JPH0455155B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a silicon carbide single crystal substrate.

(Conventional technology) Silicon carbide semiconductors have a wide forbidden band width (2.2~
3.3 eV), and is extremely stable thermally, chemically, and mechanically, and is resistant to radiation damage. Therefore, it has been difficult to use semiconductor elements using silicon carbide with other conventional semiconductors such as silicon. It is expected to be applied in a wide range of fields as a material for devices that can be used under harsh conditions such as high temperatures, high output, and radiation damage.

As described above, although silicon carbide semiconductors are materials with many advantages and possibilities, the reason for their practical application is that they cannot be used on an industrial scale where good productivity is required. The reason for this is that crystal growth technology that can stably supply large-area, high-quality single crystals with controlled dimensions and shapes required for mass production has not yet been established.

Recently, the present inventors have invented a method for growing high-quality, large-area 3C-type silicon carbide single crystals on silicon single-crystal substrates by vapor phase epitaxy (CVD) (application number: 76842/1983). ). This method is a method of vapor phase growth of a large-area, high-quality silicon carbide single crystal with controlled crystal structure, impurity concentration, size, shape, etc. on a cheap and easily available silicon single crystal substrate.
We have also developed a method in which a thin film of silicon carbide is formed on the surface of a silicon single crystal substrate by heating and carbonizing it in a hydrocarbon gas atmosphere, and a single crystal of silicon carbide is grown on this thin film using the CVD method. has been done.

(Problems to be Solved by the Invention) In all of the above methods, silicon carbide is grown on a single wafer, so there is a difference in lattice constant between the silicon single crystal substrate and the grown silicon carbide single crystal. The internal stress caused by this cannot be completely removed, causing warping, cracking, etc., which causes problems during the device fabrication stage.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a plurality of grooves that intersect with each other in advance on the surface of a silicon single crystal substrate on which a silicon carbide film is to be grown. By dividing the surface into many regions, the region in which each silicon carbide single crystal grows becomes smaller.

(Function) In this way, since the growth region of each silicon carbide single crystal is reduced, internal stress is reduced, and a high quality silicon carbide single crystal substrate can be obtained.

(Example) A silicon single crystal substrate 15 having a film thickness of 450 μm as shown in FIG. , a plurality of grooves with a depth of 150 μm are provided in an intersecting manner. The width of the groove is preferably 100 μm or less, and the depth is preferably 50 μm or more. Other methods such as chemical etching or dry etching may also be used to form the grooves 14.

A silicon single crystal substrate 15 having grooves 14 in this way
The graphite sample stage 2 of the CVD device shown in Figure 2
Place it on top. In FIG. 2, the reaction tube 1 is fixed to the flange 8 by washers 9, bolts 10, and nuts 11, and is kept airtight by packing 12. Gas flows from the inlet branch pipe 5 to the outlet branch pipe 13. Cooling water is injected into a container 1' for cooling the reaction tube 1 from a branch pipe 6 of a water inlet, and is discharged from a branch pipe 7 of a drain port. 4 is a coil through which a high frequency current for heating is passed, and 3 is a support stand on which the graphite sample stand 2 is placed.

Hydrogen (H ₂ ) gas as carrier gas at 10% per minute
In addition, propane (C ₃ H ₈ ) gas is flowed at about 1.0 cc per minute for carbonization, and a high frequency current is supplied to the coil 4 to induction heat the sample stage 2 to increase the temperature of the silicon single crystal substrate 15 having the grooves 14. Raise the temperature to approximately 1350℃. At this temperature, the surface of silicon single crystal substrate 14 is carbonized, and an extremely thin film of silicon carbide single crystal is formed. While maintaining this temperature, monosilane (SiH ₄ ) as a silicon source gas and propane (C ₃ H ₈ ) as a carbon source gas are supplied onto the silicon carbide single crystal together with hydrogen (H ₂ ) as a carrier gas. , a silicon carbide single crystal film 16 is grown by the CVD method, as shown in FIG. 1c. The gas flow rates in this case are 0.9 cc/min for each of monosilane and propane, and 10 cc/min for hydrogen.

According to the results of an inspection using reflected electron beam diffraction, the divided regions on the surface of the silicon single crystal substrate 15 contain:
It can be seen that single-crystal silicon carbide films are grown in each case. Furthermore, when this is observed using a transmission electron microscope, it is found that it is a high-quality single crystal with few crystal defects.

Note that although a silicon carbide single crystal does not grow at the bottom of the groove 14, a silicon carbide polycrystal may grow.

An example of a Schottky barrier junction field effect transistor (MESFET) will be described as a silicon carbide semiconductor device using the silicon carbide single crystal film obtained in the above embodiment.

Silicon single crystal substrate 15 having grooves 14 in FIG. 4a
A silicon carbide single crystal film is grown on the surface of the substrate by the CJD method using monosilane (SiH ₄ ) and propane (C ₃ H ₈ ). At that time, first the silicon single crystal substrate 1
By adding diborane (B ₂ H ₆ ) gas onto 5, a p-type silicon carbide single crystal film 17 of about 5 μm is grown as shown in FIG. 4b, and then diborane (B ₂ H ₆ ) The gas supply is cut off, and a non-doped n-type silicon carbide film 18 is formed on the surface of the silicon carbide single crystal film 17.
Grow 0.5 μm. Furthermore, as shown in FIG. 4c, a source 19 and a drain 21 are formed on the surface of the silicon carbide film 18.
Each electrode is formed by vacuum evaporating aluminum (Al) for both electrodes and gold (Au) for the gate shot key electrode.

(Effects of the invention) By using a silicon carbide single crystal whose surface is divided into multiple regions, internal stress is reduced, and a field effect transistor (FET) can be built on a silicon carbide single crystal with few crystal defects and good crystal properties. Can be formed. The mutual conductance (gm) is 0.5 mS/mm when using a silicon carbide single crystal with an undivided surface.
On the other hand, when a silicon carbide single crystal with a segmented surface is used, it increases to 2 mS/mm, which shows an improvement in the characteristics. In the above embodiment, one FET was formed in one region of the divided surface, but it is also possible to form a plurality of other elements such as diodes and transistors in one region. Furthermore, it is also possible to connect elements in adjacent regions by wiring. In this way, the characteristics of the device can be significantly improved, contributing to the development of a wide range of application fields for silicon carbide semiconductors.

[Brief explanation of drawings]

Figures 1a, b, and c show the state of the device at each stage of the process according to the present invention, Figure 2 is a schematic of the CVD equipment, Figure 3 is the surface of the device when the present invention is carried out, and Figures 4a, b and c show the state of the device at each stage during the manufacturing process of the FET according to the present invention. 14... Groove, 15... Silicon single crystal substrate, 16... Silicon carbide single crystal film, 17... P-type silicon carbide single crystal film, 1
8... N-type silicon carbide single crystal film, 19... Source, 20
...Shotkey Gate, 21...Drain.

Claims (1)

[Claims] 1. A plurality of intersecting grooves are formed in a silicon single crystal substrate to divide the surface of the silicon single crystal substrate into a plurality of regions, and a silicon carbide single crystal thin film is formed on each region by a CVD method. A method for manufacturing a silicon carbide single crystal substrate.