JPH0745141A - Method for forming film using laser ablation technique - Google Patents

Abstract

PURPOSE:To form a film having improved in-plane orientation characteristics, by irradiating a film with an exima laser from a direction defining 5 deg. to 85 deg. with respect to the film surface during or after film formation. CONSTITUTION:Laser light is applied onto a target and the substance that splashes from the target surface is deposited on a substrate to thereby form a film. During or after film formation, excimer laser is applied onto the film from a direction defining 5 deg. to 85 deg. with respect to the film surface. As a result, the film substance is grown so that the SiC direction may become perpendicular to the substrate surface, and within the substrate surface as well, the film substance orientation also occurs. Thereafter, when the laser ablation technique is used, an oxide superconductive film is obtained which has improved in-plane orientation characteristic and improved critical current density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film forming method using a laser ablation method, and more particularly to a method for forming an in-plane oriented film by a laser ablation method.

[0002]

2. Description of the Related Art In recent years, the development of a laser device has been remarkable, and film formation by a laser ablation method using it has been actively performed. In the laser ablation method, by irradiating the target with a laser, the particles of the substance constituting the target are scattered in the form of atoms and particles from the irradiation part of the target, and these scattered particles reach the substrate and are deposited on the substrate. A film is formed.

The film formation by the laser ablation method has a very high film formation rate as compared with other vapor phase methods such as the sputtering method, the vacuum vapor deposition method and the CVD method, and therefore the production rate can be industrially increased. it can. Further, the film formation by the laser ablation method is suitable for film formation of oxides, nitrides, etc. because the film formation atmosphere can be changed relatively freely as compared with other vapor phase methods.

For these reasons, the laser ablation method has recently been very often used for industrial production.

[0005]

However, it may be difficult to obtain in-plane orientation of the film formed by the laser ablation method described above. In particular, when a film is formed on a polycrystalline substrate, the film formed by the laser ablation method becomes polycrystalline, and even if the a-axis and b-axis of the crystal are
Even if one of the axis and the c-axis was perpendicular to the substrate, there was usually no in-plane orientation.

On the other hand, the oxide high-temperature superconducting material discovered in recent years has a large critical current density due to the existence of crystal grain boundaries, which is below. Therefore, when trying to obtain a high critical current density, it is desirable to be as close as possible to a single crystal. However, a film formed by a laser ablation method on a polycrystalline substrate by a conventional technique is, for example, Y ₁ Ba ₂ C.
In the case of u ₃ O _7-x superconducting film, the so-called c-axis orientation in which the c-axis is perpendicular to the substrate is obtained, but the a-axis or b-axis is obtained.
The direction of the axis was parallel to the substrate surface, but the in-plane direction was random. Therefore, the critical current density of the obtained superconducting film is also low, and is 5 × 10 ⁴ A / 77 K at 77K.
I could only get a value of cm ² .

An object of the present invention is to solve the above-mentioned problems and to provide a film forming method by a laser ablation method which can form a film having in-plane orientation.

A further object of the present invention is to improve the in-plane orientation to produce a Y ₁ Ba ₂ Cu ₃ O _7-x oxide superconducting film having an improved critical current density. It is to provide a film forming method by an ablation method.

[0009]

A film forming method using a laser ablation method according to the invention of claim 1 forms a film by depositing a substance scattered from a target surface on a substrate by irradiating the target with a laser. The film forming method using the laser ablation method is characterized in that the film surface is irradiated with an excimer laser from a direction of 5 ° or more and 85 ° or less.

The film forming method using the laser ablation method according to the second aspect of the present invention is a laser ablation method for forming a film by irradiating a target with a laser to deposit a substance scattered from the target surface on a substrate. The film forming method used is characterized in that the film is irradiated with an excimer laser from a direction of 5 ° or more and 85 ° or less before film formation.

In the film forming method using the laser ablation method according to the third aspect of the present invention, the target is irradiated with a laser to deposit a substance scattered from the target surface on the substrate, and Y ₁ Ba ₂ Cu ₃ O ₇ is deposited. _-x is a film forming method using a laser ablation method for forming an oxide superconducting film, which is performed before, during or after film formation.
The feature is that the substrate or the film surface is irradiated with an excimer laser from a direction of 5 ° or more and 85 ° or less.

Laser ablation according to the invention of claim 4
The film-forming method using the
The material that scatters from the target surface is
To form an intermediate layer on the substrate by
On the middle layer Y₁Ba₂Cu ₃O_7-xOxide superconducting film
Film forming method using laser ablation method for forming film
Of the base layer before, during, or after the formation of the intermediate layer.
From the direction of 5 ° or more and 85 ° or less with respect to the plate or film surface
It is characterized by irradiating a xima laser.

[0013]

According to the present invention, the excimer laser is irradiated onto the substrate or the film surface from a direction of 5 ° or more and 85 ° or less before, during, or after the film formation. Therefore, a film having in-plane orientation can be formed.

When the irradiation angle of the excimer laser is less than 5 °, the surface of the crystal is irradiated with the laser in a substantially parallel manner, and the crystal having a certain azimuth is not scraped off so that in-plane orientation can be obtained. I will not be able to. Further, if the angle of irradiation with the excimer laser is larger than 85 °, it becomes close to perpendicular to the crystal plane, and the crystal rotates in the plane perpendicular to the direction of laser irradiation, that is, the substrate plane, so that in-plane orientation cannot be obtained. .

Further, even when the substrate is polycrystalline, when the substrate is irradiated with an excimer laser from a predetermined direction, the substrate surface is scraped off in a certain direction, and the polycrystalline substrate is as if a single crystal substrate at the time of film formation. The thin film is formed as if the state was changed to the above state, the thin film becomes a single crystal state, and the in-plane orientation is improved.

On the other hand, in Y-based, Bi-based, and Tl-based oxide superconducting thin films, the c-axis orientation in which the c-axis of the crystal is perpendicular to the substrate surface can be obtained relatively easily, but the a-axis and the b-axis are It was randomly oriented in the plane of the substrate, and a sufficient critical current density could not be obtained. In order to obtain a high critical current density, the a-axis and the b-axis must be orthogonal or in the same direction. According to this invention, the film surface is irradiated with the excimer laser from a predetermined direction during film formation. Therefore, it is possible to obtain a film that is c-axis oriented and has in-plane orientation in which the a-axis and the b-axis are orthogonal to each other in the substrate plane, and as a result, the critical current density of the film increases.

[0017]

【Example】

(Example 1) A SiC target was irradiated with a KrF excimer laser having a wavelength of 248 nm at a frequency of 15 Hz,
A SiC film was formed on a MgO single crystal substrate in a carbon dioxide atmosphere of 400 mTorr. Before film formation, wavelength 19
Irradiation with a 3 nm ArF excimer laser was performed at a frequency of 10 Hz toward the film surface from two directions, that is, a direction inclined by 45 ° and a direction inclined by 135 ° with respect to the substrate surface. Irradiation of the excimer laser on the film surface was performed 0.05 seconds after the irradiation of the excimer laser on the target.

After forming the thin film of SiC, the film was examined and found to be S
The iC was grown so that the (100) direction was perpendicular to the substrate surface, and was also oriented in the substrate surface.

(Example 2) A target of Y ₁ Ba ₂ Cu ₃ O _7-x was irradiated with a KrF excimer laser having a wavelength of 248 nm at a frequency of 10 Hz, and Y ₁ Ba was deposited on a Hastelloy substrate in an oxygen atmosphere of 600 mTorr. ₂ Cu ₃ O _7-x
Was formed. During film formation, the KrF excimer laser is tilted toward the film surface from a direction inclined by 55 ° with respect to the substrate surface.
Irradiation with a frequency of Hz. The irradiation of the excimer laser on the film surface is 0.02 of the irradiation of the excimer laser on the target.
I decided to do it in seconds.

Y₁Ba₂Cu₃O_7-xAfter forming the thin film of
When I inspect the membrane, Y₁Ba₂Cu₃O _7-xIs based on the c-axis direction of
It grows so as to be perpendicular to the plate surface, and a
The axes b and b are orthogonal to each other or face the same direction
It was

On the other hand, when the film surface is not irradiated with an excimer laser during the film formation, the thin film has a crystal structure of Y ₁ Ba ₂ Cu ₃ O _7-x and is c-axis oriented, but not in-plane oriented. It was

Measure the critical current density at 77.3K
And the former film is 137,000 A / cm ²And the latter
Membrane is 3200A / cm²Met.

(Example 3) In Example 2, while changing the angle of the excimer laser for irradiating the film surface from 1 ° to 89 °, Y ₁ Ba ₂ Cu ₃ O was used under the same conditions.
_{A 7-x} film was formed. After forming the film, the critical current density was measured.

The results are shown in FIG. In Fig. 1, the horizontal axis is the angle (°) to the film surface when the excimer laser is irradiated.
And the vertical axis represents the critical current density (A / cm ² ).

As is clear from FIG. 1, when the angle of the excimer laser irradiation is 5 ° or more and 85 ° or less, the critical current density is improved.

Example 4 A YSZ target was irradiated with a KrF excimer laser having a wavelength of 248 nm at a frequency of 100 Hz, and a YSZ film was formed on a Hastelloy substrate in an oxygen atmosphere of 100 mTorr. During film formation, K
Irradiation with rF excimer laser was performed at a frequency of 100 Hz toward the film surface from a direction inclined by 30 ° with respect to the substrate surface. Irradiation of the excimer laser onto the film surface was performed 0.005 seconds after the irradiation of the excimer laser onto the target.

After the thin film of YSZ was formed, when the film was examined, Y
The SZ was grown so that the (100) direction was perpendicular to the substrate surface, and was also in-plane oriented.

Furthermore, a KrF excimer laser having a wavelength of 248 nm is used as a target of Y ₁ Ba ₂ Cu ₃ O _7-x.
Irradiate at a frequency of 0 Hz, deposit YSZ on a Hastelloy substrate in an oxygen atmosphere of 600 mTorr, and then perform Y ₁ B deposition.
A film of a ₂ Cu ₃ O _7-x was formed.

Y₁Ba₂Cu₃O_7-xAfter forming the thin film of
When I inspect the membrane, Y₁Ba₂Cu₃O _7-xIs based on the c-axis direction of
It grows so as to be perpendicular to the plate surface, and a
The axes b and b are orthogonal to each other or face the same direction
It was

On the other hand, during the YSZ film formation, the film surface is subjected to excimer
If the laser is not irradiated, the same film formation method₁B
a₂Cu₃O_7-xThe thin film formed by₁Ba₂
Cu ₃O_7-xHas a c-axis orientation in the crystal structure of
I wasn't going.

Measure the critical current density at 77.3K
And the former film is 583000A / cm ²And the latter
Membrane is 11000A / cm²Met.

By the way, in the laser ablation method,
In addition to the above-mentioned problems, there is a problem that a substance having a crystal structure different from the main crystal structure of the film or a substance having a crystal orientation is likely to be generated in a part of the film because of the high film formation rate. When the film formation speed is slow, the bond between the substrate and the film surface can be easily strengthened by mutual diffusion, and it is relatively easy to be affected by the crystal structure of the substrate. Alternatively, the crystal orientation can be grown based on the crystal structure of the substrate. However,
In the case of film formation by the laser ablation method, the film formation speed is often increased, and in that case, if the adhesion between the substrate and the film interface is not good, or if the crystal structure or crystal orientation of the obtained film is In some cases, it was difficult to be affected by the crystal structure and orientation of the substrate.

In the film formation using the laser ablation method, if the excimer laser is irradiated to the substrate or the film surface from one direction or a plurality of directions before, during, or after the film formation, the in-plane orientation is made uniform. In addition, the effect of improving the adhesion strength between the substrate and the interface, transmitting the good crystal structure of the crystal of the single crystal substrate, the periodicity of the crystal to the thin film, or aligning the crystal orientation of the film itself. can get. These will be described in detail in the following examples.

(Example 5) A target of Y ₁ Ba ₂ Cu ₃ O _7-x was irradiated with a KrF excimer laser having a wavelength of 248 nm at a frequency of 10 Hz, and a MgO single crystal substrate was irradiated on an MgO single crystal substrate in an oxygen atmosphere of 200 mTorr. Y ₁ Ba ₂ Cu ₃ O
_{A 7-x} film was formed. During film formation, the ArF excimer laser with a wavelength of 193 nm is delayed from the substrate surface by 30 μsec after the oscillation of the excimer laser with which the target is irradiated.
Film formation was performed by irradiating the film surface at a frequency of 10 Hz from the tilted direction. After film formation, when X-ray diffraction is performed,
It was a single phase of Y ₁ Ba ₂ Cu ₃ O _7-x .

On the other hand, when the film surface is not irradiated with an excimer laser during film formation, the film after film formation was observed by X-ray diffraction, and as a result, a film having a crystal structure other than Y ₁ Ba ₂ Cu ₃ O _7-x was observed. In addition, the existence of Y ₂ Ba ₁ Cu ₁ O _Y having a crystal structure was confirmed.

In the laser ablation method in which a target is irradiated with an excimer laser during film formation and a plume generated from the target surface reaches the substrate surface to form a film, the thin film formed or being formed is exposed to the excimer laser. When irradiating, the excisioner laser irradiates from the direction where the main crystal structure constituting the film is scraped off at a small rate and the different crystal structure is scraped off at a large rate, and the deposition rate of the substance of the main crystal structure in the film increases, The deposition rate of crystalline structured materials that are undesirable to be included is reduced.

(Example 6) A TiN target was irradiated with a KrF excimer laser having a wavelength of 248 nm to obtain 300
TiN on stainless steel substrate in mTorr nitrogen atmosphere
Was formed. When the substrate is irradiated with an excimer laser having a wavelength of 308 nm for 3 minutes from another excimer laser device before the film formation, TiN after the film formation is not peeled off even if the substrate is folded back in two and then returned. It was

On the other hand, when the substrate was not irradiated with the excimer laser before the film formation, TiN was subjected to the same bending test.
Has peeled off the substrate.

Irradiating the substrate surface with an excimer laser from a certain direction before film formation has the effect of removing the deposits on the substrate surface and strengthening the adhesion between the thin film to be subsequently formed and the substrate.

Example 7 A target of Y ₁ Ba ₂ Cu ₃ O _7-x was irradiated with a KrF excimer laser having a wavelength of 248 nm at a frequency of 10 Hz, and Y was deposited on a MgO single crystal substrate in an oxygen atmosphere of 200 mTorr. ₁ Ba ₂ Cu ₃ O
_{A 7-x} film was formed. Before film formation, A with a wavelength of 193 nm
Irradiation with an rF excimer laser was performed at a frequency of 150 Hz toward the film surface from a direction inclined by 45 ° with respect to the substrate surface. As a result, the (100) plane of the MgO substrate was preferentially scraped off. After film formation, the film was inspected to find that Y ₁ Ba ₂ Cu ₃ O _7-x
It was a single crystal.

On the other hand, when the excimer laser irradiation is not performed on the substrate surface before the film formation, the thin film has a crystal structure of Y ₁ Ba ₂ Cu ₃ O _7-x and is c-axis oriented, but not in-plane oriented. It was

In the case where the substrate is a single crystal, generally, the surface of the film formed thereafter tends to be in a polycrystalline state only by polishing the surface of the substrate smoothly, but the substrate is prioritized depending on the direction of the excimer laser with which the surface of the substrate is irradiated. Since there is a crystal orientation that is shaved off, the crystal of the thin film succeeds the single crystal of the substrate in the subsequent film formation, so that there is an effect that the thin film becomes close to the single crystal state.

Example 8 A SiC target was irradiated with a KrF excimer laser having a wavelength of 248 nm at a frequency of 15 Hz to form a SiC film on a MgO single crystal substrate in a carbon dioxide atmosphere of 400 mTorr. Before the film formation, an ArF excimer laser having a wavelength of 193 nm was irradiated toward the film surface at a frequency of 10 Hz from a direction inclined by 45 ° with respect to the substrate surface. Irradiation of the excimer laser on the film surface was performed 0.05 seconds after the irradiation of the excimer laser on the target. After forming the thin film of SiC, the film was examined, and it was found that the (100) direction of SiC was perpendicular to the substrate surface.

On the other hand, when the film was formed without irradiating the excimer laser, the (100) direction was oriented randomly.

When the excimer laser is irradiated from a certain direction on the film surface during film formation, a certain crystal orientation of the film is easily scraped off. As a result, the growth of the film has an effect of advancing to a certain crystal orientation. . Further, in some cases, even if a conventional single crystal thin film cannot be obtained, the single crystal film is formed by maintaining the directionality of the crystal by irradiation of the excimer laser from a certain direction on the film surface. There is an effect that can be obtained. Irradiation of the excimer laser may be performed in a certain fixed direction, and even in one direction, the effect can be obtained in a plurality of directions. Irradiation of the excimer laser on the film surface is performed before film formation.
The effect is obtained during the film formation or after the film formation.

[0046]

According to the present invention, a film having an improved in-plane orientation can be formed by the laser ablation method.

When the present invention is applied to the formation of an oxide superconducting film, the oxide superconducting film having an improved critical current density can be obtained by improving the in-plane orientation.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between an angle of an excimer laser with respect to a film surface and a critical current density.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI technical display location // H01B 12/06 ZAA 7244-5G (72) Inventor Ken Ken Hayashi 1-3, Shimaya, Konohana-ku, Osaka No. Sumitomo Electric Industries, Ltd. Osaka Works (72) Inventor Gozo Fujino 1-3-3 Shimaya, Konohana-ku, Osaka City Sumitomo Denki Industries Co., Ltd. Osaka Works (72) Inventor Tsukushi Hara Nishiazajigaoka, Chofu-shi, Tokyo 2-4-1, Tokyo Electric Power Co., Inc. Technical Research Laboratory (72) Inventor Hideo Ishii 2-4-1, Nishi Tsutsujigaoka, Chofu City, Tokyo Tokyo Electric Power Co., Inc. Technical Research Institute

Claims (4)

[Claims] 1. A film forming method using a laser ablation method for forming a film by depositing a substance scattered from a target surface on a substrate by irradiating the target with a laser, which is during or during film formation. A film forming method using a laser ablation method, which comprises irradiating the film surface with an excimer laser from a direction of 5 ° or more and 85 ° or less. 2. A film forming method using a laser ablation method for forming a film by depositing a substance scattered from a target surface on a substrate by irradiating a target with a laser, wherein the substrate is formed before the film formation. A film forming method using a laser ablation method, which comprises irradiating an excimer laser from a direction of 5 ° or more and 85 ° or less. 3. A laser ablation method for forming a Y ₁ Ba ₂ Cu ₃ O _7-x oxide superconducting film by depositing a substance scattered from a target surface on a substrate by irradiating the target with a laser. A film forming method used, characterized by irradiating the substrate or film surface with an excimer laser from a direction of 5 ° to 85 ° before, during or after film formation. A film forming method using an ablation method. 4. An intermediate layer is formed on the substrate by depositing a substance scattered from the target surface on the substrate by irradiating the target with a laser, and Y ₁ Ba ₂ Cu ₃ is further formed on the intermediate layer. A film forming method using a laser ablation method for forming an O _7-x oxide superconducting film, wherein the substrate or film surface is formed before, during or after forming the intermediate layer. A film forming method using a laser ablation method, which comprises irradiating an excimer laser from a direction of 5 ° or more and 85 ° or less.