JPH0791152B2 - Method for manufacturing superconductor thin film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a superconductor thin film which enables a high superconducting transition temperature.

Conventional Technology The highest transition temperature of conventional superconducting materials was 2.3 ° k for Nb ₃ Ge. In addition, 17 ° K of Nb ₃ Sn is the highest practical material, and cooling with expensive liquid helium (boiling point 4.2 ° k) was required to use the above materials in actual devices and systems. .

On the other hand, recently it has been suggested that the oxide superconducting material may have a high superconducting transition temperature.
A 90 ° k-class transition temperature is obtained in the k, Ba-Y-Cu-O system. These materials use liquid neon (boiling point 27 ° k) for cooling,
Since liquid nitrogen (boiling point 77 ° k) can be used, it is expected that the application of superconductivity will be greatly expanded. In particular, if thin films of these superconducting materials are synthesized, it will be possible to realize Josephson devices that operate at high temperatures and to combine them with high-speed semiconductor devices. Vapor deposition methods, spray methods, etc. are used.

Problems to be Solved by the Invention When a thin film is formed using a Ba-Y-Cu-O system, there are a sputtering method, a vacuum vapor deposition method, a spray method, etc. It can be done at low temperature, but after film formation, it must be heat treated in air or oxygen at about 800-900 ° C to become a superconducting substance. Therefore, a superconducting material can only be obtained on a substrate that can withstand high temperatures. There is a problem.

In addition, particularly inexpensive glass, organic film and the like cannot be used for the substrate.

Also, although there is a possibility that it is not necessary to perform heat treatment after film formation if the film is formed by the CVD method (chemical vapor deposition method), it is difficult to form the film by the actual CVD method because there is no gas source of Ba or Sr. It appears to be.

Means for Solving the Problems In order to solve the above problems, the present invention provides a magnetron discharge under low pressure (10 ⁴ to 10 ⁴ Torr) or a conventional sputtering method, a vacuum deposition method or a spray method. , Ba or Sr in discharge by electron cyclotron resonance (ECR)
While sputtering the target, the metal chelate of Cu or L (where L is any one element of Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu) A method for producing a superconductor thin film at a low temperature of 300 ° C. or lower by flowing a gas and an oxygen gas into the discharge plasma.

Action The inventors of the present invention sputtered Ba in a plasma obtained by magnetron discharge or electron cyclotron resonance (ECR) while Cu and L (where L is Y, La, Pr,
Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu) (organic metal chelate gas containing any one element) and O ₂ by flowing in the same plasma, 300 ℃ or less At low temperature of Ba-L
It was found that a thin film of a -Cu-O-based superconductor oxide can be obtained.

In this way, it is possible to synthesize superconducting thin films with high transition temperatures at temperatures below 300 ° C under low pressure (10 ⁴ to 10 ⁴ To
rr) in high density plasma using magnetron discharge or ECR discharge (electron temperature is very high but glass temperature is low), chemical species such as active radicals and ions that cause chemical reaction at low temperature. This is because there are many types of reactions, and the reactions that cannot occur energetically can occur at a low temperature of 300 ° C or less in the ordinary sputtering method (RF sputtering or DC sputtering), vacuum deposition method, or spray method.

In addition, in the ordinary CVD method (thermal CVD method), since there is no gas source of barium or strontium, the CVD method uses Ba-L-Cu-O.
It is not possible to obtain superconducting oxide thin films of the system. However, according to the method of the present application, L which is a gas raw material is present during sputtering while targeting a metal such as barium or strontium (where L is Y, La, Pr, Nd, Sm, Eu, Gd, Dy, H).
o, Er, Tm, Yb, Lu), Cu, O ₂ -based gas is flowed in high-density plasma to cause decomposition and deposition reaction on the substrate at a low temperature of 300 ° C or lower. In addition, a superconductor oxide thin film having good crystallinity can be obtained.

Embodiment One embodiment of the present invention will be described below with reference to the drawings. The figure shows a schematic view of a sputtering type plasma CVD apparatus using magnetron discharge in one embodiment of the present invention.

In the figure, 11 is a reaction chamber, 12 is a high-frequency electrode containing a magnet for performing magnetron discharge, 13
Is a high frequency power supply, 14 is a substrate holder, 15 is a substrate, 16 is a barium or strontium target, 17 is a metal chelate bubbler containing copper, 18 is L [however, L
Is any one of Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu], a metal chelate bubbler, 19
Is a nitrogen (N ₂ ) carrier gas cylinder, 20 is an O ₂ reaction gas cylinder, and 21 is an exhaust system.

First, barium is attached to the high-frequency electrode portion as a target. Next, copper acetylacetone [Cu (C ₅ H ₇ O) ₂ ] and yttrium acetylacetone [Y (C ₅ H ₇ O) ₃ ]
The bubblers 16 and 17 heated at 0 ° C. were respectively charged, N ₂ gas 20 for bubbles was flowed at 10 cc / min and 3 cc / min, respectively, and these vapors were stored in the reaction chamber 11 which had been decompressed by the exhaust system 21. It is introduced into the SiO ₂ substrate 15. Next, oxygen (O ₂ ) 19, which is also a reaction gas, is flown on the same SiO ₂ substrate at a flow rate of 5 cc / min, and high-frequency power (13.56 MHz) is applied at 500 w (5 w / cm ² ) for Ba.
Sputter the target. With these sputtering
The CVD reaction was performed for about 25 minutes. The gas pressure at this time is 1.0
The substrate temperature was 200 ° C. at × 10 ² Torr. The film thickness of Ba ₂ YCu ₃ O _7-y deposited on the substrate at this time was about 4500Å. Next, for this film, analysis of the crystal structure by X-ray,
And the superconducting transition temperature was measured by the 4-terminal method.

The result at that time is shown in Sample No. 1 in the table. Similarly, X-ray analysis when changing the substrate temperature, target type, chelate type, bubbler amount (N ₂ and O ₂ flow rate), pressure in the reaction chamber, plasma generation method, etc. The superconducting transition temperature is shown in sample numbers 2 to 21 in the table. Further, sample numbers 22 to 23 are comparative examples outside the present invention.

It should be noted that in the claims, the pressure reduction in the chamber is 10
^{4 Torr~10 4} Torr and the is given, 10 ⁴ Torr than atmospheric pressure is high, the various particles in the chamber (neutral radicals, ions, etc.)
The mean free path of is shortened, and it becomes difficult for various particles to contribute to the reaction with some kinetic energy.
Therefore, a superconducting oxide having good crystallinity cannot be obtained at low temperature. Further, if it is 10 ⁴ Torr or less, it is difficult to maintain the discharge, and the growth rate of the oxide superconducting film becomes low.

EFFECTS OF THE INVENTION As described above, the present invention skillfully utilizes sputtering and CVD reaction in a low-pressure plasma, and
A method for synthesizing a superconducting oxide at the following low temperature,
This is an extremely useful invention in the industry.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a plasma CVD apparatus combined with sputtering according to an embodiment of the present invention. 11 ... Reaction chamber, 12 ... High-frequency electrode with built-in magnet for magnetron discharge, 13 ... High-frequency power supply, 14 ... Substrate holder, 15 ... Substrate, 16 ... Barium or strontium target, 17 …… Copper-containing metal chelate bubbler, 18 …… L [where L is any of Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu] A metal chelate bubbler containing
19 …… Nitrogen (N ₂ ) carrier gas cylinder, 20 …… Oxygen (O ₂ ) reaction gas cylinder, 21 …… Exhaust system.

Claims (4)

[Claims] 1. A 10 ^-4 Torr~10 ^-4 Torr decompressed chamber, a magnetron discharge or caused discharge by electron cyclotron resonance (ECR), barium therein (Ba) or strontium (Sr) While sputtering copper (Cu) and L [where L is yttrium (Y), lanthanum (La), praseodymium (Pr),
Neodymium (Nd), Samarium (Sm), Europium (Eu), Gadolinium (Gd), Dysprosium (Dy),
Holmium (Ho), Erbium (Er), Thulium (T
m), ytterbium (Yb), lutetium (Lu)] and a chelate vapor containing oxygen and oxygen gas (O ₂ ) as a reaction gas are introduced into the chamber, and the general formula M ₂ LC
u ₃ -O _7-y [where M is Ba or Sr and L is Y, La, Pr, N
d, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu, any one element, y is a number of 0.1 ~ 0.3], a superconductor characterized by depositing a thin film Thin film manufacturing method. 2. Cu and L (where L is any one element of Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu) as a metal chelate. The method for producing a superconductor thin film according to claim 1, wherein an acetylacetone chelate is used. 3. As a metal chelate, Cu and L (where L is any one element of Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu) The method for producing a superconductor thin film according to claim (1), characterized in that a dipivaloylmethane complex is used. 4. Cu and L (where L is any one element of Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu) as a metal chelate. The method for producing a superconductor thin film according to claim (1), wherein a trifluoroacetylacetone complex is used.