JPH0753638B2 - Method for forming superconducting thin film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for forming a superconducting thin film, particularly a ceramic superconducting thin film.

[Conventional technology]

Recently, ceramic-based superconducting materials have attracted attention as materials exhibiting high-temperature superconductivity. Such materials are, for example, II
After drying powders of oxides of Group Ia and Group Ib and carbonates of Group IIa, press molding, pre-sintering and crushing were repeated several times, the resulting powder was pressed again. It is molded and finally sintered to form a disc-shaped sintered body.

As described above, in order to obtain a dense and uniform sintered body, it is necessary to repeat the process, which requires a lot of labor, and the thickness is limited. Is difficult.

[Problems to be Solved by the Invention] Therefore, although the sputtering method or the vapor deposition method is used, the crystallinity of the oxide thin film itself is good and the smoothness of the surface is also important in order to obtain a product having good characteristics.

However, the oxide thin films obtained by these methods are
There is a problem that the material is easily decomposed in the air to become amorphous, or that it is made into a paste and fired at a high temperature has a rough surface.

Therefore, a method of annealing after forming the oxide thin film is conceivable, but of course this is disadvantageous in terms of process.

Therefore, an object of the present invention is to obtain a superconducting thin film which exhibits superconducting property without annealing after film formation and has a smooth surface and excellent crystallinity.

[Means for solving problems]

In order to solve the above problems, in the present invention, strontium or barium and rare earth elements and Cu simple substances or compounds in ultrahigh vacuum are separately heated and vaporized to generate molecular beams, and in an atmosphere containing oxygen. Then, the ceramic-based superconducting thin film was formed by depositing it on the heated substrate.

[Action]

By making the ultra-high vacuum, gas in the atmosphere, especially water, is almost completely removed, and the reaction can proceed in an extreme state in which decomposition and abnormal growth are suppressed.

Then, each of the elements or compounds becomes a vapor in an amount suitable for a desired product by the controlled heating temperature, and these vapors adhere to the substrate and are heated at a high temperature while being combined and combined with the supplied oxygen. Then, a smooth crystalline superconducting thin film is deposited directly on the substrate.

〔Example〕

As shown in the figure, the growth chamber 1 has a suction port 2 communicating with an ultra-high vacuum pump, a crucible 3 for loading raw materials A and B is arranged in the lower part of the growth chamber 1, and an oxygen atmosphere is generated. Source 6
Are arranged. A rotatable holder 5 incorporating a heater 4 is attached to the upper part of the growth chamber 1, and a substrate S is supported by the holder 5.

Now, each of the crucibles 3 is loaded with a single metal or a compound, and the inside of the growth chamber 1 is maintained at an ultrahigh vacuum of about 10 ^-8 to 10 ^-11 Torr, and high frequency heating, resistance heating, electron beam heating, etc.
Evaporate by heating to a temperature of ℃ ~ 2500 ℃.

On the other hand, the rotating holder 5 is equipped with a zirconia plate or the like as the substrate S, and is heated by the heater 4 to 500 ° C to 900 ° C.
Is heated to the temperature of 1 and the oxygen gas is blown from the oxygen atmosphere generation source 6 to the substrate S. The oxygen atmosphere may be formed by supplying oxygen gas, or by irradiating the substrate in an active state such as oxygen ion beam, oxygen plasma, or oxygen radical.

In this way, the evaporated raw material becomes a molecular beam and adheres to the substrate S, and is deposited while being combined and combined with oxygen to form a thin film.

Furthermore, after the substrate S is masked in advance to form the ceramic thin film, the masking may be removed or the masking may be left as it is to form the superconducting circuit.

Next, more detailed examples will be described.

Now, after filling each of La, Sr, and Cu as raw materials into the crucible, the growth chamber is depressurized to about 10 ^-8 to 10 ^-11 Torr, the zirconia substrate is heated to about 600 ° C, and rotated at 15 rpm, and oxygen is added. In an atmosphere with a partial pressure of 10 ^-3 to 10 ^-7 Torr, La, Sr, and Cu are simultaneously heated and evaporated by an electron beam to generate a molecular beam with an intensity of 1 × 10 ^-7 to 1 × 10 ^-5 Torr. A superconducting thin film made of La-Sr-Cu-O ceramic was formed on the zirconia substrate. The thin film was about 1 μm, the surface was smooth, and the critical temperature was about 40 ° K.

〔effect〕

According to the present invention, as described above, since the raw material is molecular beam-formed and deposited on the substrate in the oxygen atmosphere while heating the substrate under the ultra-high vacuum, the pollution source in the atmosphere is almost completely removed. The reaction proceeds in the removed state, and a smooth crystalline superconducting thin film having a uniform structure with few oxygen vacancies can be directly obtained without annealing. Therefore, various superconducting materials with excellent performance can be easily prepared. .

[Brief description of drawings]

 The figure is a diagram showing an example of an apparatus used in the present invention. 1 ... Growth chamber, 2 ... Suction port, 3 ... Crucible, 4 ... Heater, 5 ... Holder, 6 ... Oxygen atmosphere generation source, A, B ... Raw material, S ... Substrate.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location H01B 13/00 565 D 7244-5G H01L 39/12 ZAA C 9276-4M (72) Inventor Hideki Yao Sumitomo Electric Industries, Ltd. Osaka Works, 1-3-1, Shimaya, Konohana-ku, Osaka-shi, Osaka (56) Reference JP-A-63-237313 (JP, A)

Claims (3)

[Claims] 1. A strontium or barium elemental metal or compound of a rare earth element and copper in an oxygen atmosphere under ultrahigh vacuum is heated and vaporized to generate a molecular beam, which is deposited on a heated substrate by deposition. A method of forming a superconducting thin film, which comprises directly forming a superconducting thin film on a substrate. 2. The method for forming a superconducting thin film according to claim 1, wherein the rare earth element is any one of lanthanum, yttrium and scandium. 3. The oxygen atmosphere is any one of an oxygen gas atmosphere, a high temperature oxygen gas atmosphere, an oxygen plasma atmosphere, an oxygen ion atmosphere, an oxygen radical atmosphere, or a mixture of at least two kinds thereof. ) The method for forming a superconducting thin film according to the item.