JPH0641400B2 - Method for producing silicon carbide single crystal - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a silicon carbide single crystal in which a silicon carbide single crystal with reduced stacking faults is grown on a silicon substrate.

(Prior Art) Silicon carbide is a semiconductor material having a wide band gap (2.2 to 3.3 eV). In addition, it has the excellent characteristics that it is extremely stable thermally, chemically, and mechanically and is resistant to radiation damage. Devices using conventional semiconductor materials such as silicon are difficult to use, especially under severe conditions such as high temperature, high output drive, and radiation irradiation. Therefore, semiconductor devices using silicon carbide are expected to be applied in a wide range of fields as semiconductor devices that can be used even under such severe conditions.

However, a crystal growth technique that has a large area and is capable of stably supplying a high-quality silicon carbide single crystal on an industrial scale in consideration of productivity has not been established. Therefore, although silicon carbide is a semiconductor material having many advantages and possibilities as described above, its practical use is hindered.

Conventionally, in a laboratory scale, for example, a silicon carbide single crystal is grown by a sublimation recrystallization method (Rayleigh method), or a silicon carbide single crystal obtained by the method is used as a substrate, and a vapor phase growth method (CVD method is applied thereto. ) Or a liquid phase epitaxial growth method (LPE method) to epitaxially grow a silicon carbide single crystal layer,
We have obtained a silicon carbide single crystal of a size that allows trial manufacture of semiconductor devices. However, with these methods, the area of the obtained single crystal is small, and it is difficult to control the size and shape with high accuracy. Further, it is not easy to control the crystal polymorphism and the impurity concentration of silicon carbide.

In order to solve these problems, the present inventors have proposed a method for vapor phase growing a silicon carbide single crystal on an inexpensive and easily available silicon single crystal substrate (Japanese Patent Application No. 58-76842). .
Further, the surface of the silicon single crystal substrate is heated and carbonized in a hydrocarbon gas atmosphere to form a silicon carbide thin film on the surface, and then a silicon carbide single crystal layer is grown on the thin film by vapor phase growth. Laws are also being developed. These methods are called heteroepitaxial growth methods because they grow heterogeneous single crystal layers on a single crystal substrate.

(Problems to be Solved by the Invention) However, in general, in the heteroepitaxial growth method, there is a difference in lattice constant, thermal expansion coefficient, and chemical bond between the growth layer and the substrate single crystal. Particularly, stacking faults are likely to occur. There is a difference of about 20% in lattice constant between the silicon single crystal and the silicon carbide single crystal. Therefore, a large number of stacking faults on the {111} plane exist in the silicon carbide single crystal grown on the silicon substrate. These stacking faults adversely affect the electrical characteristics of the obtained silicon carbide single crystal, which is a serious problem in applying the silicon carbide single crystal as various electric materials. It is difficult to obtain a silicon carbide single crystal with reduced stacking faults with good reproducibility by using any of the above methods. Therefore, there is a need for a manufacturing method capable of stably supplying such a silicon carbide single crystal having excellent crystallinity on an industrial scale.

The present invention solves the above conventional problems, and an object of the present invention is to provide a method for producing a silicon carbide single crystal capable of producing a silicon carbide single crystal with reduced stacking faults with good reproducibility. It is in.

(Means for Solving the Problems) The present invention is a method for manufacturing a silicon carbide single crystal in which a stacking fault-reduced silicon carbide single crystal is grown on a silicon substrate. A step of providing a growth region, and growing a silicon carbide single crystal in the growth region so that the thickness thereof is equal to or more than the thickness peculiar to the growth plane orientation of the substrate, and stacking the silicon carbide single crystal. Reducing the defects, whereby the above object is achieved.

Many stacking faults on the {111} plane are distributed in the silicon carbide single crystal grown on the silicon substrate. When a Si (111) substrate is used, such a stacking fault appears as a regular triangle defect pattern on the surface of the growth layer of the silicon carbide single crystal formed on the substrate. This defect turn corresponds to a cross section on the growth layer surface of a regular tetrahedron in which stacking faults are gathered as follows. This regular tetrahedron, as shown in FIG.
It has a structure in which the (111) plane of the growth layer surface with the point O as the origin is the bottom, the vertex X is on the substrate, and each plane is the {111} plane. This is called a stacking fault regular tetrahedron.
The {111} planes that form the sides form 70 ° 32 'with the substrate surface.

Since stacking faults extend along the surface of the above tetrahedron,
As the layer thickness of the growth layer increases, the defect pattern appearing on the surface of the growth layer increases. Therefore, if there is no influence of stacking faults extending from other regions, the region where stacking faults do not exist expands as the layer thickness increases. By limiting the growth region of the silicon carbide single crystal on the silicon substrate to a predetermined size, stacking faults from other regions can be prevented from entering the growth layer. Therefore, if a silicon carbide single crystal is grown in this growth region to a certain thickness or more, stacking faults can be eliminated from the surface of the growth layer of the silicon carbide single crystal. Such a thickness of the growth layer depends on the growth plane orientation of the substrate, and will be referred to herein as a thickness specific to the growth plane orientation of the substrate.
If the layer thickness of the growth layer exceeds this thickness, stacking faults will not appear on the surface of the growth layer thereafter.

Generally, the thickness peculiar to the growth plane orientation of the substrate is determined by the growth plane orientation of the substrate used and the typical size of the growth region of the silicon carbide single crystal. The shape of the growth region is appropriately selected according to the growth plane orientation of the substrate used. Typical dimensions of the growth region are defined by the shape of the growth region. For example, when a Si (100) substrate is used, a (100) plane, which is a natural surface, is likely to appear on the surface of the growth layer of a silicon carbide single crystal, and thus a square is typically selected as the shape of the growth region. In this case, the typical dimension of the growth region is the length of one side of the square. Or, as the shape of the growth region,
A circular shape can also be used. In this case, the diameter of the circle is the typical size of the growth area. Generally, the shape of the growth region is a circle or a polygon including a triangle. Then, the thickness specific to the growth plane orientation of the substrate can be expressed as a function of the growth plane orientation and the typical dimension of the growth region.

The principle of eliminating stacking faults from the growth layer of silicon carbide single crystal will be described with reference to FIG. First, the growth region B is provided on the silicon substrate A. The growth surface of the silicon substrate A is assumed to be the (100) surface. Then, a growth layer C of silicon carbide single crystal is formed in the growth region B. In this case, the stacking fault has an apex X on the substrate and forms a regular quadrangular pyramid having the {111} plane around the apex X as the side surface. Stacking faults E1 and E2 in Fig. 1
Corresponds to the side surface of this regular quadrangular pyramid, and when the layer thickness of the growth layer C is small, appears as a square defect pattern on the surface of the growth layer C. The {111} surface forming the side surface is 54
44 ° is formed.

As described above, the surface D1 of the growth layer C has a natural surface (1
00) The surface is likely to appear. Therefore, the plane orientation of the surface D1 is (10
0). Therefore, in order to eliminate all stacking faults from the growth layer surface D1, it is sufficient to eliminate the other stacking faults F1 and F2 extending from both ends of the growth region B. this is,
As is apparent from FIG. 2, the layer thickness of the growth layer C is represented by ▲ √ ▼ (≈tan (54 ° 44 ′)) of the typical dimension d of the growth region B.
It is achieved by doubling. In this case, the thickness peculiar to the growth plane orientation of the substrate A is ▲ √ ▼ d. When the layer thickness of the growth layer C exceeds this value, all stacking faults are eliminated from the surface of the growth layer thereafter.

When a Si (nll) substrate (where n is an integer of 2 or more) is used, the plane orientation of the growth layer surface D2 is (nll). Stacking fault F
1 and F2 also extend along the {111} plane. As shown in FIG. 1, the stacking fault F1 forms a larger angle with the surface D2 than the stacking fault F2. Therefore, when the silicon carbide single crystal is grown in the limited growth region, the stacking fault F1 is more likely to appear on the growth layer surface D2. On the other hand, the stacking fault F2 is easily eliminated from the growth layer C. In this case, the defect pattern appearing on the growth layer surface D2 is trapezoidal. The upper side of the trapezoid corresponds to the stacking fault F1 and the lower side corresponds to the stacking fault F2. And these sides of the trapezoid are parallel to the [011] axis.
Therefore, the shape of the growth region is polygonal, and one side of it is [01
By aligning with the [1] direction, a defect-free silicon carbide single crystal can be grown in a growth region having a shape elongated in the direction. Although the case of using a Si (n11) substrate has been described here, in general, a defect-free silicon carbide single crystal can be grown in a growth region elongated in a specific direction determined by the growth plane orientation of the substrate used. .

The manufacturing method of the present invention is carried out based on the above-mentioned principle, for example, as follows.

First, the growth plane orientation of the silicon substrate is selected, and the shape of the growth region suitable for it is determined. As the substrate, for example, Si (10
0) substrate, Si (n11) substrate (where n is an integer of 1 or more),
Alternatively, these off-angle substrates can be used. The shape of the growth region is as described above. The typical size of the growth region is preferably within the range of 0.1 to 100 μm. The typical size of the growth region can be refined by a fine processing method. However, the size thereof is appropriately determined according to the dimensions of a semiconductor element to be created later.

Next, a growth region of silicon carbide single crystal is provided on the substrate.
At this time, in order to eliminate stacking faults from the regions other than the growth region, for example, a step is provided between the growth region and an adjacent growth region, or the growth regions are arranged discretely to form a growth region. Limit the size of. The growth region may be provided directly on the silicon substrate, or may be provided on the silicon carbide single crystal film formed on the silicon substrate. Hereinafter, unless otherwise specified, the substrate means a silicon substrate or a silicon carbide single crystal film formed on a silicon substrate. It is effective to form a silicon single crystal film on the silicon substrate after etching in order to reduce the influence of damage on the silicon substrate due to etching.

Methods for providing a step between the growth regions include plasma etching, reactive ion etching, and chemical etching. As the size of the growth region becomes finer, the layer thickness of the growth layer without defects becomes smaller. Therefore, when a step structure is provided on the substrate, the size of the step can be reduced. Further, stacking faults can be reduced also in the valley growth region of the step structure. Therefore, if growth is continued, a defect-free silicon carbide single crystal can be obtained over the entire surface of the substrate. As a result, using the obtained defect-free silicon carbide single crystal as a substrate, a semiconductor element having excellent electrical characteristics can be freely formed on the substrate.

For example, the following method can be used to arrange the growth regions discretely. By irradiating the substrate with an electron beam or an ion beam to reduce the crystallinity of the irradiation region, the non-irradiation growth region and the irradiation region are separated by the difference in crystallinity. Alternatively, after covering the substrate with a film that is not a single crystal such as silicon oxide or nitride, only the growth region is opened.
Since the crystallinity of the region other than the growth region is lowered, the silicon carbide grown in the region is not a single crystal. On the other hand,
A silicon carbide single crystal grows in the growth region. Therefore, these growth regions are arranged discretely.

Silicon carbide is then grown on the substrate provided with the growth region of a predetermined size. As a method for growing silicon carbide, vapor phase epitaxy method (CVD method), liquid phase epitaxy method (LPE method), molecular beam epitaxy method (MBE method)
and so on. By using any of these methods, a silicon carbide single crystal with reduced stacking faults can be obtained by growing silicon carbide based on the above-mentioned principle.

Here, the vapor phase growth method will be described. FIG. 3 is an example of a vapor phase growth apparatus used in the embodiment of the present invention. Inside the double quartz reaction tube 1, a graphite sample stand 2 coated with silicon carbide is installed by a graphite support rod 3. The sample table 2 may be installed horizontally or may be tilted appropriately. A work coil 4 is wound around the outer periphery of the reaction tube 1,
The sample stage 2 can be heated to a desired temperature by passing a high frequency current. A branch pipe 5 serving as a gas inlet is provided on one side of the reaction tube 1, and cooling water is supplied into the quartz tube outside the double quartz reaction tube 1 through the branch pipes 6 and 7. The other end of the reaction tube 1 is closed by a flange 8 made of stainless steel, and is sealed by a stopper plate 9, a bolt 10, a nut 11, and an O-ring 12 arranged on the peripheral portion of the flange 8. A branch pipe 13 serving as a gas outlet is provided at the center of the flange 8.

In the silicon substrate provided with the growth region, the surface of the silicon substrate may be changed to an extremely thin silicon carbide single crystal film if necessary. This is performed as follows using the vapor phase growth apparatus of FIG. First, the silicon single crystal substrate 15 is placed on the sample table 2. While flowing the carbon source gas and the carrier gas from the branch pipe 5 into the reaction tube 1, a high-frequency current is passed through the work coil 4 to heat the sample table 2 and the silicon substrate 15 to a predetermined temperature. By maintaining this temperature for a predetermined time, the surface of the silicon substrate is carbonized and a silicon carbide single crystal film is formed.

CH ₄ , C ₂ H ₆ , C ₃ H ₈ and the like are used as the carbon source gas, and hydrogen, argon and the like are used as the carrier gas. The time for forming the single crystal film varies depending on the heating temperature of the substrate and the flow rates of the carbon source gas and the carrier gas. Normally, the flow rates of carbon source gas and carrier gas are
0.1-1.0 cc / min and 1-5 / min, respectively. The heating temperature of the substrate is in the range of about 1,200 to 1,400 ° C., and the single crystal film is formed in about 1 to 5 minutes.

After providing a growth region of a predetermined size on a silicon substrate or a silicon substrate on which a silicon carbide single crystal film is formed, silicon carbide is grown in the same manner as above. At this time, the silicon source gas is supplied into the reaction tube 1 together with the carbon source gas and the carrier gas. Silicon source gas includes SiH ₄ , SiCl ₄ , SiH
₂ Cl ₂ , (CH ₃ ) ₃ SiCl, (CH ₃ ) ₂ SiCl _2, etc. are used. Normally, the flow rate of silicon source gas is 0.1 to 1.0 cc per minute. The types and flow rates of the carbon source gas and the carrier gas, and the substrate heating temperature can be the same as above.
The growth time is set so that the silicon carbide single crystal layer has a desired layer thickness.

The obtained silicon carbide single crystal is used as a semiconductor material together with the silicon substrate or after removing the silicon substrate by etching or the like as necessary.

According to the manufacturing method of the present invention, since the silicon carbide single crystal grows in the growth region of a predetermined size provided on the substrate, stacking faults of the silicon carbide single crystal in the region are reduced. Such a silicon carbide single crystal is used, for example, in a field effect transistor.
It can be used to create semiconductor devices such as (FET) and complementary MOS (C-MOS). By using the growth region of the silicon carbide single crystal as a semiconductor element and using the other region mainly as a power supply region, a semiconductor device having excellent electrical characteristics is manufactured. The growth region of the ultrafine pattern is provided by the method of ultrafine processing, and 1 is applied to the plurality of growth regions.
It is also possible to manufacture a semiconductor device in which individual elements are formed. In this case, even better results can be obtained by polishing and etching the surface of silicon carbide after growth.

(Examples) The present invention will be described below with reference to Examples.

Example 1 A Si (100) substrate was used as the substrate. A growth region having a typical size of 0.1 μm was drawn on the substrate with an electron beam at intervals of 0.1 μm. The thickness peculiar to the growth plane orientation of the silicon substrate used is about 0.14 μm. Therefore,
A step of 0.14 μm was formed between adjacent growth regions by reactive ion etching.

Then, the surface of the silicon substrate provided with the growth region is
The vapor phase apparatus shown in the figure was used to change to an extremely thin silicon carbide single crystal film as described above. Propane gas was used as the carbon source gas, hydrogen gas was used as the carrier gas, and the flow rates were 0.5 cc / min and 3 / min, respectively. The substrate heating temperature was 1,300 ° C.

After forming the silicon carbide single crystal film, vapor phase growth of the silicon carbide single crystal was continued. In addition to propane gas and hydrogen gas, monosilane gas as a silicon source gas is added at 0.5 c / min.
It was supplied at a flow rate of c. The substrate heating temperature was 1,300 ° C. The growth time required for the layer thickness of the silicon carbide single crystal to be 0.14 μm was 3 minutes. When the obtained silicon carbide single crystal was observed with a transmission electron microscope, stacking faults were reduced over the entire growth layer.

After performing vapor phase growth for another 30 minutes under the same conditions as above, a complementary MOS having a gate length of 3 μm was prepared using the obtained silicon carbide single crystal, and showed excellent electrical characteristics.

Example 2 A Si (100) substrate was used as the substrate. An octagonal or circular growth region having a typical dimension of 20 μm was formed on the substrate by photolithography. If the growth region is octagonal, a typical dimension is the spacing between two opposite sides of the octagon. Then, by using the ion implantation method, P ⁺ on was implanted into the peripheral regions of the growth region to reduce the crystallinity of these peripheral regions. As the implantation conditions, an acceleration voltage of 100 keV and a P ⁺ ion implantation amount of 1 × 10
It was ¹⁵ cm ^-2 .

In this way, on the silicon substrate where the growth regions are discretely provided,
A silicon carbide single crystal was grown in the same manner as in Example 1. In this case, the thickness peculiar to the growth plane orientation of the substrate is 28 μm. The growth time required to obtain a silicon carbide single crystal having such a layer thickness was 8 hours.

When the grown silicon carbide was observed with a transmission electron microscope,
Only the silicon carbide grown in the growth region was a single crystal, and the silicon carbide in the peripheral region had poor crystallinity. It was also found that the stacking gap on the surface of the silicon carbide single crystal layer in the growth region was reduced, and stacking faults did not enter from the peripheral region.

Example 3 A silicon carbide single crystal was grown in the same manner as in Example 2 except that a step of 1 μm was provided between adjacent growth regions by chemical etching using a KOH aqueous solution.

When the obtained silicon carbide single crystal was observed with a transmission electron microscope, stacking faults were reduced over the entire growth layer.

Example 4 A Si (100) substrate was used as the substrate. A 0.5 μm silicon nitride film was formed on the substrate by a chemical vapor deposition method using plasma. Then, a growth region similar to that in Example 2 was formed.
It was formed by photolithography. Then, the growth region was opened by chemical etching, and a step was provided between the growth region and the peripheral region.

In this manner, a silicon carbide single crystal was grown in the same manner as in Example 2 on the silicon substrate having the growth regions discretely provided and having a step between the growth region and the peripheral region.

When the grown silicon carbide was observed with a transmission electron microscope,
Only the silicon carbide grown in the growth region was a single crystal, and the silicon carbide in the peripheral region had poor crystallinity. It was also found that the stacking faults on the surface of the silicon carbide single crystal layer in the growth region were reduced, and the stacking faults did not enter from the peripheral region.

Example 5 A Si (611) substrate was used as the substrate. This silicon carbide single crystal is parallel to the [111] axis by 30 μm in the parallel direction and 10 μm in the vertical direction.
A rectangular growth region of m was provided by reactive ion etching. In this case, the typical method for the growth region is 10 μm.

In this way, on the silicon substrate where the growth regions are discretely provided,
In the same manner as in Example 1, a silicon carbide single crystal having a thickness of 50 μm was grown.

C-MOS was created in the growth region by thermally oxidizing the surface of the obtained silicon carbide single crystal to form a SiO ₂ film, then performing ion implantation, and forming an electrode by opening by photolithography. . The thermal oxidation of silicon carbide was performed at 1,100 ° C. for 3 hours to obtain a 0.05 μm SiO ₂ film. The channel of N-type FET and the source and drain of P-type FET are
It was prepared by implanting B ⁺ ions at acceleration voltages of 100 keV and 30 keV. After that, the source and drain of the N-type FET were formed by ion implantation of P ⁺ . Aluminum metal was vapor-deposited while the electrodes were opened using an appropriate mask pattern.

An 11-stage ring oscillator was constructed by sequentially connecting the C-MOS on each growth region thus created with aluminum metal. The oscillation frequency of this ring oscillator was measured and found to be 5.0 MHz. Therefore, this
The propagation delay time of C-MOS was about 10 nsec, and it was found that the semiconductor device made of the above silicon carbide single crystal exhibited excellent electrical characteristics.

(Effect of the Invention) According to the present invention, a silicon carbide single crystal with reduced stacking faults can thus be formed in a large number of growth regions provided on a silicon substrate. A semiconductor device using such a silicon carbide single crystal has excellent electrical characteristics. Furthermore, since a silicon carbide single crystal with reduced stacking faults can be obtained with good reproducibility, a silicon carbide single crystal with excellent crystallinity can be stably supplied, and a large-scale integrated circuit using the same can be produced on an industrial scale. It becomes possible to produce.

[Brief description of drawings]

Fig. 1 is a conceptual diagram showing the principle of stacking fault elimination from the growth layer of a silicon carbide single crystal in the growth region, and Fig. 2 is a tetrahedron formed by stacking faults on the {111} plane of a silicon carbide single crystal. FIG. 3 is a schematic cross-sectional view showing an example of a vapor phase growth apparatus used in the manufacturing method of the present invention. A ... Silicon substrate, B ... Growth region, C ... Growth layer of silicon carbide single crystal, E1, E2, F1, F2 ... Stacking fault.

Claims (1)

[Claims] 1. A method of manufacturing a silicon carbide single crystal in which a silicon carbide single crystal is grown on a silicon substrate, comprising a step of providing a growth region of the silicon carbide single crystal on the substrate, and a silicon carbide single crystal in the growth region. And a step of growing the crystal so that its thickness is equal to or more than the thickness peculiar to the growth plane direction of the substrate, and a method for producing a silicon carbide single crystal.