JPH04224112A - Production of thin film of oxide superconductor - Google Patents

Abstract

PURPOSE:To lower deposition temp. and to improve superconductivity by introducing beta-diketone metallic complexes containing Y, Ba, and Cu into a reaction furnace having specific partial pressure of oxygen and subjecting the complexes to chemical vapor deposition. CONSTITUTION:Oxygen gas 6 is introduced into a reaction furnace 7 and the pressure in the reaction furnace 7 is reduced by means of a vacuum pump 10, by which the partial pressure of oxygen in the reaction furnace 7 is held at <=0.5Torr. Subsequently, beta-diketone metallic complexes 1,2,3 containing Y, B, and Cu are heated by heaters 4, respectively, and evaporated, and the evaporated complexes 1,2,3 are introduced on inert gases 5 into the reaction furnace 7 and decomposed by means of heating by a heater 9, by which a thin film of oxide superconductor can be deposited onto a substrate 8.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a Y-based oxide superconducting thin film formed by chemical vapor deposition.

0002

[Prior art] Chemical vapor deposition method (also referred to hereinafter as CVD)
Y-based oxide superconducting thin film (YBa2 Cu3 O7
-y) has already been used to provide thin films with excellent superconducting properties such as superconducting transition temperature (Tc) and critical current density (Jc). Furthermore, thin films synthesized by CVD have the characteristic of maintaining a high Jc even in high magnetic field widths of 20 Tesla (T) or more, and are expected to be put into practical use. However, the deposition temperature of thin films that have been reported to have excellent superconducting properties is 850°C to 950°C, and in order to apply CVD thin films to superconducting devices, it is necessary to lower the deposition temperature.

[0003] Attempts to synthesize Y-based oxide superconducting thin films at low temperatures include thermal CVD using N2O gas or O3 gas as the oxidizing gas, and thermal CVD that adjusts the total pressure in the furnace during thin film synthesis.
D, CVD using plasma such as microwave plasma, etc. are being considered.

[0004] Thermal C using N2 O or O3 as oxidizing gas
In VD, a superconducting thin film is synthesized at a deposition temperature of 650°C, but the value of Tc zero is 80K or less. In addition, in thermal CVD by adjusting the total pressure in the furnace during synthesis, the total pressure in the furnace is 1
．． A Tc of 83 K at a precipitation temperature of 700° C. is reported to be 5 Torr. However, there has been no report on Jc in the synthesis of superconducting thin films by these methods, and no thin film with high Jc has been obtained at a deposition temperature of around 700°C.

In plasma CVD, by introducing microwave plasma, Tc is 85K and 77K at a deposition temperature of 580°C.
A film with a Jc of 105 A/cm2 at K and OT has been synthesized. In addition, N2O is added to the oxidizing gas by plasma CVD.
Tc was 89K at a precipitation temperature of 670°C to 730°C.
, 77K, OT of 105 A/cm2 has been reported. However, in order to introduce plasma, heat C
It requires a higher vacuum than VD, and also requires an oscillator to generate plasma. For this reason, thin film synthesis equipment becomes extremely expensive, and it is more difficult to increase the size of the equipment than in the case of thermal CVD.

[0006]

[Problems to be Solved by the Invention] The present invention has been made by focusing on the problems of the prior art described above. The object of the present invention is to provide a method for manufacturing a Y-based superconducting thin film with excellent superconducting properties.

[0007]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a Y-based superconducting thin film produced by chemical vapor deposition using a β-diketone metal complex containing at least yttrium, barium, and copper as an evaporation source material. This method uses a method to control the oxygen partial pressure in the reactor during thin film synthesis.

More specifically, the manufacturing method of the present invention includes the flow rate of an inert gas such as Ar introduced into the reactor and oxygen gas, or a mixed gas in which oxygen gas is diluted with an inert gas such as Ar gas. The oxygen partial pressure in the reactor is controlled by the flow rate and the pressure in the reactor.

The flow rate of the inert gas introduced into the reactor is the flow rate of the carrier gas used to introduce each raw material vapor onto the substrate in the reactor. Further, the carrier gas and the carrier gas are flow rates of an inert gas introduced into the reactor through separate routes. Furthermore, it is the flow rate of the inert gas in a gas obtained by diluting these inert gases and oxygen gas with an inert gas.

The flow rate of oxygen gas is the flow rate of oxygen gas introduced or the flow rate of oxygen gas in a gas diluted with an inert gas. Here, the flow rate of oxygen gas introduced into the reactor means a flow rate at which each raw material vapor introduced into the reactor can be decomposed and polymerized to form a Y-based oxide superconductor.

The pressure inside the reactor is reduced, and the heat Torr
to several tens of Torr is preferable. Several 10 Torr
At the above pressure, the flow rate of the gas in the reactor becomes slow, and the ratio of decomposition and polymerization of the raw material gas in front of the substrate increases, making it difficult to form a thin film. Also, the number To
At pressures below rr, a large vacuum pump or mechanical pump is required to increase the evacuation capacity of the evacuation device.

[0012] The oxygen partial pressure in the reactor can be arbitrarily controlled by the flow rate of oxygen gas relative to the flow rate of all gases in the reactor and the pressure in the reactor, and the oxygen partial pressure to be controlled is at least 0.5 Torr or less. . When a film is synthesized at an oxygen partial pressure higher than 0.5 Torr, it is difficult to obtain a thin film with excellent superconducting properties at a low deposition temperature of 800° C. or lower. Preferably, the oxygen partial pressure is on the order of 10-eTorr.

[0013]

[Function] According to the manufacturing method described above, a Y-based superconducting thin film can be synthesized at a low deposition temperature by ordinary thermal CVD without using plasma or oxidizing gases other than oxygen.

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3.

(Embodiment 1) FIG. 1 is a diagram showing an example of a hot wall type thermal CVD apparatus applicable to the manufacturing method of the present invention.

[0016] A thd complex of Y, Ba, and Cu (
thd:2,2,6,6-tetramethyl-3,
5-heptanditotonato) 1, 2, and 3 were used. Each raw material is heated and evaporated with a heater 4 in the range of 106°C to 242°C, each with a flow rate of 150ml/min.
The Ar gas 5 was introduced into the reactor 7 using Ar gas 5. As the oxygen gas 6, an Ar dilution gas containing 1% oxygen gas was used and introduced into the reactor at a flow rate of 250 ml/min through a separate route. The pressure inside the reactor 7 is reduced by the vacuum pump 10, and the pressure is 10
Torr. The oxygen partial pressure under this condition is 0.036T
It is orr. The substrate 8 is made of mirror-polished SrTiO3.
A (100) single crystal substrate was used. Film formation was performed at a deposition temperature of 650° C. and 700° C. using a heater 9. The precipitation time is 3
It was set to 0 minutes. After the precipitation is completed, in-si cooling is performed at a rate of 10°C/min from the precipitation temperature to approximately 150°C under 1 atm of oxygen.
tu oxygen treatment was performed.

The X-ray diffraction pattern of the film obtained at a precipitation temperature of 700° C. is shown in FIG. The intensity of the (001) peak was high, and a c-axis oriented film was formed. Precipitation temperature 650℃
Also, a c-axis oriented film was formed. 70 in Figure 3
The temperature dependence of the resistivity of a film deposited at 0°C is shown. The resistivity of this film decreases linearly with decreasing temperature, 89
It showed zero resistance at K. The film deposited at 650℃ also has a temperature of 83K.
It showed zero resistance. The film deposited at 700℃ is 77K
, showed a Jc of 2.2×106 A/cm2 in OT.

(Example 2) Same raw materials 1, 2, and as in Example 1
Each raw material was heated and evaporated in the range of 128° C. to 242° C. using Ar gas 5 at a flow rate of 150 ml/min. Oxygen gas 6 is 0
．． Ar dilution gas containing 5% oxygen gas was introduced into the reactor at a flow rate of 250 ml/min via a separate route. The pressure inside the reactor is reduced by a vacuum pump 10, and the pressure is 10 Torr.
It was set as r. The oxygen partial pressure under this condition is 0.018 Torr
It is. The substrate 8 is made of mirror-polished SrTiO3 (1
00) A single crystal substrate was used. Deposition temperature 6 by heater 9
Film formation was performed at 50°C and 700°C. The precipitation time was 30 minutes. After the completion of precipitation, the temperature is reduced to about 15% from the precipitation temperature under 1 atm of oxygen.
In-situ oxygen treatment was performed by cooling to 0°C at a rate of 15°C/min.

A c-axis oriented film was formed at any precipitation temperature. Further, the film had a Tc higher than the liquid nitrogen temperature, and the film deposited at 700°C showed a temperature of 87K, and the film deposited at 650°C showed a temperature of 85K.

(Example 3) Using the same raw materials as in Example 1,
Each raw material is heated and evaporated in the range of 128°C to 242°C,
Ar gas was introduced into the reactor at a flow rate of 150 ml/min. Furthermore, Ar gas was introduced into the reactor through a different route from the above Ar gas at a flow rate of 215 ml/min. Pure oxygen gas (99.9%) was used as the oxygen gas,
A flow rate of 35 ml/min was introduced into the reactor via a separate route. The oxygen partial pressure under this condition is 0.5 Torr.

The substrate is made of mirror-polished SrTiO3 (
100) A single crystal substrate was used. Precipitation temperature 750℃ and 80℃
Film formation was performed at 0°C. The precipitation time was 30 minutes. After the completion of the precipitation, the temperature was increased from the precipitation temperature to approximately 150°C for 15 minutes under 1 atm of oxygen.
In-situ oxygen treatment was performed with cooling at °C/min.

A c-axis oriented film was formed at any precipitation temperature. 88K, 7 for a film deposited at 800℃
The film deposited at 50° C. also showed a Tc of 88K. In addition, the film deposited at 800℃ was 3×105 at 77K, OT.
It showed a Jc of A/cm2.

[0023]

[Effect of the invention] Y synthesized by the above-mentioned production method
Since superconducting thin films are formed at low precipitation temperatures and have excellent superconducting properties, they can be applied to superconducting devices and devices combined with semiconductor devices.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an apparatus that can be used in the manufacturing method of the present invention.

FIG. 2 is an X-ray diffraction pattern of a thin film according to an example of the present invention.

FIG. 3 is a diagram of temperature dependence of resistivity of a thin film according to an example of the present invention.

[Explanation of symbols]

1, 2, 3...raw materials 4... Raw material heating heater 5...Inert gas 6...Oxygen gas 7...Reactor 8...Substrate 9...Substrate heating heater 10...Vacuum pump

Claims (2)

[Claims] Claim 1: β- containing at least Y, Ba, and Cu
In a method for producing an oxide superconducting thin film of YBa2 Cu3 O7 -y by a chemical vapor deposition method using a diketone metal complex as an evaporation source material, the oxygen partial pressure in the reactor during thin film formation is set to 0.5 Torr or less. A manufacturing method for manufacturing a thin film characterized by the following. 2. The thin film manufacturing method according to claim 1, wherein the oxygen partial pressure in the reactor is controlled by the flow rates of inert gas and oxygen gas introduced into the reactor and the total pressure in the reactor. .