JP2004134620A - Gallium nitride epitaxy method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To carry out the epitaxial growth of a GaN (gallium nitride) film with a good crystallinity on an SiC (silicon carbide) substrate without a buffer layer. <P>SOLUTION: In a hot wall epitaxy apparatus, a substrate 34 to be treated has at least a vapor deposition surface composed of an SiC single crystal. Metal Ga is used as a source material 28, and a nitrogen-containing gas such as NH<SB>3</SB>(ammonia) is introduced as a reactive gas G in a passage for Ga vapor via a gas introduction pipe 38. Since the epitaxial growth is carried out using this apparatus, the GaN film is epitaxially grown directly and continuously to the SiC single crystal on the vapor deposition surface of the substrate 34. As the source material 28, an organic source of TMG (trimethylgallium) or the like can be used, and as the nitrogen-containing gas, a nitrogen radical-containing gas can be used. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a GaN epitaxy method for epitaxially growing a GaN (gallium nitride) film on a SiC (silicon carbide) substrate.
[0002]
[Prior art]
Conventionally, as a method of epitaxially growing a GaN film on a SiC substrate via a buffer layer, a method using a CVD (chemical vapor deposition) method or an MBE (molecular beam epitaxy) method is known.
[0003]
[Problems to be solved by the invention]
According to the conventional technique described above, the crystal growth is performed in a thermally non-equilibrium state regardless of the method used in the CVD method or the MBE method, so that a GaN film having good crystallinity cannot be obtained. There is. In addition, since a buffer layer made of GaN, GaAlN, or the like is formed on the SiC substrate in advance, there is a problem that the cost is increased.
[0004]
An object of the present invention is to provide a novel GaN epitaxy method capable of growing a GaN film having good crystallinity on a SiC substrate without a buffer layer.
[0005]
[Means for Solving the Problems]
The GaN epitaxy method according to the present invention comprises:
A chamber evacuated to vacuum,
A storage means disposed in the vacuum chamber for storing the source material;
First heating means for heating the source material contained in the containing means to evaporate;
Holding means disposed above the accommodation means in the vacuum chamber, and holding the substrate to be processed in a state where the deposition surface faces the accommodation means,
A second heating unit that heats the substrate to be processed held by the holding unit from a surface opposite to the deposition surface;
Guiding means for guiding the vapor of the source material contained in the containing means in the vacuum chamber to the deposition surface of the substrate to be processed held by the holding means;
Third heating means for heating the vapor of the source material guided by the guiding means;
Introducing means for introducing a reaction gas reacting with the vapor of the source material from the outside of the vacuum chamber to a passage of the vapor of the source material, using a hot wall type epitaxy apparatus, the GaN epitaxy method comprising:
At least the surface to be deposited is formed of a single crystal of silicon carbide as the substrate to be processed, gallium is used as the source material, and the nitrogen-containing gas is used as the reaction gas. Gallium nitride is epitaxially grown directly and continuously on a single crystal of silicon carbide.
[0006]
According to the GaN epitaxy method of the present invention, in a hot-wall type epitaxy apparatus, the distance between the substrate to be processed and the guide means (hot-wall portion) is as narrow as about 1 cm, and the coupling from the hot-wall portion is weak due to radiation and infrared energy. Since the unstable crystal is re-evaporated, a GaN film having good crystallinity can be obtained without a buffer layer.
[0007]
In the GaN epitaxy method of the present invention, the third heating means may be constituted by a lamp heater, and the radiation of the lamp heater may be applied to the deposition surface of the substrate to be processed. By doing so, the crystallinity of the GaN film can be further improved.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
1 and 2 show a GaN epitaxy method according to an embodiment of the present invention.
[0009]
In the step of FIG. 1, a SiC substrate 10 made of single crystal SiC is prepared. The substrate 10 may have at least a deposition surface made of a single crystal of SiC, and other portions may be made of a polycrystal of SiC. Next, the substrate 10 is subjected to thermal annealing at a substrate temperature of around 1000 ° C. to remove a natural oxide film and impurities, thereby cleaning the substrate surface.
[0010]
In the step of FIG. 2, a GaN film (GaN single crystal film) 12 is epitaxially grown directly on the deposition surface of the substrate 10 directly on the SiC single crystal using the hot wall type epitaxy apparatus shown in FIG. The lattice constants of SiC and GaN are 3.081 and 3.189, respectively, but a GaN film 12 with good crystallinity was obtained without a buffer layer.
[0011]
In the hot wall type epitaxy apparatus shown in FIG. 3, the vacuum chamber 20 is evacuated to a vacuum through an exhaust port 20a. In the vacuum chamber 20, a support base 22 is disposed at the bottom. In the vacuum chamber 20, a cylindrical hot wall pipe 24 made of, for example, stainless steel is supported on a support table 22 in an upright state. A quartz tube 26 is disposed in the hot wall tube 24, and a peripheral portion of a flange 26 a provided around the open end of the quartz tube 26 is supported by the open end of the hot wall tube 24.
[0012]
The quartz tube 26 is roughly divided into a source accommodating portion 26A that accommodates the source material 28 and a vapor guide portion (hot wall portion) 26B that guides the vapor of the source material 28 upward. In the quartz tube 26, the source accommodating portion 26A may be configured to have a smaller diameter than the steam guide portion 26B as shown by a broken line A. Between the quartz tube 26 and the hot wall tube 24, a plurality (for example, eight) of lamp heaters 30A are provided so as to surround the source accommodating portion 26A, and a plurality (for example, so as to surround the steam guide portion 26B). (Eight) lamp heaters 30B.
[0013]
The plurality of lamp heaters 30A are for heating the source material 28 accommodated in the source accommodating portion 26A so as to evaporate. The plurality of lamp heaters 30B are for heating the vapor of the source material 28 that is guided upward by the vapor guide 26B, and the radiated light is transmitted through the opening end of the quartz tube 26 and the flange 26a in parallel. Irradiation is performed on the deposition surface of the substrate to be processed 34 (the surface facing the opening end of the quartz tube 26). Since each lamp heater among the plurality of lamp heaters 30B emits visible light together with infrared light, flying atoms having a weak bond are eliminated by irradiation of high-energy radiant light on the evaporation surface of the substrate 34, and strong vapor is emitted. A thin film having good crystallinity is formed mainly by the atoms coming from the bond.
[0014]
The hot wall tube 24 is for shielding heat radiation from the plurality of lamp heaters 30A, 30B. The hot wall tube 24 is provided with an annular partition portion 24S protruding inward to shield thermal radiation between the plurality of lamp heaters 30A and the plurality of lamp heaters 30B. When the hot wall pipe 24 is made of a metal such as stainless steel, the partition 24S can be formed integrally with the pipe main body. The temperature control circuit of the plurality of lamp heaters 30A and the temperature control circuit of the plurality of lamp heaters 30B are independent of each other, and can set the heating temperature separately.
[0015]
Above the quartz tube 26, a substrate holder 32 that holds a substrate 34 to be processed is arranged. The substrate holder 32 holds the substrate 34 such that the deposition surface of the substrate 34 is located at a distance D from the opening end of the quartz tube 26. The distance D is about 1 cm. A lamp heater 36 for heating the substrate 34 is provided on the side opposite to the deposition surface of the substrate 34. In the temperature control circuit of the lamp heater 36, the heating temperature of the substrate 34 can be appropriately set.
[0016]
The gas introduction pipe 38 is for introducing a reaction gas G reacting with the vapor of the source material 28 from outside the vacuum chamber 20 to the vapor passage of the source material 28. Although the tip of the gas introduction pipe 38 is arranged near the opening end of the quartz tube 26 as an example, it may be arranged inside the steam guide portion 26B.
[0017]
When performing the epitaxial growth process of FIG. 2 using the epitaxy apparatus of FIG. 3, the SiC substrate 10 is set on the substrate holder 32 as the substrate 34 to be processed. Further, metal Ga is used as the source material 28, and NH ₃ (ammonia) is used as the reaction gas G. The temperature of the substrate 10 is 950 to 1050 ° C., the heating temperature of the metal Ga is 700 to 800 ° C., and the pressure in the vacuum chamber 20 is 0.133 Pa (10 ⁻³ Torr). By performing epitaxial growth under such conditions, a GaN film 12 having good crystallinity was obtained.
[0018]
FIG. 4 shows the light emission characteristics of a light emitting diode manufactured by using the GaN epitaxy method of the present invention. According to FIG. 4, since the emission intensity at the band edge is strong and the width of the emission wavelength region is narrow, it is evaluated that the crystallinity is good. When the crystallinity is not good, the emission intensity at the band edge is weak and the emission wavelength range is wide.
[0019]
In the above-described embodiment, an organic source such as TMG (trimethyl gallium) may be used as the source material 28, and a nitrogen radical obtained by plasma excitation of N ₂ may be used as the reaction gas (nitrogen-containing gas) G. Alternatively, a gas or the like may be used.
[0020]
【The invention's effect】
As described above, according to the present invention, the GaN film is epitaxially grown directly on the SiC substrate by using the hot wall type epitaxy apparatus, so that the crystallinity of the GaN film can be improved and the cost can be reduced. Is obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a thermal annealing step in a GaN epitaxy method according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing an epitaxial growth step following the step of FIG. 1;
FIG. 3 is a sectional view showing a hot wall type epitaxy apparatus used in the epitaxial growth step of FIG. 2;
FIG. 4 is a graph showing light emission characteristics of a light emitting diode manufactured by using the GaN epitaxy method of the present invention.
[Explanation of symbols]
10: SiC substrate, 12: GaN film, 20: vacuum chamber, 22: support, 24: hot wall tube, 26: quartz tube, 26A: source housing, 26B: vapor guide, 28: source material, 30A, 30B, 36: lamp heater, 32: substrate holder, 34: substrate to be processed, 38: gas inlet tube.

Claims (2)

A chamber evacuated to vacuum,
A storage means disposed in the vacuum chamber for storing the source material;
First heating means for heating the source material contained in the containing means to evaporate;
Holding means disposed above the accommodation means in the vacuum chamber, and holding the substrate to be processed in a state where the deposition surface faces the accommodation means,
A second heating unit that heats the substrate to be processed held by the holding unit from a surface opposite to the deposition surface;
Guiding means for guiding the vapor of the source material contained in the containing means in the vacuum chamber to the deposition surface of the substrate to be processed held by the holding means;
Third heating means for heating the vapor of the source material guided by the guiding means;
A gallium nitride epitaxy method using a hot-wall type epitaxy apparatus, comprising: introduction means for introducing a reaction gas reacting with the vapor of the source material from outside the vacuum chamber into a passage of the vapor of the source material.
At least the surface to be deposited is formed of a single crystal of silicon carbide as the substrate to be processed, gallium is used as the source material, and the nitrogen-containing gas is used as the reaction gas. A gallium nitride epitaxy method wherein gallium nitride is epitaxially grown directly and continuously on a silicon carbide single crystal. 2. The gallium nitride epitaxy method according to claim 1, wherein said third heating means comprises a lamp heater, and irradiates radiant light of said lamp heater onto a deposition surface of said substrate to be processed.

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