JP2003095796A - METHOD OF MANUFACTURING EPITAXIAL THIN FILM OF alpha-SiC AND Α-SiC HETEROEPITAXIAL THIN FILM - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method in which the α-SiC epitaxial thin film is deposited at a low temperature on other kinds of substrate than an SiC single crystal, and to provide the α-SiC heteroepitaxial thin film manufactured by the same. SOLUTION: The method of manufacturing the α-SiC epitaxial thin film by laser abrasion comprises evaporating by irradiating a target of a single crystal or a polycrystal of an α-SiC with a pulse laser in a low pressure inert gas atmosphere and depositing the film on a heated other kinds of substrate than the SiC single crystal. Furthermore, the α-SiC heteroepitaxial thin film of the high temperature phase is also provided.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing an α-SiC epitaxial thin film and an α-Si obtained by the method.
More specifically, the present invention relates to a C semiconductor thin film, and more specifically, to a film forming method capable of producing a heteroepitaxial thin film of α-SiC on a low-cost heterogeneous substrate at a low substrate temperature, and particularly to an inexpensive sapphire or the like. And a high-temperature phase α-produced by the method for producing an α-SiC epitaxial thin film as a base of high-temperature semiconductor electronics at a low substrate temperature of about 800 ° C.
The present invention relates to a SiC heteroepitaxial thin film.

[0002]

2. Description of the Related Art Silicon carbide (SiC) has recently attracted attention as a high temperature semiconductor material because it has a wide band gap. SiC is divided into a high temperature stable α phase and a low temperature β phase depending on its crystal structure. Among these, the α-phase SiC (α-SiC) having a wide band gap width is being actively researched toward its practical application as an electronic device material. In order to use this α-SiC as an element, a technique for manufacturing the epitaxial thin film is important as a basic technique. As a conventional technique relating to a method for producing an α-SiC epitaxial thin film, for example, liquid phase epitaxial growth or chemical vapor deposition (CV) is performed on an α-SiC single crystal substrate.
D) is available (reference: A. Suzuki, M. Ikeda,
H. Matsunami, and T. Tanaka: J. Electrochem. Soc.
122 (1975) 1741 (liquid phase epitaxy method), H. Matsun
ami, T. Ueda, and H. Nishino: Mat. Res. Soc. Symp.
Proc. Vol. 162 (1990) 397 (CVD method) etc.). However, in these methods, since the melting temperature of SiC is high, it is necessary to raise the substrate temperature to 1500 ° C. or higher to form a film. Since the film is formed at such a high temperature,
A substrate having a low melting point such as Si cannot be used, and it is necessary to use the same SiC single crystal substrate as the film itself.

Since a SiC single crystal substrate is difficult to manufacture, a commercially available SiC single crystal wafer has a maximum size of only 2 inches, and its price is very expensive. . Furthermore, the single crystal has a fatal micropipe defect in device fabrication, and at this stage it cannot be completely removed. Further, since the film forming process at high temperature causes mutual diffusion, it becomes a great obstacle in manufacturing a device structure such as a laminated type. These process and manufacturing cost issues have become a major bottleneck in the spread of SiC semiconductor technology. In the future, the film formation temperature should be 1
It is considered to be an important issue to lower the temperature to 000 ° C or lower.

In order to solve these problems, there is a demand for a technique of epitaxially growing α-SiC (heteroepitaxial) on an inexpensive different substrate at a lower substrate temperature. There are pulse laser deposition method and molecular beam epitaxy method as a method for producing a SiC thin film on a different substrate (reference: JS Pelt, ME Ramsey, and
SM Durbin: Thin Solid Films 371 (2000) 72 (Pulse laser deposition method), S. Kaneda, Y. Sakamoto, C. Nis
hi, M. Kanaya, and S. Hannai: Jpn. J. Appl. Phys 2
5 (1986) 1307 (Molecular beam epitaxy method) and the like, films formed by these methods are all low-temperature β-phases, and high-temperature α-SiC epitaxial thin films could not be formed.

[0005]

Under these circumstances, the present inventors have taken the above-mentioned prior art into consideration by considering the use of α-SiC.
As a result of intensive research aimed at developing a method for synthesizing an epitaxial thin film on a heterogeneous substrate at a low temperature, as a result, a high-temperature phase α-SiC was used as a target, and laser ablation was performed in a low-pressure inert gas atmosphere. Α-SiC having in-plane orientation by producing
We succeeded in producing a thin film and completed the present invention. The present invention solves the above-mentioned problems of the prior art, a method for producing an α-SiC epitaxial thin film on an inexpensive heterogeneous substrate at a low substrate temperature, and an α-Si obtained by this method.
It is intended to provide a C semiconductor thin film.

[0006]

The present invention for solving the above-mentioned problems comprises the following technical means. (1) A method for producing an α-SiC epitaxial thin film, which is a high-temperature phase α-SiC in a low-pressure inert gas atmosphere.
The method of producing an α-SiC epitaxial thin film, which comprises producing an α-SiC epitaxial thin film by irradiating the target with a pulse laser to evaporate (ablate) the target and deposit the target on a heated substrate. (2) The film forming method as described in (1) above, wherein the low-pressure inert gas is argon. (3) The film forming method as described in (1) above, wherein the target is a single crystal or polycrystal of α-SiC. (4) The film forming method according to (1), wherein the substrate is a heterogeneous single crystal substrate other than the α-SiC single crystal substrate. (5) A high temperature formed on a heterogeneous single crystal substrate other than an α-SiC single crystal substrate, which is produced by the method for producing a thin film according to any one of (1) to (4) above. Phase α-SiC heteroepitaxial thin film.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail. The present invention is a heterogeneous single crystal substrate such as a sapphire substrate in which a pulsed laser beam is focused and irradiated on the surface of an α-SiC target in a container filled with a low-pressure inert gas to ablate the target, and the evaporated substance is heated. The above-mentioned object is achieved by depositing on the above.
In the present invention, film formation is performed by the laser ablation method using a pulse laser in order to achieve the above object for the following reasons. Thermal energy above a certain level is required for epitaxially growing a thin film. This energy is usually supplied by raising the substrate temperature. The α-SiC thin film is made the same as the α-S film by the CVD method or the like.
A substrate temperature of 1500 ° C. or higher is required for epitaxial growth on an iC single crystal substrate. On the other hand, in the laser ablation method, the kinetic energy (e.g.
It has the characteristic of having V). By using this method, it is possible to lower the thermal energy, that is, the substrate temperature, by the high kinetic energy of the evaporated substance.

In the present invention, a polycrystalline or single crystal target of α-SiC having the same composition and crystal structure as the film is used. In the process of ablation, the surface portion of the target is instantaneously peeled off by the irradiation of the pulsed laser.
Then, the ablated particles are deposited on the substrate while maintaining the composition of the target, and the target α-
A thin film of SiC is obtained.

However, even if a film is formed by a laser ablation method using an α-SiC target in vacuum,
For example, an epitaxial thin film could not be formed at a substrate temperature as low as about 800 ° C. In the present invention, α-Si is formed by forming a film in a low pressure inert gas atmosphere.
This makes it possible to produce a C heteroepitaxial thin film. In the present invention, the low pressure inert gas is 1 × 10 ⁻³
Pa to 200 Pa argon, neon, helium, xenon, krypton, etc. are used. The following two can be considered as the effect of performing ablation in a low pressure inert gas atmosphere. First, the particles of the evaporated material and the inert gas molecules collide with each other to scatter the particle components having a low kinetic energy, and as a result, only the particles having a high kinetic energy for crystal growth are selectively formed on the substrate surface. Can be reached, and the epitaxialization of the film is promoted. Second, the vaporized substance having a high kinetic energy collides with gas molecules to be excited into a plasma state, and the activated state of the vaporized substance greatly contributes to lowering the temperature of the film forming process.

By the above means, even if a very expensive SiC single crystal substrate is not used as the substrate material, an α-SiC epitaxial film can be formed at a low substrate temperature of about 800 ° C. by using a cheaper heterogeneous single crystal substrate such as sapphire. Can be produced. As the substrate, a heterogeneous single crystal substrate other than the α-SiC single crystal substrate is used, and for example, sapphire, silicon, magnesium oxide, strontium titanate or the like is used. The substrate is heated to 800-1200 ° C, more preferably 820-1000 ° C.

As the pulsed laser light, high-power ultraviolet light from Nd: YAG pulsed laser or excimer laser is used. The vapor deposition time is about 5 to 60 minutes, and can be increased or decreased depending on the required film thickness. According to the method of the present invention, α-SiC
A high-temperature phase α-SiC heteroepitaxial thin film formed on a heterogeneous single crystal substrate having a lower melting point than the single crystal substrate of No. The reason why film formation is possible at a lower temperature than before by performing film formation in a low-pressure inert gas atmosphere is that low-pressure inert gas acts as a buffer and particles with sufficiently high energy for crystal growth. It is conceivable that only the substrate can selectively reach the substrate surface. .

[0012]

EXAMPLES Next, the present invention will be specifically described based on examples, but the present invention is not limited to the following examples. Example In this example, an embodiment of a method for producing an epitaxial thin film and an α-SiC epitaxial thin film obtained by using the method will be described in detail with reference to the drawings. As an apparatus for producing an epitaxial thin film, a high vacuum chamber capable of vacuuming up to the order of 10 ⁻⁹ Pa shown in FIG. 1 and equipped with an inert gas introduction system is used, and Nd:
A YAG pulse laser (4th harmonic) was used. As one embodiment of the present invention, an example of forming the film on a (001) plane sapphire single crystal substrate is shown. First, the container 1 is evacuated to 6.0 × 10 ⁻⁷ Torr using a vacuum exhaust system (a turbo molecular pump and a rotary pump), and then,
Inert gas (argon) was introduced up to 50 Pa (Fig. 1). Ultraviolet (wavelength 266 nm) of the fourth harmonic of Nd: YAG laser was used as the pulsed laser light. The pulse frequency is 2 Hz. The pulsed laser light is condensed using a condenser 6 (convex lens made of quartz, etc.), and a window 5 for introducing light (quartz, etc.)
The target 4 is irradiated through the target 4 to evaporate (ablate) the target to deposit a thin film on the substrate.
An α-SiC sintered body was used for the target 4. The laser energy density on the target is 20 J / cm ² . The target was rotated during laser irradiation in order to prevent the laser beam from being concentrated and damaged at one location on the target. The substrate heater 2 was placed facing the target, and the substrate 3 was fixed on the heater surface and heated to 820 ° C. A sapphire (001) plane single crystal was used for the substrate 3. The vapor deposition time was 30 minutes.

FIG. 2 shows sapphire Al ₂ O ₃ (001)
FIG. 3 is an X-ray diffraction diagram of a SiC thin film formed on a substrate, measured by θ-2θ sweep. In addition to the peak of the substrate, a diffraction peak due to the (001) plane of α-SiC is observed. Further, other peaks other than the (001) plane due to α-SiC were not detected. In order to investigate whether this film was an alignment film, X-ray diffraction measurement by ω sweep was further performed on the peak from the α-SiC (001) plane.
As a result, a diffraction pattern having a peak characteristic of the alignment film was obtained (FIG. 3). From these results, it can be seen that this thin film is an α-SiC film that is c-axis oriented perpendicular to the substrate.

Next, FIG. 4 shows a reflection type high-speed electron diffraction (R
The result of the surface observation by HEED) is shown. In the figure,
(A) and (b) are RHEED diffraction patterns of the (001) plane of the sapphire single crystal substrate before vapor deposition. The incident directions of the electron beam are [100] and [210], respectively. As expected from the hexagonal plane lattice on the substrate surface, 3
A diffraction pattern having a streak symmetrical in these two directions, which are different by 0 degree, is observed and observed with a 60 degree period. After film formation, the RHEED diffraction pattern in the substrate [100] direction changed as shown in FIG. On the other hand, in the [210] direction, the diffraction pattern of FIG. Since two different patterns (FIGS. (C) and (d)) are seen in different directions every 30 degrees, it can be seen that the manufactured film also has the same 6-fold symmetry as the substrate. Also, Figure (c)
From the distance between the diffraction spots of (d) and (d), the lattice constant of the a-axis of the film is estimated to be about 3.02Å. This is α-Si
It matches the lattice constant of C (a = 3.08Å) within the error range. These results indicate that the produced thin film has in-plane orientation.

From the results of the above-mentioned plane vertical alignment by X-ray diffraction and in-plane alignment by reflection type high-energy electron diffraction (RHEED), it is possible to use the method of the present invention at 820 ° C.
At a low substrate temperature of α even on a heterogeneous single crystal substrate such as a sapphire (001) plane single crystal substrate without using a SiC single crystal.
It was found that an epitaxial thin film of —SiC can be produced.

[0016]

As described above, the present invention provides a method of forming a film by a laser ablation method using α-SiC as a target in an atmosphere of a low pressure inert gas such as argon, and an α-obtained thereby. The present invention relates to a SiC heteroepitaxial thin film, and according to the present invention, 1) without using a SiC single crystal, on an inexpensive dissimilar single crystal substrate such as a sapphire single crystal substrate, at a very low substrate temperature of about 800 ° C.
A heteroepitaxial thin film of SiC can be produced. 2) By using the film forming method of the present invention and the α-SiC epitaxial thin film produced by the present method, it can be produced on a previously expensive SiC single crystal substrate at a high substrate temperature. It is possible to produce the SiC semiconductor element structure which has been performed on an inexpensive substrate with a simple device, which is a particular effect.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an apparatus used in a method for producing an α-SiC epitaxial thin film according to an embodiment of the present invention.

FIG. 2 illustrates sapphire (00
1) An X-ray diffraction diagram of an α-SiC epitaxial thin film formed on a single crystal substrate, measured by θ-2θ sweep.

FIG. 3 is an X-ray diffraction diagram of a diffraction peak from SiC (001) observed in FIG. 2 measured by ω sweep.

FIG. 4 is a diffraction pattern by reflection high-energy electron diffraction (RHEED) in two directions (a) and (b) different by 30 degrees on the sapphire substrate (001) surface, and the same substrate according to an embodiment of the present invention. It is a RHEED pattern in the same two directions of the alpha-SiC epitaxial film produced above.

[Explanation of symbols]

1 container (a container such as a vacuum chamber kept in a low pressure inert gas atmosphere) 2 substrate heater 3 substrate (sapphire (001) substrate etc.) 4 target (α-SiC) 5 light introduction window (quartz etc.) 6 light concentrator (Convex lens made of quartz, etc.)

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 4G077 AA03 BE08 DA03 EA05 EA06                       ED06 SB10                 4K029 AA04 AA07 BA56 BB10 CA01                       DB05 DB20                 5F103 AA10 BB23 BB55 DD17 HH04                       NN01 RR10

Claims (5)

[Claims] 1. A method for producing an α-SiC epitaxial thin film, comprising a high-temperature phase α in a low-pressure inert gas atmosphere.
A method for producing an α-SiC epitaxial thin film, which comprises producing an α-SiC epitaxial thin film by irradiating a pulsed laser on the SiC target to evaporate (ablate) the target and deposit the target on a heated substrate. . 2. The film forming method according to claim 1, wherein the low-pressure inert gas is argon. 3. The film forming method according to claim 1, wherein the target is a single crystal or a polycrystal of α-SiC. 4. The film forming method according to claim 1, wherein the substrate is a heterogeneous single crystal substrate other than an α-SiC single crystal substrate. 5. A high temperature phase formed on a heterogeneous single crystal substrate other than an α-SiC single crystal substrate, which is produced by the method for producing a thin film according to any one of claims 1 to 4. Α-SiC heteroepitaxial thin film.