JPH0238310A - Production of oxide high temperature superconductive thin film - Google Patents

Abstract

PURPOSE:To provide the subject thin film at a low base plate-heating temperature without any heat-treating process by adopting specific conditions in a method of forming the oxide high temperature superconductor thin film with a rf magnetron or opposed target sputter device. CONSTITUTION:In a method of forming the thin film of an oxide high temperature superconductor of AxByCuzOdelta (A and B are selected from Ca, Sr, Ba, etc., in the group IIa, Y and lanthanum in the group IIIa, Bi in the group IIIb, etc.,) or AxByCzCuepsilonOdelta (A-C are selected from the above-mentioned elements) with a rf magnetron or opposed target sputter device, an O2 plasma-generating device 2 is newly disposed on the peripheral portion of a base plate 9 and an oxide sintered product used as a target 4 is spattered in an atmosphere of Ar gas 5 and simultaneously O2 plasma is locally generated on the surface of the base plate 9 to form a <= approximately 1mum thick film on the base plate at a heating temperature of <=600 deg.C. After the electric discharge is stopped, the thin film-formed base plate is gradually cooled to room temperature by supplying plasma-free O2 gas 6 on the thin film or by cooling the base plate to 350-370 deg.C in an atmosphere of O2 gas 6 and subsequently keeping the base plate for several hours.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a method for manufacturing an oxide high temperature superconducting thin film, and more specifically, a method for manufacturing an oxide high temperature superconductor thin film at a low substrate temperature by RF magnetron sputtering or facing target sputtering. The present invention relates to a method of manufacturing a crystalline thin film.

[Prior art]

rf sputtering method, rf magnetron sputtering method.

Manufacture of oxide superconducting thin films by facing target sputtering etc. is possible using rare earth oxides such as Y-Ba-Cu-0, Ba-5r-Cu-0 oxides, Ba-P
This process is mainly performed on b-B1-0 type oxides, but also on many other oxides.

By the way, in order to manufacture an oxide high temperature superconducting thin film by each of the above-mentioned sputtering methods, for example, Ar gas: 0□ gas 49
: In a mixed gas atmosphere with a pressure ratio of 1 (pressure ratio), the substrate temperature is 6
After forming a film at 50'C to 700°C, it is annealed in an electric furnace in air or in an oxygen gas atmosphere above the substrate temperature, and then slowly cooled to achieve a high critical temperature (Y-B
A single crystal (C-axis oriented) film with a-Cu-0 system (86 to 88 K) is obtained. However, if this high-temperature substrate heating method is adopted, the quality of the manufactured thin film inevitably deteriorates, elements that make up the substrate diffuse into the thin film, and problems such as cracks may occur. become.

On the other hand, in the above method, when a film is formed by heating the substrate at 500°C to 600°C, the thin film does not exhibit superconductivity phenomenon by itself, and a high critical temperature cannot be obtained unless the subsequent heat treatment is performed sufficiently. do not have. Therefore, there are almost no examples of films formed by sputtering at low substrate temperatures that exhibit superconductivity and have a high critical temperature without being annealed in air or in an electric furnace in an oxygen gas atmosphere. The reality is that there is not.

Er, Ba, Cu4. The MgO substrate was sputtered by heating it to 650°C using an Ox target, Ar gas: 0□ gas'': 4:1 (pressure ratio), and a gas pressure of about 3 mtorr, and then rapidly cooling it to room temperature in an oxygen gas atmosphere. An example where the resistance of the thin film becomes 0 at about 86% (App Q, Ph
ys, Lett.

51 (26) 19872263), but here the critical temperature of the thin film largely depends on the distance between the substrate and the target, and when the distance is 35 mm, the critical temperature of the thin film is 86 mm.
K, and when the distance is 40nw++, it is about 60~7
Although it shows 0K, the thin film is a C-axis oriented crystal film.

Note that many methods have been proposed for manufacturing oxide high-temperature superconducting thin films using the CVD method, but although this method has the advantage of expanding the range of substrate selection, it requires heating the substrate temperature to over 700°C. Therefore, the thin film is likely to be polycrystalline. In addition, methods for manufacturing oxide high-temperature superconducting thin films using electron beam evaporation and cluster ion beam methods have also been proposed, but even with these methods, in order to obtain single crystal thin films, it is necessary to heat the substrate at high temperatures, It requires heat treatment in an electric furnace, and therefore has the disadvantage that it is difficult to obtain a film of good quality.

Superconducting transistors, D
This is desirable as an element for C-8QUID or other ultra-low-temperature optoelectronic materials.

〔the purpose〕

The present invention is capable of forming a film with a C-axis oriented single crystal and exhibiting a high critical temperature without heating the substrate at high temperatures and/or high-temperature heat treatment (post-treatment) of the thin film, which was done in the conventional method. The present invention provides a method for manufacturing a high-temperature superconducting thin film.

〔composition〕

The present invention provides an oxide high temperature superconductor AxByCuzOδ(A
, B is a combination of two selected from Ca, Sr, Ba, etc. of the Ira group, Y of the ma group, Bi, etc. of the IIIb group, such as lanthanum type), or AxByCzCU
In the method of forming an oxide high temperature superconducting thin film of εOδ (A, B, and C are selected and combined from three of the above elements) using an RF magnetron sputtering device or a facing target sputtering device, an oxygen plasma generation device is newly added. is provided around the substrate, and the oxide sintered body is sputtered in an Ar gas atmosphere. At the same time, oxygen plasma is locally generated on the upper surface of the substrate to heat the substrate to a temperature of 600.
After forming a film with a thickness of about 1 μm or less at a temperature of 0.degree. Or 350℃ after stopping the above discharge.
It is characterized in that the film is cooled to ~370°C in an oxygen gas atmosphere, maintained at that temperature for several hours, and then slowly cooled to room temperature.

Incidentally, the present inventor has discovered that if an oxide high-temperature superconducting thin film is manufactured using a new oxygen plasma generator installed in a specific position of a conventionally used sputtering apparatus,
It was confirmed that the above objectives were achieved. The method of the present invention is based on this.

The method of the present invention will be explained in more detail below with reference to the accompanying drawings, but as mentioned earlier, the oxide high temperature superconducting thin film produced by the method of the present invention has the formula % formula % the formula ( Especially in the combination of A and B in 1), (Y
, Ba), (Larsr), (La, Ba), etc. are preferable, and xrYrZ*δ is 1≦XyytZ+δ≦20
is a real number.

In particular, the combinations of A, B, and C in formula (2) include (Bi, Sr, Ca), (T Q , Ba, Ca), (
Bi, Ba, Ca) etc. are preferable, and X+y+Z+
ε, δ are the same as the above formula (1), 1≦x+y+Z+ε, δ≦
It is a real number of 20.

Therefore, in the method of the present invention, the formula (1) or (
An oxide sintered body having the same or almost the same composition as in 2) is used as a target.

FIG. 1 is a schematic diagram of an RF magnetron sputtering apparatus suitable for carrying out the method of the present invention. In the figure, 1 and 11 are high frequency power supplies, 2 is a high frequency power supply for oxygen plasma generation, and 3 is Sm-
An electrode part having a magnet such as Go, 4 a target, 5 an Ar gas outlet, 6 a 0□ gas outlet, 7 an electrode (for example, made of copper), and 8 a heater for heating the substrate wound with a Kanthal wire. , 9 is a substrate, and 10 is an electrode. Here, the frequencies of high frequency power supplies 1, 11 and 2 are all the same, 13.5
It is 6KHz. It is also advantageous to attach a magnet to the electrode 10 to promote the plasma formation of oxygen.

The target 4 and the substrate 9 are arranged facing each other,
An electrode 10 connected to an oxygen plasma generation power source 2 is arranged on the side of the surface of the substrate 9. The oxygen gas outlet 6 is the first
In the figure, it is attached to the upper part of the electrode 10, but since it is sufficient to supply 0□ gas to the surface of the substrate 9, it may be attached to the lower part of the electrode 10. Furthermore,
As shown in FIG. 2, the electrode 10 is connected to the oxygen gas outlet 6.
The Ar gas ejection port 5 is arranged between the target 4 and the substrate 9, and may be arranged on the side of the surface of the substrate 9.

Now, with this device (the one in Figure 1), the ultimate vacuum degree I
X IF' torr to Ar gas pressure: 0□Gas≠9
= 1.4:1 or 1:1 ratio of mixed gas pressure 2
The film is formed in a vacuum state of 10-3 to 10.times.10-3 torr with a power of 1 to 5 W/aj. At that time, the substrate used is 5rTi03 single crystal, MgO single crystal, etc.6
heated to 00°C or lower, preferably 400°C to 600°C,
The oxidation reaction of the film being formed is carried out using oxygen plasma present near the surface of the substrate.

The appropriate deposition rate is 20 to 100 people/min, and the thickness is about 1
After forming a film of .mu.m or less, the discharge is stopped, the supply of Ar gas is stopped, and the chamber is cooled to room temperature while passing 0□ gas, and the inside of the chamber is immediately returned to atmospheric pressure. Further, when the deposited film becomes about 1 μm or less, the supply of Ar gas is stopped and the discharge is stopped, and the oxygen plasma state is left as it is and the substrate temperature is cooled to around 350°C to 360°C.
It may be cooled to room temperature while flowing oxygen gas.

According to this means, a film that conventionally required a substrate heating temperature of 650° C. to 700° C. can be formed at a lower substrate heating temperature due to the oxygen plasma present on the film surface.
By keeping the film in an oxygen gas atmosphere during film cooling, it is possible to produce a thin film exhibiting superconductivity without the need for post-heat treatment, which is conventionally performed.

FIG. 2 is a schematic diagram of a facing target sputtering apparatus suitable for carrying out the method of the present invention. In the figure, the numbers 1 to 11 have the same meanings as in FIG. 1, but the high frequency power source 1 here is the negative electrode, and the high frequency power source 11 is the anode (ground).

Further, the two targets 4 are arranged to face each other and to be perpendicular to the substrate 9.

Now, with this device (shown in Figure 2), 1X IF'
From the ultimate vacuum of torr, Ar gas pressure 202 gas pressure Cape 4
:1 or 1:1 ratio of mixed gas pressure I
'~5 X 1O-3 torr vacuum state, power 1.0~1.51/a#, substrate heating temperature 600℃ or less (
(preferably 400 to 600° C.) and a deposition rate of 10 to 80 people/win. At that time, the surface of the film being deposited and formed is oxidized in oxygen plasma to a thickness of approximately 1 μm.
Make a film from the bottom. Thereafter, the discharge is stopped, the supply of Ar gas is stopped, and the temperature is slowly cooled to room temperature in an 02 gas atmosphere, or the temperature is cooled to around 350 to 360°C in oxygen plasma, and then cooled to room temperature in an oxygen gas atmosphere. Then, return the chamber to atmosphere.

According to this method, the same effects as the RF magnetron sputtering method shown in FIG. 1 can be obtained, and there is also the advantage that there is little deviation between the target composition and the manufactured thin film composition.

The present invention is a method for producing a high-temperature superconducting oxide thin film, but this technology can also be applied to producing 5QUIDs (superconducting quantum interference devices), infrared sensors, superconducting transistors, and the like.

Example I Each powder of Y, O, BaCO3, CuO was converted into Y:Ba:C
Weighed at a weight ratio of u = 1:2:3, mixed well, sintered at 950°C for 8 hours, crushed and mixed again to about 1μ
After reducing the particle size to less than m, a non-aqueous binder (PVB 1%
solution) and 200 kg/cd (7) pressure to make a diameter 10
] was solidified into a disk shape with a thickness of 2 ma+, sintered at 930°C for 6 hours, and used as a target.

Using this target and an Mg0 (100) single crystal substrate, an ultimate vacuum level of l x 10-' torr was obtained by the facing target sputtering method shown in FIG.

Ar gas pressure 1.8 x 10-'torr, 0. Gas pressure 0
, 2 X 1O-3 torr and a power of about 1 s/alt, the substrate was heated at 500 to 550 degrees Celsius in oxygen plasma, and then the film was formed, and the discharge was stopped for about 4 hours.
The supply of r gas was stopped, and the substrate was cooled to room temperature in an oxygen gas atmosphere of 5×IF 3 torr. When the substrate temperature reached about 25° C., the inside of the chamber was returned to atmospheric pressure. At this time, the membrane (
The thickness of the oxide high temperature superconducting thin film was approximately 0.8 μm.

When the electrical resistance of this thin film was measured by a four-terminal method using Au as an electrode, the critical temperature Tc at which the electrical resistance became O was found to be 88. Furthermore, X-ray analysis data showed that this thin film was a C-axis oriented single crystal film, and magnetic susceptibility measurements confirmed the Meissner effect.

〔effect〕

According to the method of the present invention, since the substrate heating temperature can be as low as 600° C. or less, a dense high-temperature superconducting oxide thin film with a smooth surface (electrical resistance at a maximum of 90° C.) can be obtained. In addition, there is no need for annealing in air or oxygen using an electric furnace as in the conventional method.

[Brief explanation of the drawing]

1 and 2 are schematic views of two sides of an apparatus suitable for carrying out the method of the invention. 1.11...High frequency power supply 2...High frequency power supply for oxygen plasma generation 3...Electrode part 5...Ar gas outlet a, 10...Electrode 9...Substrate

Claims (1)

[Claims] 1. Oxide high temperature superconductor AxByCuzOδ (A, B are
Group IIa such as Ca, Sr, Ba, etc., Group IIIa Y
or AxByCzCuεOδ(
In the method of forming a thin film of three elements A, B, and C selected and combined from the above-mentioned elements using an RF magnetron sputtering device or a facing target sputtering device, an oxygen plasma generator is newly installed in the peripheral part of the substrate. , sputtering the oxide sintered body in an Ar gas atmosphere, and at the same time generating oxygen plasma locally on the upper surface of the substrate,
After forming a film with a thickness of about 1 μm or less at a substrate heating temperature of 600°C or less, the discharge is stopped, and oxygen gas that is not in a plasma state is supplied from the oxygen plasma generator to the film surface, and the film is slowly heated to room temperature. or cooling the film in an oxygen gas atmosphere to 350°C to 370°C after stopping the discharge, maintaining it at that temperature for several hours, and then slowly cooling it to room temperature. Method for manufacturing high-temperature superconducting thin films.