 ² Ω · cm) is formed, and a spiral inductor is formed on the thin film. Further, the high-resistance Ba ferrite thin film 106 is replaced with a low-resistance Ba ferrite having a thickness of 9.1 μm. Thin film (specific resistance: 9
× 10 ² Ω · cm) was formed (thin film inductor element B).

The dimensions of the thin film inductor elements A and B were examined by a high resolution scanning microscope (SEM) and a laser microscope. As a result, in both the thin film inductor element A and the thin film inductor element B, the conductor layer (second wiring metal 105) had an inner diameter of 50 μm, a wiring width of 6 μm, a wiring interval of 4 μm, a wiring thickness of 3 μm, and five turns. Also,
The thickness of the magnetic core material is high resistance Ba ferrite thin film (103)
Is 8.2 μm, low resistance Ba ferrite thin film is 9.1 μm
Met.

10 of the thin film inductor element produced in FIG.
The frequency characteristic in 0 MHz-5 GHz is shown. As shown in FIG. 5, in the thin film inductor element B using the low resistance Ba ferrite thin film as the magnetic core material, the inductance decreases at a frequency of 100 MHz or more, but the thin film inductor element A using the high resistance Ba ferrite thin film as the magnetic core material. Then, it can be seen that no reduction in inductance is observed and that it can be used up to 5 GHz.

Even when a high resistance Sr ferrite thin film or a high resistance Pb ferrite produced by the manufacturing method described in Examples 2 and 3 is used as the magnetic core material instead of the high resistance Ba ferrite thin film, the high resistance is obtained. Similar to the case where the Ba ferrite thin film was used, no decrease in inductance was observed in the measurement frequency region, and it was possible to use up to 5 GHz.

Although oxygen was used as the reaction gas in the production of the ferrite thin film in the above-mentioned examples, in addition to oxygen, N ₂ O, O ₃
Even when a gas containing oxygen such as H ₂ O was used as a reaction gas, a ferrite thin film having a magnetoplumbite type crystal structure showing excellent high frequency characteristics was similarly obtained.

Further, in the above-mentioned embodiment, the inductively coupled plasma generation system was used for producing the ferrite thin film. However, even when the capacitively coupled plasma generation system is used, similarly excellent high frequency characteristics are obtained. A ferrite thin film having the magnetoplumbite type crystal structure shown was obtained.

In the above embodiment, the plasma source is r
f plasma was used, but microwaves other than this (2.
45 GHz) plasma, electron cyclotron resonance (EC
Even when R) plasma was used, a ferrite thin film having a magnetoplumbite type crystal structure showing excellent high frequency characteristics was similarly obtained.

[0044]

As described above, according to the ferrite thin film of the present invention, the ferrite thin film having the magnetoplumbite type crystal structure is substantially free of Fe ²⁺ . Fe ²⁺ and Fe in the crystal that occurred in the ferrite of magnetoplumbite type crystal structure
There is no decrease in resistivity due to hopping conduction with ^3+, and it has a resistivity of 1 × 10 ⁴ Ω · cm or more, and eddy current loss is small even in the high frequency region of the GHz band, and it has excellent softness. It becomes a ferrite thin film with magnetic properties.

According to the method for producing a ferrite thin film of the present invention, the substrate held by the substrate holder and heated to a predetermined temperature in the plasma discharge region of the reaction gas containing oxygen in the reduced pressure reaction chamber is used as the substrate. In the method for producing a ferrite thin film, which is rotated by rotating a holder, a raw material gas for ferrite is supplied into the reduced pressure reaction chamber, and a ferrite thin film having a magnetoplumbite type crystal structure is grown on the rotating substrate. The source gas is selectively supplied to a partial region on the rotating substrate holder, and the formation of the ferrite thin film and the oxidation of the ferrite thin film are alternately repeated on the substrate while the magnetoplumbite is used. Since the ferrite thin film having a type crystal structure is grown, the degree of oxidation is extremely high. Big magnetoplumbite Plum byte type crystal structure can be grown ferrite thin film having,
It is possible to manufacture a ferrite thin film having a magnetoplumbite type crystal structure having a specific resistance of 1 × 10 ⁴ Ω · cm or more.

The thin film inductor element according to the present invention is a thin film inductor element using a ferrite thin film having a magnetoplumbite type crystal structure as a magnetic core material, and has a ratio of the ferrite thin film having the magnetoplumbite type crystal structure. Since the resistance is 1 × 10 ⁴ Ω · cm or more, the eddy current loss in the high frequency region of the gigahertz band of the ferrite thin film which is the magnetic core material is small, so that the inductor element has excellent inductor characteristics.

[Brief description of drawings]

FIG. 1 is a sectional view showing a specific example of a manufacturing apparatus used for manufacturing a ferrite thin film of the present invention.

FIG. 2 is a perspective view showing a substrate holder and its peripheral region in the manufacturing apparatus of FIG.

FIG. 3 is a sectional view showing a specific example of a thin film inductor element using a Ba ferrite thin film having a magnetoplumbite type crystal structure of the present invention.

FIG. 4 B of the magnetoplumbite type crystal structure of FIG.
It is a top view of a thin film inductor element using a ferrite thin film.

FIG. 5 is a diagram showing frequency characteristics of a thin film inductor element according to Example 4 of the present invention and a conventional thin film inductor element.

[Explanation of symbols]

 1 Reaction Chamber 2 Substrate Heating Heater 3 Substrate 4 Substrate Holder-5 High Frequency Coil 6 Exhaust Means 7 Rotation Mechanism 8 Raw Material Gas Supply Means 9 Reactive Gas Supply Means 10 Plasma Discharge Area 11, 12 Vaporizer 13, 14 Raw Material Gas Supply Valve 15 , 16 Carrier gas supply valve 17 Oxygen gas supply valve 18, 19 Starting material 20 Nitrogen cylinder 21 Oxygen cylinder 22 Film forming area 23 Oxidation area 24 Flange 25, 26 Raw material gas supply valve 50 Mixed vapor 101 Semi-insulating GaAs substrate 102 Si3N4 insulation Film 103 Ba ferrite thin film 104 First layer wiring metal 105 Second layer wiring metal (spiral inductor) 106 Ba ferrite thin film

Claims (7)

[Claims] 1. A ferrite thin film having a magnetoplumbite type crystal structure, which is substantially free of Fe ²⁺ . 2. The ferrite is Ba ferrite, Sr ferrite or Pb ferrite.
The ferrite thin film described in 1. 3. A substrate held by a substrate holder and heated to a predetermined temperature is rotated by rotating the substrate holder in a plasma discharge region where a reaction gas containing oxygen is plasma-discharged in a reduced pressure reaction chamber. , Supplying a source gas into the reduced pressure reaction chamber,
In a method of manufacturing a ferrite thin film for growing a ferrite thin film having a magnetoplumbite type crystal structure on the rotating substrate, the raw material gas is selectively supplied to a partial region on the rotating substrate holder. A method for producing a ferrite thin film, wherein the ferrite thin film having the magnetoplumbite crystal structure is grown while alternately forming the ferrite thin film and oxidizing the ferrite thin film on the substrate. 4. The ferrite according to claim 3, wherein the source gas is drawn into the reduced pressure reaction chamber from the outside of the reduced pressure reaction chamber, and the supply port is supplied by the source gas supply means arranged near the substrate holder. Thin film manufacturing method. 5. The source gas is vapor of a compound containing iron,
The method for producing a ferrite thin film according to claim 3 or 4, wherein the mixed gas is a mixed gas with vapor of a compound containing barium, strontium or lead. 6. A thin film inductor element using a ferrite thin film having a magnetoplumbite type crystal structure as a magnetic core material, wherein the ferrite thin film having the magnetoplumbite type crystal structure has a specific resistance of 1 × 10 ⁴ Ω · cm.
A thin film inductor element characterized by the above. 7. A first-layer wiring layer is formed on one main surface of a ferrite thin film having a magnetoplumbite type crystal structure, and a second-layer wiring layer including a spiral inductor is formed on the other main surface. 7. The thin film inductor according to claim 6, wherein the one wiring layer and the spiral inductor are electrically connected to each other by a contact hole formed in the ferrite thin film having the magnetoplumbite type crystal structure and a metal embedded in the contact hole. element.