JPH0441665A - Production of thin film by vapor deposition with laser - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing a thin film by laser vapor deposition. More specifically, the present invention relates to a method of producing a high-quality thin film using a laser vapor deposition method.

BACKGROUND OF THE INVENTION Various methods are used to produce thin films, but the laser deposition method has advantages such as easy control of composition and fast film formation rate. In addition, since it does not require a negative stirrup field, it is considered to be a suitable method for producing high-quality thin films.

Conventionally, when producing thin films using laser evaporation, the substrate and target are placed inside a deposition chamber that can be evacuated to a high vacuum and any atmospheric gas can be introduced, and the laser device is placed outside the deposition chamber. The emitted laser light was guided by optical means and irradiated onto the target.

Problems to be Solved by the Invention However, in general, in the laser vapor deposition method, the area of the target that is irradiated with laser light is very small compared to the area of the entire target. For this reason, most of the target is not used effectively, so the position of the target has been shifted or the position where the laser beam is irradiated has been moved.

In addition, when a thin film is produced using a laser vapor deposition method, the film is formed at the tip of a plasma state called a wax-like plume that is generated when a target is irradiated with laser light. This is because there are many oxidized and active film-forming particles at the tip of the plume, and a thin film with good properties can be obtained by forming a film at this part. However, since the irradiation area of the laser beam is minute, the plume is also minute, and the area of the thin film that can be produced by laser evaporation is extremely small.Furthermore, when a thin film of normal size is produced, the distribution of film thickness is large. Moreover, the purpose of the present invention is to solve the problem of non-uniform film formation in a small area, which is a disadvantage of laser evaporation, and to solve the problem of non-uniform film formation in a small area, which is a disadvantage of laser evaporation. The object of the present invention is to provide a method for producing a thin film having an area of .

Means for Solving the Problems According to the present invention, a method for producing a thin film by a laser evaporation method in which a target is irradiated with laser light and a thin film is deposited on a substrate placed opposite to the target, includes: A method for producing a thin film is provided, characterized in that a position on the target to which the laser beam is irradiated is determined using random numbers.

Function The main feature of the method of the present invention is that the position on the target in the film forming chamber to which the laser beam is irradiated is determined by random numbers, and the laser beam is irradiated continuously or intermittently.

Plasma, which is a collection of active film-forming particles called a plume, is generated above the position of the target that is irradiated with the laser beam, and its tip reaches the substrate placed opposite the target. In the laser deposition method, the actual film is deposited at the tip of the plume. When the laser beam irradiation position of the target moves, the plume position also moves together.

In the method of the present invention, the laser beam irradiation position of the target is determined using random numbers and moved. Specifically, the surface of the target is divided into a grid, each part is numbered, and a random number generator or the like generates random numbers to determine the irradiation position. In the method of the present invention, a more homogeneous thin film can be produced because the laser beam irradiation position is not moved in a specific order but is moved randomly using random numbers. Therefore, with the method of the present invention, it is possible to produce a uniform thin film with an area approximately equal to the entire area over which the laser beam irradiation position moves.

In the laser vapor deposition method, laser light emitted by a laser device is usually focused by a lens or the like, and guided by an optical means such as a mirror for irradiation. Therefore, in the method of the present invention, in order to move the laser beam irradiation position on the target, a mirror whose direction changes according to the random number is used as the mirror. In particular, when the laser is a pulsed laser, it is preferable to use a mirror whose direction changes in synchronization with the laser pulse.

It is preferable that the mirror is placed near the lens and as far away from the target as possible.

This is because when the mirror is placed near the target, the angle of incidence of the laser beam on the target changes greatly. This is because if the change in the incident angle is large, the irradiation area of the laser beam on the target changes greatly, and the energy density changes accordingly, causing the film forming conditions to differ depending on the irradiated position of the target.

Hereinafter, the present invention will be explained in more detail with reference to Examples.
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 an example of a laser vapor deposition apparatus for carrying out the method of the present invention. In the laser vapor deposition apparatus shown in FIG.
The laser light generated by the laser beam, passed through the condensing lens 9 and reflected by the mirror 8, enters the laser entrance window 7 of the chamber 1, and irradiates the raw material target 5 held within the chamber 1. In the device of this embodiment, a laser device 10 oscillates a pulsed laser beam, and a mirror 8 is a control device 1 equipped with a random number generator.
1, c) The angle is changed for each Lt step, and the pulsed light is irradiated one pulse at a time to a position determined by a random number on the target 5. The inside of the chamber 1 can be evacuated to a high vacuum, and a substrate 2 is fixed to a substrate holder 3 so as to face a target 5. A heater 4 for heating the substrate 2 is provided inside the substrate holder 3 .

Further, a nozzle 6 for supplying a gas containing oxygen is provided near the target 5.

Using the above laser evaporation apparatus and the method of the present invention, Y
+ A Ba2Cu307-x oxide superconducting thin film was produced.

For the substrate 2, an Mg○ single crystal substrate and a 5rTi03 single crystal substrate were used, and the substrate temperature was set at 650°C to 750°C. Target 5 is Y1Ba2Cu3O with a diameter of 8 cm.
A sintered body of No. 7-X was used. In addition, substrate 2 and target 5
The distance between them was 7 cm. 1x1 inside of chamber 1
After exhausting to 0'Torr, oxygen gas was introduced to 100
I set it to mTorr.

The laser uses an excimer laser with a wavelength of 193 nm.
The laser output was 3.5 J/cI11, the laser beam irradiation area was 2×4 mm2, and the pulse frequency was 5 Hz.

The mirror 8 is a mirror glass coated with a dielectric thin film and can reflect 99% or more of a laser beam having a wavelength of 193 nm, and can be changed in direction by ±20° vertically and horizontally by a control device 11.

The horizontal distance between the target 5 and the mirror 8 was set to 30 cm, the angle of the mirror 8 was changed according to a random number by the control device 11, and a 3×3 CI'II area of the target 5 was irradiated with laser light.

Under the above conditions, open film formation was performed for 30 minutes, and the film thickness distribution and superconducting properties of the obtained oxide superconducting thin film were measured.

As a result, the film thickness distribution of the oxide superconducting thin film produced by the method of the present invention was 35 × 35 fl] [[±10 in the range of 12
%Met. On the other hand, with other film forming conditions being the same, the film thickness distribution in the conventional method of irradiating a single point on the target with a laser beam was ±10% in the range of 10×10×10.

Table 1 shows the measurement results of the critical temperature and film thickness of the oxide superconducting thin film produced by the method of the present invention.

Table 1 FIG. 1 is a schematic diagram of an example of a device.

As described in detail, according to the present invention, it is possible to fabricate a thin film with a larger area and less thickness distribution than before. This is an effect unique to the method of the present invention in which the laser beam is scanned over the target to perform laser deposition.

[Brief explanation of the drawing]

FIG. 1 shows a laser evaporation system for realizing the method of the present invention [main reference numbers] 1...Chamber 2...Substrate 3...Substrate holder 4...Heater 5...Target 6... Nozzle 7...Entrance window 8...Mirror-9...Condensing lens 10...Laser device 11...Mirror control device

Claims (1)

[Claims] In a method for producing a thin film by a laser evaporation method in which a target is irradiated with laser light and a thin film is deposited on a substrate placed opposite to the target, the position on the target to which the laser light is irradiated is determined. A method for producing a thin film, characterized in that the method is determined using random numbers.