JPH0280305A - Production of crystalline high temperature superconducting thin film - Google Patents

Abstract

PURPOSE:To obtain a high temp. superconducting thin film having satisfactory crystalline property by prepg. the crystalline thin film basing on an organometallic vapor growth process while supplying ozone as at least a part of oxidizing gas. CONSTITUTION:A crystalline thin film of an oxide high temp. superconducting material is prepd. by supplying ozone as at least a part of oxidizing gas in a stage of prepg. the crystalline oxide high temp. superconducting thin film basing on an organometallic vapor growth process. It is desirable to irradiate a base plate with light having 150-600nm wavelength in order to prepare a thin film having satisfactory crystalline property on a base plate at a relatively low temp. Examples for the crystalline oxide high temp. superconducting thin film prepd. by the organometallic vapor growth are those comprising Bi-alkaline earth element-Cu-O type superconducting ceramic, or rare earth element-alkaline earth element Cu-O type superconducting ceramic, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing an oxide high temperature superconducting crystalline thin film by organometallic chemical vapor deposition.

(Prior art and its problems) Rare earth element-alkaline earth element-Cu oxide system high temperature superconducting ceramics represented by Y-Ba-Cu-0 system, B
High-temperature superconducting ceramics made of Bi-alkaline earth element-Cu oxides, represented by the 1-Ca-3r-Cu-0 system, are expected to have a wide range of applications in transportation, heavy electrical equipment, computers, and medical equipment. has been done.

These oxide-based high-temperature superconducting ceramics become superconducting even when cooled with an inexpensive refrigerant such as liquid nitrogen, so they are similar to Nb-Ti-based superconducting alloys that only exhibit super II conductivity in liquid helium. If it can be used instead for superconducting magnets, etc., it would have a great economic advantage. When applying oxide-based high-temperature superconductors to electronic devices, it is possible to use a superconducting crystalline thin film on a substrate, or an insulating thin film and a superconducting crystalline thin film. It is necessary to form a multilayer film.

Conventionally, various methods are known for forming crystalline thin films, but the so-called organometallic chemical method involves sending the vapor of an organometallic complex along with gas to a thermal decomposition furnace and thermally decomposing it on a substrate to form a thin film. Vapor phase growth method (Metal Organ
ic Chemical Vapor Deposit
ion HMOCVD method) is commonly used because it is easy to control the thin film formation rate, it can be manufactured at around normal pressure, and mass production is easy.

In manufacturing a superconducting crystalline thin film by the MOCVD method, a thin film made of a composite metal oxide is formed by a thermal decomposition reaction between an organometallic complex of a constituent metal of a superconducting crystal and supplied oxygen on a heated substrate. However, it is difficult to determine the appropriate selection and combination of raw material organometallic complexes, decomposition reaction atmosphere gas, substrate temperature range, etc., and there are problems in that superconducting crystalline thin films with good crystallinity cannot be obtained with good reproducibility. was there.

(Technical means for solving the problem) As a result of intensive research into the above problem, the present inventors found that
This led to the present invention.

The present invention provides for supplying ozone as at least a part of the oxidizing gas and supplying a raw material gas for a copper-containing organometallic compound when manufacturing an oxide high temperature superconducting crystalline thin film by organometallic chemical vapor deposition. , relates to a method for producing an oxide high-temperature superconducting crystalline thin film with good reproducibility, characterized in that it is supplied to the vicinity of a substrate independently without being mixed with other raw material gases in advance.

Moreover, in order to manufacture a thin film with good crystallinity on a relatively low-temperature substrate, there is a method for manufacturing an oxide high-temperature superconducting crystalline thin film in which the substrate is irradiated with light having a wavelength of 150 to 600 nm.

The oxide high temperature superconducting crystalline thin film produced by the MOCVD method of the present invention includes Bi-alkaline earth element-Cu oxide superconducting ceramics, rare earth element-alkaline earth element-Cu oxide superconducting ceramics, etc. For example, a crystalline thin film consisting of

Bi-alkaline earth element-Cu oxide-based high temperature superconducting ceramics is represented by the following general formula, Bi,AxCuyO7. In the formula, A represents at least one alkaline earth element selected from Mg, Ca, Ba, and Sr. In the above formula, 1<x×4.1<y<4.3,
5 < z < 9, those in the range of 5 are particularly preferred.

The rare earth element-alkaline earth element-Cu oxide-based superconducting ceramic has the following general formula: R, AXCu.

It is represented by 08. In the formula, R is Y, La, Nd, Sm, Eu
, Cd, Dy, HoXTm5Tb, Lu and Er, and A represents at least one alkaline earth element selected from Ba and Sr. In the above formula, 1.5<x<2.5
．． The range of 2.5<y<3°5.6.5<z<7 is preferable.

Acetylacetone, hexafluoroacetylacetone, dipivaloylmethane, or cyclopencdiene can be used as the organic moiety (ligand) of the organometallic complex as a raw material used in the present invention. Preferred ligands include organic compounds of the following formula: CH.

RCCHz CCCH:1 0　　　　0　　C9H.

[In the formula, R represents a fluorinated lower alkyl group having 1 to 4 carbon atoms.] When this ligand is used, synthesis and isolation are easy, and the vapor pressure of the organometallic complex itself is low, making it possible to form a thin film. It has the advantage of high speed.

As a method for producing the organometallic complex used in the present invention, techniques for producing ordinary metal complexes can be employed. For example, metals that are components of a desired high-temperature superconducting single crystal (e.g., rare earth elements such as Bi, Cu, Ca, Ba, Sr, and Y)
It can be easily obtained by recrystallizing crude crystals obtained from an aqueous solution of a metal compound such as a hydroxide or a metal salt and an organic compound of the above formula by adjusting the pH from ethanol-water and further drying. Examples of R in the above formula include a trifluoromethyl group (hereinafter abbreviated as TPM), a pentafluoroethyl group (hereinafter abbreviated as PPM), and a heptafluoropropyl group.

In the production of an oxide high temperature superconducting crystalline thin film by the MOCVD method of the present invention, a raw material organic material, which is entrained in an ozone-containing oxidizing gas and a carrier gas, is placed in a reaction tube equipped with a heated substrate for producing a crystalline thin film. This can be carried out by supplying a metal complex gas and oxidizing and thermally decomposing the organometallic complex in the reaction tube on the substrate.

Oxygen gas has conventionally been used as the oxidizing gas, but by replacing at least a portion of it with ozone, a superconducting ceramic thin film with good crystallinity can be produced. By irradiating oxygen containing ozone with light, various active oxygen excited species such as excited oxygen molecules and atomic oxygen are generated, and these play an important role in the formation of crystalline superconducting ceramic thin films. It is estimated that

In the above, at the same time that the oxidizing gas and the organometallic complex gas are supplied, a wavelength of 150 to 600 nm is applied onto the substrate.
By irradiating the reaction tube with light to cause oxidative thermal decomposition and photodecomposition of the organometallic complex in the reaction tube on the substrate, an oxide high temperature superconducting crystalline thin film can be produced at a relatively low substrate temperature.

Generally, in the production of oxide high temperature superconducting crystalline thin films,
When the temperature of the substrate is raised (then, when forming a different type of superconducting crystalline thin film or a multilayer film of an insulating thin film and a superconducting crystalline thin film on the substrate, it will be affected by the already formed superconducting crystalline thin film or insulating thin film). , impurities diffuse into the superconducting crystalline thin film, and the properties of the formed multilayer film are likely to be impaired.

When irradiating light with the above wavelength, the substrate temperature can be lowered, so a crystalline thin film that does not have the above-mentioned problems can be manufactured.

In one embodiment of the production of an oxide high temperature superconducting crystalline thin film by the MOCVD method of the present invention, among the raw material organometallic complex gases that are accompanied by a carrier gas and supplied into the reaction tube, the copper organometallic complex gas is The gas is not mixed in advance with other raw material organometallic complex gases, and is supplied onto the substrate independently from a nozzle near the substrate. Organometallic complexes of copper react with organometallic complexes of alkaline earth elements or rare earth elements in the presence of oxidizing gas, such as BaCu○2, Y2
Cu z Os is easily produced, and slight differences in manufacturing conditions make it difficult to produce the desired crystalline high-temperature superelectric "JTR" film with good reproducibility. By supplying it to the substrate independently,
The above-mentioned inconveniences can be eliminated.

The method for producing the oxide high temperature superconducting crystalline thin film according to the present invention will be described in detail below.

The temperature control of the supply container filled with each raw material differs depending on the type of organometallic complex, but in practical terms it is 30 to 250 degrees.
The temperature is controlled at C. Examples of the carrier gas include inert gases such as argon and nitrogen, and the gas flow rate varies depending on the type of raw material.
Usually 1 to 1000 Id/min is selected. In order to avoid problems such as condensation of the organometallic complex, the piping from the supply container to the reaction tube is preferably kept at a temperature lower than the decomposition temperature. The preferred temperature range is 100-250°C
It is. The gas of the organometallic complex of copper as a raw material is supplied onto the substrate from a nozzle provided near the substrate in the reaction tube. The organometallic complex gas as a raw material other than copper can also be mixed before being introduced into the reaction tube.

The speed of the ozone-containing oxidizing gas supplied to the reaction tube is 1
rI11/min, ~101/min, is selected. The ozone-containing oxidizing gas may be a mixed gas of ozone, oxygen and/or an inert gas, and the ozone content is at least 0.1 mol%, preferably at least 1 mol%. It is more preferable that the ozone-containing oxidizing gas is mixed with all or part of the gas of the raw material organometallic complex other than copper before being introduced into the reaction tube in which the substrate is installed.

As the substrate provided in the reaction tube, MgO1A ff
i 203, Z r Oz S r T i Ch,
Silicon single crystal or the like can be used. The substrate is fixed to a substrate heating holder equipped with a heater, for example made of quartz, and the temperature of the substrate is 300 to 900°C, preferably 400 to 80°C.
00'' C. Furthermore, it is preferable that the substrate surface is tilted by 3 to 50 degrees with respect to the raw material gas inlet.

The temperature of the inner wall of the reaction tube is preferably maintained at a temperature in the range of 100 to 250°C to prevent condensation and decomposition for the same reason as above. Pyrolysis furnaces include ribbon heaters, electric furnaces,
Heating can be done using a constant temperature bath or the like.

The substrate is heated to a relatively low temperature within the temperature range, e.g.
When maintaining the temperature at 00° C. or lower to promote decomposition of the raw material organometallic complex on the substrate, as already explained, the substrate is irradiated with light with a wavelength of 150 to 600 nm from outside the reaction tube. As the light source, commonly known lamps containing ultraviolet light such as low-pressure and high-pressure mercury lamps, xenon lamps, and deuterium lamps, argon lasers, excimer lasers, and laser light multiplied by argon laser light can be used.

The reaction tube provided with the substrate and gas inlet can be made of stainless steel, but in the case of irradiation with light, it is preferable to use one that has good transparency for light with a wavelength of 150 to 600 nm. or a stainless steel reaction tube with a quartz window are preferably used.

The pressure inside the reaction tube is 0.1 to 1000 torr, preferably 10 to 760 torr.

(Example) The present invention will be explained in more detail with reference to Examples below.

Example 1 A substrate of SrTiO3 [single crystal with a surface index (100)] after degreasing and cleaning was fixed in a quartz reaction tube to a substrate holder with a built-in heater tilted at 5 degrees with respect to the direction of the supply gas port.
Before flowing the raw material gas, oxygen was passed through the reaction tube at 3ffi/min to keep the substrate at 800°C for 5 minutes, and then 7
The substrate temperature was lowered to 00°C.

Y (PPM)1, Ba (PPM) in a stainless steel container
)z are kept at 130°C and 200°C, respectively, and argon gas is supplied to each at 50ml/min, 100°C.
3f/m from an ozone generator.
After mixing with a mixed gas of ozone, oxygen, and argon (molar ratio: 0.05:1:1), the mixture was supplied into the reaction tube. At the same time, 30 ml of argon gas was added to Cu(PPM) in a stainless steel container kept at 90°C.
min, and was directly supplied onto the substrate in the reaction tube.

The reaction tube and the flow path leading to the reaction tube were kept at a temperature of 200 to 220°C to prevent condensation of the organometallic complex.

As a result of measuring the electrical resistance of the Y--Ba--Cu oxide superconducting thin film obtained by growing a crystalline thin film on a substrate for about 1 hour, the electrical resistance became zero at 92. The X-ray diffraction spectrum of this thin film showed only a peak based on the (00) plane, indicating that this thin film was a C-axis oriented oxide high temperature superconducting crystalline thin film with good crystallinity.

Example 2 Y(PPM):l, Ba(PPM)z and Cu(PP
M) instead of 2, y (TPM), , Ba (TPM)
A thin film was formed in the same manner as in Example 1 except that z and Cu(TPM)z were used.

As a result of measuring the electrical resistance of the obtained Y-Ba-Cu oxide superconducting thin film, the electrical resistance became zero at 93. The X-ray diffraction spectrum of this thin film showed only a peak based on the 00 plane, indicating that this thin film was a C-axis oriented oxide high temperature superconducting crystalline thin film with good crystallinity.

Example 3 A substrate of SrTiO3 [single crystal with surface index (100)] was fixed in a quartz reaction tube to a substrate holder with a built-in heater tilted at 5 degrees with respect to the direction of the supply gas port, and before flowing the raw material gas. Oxygen was then passed through the reaction tube at 3 f/min to keep the substrate at 800"C for 5 minutes. After that, the substrate temperature was lowered to 600°C, and the substrate was irradiated with light from outside the reaction tube using a 500W high-pressure mercury lamp. It started.

A mixed gas of ozone, oxygen and argon (molar ratio 1:1:2), Y(PPM), Ba(
PPM)z and Cu(PPM)2 were fed. The reaction tube and the flow path leading to the reaction tube were kept at a temperature of 200 to 220°C to prevent condensation of the organometallic complex.

As a result of measuring the electrical resistance of the Y-Ba-Cu oxide superconducting thin film obtained by growing a crystalline thin film on the substrate for about 1 hour, the electrical resistance became zero at 94. The X-ray diffraction spectrum of this thin film showed only a peak based on the 00 plane, indicating that this thin film was a C-axis oriented oxide high temperature superconducting crystalline thin film with good crystallinity.

Example 4 A substrate of 5rTiO3 (single crystal with a surface index of 100) was fixed in a quartz reaction tube at 5 degrees with respect to the direction of the supply gas port (fixed to a substrate holder with a built-in heater, and the raw material gas was allowed to flow). First, oxygen gas was passed through the reaction tube at 3ffi/min to keep the substrate at 800°C for 5 minutes, and then heated at 650°C.
The substrate temperature was lowered to 'C, and light irradiation onto the substrate was started from outside the reaction tube using a 500 W high-pressure mercury lamp.

B i ((, H3) 3, S in a stainless steel container
r(PPM)2, Ca(PPM)z, and Cu(PP
M) z is 30°C, 225°C1160°C1 respectively
and 90'C, and argon gas was supplied to each at 1ml/min, 200! d/min, 200m
1! It was distributed at a rate of 100 relatives/min. The copper organometallic complex gas is supplied directly onto the substrate in the reaction tube,
Organometallic complex gases of bismuth, calcium, and strontium are 3p from an ozone generator! ,/min,
A mixed gas of ozone, oxygen and argon (in a molar ratio of 0
．． 05:1:1) and supplied into the reaction tube. The reaction tube and the flow path leading to the reaction tube were kept at a temperature of 230 to 240°C to prevent condensation of the organometallic complex.

As a result of measuring the electrical resistance of the B1-Ca-3r-Cu oxide superconducting crystalline thin film obtained by growing a crystalline thin film on a substrate for about 1 hour, the electrical resistance became zero at points 102 to 106. The magnetic susceptibility of this thin film, the results of X-ray diffraction measurements,
This thin film was found to be an oxide high-temperature superconducting crystalline thin film consisting of low-temperature and high-temperature phases and having good C-axis orientation.

Comparative Example 1 A thin film was formed in the same manner as in Example 1, except that ozone was not used at all and a gas of an organometallic complex of copper, yttrium, and barium was mixed and supplied into the reaction tube.

As a result of measuring the electrical resistance of the obtained thin film, the electrical resistance became zero at 80°C, but according to the measurement of X-ray diffraction, an oxide high temperature superconducting crystalline thin film with C-axis orientation and good crystallinity was produced. I couldn't.

Comparative Example 2 A thin film was formed in the same manner as in Example 3, except that all ozone was not used and a gas of an organometallic complex of copper, yttrium, and barium was mixed and supplied into the reaction tube.

The electrical resistance of the obtained thin film became zero at 81, but according to X-ray diffraction measurements, it was not possible to produce a high temperature superconducting oxide crystalline thin film with C-axis orientation and good crystallinity.

Comparative Example 3 A thin film was formed in the same manner as in Example 4, except that ozone was not used at all and gases of organometallic complexes of copper, bismuth, calcium, and strontium were mixed and supplied into the reaction tube.

Although the electrical resistance of the obtained thin film became zero at 85 to 95, X-ray diffraction measurements showed that a C-axis oriented oxide high temperature superconducting crystalline thin film with good crystallinity could be produced. There wasn't.

Patent applicant: Ube Industries Co., Ltd.

Claims (4)

[Claims] (1) An oxide high temperature superconducting crystalline thin film characterized in that ozone is supplied as at least a part of the oxidizing gas when the oxide high temperature superconducting crystalline thin film is produced by an organometallic chemical vapor deposition method. Manufacturing method. (2) A method for producing an oxide high temperature superconducting crystalline thin film according to claim 1, characterized in that the substrate is irradiated with light having a wavelength of 150 to 600 nm. (3) When manufacturing an oxide high temperature superconducting crystalline thin film by organometallic chemical vapor deposition, the raw material gas for the copper-containing organometallic compound is supplied to the vicinity of the substrate independently without being mixed with other raw material gases in advance. A method for producing an oxide high temperature superconducting crystalline thin film characterized by: (4) The oxide high temperature superconducting crystalline material according to claim 3, characterized in that ozone is supplied as at least a part of the oxidizing gas and/or the substrate is irradiated with light with a wavelength of 150 to 600 nm. Method of manufacturing thin films.