JPS6014000B2 - Manufacturing method of silicon carbide substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a large-area silicon carbide (SIC) substrate, and in particular, to a method of manufacturing a silicon carbide (SIC) substrate, which is an effective technique for separating a silicon carbide film grown on a silicon substrate. This is what we provide.

There are many crystal structures in SIC, and 2
．． It has an energy gap of 4 to 33 electron volts (eV), is extremely stable thermally, chemically, and mechanically, and is resistant to radiation damage.It is also rare as a wide gear semiconductor, and is co-stable for P-type and n-type. It is a material that exists.

Therefore, it is promising as a semiconductor material for Fujiwarm operation devices, high-power devices, high-reliability semiconductor devices, radiation-resistant devices, etc. Furthermore, it is a material that can be used even under difficult environments for devices using conventional semiconductor materials, and can significantly expand the range of applications of semiconductor devices. In addition, considering its energy gap value, it is an interesting semiconductor material as a material for optical fin conversion elements between visible short wavelengths and near-ultraviolet light. Furthermore, while other wide-gap semiconductors generally contain heavy metals as their main components, which poses pollution and resource problems, SICs are free from both of these problems, making them an excellent electronic material. This is seen as promising. Despite this material having many advantages and possibilities, it is difficult to put it into practical use because of the high quality, large area substrates required for mass production on an industrial scale with productivity in mind. The reason for this is that no reproducible crystal growth technology has been established to obtain such crystals.

Conventionally, as a method for obtaining SIC substrates on a laboratory scale, the so-called sublimation recrystallization method (Raley method and ), the so-called solution method to obtain an SIC substrate by melting silicon or a mixture of silicon and iron, cobalt, platinum, etc. in a graphite melting pot, and the Acheson method, which is generally used to obtain polishing materials industrially. There is a method using an incidentally obtained SIC board.

However, although it is possible to obtain a large number of single crystals using the sublimation recrystallization method and the solution method, it is difficult to obtain large-sized SIC substrates because many crystal nuclei are generated at the initial stage of crystal growth. This is an incomplete method for obtaining a large SIC single crystal with a single crystal structure with good reproducibility. In addition, SIC substrates accidentally obtained by the Acheson method have problems with purity and crystallinity when used as semiconductor materials, and even if relatively large SIC substrates can be obtained, they are obtained accidentally. , is not suitable as a method for industrially obtaining SIC substrates. On the other hand, with the improvement of semiconductor technology in recent years, relatively high-quality, large-sized single-crystal substrates are now available on heterogeneous silicon substrates. The energy gap is ~2.V) A single crystal thin film can now be obtained. As a heteroepitaxial growth method on a silicon substrate, '11 silicon source is SiH4, SIC14, (CH3)3.
SIC1, (C is)bujC12, and also CC14 as a carbon source, hydrocarbon gas (C2 day 2, C2 ratio, CM
Using hydrogen, argon, etc. as a carrier gas, the temperature of the Si substrate is set at 1200 qo to 1400 qo, and the vertical SI is grown by vapor phase growth technology (CVD technology).
Method for obtaining a C single-crystal thin film ■ 1200q of carbon produced by thermal decomposition of graphite and hydrocarbons on the surface of a Si substrate
A method for obtaining a long SIC single crystal thin film by diffusing at a temperature of about 1,400 qo to 1,400 qo to convert the surface of a Si substrate into SIC. Argon, hydrocarbon gas activated by direct current or alternating current glow discharge of 3-grain vapor There is a method (vapor deposition method) in which an SIC single crystal thin film is vapor-deposited on a Si substrate by passing through the Si substrate. However, the thickness of the parent type SIC thin film single crystal obtained by the heteroepitaxial technique on a Si foreign substrate such as '11, ■, '3} is as thin as 1 to 10 m. In general, the integrity of the crystals is also not good. The reason for this is that the Si substrate jump-type SI
Due to the large difference in the lattice constant of the C crystal, many misfit dislocations occur especially near the interface between the SIC substrate and the epitaxial father SIC, and the influence extends to the inside of the epitaxial layer. Due to the difference in thermal expansion coefficient of SIC crystal, SIC
This is thought to be due to the accumulation of strain in the epitaxial layer. Also, if such a method were used to create a large-area and high-quality broadside SIC,
Even if (the energy gap Eg is ~2.umbrella V) is obtained, the SI of the crystal structure with a larger energy gap
C, for example, thin (Eg is ~3.0saV), 4 days (Eg is ~
When attempting to obtain an o-type SIC such as 3.2 Sagi V) Misaki (Eg is ~2. Kazu V) by epitaxial growth, the growth temperature is generally higher than 1600°C, and the Si substrate and the aforementioned Si The melting point of Si is 14100 for substrates on which *type SIC thin films are grown ($type SIC/Smi structure).
If it is 0, it cannot be used as a substrate for SiC hair epitaxial growth. However, S
The result that it is possible to grow a *-type single crystal thin film by heteroepitaxial growth on an i-substrate is a hopeful sign that at least a large-area SIC can be obtained. In other words, if it becomes possible to separate the *type SIC single crystal thin film formed on the Si substrate by some method,
Using the *type SIC single crystal thin film separated from this Si substrate as the primary substrate, a new epitaxial growth method was applied to
It becomes possible to grow an improved father-type SIC crystal from the primary substrate and to grow a Q-type SIC crystal at a growth temperature of 1600° C. or higher. Such epitaxial growth on a SIC thin film substrate separated from a Si substrate results in homoepitaxial growth, and due to the difference in lattice constant and thermal expansion coefficient between the substrate and the growth layer, no problems occur and good crystal growth occurs. A layer of epitaxial growth is obtained. However, regarding this point, in the past, 1 to 10
Since no suitable manufacturing technology has been established to separate *-type SIC thin films with a thickness of about 100 m thick without damaging them, in reality, high-quality There are no examples of development to the point of forming *-type or Q-type SIC crystals. Conventionally, a $-shaped SIC thin film formed on a Si substrate is grown heteroepitaxially, and then the Si substrate is etched away using a mixed solution of hydrofluoric acid and nitric acid. However, the length S for the Si substrate
IC growth is performed at a relatively high temperature of about 1200 to 140 pm, and since the Si substrate and the epitaxial growth layer of the SIC have different coefficients of thermal expansion, the Si substrate and the epitaxial growth layer are Large strains are stored in the SIC epitaxial growth layer. For this reason, when the Si substrate is thinned by etching, the Si substrate and the epitaxial growth layer will become curved, and the epitaxial growth layer may crack or break, causing the S
As a result, it cannot be used as an IC thin film. In view of the above-mentioned current situation, the present invention provides an epitaxial growth layer formed by conventional heteroepitaxial technology on a Si heterogeneous substrate.
This is a new method for separating Si from a foreign substrate without damaging the IC thin film, and using this separated SIC thin film as a new substrate to form high-quality swallow-type SIC thin films and o-type SIC thin films using conventional epitaxial technology. An object of the present invention is to provide a method for manufacturing a useful SIC thin film substrate. The invention will be explained below in detail according to embodiments and with drawings.

Figures 1a, b, c, and d are SI showing the first embodiment of the present invention.
It is a manufacturing process diagram of C single crystal. As shown in Figure 1a, 2
00~ Immediate OAm thickness {111}, {110}, or {1
In a silicon substrate 1 having a plane orientation of 00} and having one side mirror-polished, the mirror-polished side is subjected to an etching process.

Next, a conventional vapor phase epitaxial growth method, for example, using hydrogen as a carrier gas, SIC14, CC
14 is 0.05 to 0.5 mol%, and the substrate temperature is 130
When grown for 60 to 24 minutes at 0 to 1360 o'clock, a $-shaped S with a thickness of 1 to 5 mm is formed from the substrate as shown in Figure 1b.
An IC single crystal layer 2 is grown, and a 10 to 150 mm thick SIC polycrystalline layer 3 is grown thereon. Although the cause of polycrystalization during growth has not yet been elucidated, it is thought to be caused by a difference in lattice constant between the substrate and the epitaxial SIC layer. After the growth, the growth wafer is taken out from the epitaxial reactor, and the Si substrate 1 is heated with nitric acid or hydrofluoric acid based Si.
The substrate is removed by etching with an etching solution to obtain a SIC substrate having a structure in which a $-shaped SIC single crystal film 2 is formed on a $-shaped SIC polycrystalline 3 as shown in FIG. 1c. Next, the above *Type SI
The size of the SIC shown in FIG.
The substrate temperature is 1300 on the single crystal epitaxial layer 2 of the substrate.
Epitaxial growth is carried out at ~1360 DEG C. for 30-200 minutes to obtain a high-quality swallow-shaped SIC epitaxial layer 4 of 3-100 mm (FIG. 1d). Unlike the $-type SIC epitaxial layer formed on the Si substrate, this epitaxial layer 4 uses a substrate composed only of SIC.
Differences in lattice constants and thermal side tension coefficients between the substrate and the ebitaxial layer do not become a problem, and it becomes possible to obtain an SIC with better crystallinity than the SIC substrate shown in FIG. 1c. Second
Figures a, b, c, d, e are SI showing the second embodiment of the present invention.
It is a manufacturing process diagram of C single crystal.

As in the first embodiment, a Si substrate 5 which has been etched as shown in FIG.
Heat to 5000℃ or CH4, C2. A hydrocarbon gas such as a C3 ratio is mixed into an argon carrier gas of about 10-1 to 10-2 mol%, and also 1250 to 1350 qo.
When the Si substrate 5 is heated at a temperature of about
Or carbon generated by thermal decomposition of hydrocarbon gas is S
Diffusion from the surface of the i-substrate 5, and gradually $ from the surface of the Si-substrate 5.
Convert to form SIC. By this method, a 1 to 10 m thick SIC single crystal thin film 6 is obtained as shown in FIG. 2b. Next, the polycrystalline iC film 7 is formed by the conventional vapor phase growth method, sputtering method, reactive vapor deposition method, etc. similar to the first embodiment.
is formed with a thickness of 10 to 200 Lm as shown in FIG. 2c.
Thereafter, the Si substrate 5 is removed by etching with a nitric acid or hydrofluoric acid based etching solution to obtain an SIC substrate having a structure in which an SIC single crystal 6 is formed on an SIC polycrystal 7. (Figure 2d). , on a substrate formed only of SIC obtained in this way,
As shown in Figure 2e, high-quality S was produced using the conventional vapor phase growth method.
An IC epitaxial layer 8 is obtained. As described above, according to the present invention, it is possible to obtain a high-quality SIC semiconductor material over a large area with good reproducibility, and therefore it is possible to mass-produce SIC semiconductor elements on an industrial scale. Since the SIC epitaxial growth in the present invention is homoepitaxial growth, the SIC due to the difference in lattice constant and thermal expansion coefficient between the SIC substrate and the epitaxial layer
Negative effects on the epitaxial layers are reduced and thus high quality SIC semiconductor materials can be produced. Another very excellent effect of the present invention other than the above is that the SIC single crystal substrate for forming the SIC epitaxial layer is reinforced with a SIC polycrystalline layer, which prevents damage or cracks in the SIC single crystal substrate during the manufacturing process. occurrence etc. is effectively prevented. That is, from a crystallographic perspective, the grain boundaries of a crystal are set at a higher energy level than the interior of the grains due to the bonding energy between adjacent crystal grains. Therefore, the larger the total grain boundary area of the polycrystal, the stronger the matrix becomes due to the grain boundary distribution, and the mechanical strength becomes stronger. Since the SIC single crystal substrate of the present invention is reinforced with this strengthened polycrystalline layer, it can be made stable in terms of strength. Furthermore, since the present invention is a manufacturing method based on a secondary vapor phase growth method, it is a highly industrially significant manufacturing technology that can achieve the various excellent effects mentioned above by effectively utilizing secondary equipment. .

[Brief explanation of the drawing]

FIG. 1 is a manufacturing process diagram of a SIC single crystal showing a first embodiment of the present invention. FIG. 2 is a process diagram for manufacturing an SIC single crystal showing a second embodiment of the present invention. 1, 5... Silicon substrate, 2,
6...SIC single crystal layer, 3,7...S
IC polycrystalline layer, 4,8...SIC epitaxial layer. Figure 1 Figure 2

Claims (1)

[Claims] 1 A two-layer crystal layer consisting of a silicon carbide single crystal layer and a silicon carbide polycrystal layer is superimposed on a silicon substrate, and as a next step, the silicon substrate is separated from the two-layer crystal layer by dissolving and removing it. A method for manufacturing a silicon carbide substrate, characterized in that the layer crystal layer is a silicon carbide substrate, and the surface of the silicon carbide single crystal layer is set as a surface on which an epitaxial layer of silicon carbide is formed.