JPH0450104A - Production of high-quality oxide superconducting thin film and equipment therefor - Google Patents

Abstract

PURPOSE:To obtain the title thin film with improved quality by making a film formation while irradiating a substrate with laser beams and observing the thin film crystal on the substrate and by proceeding with the film formation by changing the wavelength of the laser beams according to the crystal state. CONSTITUTION:A chamber 1 is evacuated to a high vacuum, a substrate 5 is heated to a specified temperature with a heater 4, and the evaporation sources 10 for superconductor constituents are heated and evaporated under control with K-cells 2 along with feeding a reaction gas, thus forming an oxide thin film on the substrate. The crystal state of the thin film is observed through the reflective high-speed electron beam diffraction technique, and the thin film is irradiated with laser beams from a laser equipment 7 by varying the wavelength according to the crystal state, thus forming the objective high-quality oxide superconducting thin film. The K-cells 2, heater 4, laser equipment 7 and reaction gas feed pipe 6 etc., are each controlled by a microcomputer 11, thus setting in-chamber atmosphere, temperature conditions, crystal structure etc.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method and apparatus for producing high quality oxide superconducting thin films. More specifically, the present invention relates to a method for producing a high-quality oxide superconducting thin film using a physical vapor deposition method, and an apparatus that can automatically perform film formation using the method.

Conventional technology Y lBa2CU307-X series, B1゜5r2Ca2C
u30X series and T12Ba2Ca2Cu301! Each of the oxide superconductors in the system has a high critical temperature and is considered promising for practical use.

In order to apply these oxide superconductors to electronic devices such as Josephson elements and superconducting transistors, it is essential to make them thin.

Methods for producing thin films of oxide superconductors include vacuum evaporation,
MBE method, sputtering method, CVD method, etc. are being considered. The most commonly used method is the sputtering method, but the vacuum evaporation method allows film formation without applying any electromagnetic field, and the MBE method allows for strict composition control, resulting in high quality. It is possible to create oxide superconducting thin films.

Problems to be Solved by the Invention For use in electronic devices as described above, an oxide superconducting thin film that is single crystal and has excellent smoothness is preferable.

However, in the conventional method, an oxide superconducting thin film with good superconducting properties could not be obtained unless the substrate temperature during film formation was high (approximately 700° C.). Therefore, usable substrates are limited, and since film formation at high temperatures causes diffusion of substrate elements, the superconducting properties of the oxide superconducting thin film in the vicinity of the substrate deteriorate.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method and apparatus for producing a high-quality oxide superconducting thin film that solves the problems of the prior art described above.

Means for Solving the Problems According to the present invention, in a method for producing a thin film of an oxide superconductor on a substrate by a physical vapor deposition method, while irradiating the substrate with a laser beam, the thin film on the substrate is A method for producing an oxide superconducting thin film is provided, which is characterized in that film formation is performed while observing a crystal, and film formation is performed by changing the wavelength of the laser beam according to the crystal state.

Further, in the present invention, as an apparatus for implementing the above method,
a chamber whose interior can be evacuated to a high vacuum; a gas supply means capable of introducing any gas into the chamber; a substrate holder that holds a substrate within the chamber; a heating means that heats the substrate; The method further comprises: observation means capable of observing the crystal structure of the thin film; laser light irradiation means for irradiating the substrate with laser light; and control means for controlling the gas supply means, heating means and laser light irradiation means. An apparatus for producing a characteristic oxide superconducting thin film is provided.

Function The method of the present invention irradiates a substrate with laser light, observes the crystal state of the oxide superconducting thin film being formed on the substrate, and changes the wavelength of the laser light based on the results. It has characteristics.

That is, in the method of the present invention, reaction energy of appropriate intensity is supplied by laser light to the oxide superconducting thin film being formed on the substrate, thereby producing a high quality oxide superconducting thin film with good crystallinity.

In the present invention, laser light supplies energy to the reacting oxide superconducting thin film on the substrate surface. Further, it is not preferable that the substrate temperature rises due to laser light irradiation. Therefore, it is preferable that the wavelength of the laser beam is short, and since the wavelength needs to be variable, for example, a dye laser or the like is preferable.

Further, in the present invention, film formation is performed while observing the crystal state of the oxide superconducting thin film, and this observation is preferably performed by reflection high-speed electron diffraction (RHEED).

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the following disclosure is merely an example of the present invention and does not limit the technical scope of the present invention in any way.

Embodiment FIG. 1 shows a schematic diagram of an example of an apparatus for implementing the method of the present invention. The device shown in FIG. 1 is an MBE device, which can be evacuated to a high vacuum, has a chamber 1 equipped with a laser entrance window 13, can heat the evaporation source 10 housed inside by controlling the temperature, and has a shutter 9. a plurality of Knudsen cells (K-cells) 2 capable of controlling the evaporation amount of the evaporation source 10; a substrate holder 3 capable of heating the mounted substrate 5 by controlling the temperature with a heater 4; A reaction gas supply vibro which is open and supplies oxygen to the vicinity of the surface of the substrate 5 is provided.

In addition, RHEED electron gun 2 for observing the surface condition of thin films
0 and a screen 21. Furthermore, chamber 1
A laser device 7 that irradiates the substrate with laser light, a condensing lens 8, and a filter 12 are arranged outside. The laser device 7 is a dye laser, and the oscillation wavelength can be changed by changing the dye cell.

The K-cell 2, the heater 4, the laser device 7, the shutter 9, and the reaction gas supply vibro valve (not shown) are controlled by a microcomputer 11. The microcomputer 11 stores the chamber internal atmosphere in the film forming process,
Data such as temperature conditions and the crystal structure of the oxide superconductor constituting the thin film to be produced are stored. Further, the microcomputer 11 receives the output of RHEED of the MBE device manually. The microcomputer 11 outputs control signals to the MBE apparatus to perform film formation based on the various data described above. It also compares the stored crystal structure data of the oxide superconductor and controls the laser device 7 to perform feedback control of the laser light wavelength.

Using the MBE apparatus of the present invention shown in FIG. 1, Y1Ba2Cu
A 30t-x film was prepared. Evaporation sources include Y, Ba and C.
u was used. The electron beam diffraction pattern was input from the RHEED to the microcomputer 11, and the microcomputer 11 controlled the pattern so that the change in electron beam diffraction intensity and the change in the laser oscillation wavelength were synchronized. Specifically, the periodic change in the center streak of electron beam diffraction (-period length is
The film was formed by changing the wavelength of the laser light in the range of 430 to 530 nm in synchronization with the time required for the superconductor to grow one unit cell. The film forming conditions are shown below.

Substrate temperature = 500°C Chamber vacuum degree: 5 xlQ 'torr Laser light wavelength = 430 to 530 nm Laser light irradiation intensity + 10 to 100 m J / cof film thickness
:200 nm For comparison, an oxide superconducting thin film was also fabricated using a conventional method in which the substrate was not irradiated with laser light, with other conditions being set the same. T of each thin film obtained. , Jc are shown below.

Tc (K) Jc (A/cI11) (Measured at 77) Invention 84 2.3 Xl06 Comparative Example
34 The thin film produced by the method of the present invention was a high-quality thin film with high smoothness in appearance and higher crystallinity.

By following the method of the present invention as described in detail, it is possible to produce an oxide thin film of higher quality than ever before. This is an effect unique to the method of the present invention, in which the substrate is irradiated with laser light while changing the wavelength in accordance with the growth of the oxide crystals constituting the thin film.

Moreover, using the apparatus of the present invention, the above-described method of the present invention can be automatically implemented.

[Main reference number]

DESCRIPTION OF SYMBOLS 1... Chamber, 2... K-cell, 3... Substrate holder, 4... Heater, 5... Substrate, 6... Reaction gas supply pipe, 7... Laser device, 8 ...Condensing lens, 9...Shutter, 10...Evaporation source, 11...Microcomputer patent applicant Sumitomo Electric Industries, Ltd.

Claims (2)

[Claims] (1) In a method of producing a thin film of an oxide superconductor on a substrate by physical vapor deposition, the film is formed while irradiating the substrate with laser light and observing the crystals of the thin film on the substrate. . A method for producing an oxide superconducting thin film, characterized in that the film is formed by changing the wavelength of the laser beam depending on the crystal state. (2) An apparatus for producing a thin film of an oxide superconductor on a substrate by a physical vapor deposition method, comprising: a chamber capable of evacuating the interior to a high vacuum; a gas supply means capable of introducing any gas into the chamber; a substrate holder for holding a substrate in a chamber; a heating means for heating the substrate; an observation means for observing a crystal structure of a thin film on the substrate; a laser light irradiation means for irradiating the substrate with laser light; the gas supply means;
1. An apparatus for producing an oxide superconducting thin film, comprising a heating means and a control means for controlling a laser beam irradiation means.