JP2005317670A - Fabricating method of cubic silicon carbide crystal film with orientation (100) - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce cost in mass production of an SiCOI construction substrate with regard to a method to grow a cubic silicon carbide (3 C-SiC) crystal film with orientation (100) at relatively low substrate temperature. <P>SOLUTION: A hot-wire catalyst material which thermally decomposes a hydrogen gas is heated up to 1,400 to 1,800°C, and the hydrogen gas is thermally decomposed to generate a hydrogen radical. Then an organic silicon compound gas including an Si-C combination in molecules is directly supplied to near a surface of a silicon thermal oxide film substrate which is heated up to 700 to 800°C to decompose by the hydrogen radical, by which crystal growth of the cubic silicon carbide film with orientation (100) on the surface of a silicon thermal oxide film is obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

In the present invention, a silicon thermal oxide film formed on a silicon substrate is formed at a relatively low substrate temperature by a CVD method using thermal decomposition of hydrogen gas by a catalytic reaction by a hot wire catalyst (1).
The present invention relates to a method for growing an oriented cubic silicon carbide (3C-SiC) crystal film.

So far, plasma CVD has been mainly used for thin film growth at low temperatures. However, thin-film devices such as liquid crystal displays and solar cells require large-area deposition technology that has a deposition area exceeding 1 m ^2, and technical issues such as maintaining uniformity are required to increase plasma size. Very difficult.

Catalytic-CVD (catalytic-CVD) is a film growth method that uses the decomposed species (radicals) to decompose gases by catalytic decomposition of filaments made of refractory metals such as tungsten, tantalum, rhenium, and platinum heated to high temperatures. : Cat-CVD) or hot wire CVD (Hot Wir
There is a growth method called e CVD (HW-CVD) or hot filament (HF-CVD) (for example, Patent Documents 1 to 7). In Cat-CVD, the deposition area can be easily increased by increasing the installation area of the catalyst body. In addition, there are many advantageous features such as no concern about damage to the film due to charged particles generated in the plasma, and a simple apparatus.

As a feature of this method, since it is not thermal decomposition of the source gas due to the substrate surface temperature when compared with the low pressure CVD method, it is possible to grow at a low substrate temperature, or when the source gas is decomposed by a metal catalyst, Unlike the plasma CVD method, radicals are generated on a two-dimensional solid surface such as a metal wire, so that the gas decomposition efficiency is high. So far, the growth temperature is 20
Amorphous Si (a-Si), polycrystalline Si (Poly-Si), amorphous SiC (a-SiC) for the application to solar cells and TFTs using Cat-CVD at a low temperature of about 0-300 ° C
), And production of microcrystalline SiC (μ _c -SiC) has been reported.

Silicon carbide (SiC) has the potential as a device material that surpasses the performance of Si and GaAs power devices and high frequency devices. When making GaN, sapphire and S
Although iC is used as a substrate, when SiC is used, device characteristics superior to those using a sapphire substrate are obtained because of its high thermal conductivity and relatively low lattice mismatch of about 3%. It has been.

The SiC / Si heteroepitaxial growth is mainly performed by using a chemical vapor deposition (CVD) method, a molecular beam epitaxy (MBE) method, or the like. However, there is a large lattice mismatch of 20% between Si and SiC, and a thermal expansion coefficient difference of about 8%. When a high growth temperature is used, a stacking fault occurs near the SiC / Si interface. And dislocation are likely to occur. In addition, when the SiC nucleus generation density is low, SiC due to external diffusion of Si atoms in the substrate
Problems of defects such as voids at the / Si interface occur.

A semiconductor element formed on a Si substrate generates a stray capacitance between the substrate and a reduction in power consumption and an increase in operating frequency have been hindered. An SOI (Silicon on Insulator) structure in which an insulating layer is inserted between a semiconductor element and a substrate is a structure that suppresses stray capacitance and is effective for increasing the speed, reducing power consumption, and increasing integration of transistors. In manufacturing electronic devices such as high-frequency devices and sensors using 3C-SiC, insulation between the Si substrate and the SiC film is also a very important technique. SiCOI (SiC on which an insulating layer is inserted between the Si substrate and the SiC film) Insulator)) known as structure.

Up to now, bonding (Bond) has been used to fabricate a structure with a SiC film on a thermal oxide film on a Si substrate.
ing) technology and Etch Back technology have been used (Non-Patent Document 1,
2). This is because, when film growth occurs due to desorption of hydrogen by thermal energy as in the CVD method, there is no selectivity as to which crystal plane of SiC grows on an amorphous oxide film substrate, and non-oriented polycrystalline So far, on an amorphous substrate called a silicon thermal oxide film (
This is because it was impossible to grow a SiC crystal film having a 100) orientation. These methods are
The Si substrate on which the SiC film is deposited is bonded to the thermal oxide film on the Si substrate, and the Si substrate is removed by etching to expose the SiC film, which requires many processes.

Q. Y. Tong et.al., J. Electrochem. Soc. 142 (1) (1995) pp.232-236, C. Serre et.al., Sensors and Actuators 74 (1999) pp.169-173 Japanese Patent Laid-Open No. 61-276976 (Japanese Patent Publication No. 3-65434) JP 63-040314 A JP-A-08-250438 JP 2000-223421 A Japanese Patent Laid-Open No. 2000-243712 JP 2002-093713 A JP 2003-155567 A JP 2004-95733 A

There are over 100 polytypes of SiC. Among the polytypes of SiC, 3C-, 4H-, and 6H-SiC have a relatively high probability of occurrence and have been studied in practical use. Here, the numbers indicate the repetition period in the C-axis direction, C means a cubic crystal, and H means a hexagonal crystal.
Among these polytypes, 3C-SiC has a relatively high electron mobility and saturation drift velocity, and thus is highly expected as a material for power devices and high-frequency devices.

In addition, 3C-SiC with zinc flash structure is a low-temperature stable polytype compared to other polytypes, and can only be epitaxially grown on Si. If this heteroepitaxial technology is improved, inexpensive large-area crystals can be obtained. Can be obtained and opens up the use of SiC as a substrate.

The hexagonal SiC (4H-, 6H-SiC) substrate produced by the improved Rayleigh method contains many defects, has a high residual carrier density, and is difficult to control conductivity by thermal diffusion. Since it is difficult to build a structure, epitaxial growth is indispensable for forming an element structure.

In manufacturing electronic devices such as high-frequency devices and sensors using 3C-SiC, Si
Although a COI (SiC on Insulator) structure is known, a technique for forming a SiCOI structure by directly growing a 3C-SiC film on a thermal oxide film of Si has not been reported so far. Moreover, since the silane-based gas used in the conventional CVD method is a pyrophoric material that is very dangerous, a method that enables the formation of a 3C—SiC film using a material gas that is an alternative to the silane gas is required. It has been.

The present invention is a thermal oxide film formed on a silicon substrate, that is, 3C-Si having (100) orientation at a relatively low substrate temperature by a CVD method using a hot wire catalyst on a silicon oxide film.
A method for growing a C crystal film is provided.

In the present invention, a hot wire catalyst body that thermally decomposes hydrogen gas is heated to 1400 to 1800 ° C. to thermally decompose the hydrogen gas to generate hydrogen radicals, and an organosilicon compound gas having a Si—C bond in the molecule Is directly supplied to the vicinity of the surface of the silicon thermal oxide film substrate heated to 700 to 800 ° C. and decomposed by the hydrogen radicals (10
0) A method for producing a (100) -oriented cubic silicon carbide crystal film, characterized by crystal growth of an oriented cubic silicon carbide film.

In the method of the present invention, the raw material organosilicon compound gas is not directly decomposed on the surface of the hot wire catalyst body, but excessive methyl groups of the organosilicon compound on the SiC film growth surface on the silicon oxide film surface or hydrogen radicals of bonded hydrogen. (100) on the silicon thermal oxide film substrate under the condition using only the chemical reaction process of hydrogen radicals without charged particles.
) It is characterized by performing low temperature growth of oriented 3C-SiC.

In the method of the present invention, a catalyst body having a mesh structure of refractory metal wires is disposed facing the substrate, and hydrogen gas is allowed to flow through the mesh holes of the catalyst body toward the substrate. It is done. Further, it is preferable to supply the organosilicon compound gas directly from the nozzle to the vicinity of the silicon thermal oxide film substrate surface.

Since the method of the present invention enables the first direct growth of a (100) -oriented cubic silicon carbide crystal film on a silicon thermal oxide film, it is very useful in terms of cost reduction in mass production of SiCOI structure substrates. is there.

FIG. 1 schematically shows an example of a hot wire CVD apparatus used in the method of the present invention. In the growth chamber 1, the substrate 2 is set on the substrate heater 4 through an insulating sheet 3 such as a PBN (pyrolytic boron nitride) plate. A hot wire catalyst body 5 serving as a catalyst body for thermally decomposing hydrogen gas is attached to a position facing the surface of the substrate 2. A current can be supplied to the substrate heater 4 and the catalyst body 5 from a current introduction terminal (not shown) of the chamber. A carbon planar heater or the like is used as the substrate heater 4. A hot wire catalyst body is placed opposite to the substrate, and hydrogen gas is passed through the hot wire toward the substrate to thermally decompose hydrogen by catalytic reaction on the surface of the catalyst body, resulting in high-density hydrogen radicals (hydrogen atoms). Is generated.

Hot wire materials include tungsten, molybdenum, tantalum, titanium, vanadium and other refractory metals, palladium, silicon, metal-attached ceramics, alumina,
Silicon carbide and the like can be raised. In particular, a tungsten wire which is a high melting point metal excellent in high temperature strength is preferable. The hot wire structure is preferably a mesh. By making it mesh, it is easy to increase the surface area of the catalyst body per unit area compared to filaments and coils, it is easy to set in the equipment, and problems such as drooping when heated horizontally when placed horizontally Does not occur.

The larger the surface area per unit area of the mesh structure, the higher the efficiency of hydrogen decomposition by catalysis, so it is preferable to use a thin wire diameter and a large number of meshes per unit area. Is a wire diameter of about 0.1 mm, mesh spacing 0.85 mm
A (30mesh / inch) tungsten mesh is exemplified. The distance between the catalyst body and the substrate surface is not particularly limited, but it is preferable to prevent an increase in the substrate surface temperature due to the radiant heat of the mesh.

Respective gases are introduced into the chamber 1 by the source gas supply systems S1 and S2, the reaction hydrogen gas supply system S3, the dilution gas, and the purge gas supply system S4. The exhaust system is constituted by a rotary pump P1 and a diffusion pump P2. The hydrogen gas for reaction is supplied from the back surface of the hot wire catalyst body and flows to the substrate side through the hot wire. The source gas is directly supplied to the substrate surface without passing through the catalyst body. In order to efficiently supply the source gas to the substrate surface, it is desirable to attach a nozzle to the tip of the source gas supply pipe. Homogeneous to large area substrate (100)
In order to grow an oriented cubic silicon carbide film, it is desirable to surround the substrate in a ring shape and to blow a gas from the holes of many gas pipes toward the substrate surface.
Dilution gas and purge gas are supplied directly into the chamber.

An organic silicon compound having an Si—C bond in the molecule is used as the source gas. As such an organosilicon compound, monomethylsilane and dimethylsilane are suitable. High purity hydrogen is used as the reaction gas. N ₂ gas or the like is used as the dilution gas and the purge gas.

The supply amount of the source gas is reduced to about 1/100 to 1/500 of the hydrogen gas supply amount. Although the source gas is supplied directly above the substrate, the ratio of hydrogen and source molecules on the actual substrate surface varies greatly depending on the position of the source gas supply nozzle, but it cannot be specified, but source molecules for hydrogen radicals on the substrate surface are not specified. The ratio is considered to be about 1/100 or more.

After evacuating the chamber, source gas, reaction gas, and dilution gas are supplied so that the gas pressure during the reaction is about 400 Pa. A voltage is applied to the substrate heater to rapidly heat up to a predetermined growth temperature, and then a voltage is applied to the hot wire catalyst body to raise the temperature of the catalyst body to a predetermined temperature to perform film deposition. In film deposition, hydrogen gas is blown onto the heated catalyst body to decompose the hydrogen gas by a catalytic decomposition reaction. Then, a raw material gas is blown near the silicon thermal oxide film substrate, and at the same time, high-density hydrogen radicals (hydrogen atoms) generated by the catalyst body are supplied onto the substrate, thereby causing a decomposition reaction on the surface of the silicon oxide film on the substrate. The (100) -oriented cubic silicon carbide (3C-SiC) film grows on the silicon thermal oxide film substrate set at 700 to 800 ° C.

At this time, in order to grow a (100) -oriented cubic silicon carbide (3C-SiC) film, the surface temperature of the hot wire catalyst body and the set temperature of the silicon thermal oxide film substrate have a narrow range of conditions. When the surface temperature is around 1600 ° C., a (100) -oriented 3C—SiC crystal having the best crystallinity grows. FIG. 2 shows an XRD spectrum of a film produced at a substrate temperature of 750 ° C. by changing the temperature of the catalyst body. Naturally, no diffraction peak related to 3C—SiC is observed in a film produced at a temperature of 1000 to 1200 ° C. of a catalyst body in which almost no film growth is observed. Temperature of catalyst body 1400-1
In the film prepared at 800 ° C., a peak related to 3C—SiC (200) was obtained when 2θ was around 41.4 °. The peak intensity becomes maximum when the temperature of the catalyst body is 1600 ° C. When the temperature exceeds 1800 ° C., the supply density of hydrogen radicals is too high and etching is dominant, and when the temperature is less than 1400 ° C., the supply density of hydrogen radicals that promote the reaction is insufficient, and neither crystal growth proceeds.

Further, FIG. 3 shows 3C-SiC (111), (220), (200
) Shows the intensity of the peak. As the growth temperature is decreased from 950 ° C., the peaks related to (111) and (220) are weakened from non-oriented polycrystals at (100) at 800 to 750 ° C.
It can be seen that the crystals are predominantly oriented, and when the temperature is further lowered below 700 ° C., no crystallinity is observed and an amorphous film is obtained.

The best setting temperature of the silicon thermal oxide film substrate is 700C to 800C.
A c (100) -oriented crystal film grows, but at 850 ° C. or higher, it becomes a SiC film composed of domains of various crystal orientations, and becomes a non-oriented polycrystal. If it is less than 700 ° C., it becomes an amorphous film and a crystal film cannot be obtained.

A SiC film was grown on the silicon thermal oxide film substrate using a CVD apparatus using a hot wire having a mesh structure schematically shown in FIG. Silicon thermal oxide substrate is silicon (100)
A substrate (n-type, ρ = 100 to 200 Ωcm) was heated at 1000 ° C. in a pure oxygen atmosphere for 6 hours to form S
The iO ₂ film was formed, and the film thickness varied, but was in the range of 0.2 to 0.3 μm.

The silicon substrate was degreased and organic matter was removed by ultrasonic cleaning for 5 minutes each using a cleaning solution in the order of pure water, methanol, acetone, methanol, and pure water. P with substrate placed on carbon heater
It was set on a BN plate.

As the hot wire catalyst body, mesh-shaped tungsten wire (30mesh / inch, mesh diameter 0.1mmφ, mesh area 20mm × 40mm) is used, and the distance between the mesh-shaped catalyst body and the substrate is 8
It was set to 0 mm. The mesh-shaped catalyst body was sandwiched between molybdenum plate electrodes, and heated by applying a voltage using a direct current stabilized power source.

Before evacuation, the chamber was baked at a temperature of about 100 ° C. for 2 hours by applying a voltage of about 50 V to the nichrome wire on the outer wall of the chamber in order to accelerate the exhaust of gas and moisture adhering to the inner wall of the chamber. The substrate holder in the chamber was also baked at about 100 ° C. for 2 hours with a carbon heater.

Subsequently, supply of monomethylsilane gas was started in a state where the pressure in the chamber was reduced to 1.33 × 10 ⁻³ Pa or less and the pressure was adjusted to 1.33 × 10 ⁻³ Pa. Next, the hydrogen flow rate was adjusted to about 2.7 × 10 ⁻² Pa while supplying hydrogen gas and monitoring with an ionization vacuum gauge. Next, a voltage was applied to the carbon heater to rapidly heat it to a growth temperature of 750 ° C. Thereafter, a voltage was applied to the catalyst body to increase the temperature of the catalyst body to 1600 ° C.

High-density hydrogen radicals (hydrogen atoms) generated by blowing hydrogen gas onto a mesh-like tungsten wire catalyst heated to 1600 ° C. were supplied toward the substrate. At the same time, monomethylsilane was sprayed by using a nozzle near the silicon thermal oxide film substrate heated to 750 ° C., so that the film was grown on the silicon thermal oxide film substrate by decomposition reaction with hydrogen radicals on the substrate surface. The total gas pressure during the reaction is about 0.4 kPa, and the hydrogen flow rate is 100 sc.
cm. The XRD spectrum of the grown film is shown in FIG. It can be seen that the (100) -oriented cubic silicon carbide (3C-SiC) film has grown.

The method of the present invention can provide a substrate obtained by growing a (100) -oriented 3C—SiC crystal film on a silicon thermal oxide film substrate by a very simple process. The substrate manufactured by the method of the present invention is a wide band gap semiconductor device material for controlling a higher voltage and power with a lower loss than a conventional Si semiconductor device. It is possible to significantly reduce power loss in devices, home appliances, and the like. Furthermore, it is expected to promote the practical application in fields such as electric vehicles and high-speed information processing.

It is the schematic which shows an example of the hot wire CVD apparatus used for the method of this invention. It is a graph which shows the XRD spectrum of the film | membrane produced by changing the temperature of a catalyst body in the method of this invention at the substrate temperature of 750 degreeC. In the method of this invention, it is a graph which shows the intensity | strength of the peak regarding 3C-SiC (111), (220), (200) in each growth temperature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Growth chamber 2 Substrate 3 Insulation sheet 4 Substrate heater 5 Hot wire catalyst body

Claims (3)

A hot wire catalyst that thermally decomposes hydrogen gas is heated to 1400 to 1800 ° C. to thermally decompose the hydrogen gas to generate hydrogen radicals, and an organosilicon compound gas having a Si—C bond in the molecule is 700 to 800. It is characterized in that a (100) oriented cubic silicon carbide film is grown on the surface of the silicon thermal oxide film by supplying directly to the vicinity of the surface of the silicon thermal oxide film heated to ℃ and decomposing with the hydrogen radicals. (100) A method for producing an oriented cubic silicon carbide crystal film. 2. The cubic crystal according to claim 1, wherein a catalyst body having a mesh structure of refractory metal wires is disposed facing the substrate, and hydrogen gas is passed through the mesh holes of the catalyst body to flow toward the substrate. A method for producing a silicon carbide crystal film. 3. The method for producing a cubic silicon carbide crystal film according to claim 1, wherein the organosilicon compound gas is directly supplied from the nozzle to the vicinity of the surface of the silicon thermal oxide film substrate.

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