JPH0143720B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing a silicon carbide single crystal film on a sapphire substrate, which is an insulating substrate.

[Prior art]

The fabrication of single crystal silicon films (SOS) on insulating substrates such as sapphire is important in silicon integrated circuit fabrication technology because it facilitates electrical isolation between elements during element integration. For similar reasons, the technique for producing a silicon carbide single crystal film on a sapphire substrate, which is an insulating substrate, is important for producing electronic or optoelectronic devices using silicon carbide. However, a silicon carbide single crystal film has hardly been formed on a sapphire substrate.

For example, when silicon carbide is grown on a sapphire substrate by chemical vapor deposition, the fiber structure film does not peel off from the substrate, but the single crystal film has a thickness of 2000 Å or more.
After film growth, the film peels off from the substrate. However, by growing an aluminum nitride single crystal film on a sapphire substrate by chemical vapor deposition and growing silicon carbide thereon, a silicon carbide single crystal film can be grown without peeling. Since this silicon carbide single crystal film contains a twin crystal structure, it has poor electrical properties, and it is necessary to improve the quality of the crystal for application to electronic devices.

[Summary of the invention]

This invention was developed in view of the above points. After growing an aluminum nitride single crystal film on a sapphire substrate, which is an insulating substrate, an aluminum oxide layer is grown on it, and then a carbide layer is grown on it. The purpose is to provide a method for growing a silicon carbide single crystal film with good crystallinity and excellent electrical properties on a sapphire substrate without peeling by growing a silicon single crystal film. be.

The present inventors have discovered that an aluminum oxide layer on an aluminum nitride single crystal film is extremely effective in achieving this objective, leading to the present invention.

Next, the technical background that led to this invention will be explained.

When growing an aluminum nitride single crystal on a sapphire substrate and then growing a silicon carbide single crystal on it, after the aluminum nitride single crystal film is grown, the surface of the aluminum nitride single crystal is exposed to the atmosphere at room temperature, and then the aluminum nitride single crystal surface is exposed to the atmosphere at room temperature. It is better to grow silicon
It was easier to grow single crystals than on aluminum nitride, which is not exposed to the atmosphere.

It has been found from depth composition analysis using Auger electron spectroscopy that an oxide layer several tens of angstroms thick is formed on the surface of aluminum nitride single crystal films when exposed to the atmosphere.

Furthermore, when a silicon carbide single crystal is grown directly on a sapphire substrate, the film peels off from the substrate within a few hours after growth, but the grown silicon carbide single crystal film is extremely good and does not contain a twin structure. It shows crystallinity.

Aluminum nitride and its oxide layer have a resistance of 10 ¹³ Ω.
The presence of aluminum nitride and its oxide layer is useful for growing silicon carbide single crystal films on insulating substrates, as they have a high resistivity of more than cm and are extremely stable both thermally and chemically. It is thought that not only does it not interfere with the process, but also it can sufficiently withstand the thermal and chemical processes applied to the silicon carbide film for device fabrication.

This invention was completed based on the above findings. Hereinafter, a method using a chemical vapor deposition method of the present invention will be explained based on Examples.

[Embodiments of the invention]

The drawing is a block diagram showing an apparatus for carrying out the present invention. Inside the vacuum chamber 1, which is evacuated to an ultra-high vacuum of 10 ^-6 Pa or less, there is a substrate heater 2 on the back or side of the substrate, a sapphire substrate 3 is placed near the substrate heater 2, and the front side is It is designed to be shut off by shutter 4. Further, in the front center of the sapphire substrate 3, a pipe 5 for introducing ammonia (NH ₃ ), oxygen (O ₂ ), and acetylene gas (C ₂ H ₂ ) is located at its opening 5a.
is placed facing the sapphire substrate 3, and the pipe 5
An aluminum (Al) evaporation source 6 and a silicon (Si) evaporation source 7 are arranged on both sides. Further, 8 is an exhaust port, and 9, 10, and 11 are control valves. Note that the temperature control device for the substrate heater 2 is omitted.

In the process of producing a silicon carbide single crystal film, the inside of the vacuum chamber 1 is evacuated to an ultra-high vacuum of 10 ^-6 Pa or less, and an aluminum molecular beam is introduced from the aluminum evaporation source 6 through the gas introduction pipe 5 facing toward the substrate. ^- ₃ Pa of ammonia is simultaneously applied to the sapphire substrate 3 heated to 1000 to 1200°C to grow an aluminum nitride single crystal film. The growth rate of the film depends on the aluminum molecular beam intensity and the ammonia partial pressure, but at 2×10 ¹⁵ /cm ² ·sec, 7×10 ^-3 Pa, it is about 2
It is Å/sec.

Next, after growing an aluminum nitride single crystal film with a predetermined thickness, the aluminum molecular beam is left as is, and the supply of ammonia gas is stopped.
While keeping the temperature of the sapphire substrate 3 the same, 10 ^-4 Pa of oxygen is introduced from the gas introduction pipe 5 toward the sapphire substrate 3 covered with the aluminum nitride single crystal film. Growth time is 5 minutes.

Furthermore, in order to stop the supply of aluminum molecular beams and oxygen, and to avoid the influence of residual gases such as ammonia gas and oxygen, the sapphire substrate 3 was
After keeping the temperature of the sapphire substrate 3 at about 1200°C for more than 60 minutes in a vacuum, the silicon evaporation source 7
A silicon molecular beam is introduced from the gas introduction pipe 5.
Acetylene of 10 ^-3 Pa is simultaneously applied to the sapphire substrate 3 covered with the aluminum nitride single crystal film and its oxide layer to grow a silicon carbide single crystal film.

The growth rate of the film depends on the silicon molecular beam intensity and acetylene partial pressure, but is 1.7×10 ¹⁵ /cm ² ·sec,
At 1×10 ^-3 Pa, it is approximately 3 Å/sec.

Even though the aluminum nitride single crystal film on the sapphire substrate 3 and the silicon carbide film on its oxide layer produced by this method have a film thickness of several μm, the temperature of the sapphire substrate 3 is kept at room temperature after production, and the film is exposed to the atmosphere. Even when the film was taken out, it did not peel off, and even when the film was rubbed, it did not come off.

Furthermore, the film created by backscattered electron beam diffraction is
It turned out to be a β (or 3C)-silicon carbide single crystal film that does not contain a twin structure.

In addition, the films produced are electrically superior to films on insulating substrates produced by conventional methods. That is, the fibrous structure grown directly on the sapphire substrate 3 and the film grown on aluminum nitride on the sapphire substrate 3 have an electron mobility of 5 to 6.
cm ² /V·sec, whereas the film produced by this method showed a large electron mobility of 24 cm ² /V·sec.

Note that the present invention is not limited to the chemical vapor deposition method shown in the above embodiments, and the entire growth process may be performed by any method such as reactive ion plating method or vapor phase growth method.

〔Effect of the invention〕

As explained above, the present invention grows an aluminum nitride single crystal film on a sapphire substrate, grows an aluminum oxide layer on the aluminum nitride single crystal film, and grows silicon carbide on the aluminum oxide layer. It is possible to grow a silicon carbide single crystal film with excellent crystallinity on an insulating sapphire substrate without peeling it off, and it can be used in various applications such as electronic devices using silicon carbide. It has promising advantages.

[Brief explanation of drawings]

The drawing is a block diagram showing an apparatus for carrying out the present invention. In the figure, 1 is a vacuum chamber, 2 is a substrate heater, 3 is a sapphire substrate, 4 is a shutter, 5 is an introduction pipe for ammonia gas, oxygen, and acetylene gas,
6 is an aluminum evaporation source, 7 is a silicon evaporation source,
8 is an exhaust port, and 9 to 11 are control valves.

Claims (1)

[Claims] 1. A silicon carbide single crystal characterized by growing an aluminum nitride single crystal film on a sapphire substrate, growing an aluminum oxide layer on the aluminum nitride single crystal film, and growing silicon carbide on the aluminum oxide layer. Membrane manufacturing method.