JPH04214862A - Film forming apparatus - Google Patents

Abstract

PURPOSE:To prevent the contamination of a laser beam injecting window and to stably execute film forming for a long time, in a laser ablation film forming apparatus, by specifying the distance between the laser beam injecting window and an irradiating spot on a target face. CONSTITUTION:A freely rotatable target 3 which is rotated by a rotary shaft 6 is arranged inside of a vacuum chamber 2, and a substrate 4 is mounted on a holding stand 8 arranged in the opposite apparatus. A laser beam 7 from a laser generating apparatus 9 is condensed by a condenser lens 10, and an irradiating spot 14 on the surface of the target 3 is irradiated with it through a window 11 provided at the edge part of a projecting port 13 in a vacuum chamber 2 to evaporate the target irradiating part and to form a film on the substrate 4. Because the target 4 is rotated, the whole face of the target 3 is irradiated by the irradiating spot 14, and the target 3 is uniformly evaporated. The distance from an entrance window 11 of a port 13 to a target irradiating spot opening is regulated to >=600mm, and the length L of the port part 13 is regulated to >=200mm, by which the contamination of the inside of the window 11 caused by vaporized grains is prevented and a film forming operation is stably executed for a long time.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film forming apparatus using a laser ablation method, and more particularly to a film forming apparatus which has been improved to enable continuous film forming over a long period of time.

0002

[Prior Art] Laser ablation methods (1) have no compositional deviation between the target and the deposited film;
2) It has the characteristics of being able to form films at low temperatures and at high speeds, and has recently attracted attention as a method for producing oxide superconducting thin films.

[0003] When forming a film by laser ablation, the following film forming apparatus is used. That is,
The film forming apparatus includes a vacuum chamber provided with a window through which laser light passes. A target and a substrate are arranged in a vacuum chamber so as to face each other. On the other hand, a laser generator that generates excimer laser light, for example, is arranged outside the vacuum chamber. Therefore, according to such a film forming apparatus, particles are scattered from the target by ablation by irradiating the target with laser light emitted from the laser generator through the window. By depositing these scattered particles on the substrate,
A predetermined film is deposited on the substrate. For example, when a target containing a component of an oxide film superconducting substance is used, an oxide superconducting thin film is formed on the substrate.

0004

Problems to be Solved by the Invention When forming a film by the above-described laser ablation method, there is a problem in that particles scattered from the target by the ablation also adhere to the window and contaminate the window.

[0005] Such window contamination absorbs or scatters laser light. This causes changes in the energy density and distribution of the laser light reaching the target surface,
As a result, the performance of the obtained membrane also changes. Therefore, windows provided in vacuum chambers must be frequently replaced with clean ones, and contaminated windows must be replaced with clean ones.
It must be polished so that it can be reused.

However, although window replacement as described above is applicable when film formation is performed in a batch manner for a relatively short time, it is necessary to perform continuous film formation or repeated film formation for a relatively long time. It cannot be easily applied in certain cases. Therefore, when performing continuous film formation or repeated film formation over a relatively long period of time, even if the energy density and its distribution that can form a film with excellent properties are initially set, over time, There was a problem that the properties of the obtained film changed. Therefore, for example, it has been difficult to continuously form a film on a long substrate over its longitudinal direction with stable quality.

[0007] Therefore, an object of the present invention is to provide a film forming apparatus that can prevent windows from becoming dirty and thereby stably obtain a film having predetermined characteristics for a long period of time.

[0008]

[Means for Solving the Problems] The present invention is directed to a film forming apparatus using a laser ablation method, and this film forming apparatus includes a vacuum chamber provided with a window through which laser light passes, and a vacuum chamber provided with a window through which laser light passes. The vacuum chamber includes a target and a substrate arranged to face each other within the vacuum chamber, and a laser generator arranged outside the vacuum chamber. Laser light emitted from the laser generator is irradiated onto the target through the window. This causes ablation at the laser beam irradiation spot on the target, and particles scattered from the target due to this ablation are deposited on the substrate, thereby achieving film formation.

In order to solve the above-mentioned technical problem, this film forming apparatus is characterized in that the distance between the laser beam irradiation spot on the target and the window is 600 mm or more.

[0010] The window is attached, for example, to the tip of a port that projects from the main body portion of the vacuum chamber. In this case, of the above-mentioned distance of 600 mm or more, the distance of 200 mm or more is preferably given by the length of the port.

Further, the film forming apparatus according to the present invention can be advantageously applied to forming an oxide superconducting thin film.

0012

[Operation] Particles scattered from the target surface by laser ablation are distributed in a direction substantially perpendicular to the target surface. The design is such that as many of these scattered particles as possible reach the substrate. However, some of the scattered particles do not reach the substrate and inevitably float inside the vacuum chamber, and some of them end up adhering to the window.

Under such circumstances, if the distance between the laser beam irradiation spot on the target and the window is set to 600 mm or more, particles attempting to fly from the target toward the window will be , the probability that the particles will be collided and scattered by the atmospheric gas in the vacuum chamber is increased, thereby making it possible to extremely reduce the probability that the particles will reach the window.

[0014]

[Effect of the invention] Therefore, according to this invention, the window is
The windows can be kept clean for a long time since they are prevented from being contaminated by particles thrown out by laser ablation. Therefore, even if film formation is performed continuously for a long time or many times using the film forming apparatus according to the present invention, a film of the same or substantially the same quality can be stably obtained.

[0015] Therefore, the film forming apparatus according to the present invention is
Particularly remarkable effects are exhibited when applied to the case where a film is continuously formed on a long substrate. Therefore, the film forming apparatus according to the present invention is particularly advantageous when applied to a case where an oxide superconducting thin film is formed on a long substrate to obtain an oxide superconducting wire.

Note that when the window is provided at the tip of the port protruding from the main body of the vacuum chamber, the above-mentioned 6.
By providing a distance of at least 200 mm out of the distance of 00 mm or more depending on the length of the port, it is possible to prevent the main body of the vacuum chamber from increasing in size, and it is possible to avoid increasing the size of the film forming apparatus.

[0017]

Embodiment FIG. 1 is an explanatory diagram showing a film forming apparatus 1 as an embodiment of the present invention.

Referring to FIG. 1, the inside of vacuum chamber 2 has an atmosphere containing, for example, oxygen. A target 3 and a substrate 4 are arranged in such a vacuum chamber 2 so as to face each other. The target 3 is held by a rotating shaft 6 that rotates as indicated by an arrow 5, so that as wide a region of the main surface of the target 3 as possible can be used as the irradiation portion of the laser beam 7. The substrate 4 is placed on a substrate stand 8. The substrate stand 8 has a built-in heater for heating the substrate 4.

A laser generator 9 is arranged outside the vacuum chamber 2 . Laser light 7 emitted from laser generator 9 passes through condensing lens 10 and window 11 and is irradiated onto target 3 . The window 11 is made of quartz or spradil, for example. The window 11 is provided at the tip of the port 13 protruding from the main body portion 12 of the vacuum chamber 2 .

In the configuration described above, the laser beam 7 emitted from the laser generator 9 is irradiated onto the target 3 through the window 11. As a result, ablation occurs at the irradiation spot 14 of the laser beam 7 on the target 3, and particles are scattered from the target 3. The particles are deposited on the substrate 4, thereby forming the desired film on the substrate 4.

In this embodiment, the length L of the port 13 is 2.
00 mm or more, thereby making the distance D between the irradiation spot 14 and the window 11 600 mm or more. In this way, by increasing the distance D, the target 3
This is intended to prevent particles scattered from the window from adhering to the window 11 and contaminating the window 11.

Next, in order to confirm the effects of this invention,
An experimental example in which a superconducting thin film having a composition of YBa2 Cu3 O7-X was formed will be described.

Experimental Example 1 An oxide superconducting thin film was formed using a target made of YBa2 Cu3 O7-X under the following film forming conditions.

Laser: KrF (248 nm) Energy density: 2.3 J/cm2 Repetition frequency: 5 Hz Oxygen pressure: 300 mTorr Substrate temperature: 650°C Target-to-substrate distance: 45 mm Film forming rate: 33 angstroms/min Laser beam incident angle: The film-forming operation was repeated multiple times using the same film-forming apparatus without replacing the 45-degree window, with a film-forming time of 4 hours each time.

First, when using a film forming apparatus in which the distance between the laser beam irradiation spot on the target and the window is 45 cm, the critical current density in liquid nitrogen (77.3 K) is 93 cm in the first film forming operation. A sample showing a value of ×104 A/cm2 was obtained, but the zero resistance temperature of the sample obtained in the second film-forming operation was less than 77.3 K, making it difficult to measure the critical current density in liquid nitrogen. It was impossible.

On the other hand, when using a film forming apparatus in which the port to which the window is attached was extended by 20 cm and the distance between the laser beam irradiation spot on the target and the window was increased to 60 cm, the first film forming operation The sample obtained is 1
It exhibits a critical current density of 50×104 A/cm2 and 3
Even in the sample obtained by the second film-forming operation, 130
It exhibited a critical current density of ×104 A/cm2.

Experimental Example 2 Bi-P was produced by laser ablation under the following conditions.
A b-Sr-Ca-Cu-O high temperature oxide superconducting thin film was fabricated.

Target: Bi1.8 Pb0.6 Sr2 Ca2
Cu3.4 Ox Sintered body substrate temperature: 200°C Laser: Q-switch Nd:YAG laser (1064
nm) Energy density: 2 J/cm2 Repetition frequency: 200 Hz Oxygen pressure: 200 mTorr Distance between target and substrate: 35 mm Deposition rate: 200-300 angstroms/min Deposition time: 1 hour The film obtained by the laser ablation method described above was ,
It was amorphous and did not exhibit superconducting properties even at 4.2K.

[0029] Therefore, in the atmosphere, at 850°C, 60
Heat treatment was carried out for an hour. By changing the length of the entrance window port, we varied the distance between the entrance window and the target and measured the change in critical temperature depending on the number of times of film formation. At this time, the focal length of the condenser lens was changed to keep the energy density on the target constant. Also, the critical temperature is 4
Measured by terminal method.

Table 1 below shows the change in critical temperature depending on the number of times of film formation when the distance between the entrance window and the target is changed.

[0031]

[Table 1]

As can be seen from Table 1 above, when the distance between the entrance window and the target is "700 mm" and "800 mm"
Sample No. 2 and 3, "450mm
” Sample No. Excellent results were obtained compared to 1.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a film forming apparatus 1 according to an embodiment of the present invention.

[Explanation of symbols]

1 Film deposition equipment 2 Vacuum chamber 3 Target 4 Board 7 Laser light 9 Laser generator 11 Window 12 Main body part 13 Port 14 Irradiation spot

Claims (3)

[Claims] 1. A vacuum chamber provided with a window through which a laser beam passes; a target and a substrate disposed to face each other within the vacuum chamber; and a laser generator disposed outside the vacuum chamber. , in a film forming apparatus using a laser ablation method, in which particles scattered from the target are deposited on the substrate to form a film by irradiating the target with laser light emitted from the laser generator through the window; ,
A film forming apparatus characterized in that a distance between a laser beam irradiation spot on the target and the window is 600 mm or more. 2. The window is provided at a tip of a port protruding from the main body portion of the vacuum chamber, and
The film forming apparatus according to claim 1, wherein a distance of 200 mm or more among the distances of mm or more is given by the length of the port. 3. The target includes a component of an oxide superconducting substance and is applied to forming an oxide superconducting thin film.
The film forming apparatus according to claim 1 or 2.