JPH03153023A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To promote that a semiconductor device utilizing a heterojunction of an HBT or the like is put to practical use by a method wherein a silicon layer is deposited on one surface of a silicon substrate having a carbonized surface, the substrate is heated in an atmosphere of a hydrocarbon and the silicon layer is carbonized. CONSTITUTION:The surface of a silicon wafer 2 is carbonized; an SiC layer is produced. Then, a temperature of the silicon wafer 2 is lowered; a movable shutter 5 is opened; the surface of the silicon wafer 2 is irradiated with an Si molecular beam. An Si layer with a thickness of about 20Angstrom is deposited on a carbonized layer on the surface of the silicon wafer 2. C2H2 gas is introduced into a vacuum container 1; the temperature of the silicon wafer 2 is raised and held; after that, an introduction of the C2H2 gas is stopped; the temperature of the silicon wafer 2 is lowered. The Si layer deposited on the surface of the silicon wafer 2 is carbonized wholly and is transformed into a single-crystal SiC layer.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a method for growing single-crystal silicon carbide on a silicon substrate.

The purpose is to make it possible to grow single-crystal silicon carbide with excellent flatness on a silicon substrate.

A step of depositing a silicon layer on one surface of a silicon substrate having a surface subjected to a carbonization treatment, and a step of heating the silicon substrate on which the silicon layer is deposited in a hydrocarbon atmosphere to carbonize the silicon layer. Configure it to include.

[Industrial Application Field] The present invention relates to a method of growing single crystal silicon carbide (SiC) to form a heterojunction on a silicon substrate.

[Conventional technology]

A hetero bipolar transistor (IIBT) has been devised as one of the semiconductor devices using a hetero junction.

On the other hand, a technology for epitaxially growing silicon carbide (SiC) on silicon wafers is being developed. By forming a SiC layer with a larger band gap than silicon on a silicon wafer, for which stable miniaturization technology has been established, and forming a hetero bipolar transistor using this SiC layer as an emitter, thermally stable high-speed and large-scale transistors can be realized. We can expect power integrated circuits.

[Problems to be Solved by the Invention] As a method for epitaxially growing SiC on a silicon wafer, a molecular beam of silicon (S3) is irradiated onto the surface of a heated silicon wafer in a vacuum chamber, and at the same time acetylene (C2H2) A type of molecular beam epitaxy (MBE) method in which gas is blown may be used. In this method, before irradiating the 1Si molecular beam, the silicon wafer surface is carbonized by spraying only C21 gas, that is, a SiC layer is generated.The residual gas in the vacuum chamber at this time is composed of Si molecules. It is necessary that the pressure is low enough so that it does not collide with the residual gas, less than 5 X 1O-5 Torr in a boat-sized growth apparatus.Since most of the residual gas is CtHz, Cz
It is necessary to spray at a partial pressure of Hz within this pressure range.

However, the SiC layer grown on the silicon wafer under the above conditions is granular and does not have a surface flatness suitable for manufacturing a semiconductor device such as the above-mentioned HBT.

The present invention is based on the above? The object of the present invention is to provide a method capable of growing a single crystal SiC layer with excellent flatness on a silicon wafer using an fBE apparatus.

[Means to solve the problem]

The above purpose includes a step of depositing a silicon layer on one surface of a silicon substrate having a surface subjected to carbonization treatment, and heating the silicon substrate on which the silicon layer is deposited in a hydrocarbon atmosphere to remove the silicon layer. A method for manufacturing a semiconductor device according to the present invention, characterized in that it includes a step of carbonizing the substrate, or a step of carbonizing the substrate in a vacuum container containing a single crystal silicon substrate heated to a first temperature (T). A first step of introducing hydrogen gas and then heating the silicon substrate to a second temperature (Tz;>T+) to generate a silicon carbide layer on the surface of the silicon substrate, and introducing the hydrocarbon gas into the vacuum container. After stopping the introduction of the silicon substrate, the silicon substrate is heated to a third temperature ('h;
a second step of heating to Tz≧Tl>T, and depositing a silicon layer on the silicon carbide layer;

a third step of holding the silicon substrate on which the silicon layer is deposited at a fourth temperature (T4: Ta < 73) in the vacuum container; Hydrocarbon gas is introduced into the vacuum container in which the substrate is housed, and the silicon substrate is heated to a fifth temperature (TS; TS≧T,) to convert the silicon layer into a single-crystal silicon carbide layer. This is achieved by the method for manufacturing a semiconductor device according to the present invention, which is characterized in that it includes a fourth step.

[For production]

10- on the surface of a silicon wafer with a carbonized surface.
``A Si layer is deposited in a high vacuum of about Torr, and this Si layer is deposited in a high vacuum of about Torr.
It is possible to epitaxially grow a flat SiC layer by carbonizing the layer by spraying a hydrocarbon gas such as C2N2 at 850°C. Therefore, by repeating the epitaxial growth of the Si layer and its carbonization, a single crystal SiC layer having a desired thickness can be formed.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing the general configuration of an MBE apparatus used in the implementation of the present invention, and the exhaust is exhausted by an exhaust device (not shown). Stainless steel vacuum container 1 with a diameter of approximately 50 ctrl
A silicon wafer 2 having a diameter of 4, for example, 3 inches is placed inside the wafer. The ultimate degree of vacuum in the vacuum container l is l x 10-
” Torr. The silicon wafer 2 can be heated up to 1200° C., for example, by a heater 3 provided on its back surface.

Inside the vacuum chamber 1, a Si molecular beam source 4 is provided so as to face the silicon wafer 2, and a movable shutter 5 is arranged between the silicon wafer 2 and the Si molecular beam source 4. Also in 1 vacuum container 1.

Reflection high-speed electron diffraction (R11EE
D) equipment is provided. The tip of the gas introduction tube 6 is extended into the vacuum chamber 1 so as to spray C and R2 gas onto the surface of the silicon wafer 2.

In the above MBE apparatus, the silicon wafer 2 is heated in the temperature cycle shown in FIG. conduct.

A SiC layer is epitaxially grown on a silicon wafer 2.

(Example 1) While evacuating the inside of the vacuum chamber 1 to I x 10-'' Torr, the silicon wafer 2 is heated to 800°C to remove the surface oxide film.Then, the temperature of the silicon wafer 2 is raised to 300°C. 'C, then C2H2 gas is introduced from the gas introduction pipe 6 at a flow rate of I SCCM.As a result, the pressure inside the vacuum vessel 1 becomes 3 x 10-' Torr.This pressure is the partial pressure of C2H, gas It can be considered as

The temperature of the silicon wafer 2 is raised to 850'C, and after this temperature is maintained for about 10 minutes, the introduction of C2H2 gas is stopped. As a result of the above, the surface of the silicon wafer 2 is carbonized,
A SiC layer is generated.

Next, the temperature of silicon wafer 2 was lowered to 800°C.

The movable shutter 5 is opened for about 1 minute, and the surface of the silicon wafer 2 is irradiated with a Si molecular beam. As a result, silicon wafer 2
A Si layer with a thickness of about 20 nm is deposited on the surface carbonized layer. At this time, the pressure inside the vacuum container 1 is 1×10-” Torr.
Met. The movable shutter 5 is closed and the temperature of the silicon wafer 2 is lowered to 300°C.

C and R2 gases with a flow rate of I SCCM were introduced into the vacuum chamber 1 again, and the temperature of the silicon wafer 2 was raised to 850°C.

After holding for about 10 minutes, the introduction of C and R2 gas was stopped.

Lower the temperature of the silicon wafer 2 to at least 300°C.

The Si layer deposited on the surface of the silicon wafer 2 is the above C!
All of the material is carbonized by heating at 850° C. in H. gas, converting it into a single crystal SiC layer. Through the above steps,
A flat SiC layer with a thickness of approximately 50 nm is formed on the surface of the silicon wafer 2. This SiC layer has specular gloss. RHE
Observation by ED confirmed that this flat SiC layer was single crystal.

(Example 2) In the above Example 1, C, H introduced into the vacuum container l
, the gas flow rate is 0. OISCCM was used, and other conditions were the same as in Example 1 to deposit SiC on the surface of the silicon wafer 2.
grow. The pressure inside the vacuum vessel 1 at the time of introducing the C2H gas is I x 10-'Torr.

In this example, about 50
A human SiC layer is produced, but this SiC layer shows graininess and is not a flat layer. According to observation by RHEED, it was confirmed that this granular SiC layer was a single crystal.

(Example 3) After heating the silicon wafer 2 to 800"C in a high vacuum of I x 10" Torr to remove the natural oxide film on the surface, the temperature of the silicon wafer 2 was increased to 300°C.
Immediately heat to 850°C without lowering the temperature to 850°C, and introduce C2H gas at a flow rate of ISCCM. After maintaining this state for about 10 minutes, the introduction of C and R2 gas was stopped.
After lowering the temperature of silicon wafer 2 to 800°C,
A molecular beam is irradiated for about 2 minutes to deposit a Si layer.

Next, C2H2 gas is introduced again at a flow rate of I SCCM, and the temperature of the silicon wafer 2 is raised to 850° C. and held in this state for about 10 minutes. Then C,)
I. Stop the introduction of gas and lower the silicon wafer 2 to room temperature.

The SiC layer formed on the silicon wafer 2 according to this example exhibits monograin nature.

As in Example 2, when the amount of C, l+2 gas introduced is low, a granular SiC layer is generated on the surface of the silicon wafer 2, but the actual situation and the reason for the granular formation are unknown.

Furthermore, before proceeding to the step of carbonizing the Si layer deposited on the surface of the silicon wafer 2 or the SiC layer, the temperature of the silicon wafer 2 is once lowered to 300°C, so that the Si
The reason why the flatness of the layer improves is still not clear.

Conventionally, in an MBE device similar to the above, 800°
When C, H, and gas are sprayed onto the silicon surface of C.

It is known that when unevenness occurs on the silicon surface, the flow rate of Czllz gas is increased (which causes the unevenness to become smaller and at the same time increase in number. (C, J, Magaba
nd H, J., Leamy, J., Appl., Phys.
, 45 (1974) 1075) In addition, the silicon surface reacts with hydrogen atoms generated by decomposition of hydrocarbons, resulting in 5il
It is known that it is etched to produce La (silane).

(Yoshinobu Hattori et al., Institute of Electrical Engineers of Japan Research Group Material EFM-89-10
, p.

1 (1989)) For these reasons, when the CzHz gas flow rate is low (as in Example 2), the etching of hydrogen atoms on the surface of the silicon wafer 2 becomes selective, and as a result, 1 large unevenness occurs. In contrast to the fact that the crystal grains of SiC with a length of Ebitaxia>14 become larger, as in Example 1, C,
It is thought that when the H gas flow rate is high, etching selectivity to the surface of the silicon wafer 2 decreases, resulting in dense formation of small irregularities, on which fine SiC of less than the optical wavelength grows epitaxially.

Regarding the third reason above, when C2H2 gas comes into contact with a silicon surface at 800°C, it immediately decomposes to produce hydrogen atoms, and the hydrogen atoms cause etching of the surface, whereas silicon at 300°C does not.

CtHz gas does not thermally decompose 1 but forms a weak bond with silicon, providing a protective effect on the silicon surface. the result,
It is considered that the SiC layer grows on the flat silicon surface because etching of the silicon surface by hydrogen atoms is suppressed.

By repeating the Si layer deposition and carbonization process using C and H2 gases in Example 1, a flat SiC layer with a desired thickness can be formed.

〔Effect of the invention〕

According to the present invention, a silicon wafer on which a SiC layer with excellent flatness is formed can be obtained, which has the effect of promoting the practical use of semiconductor devices using heterojunctions such as HBTs.

4 is a Si molecular beam source.

5 is a movable shutter.

6 is the gas introduction pipe 7A and 7B are the main parts of the electron beam diffraction apparatus.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the general configuration of an MBE apparatus used in implementing the present invention. FIG. 2 is a diagram illustrating the basic steps of the present invention. In fig. 1 is a vacuum container. 2 is a silicon wafer. 3 is a heater.

Claims (3)

[Claims] (1) A step of depositing a silicon layer on one surface of a silicon substrate having a carbonized surface, and heating the silicon substrate on which the silicon layer is deposited in a hydrocarbon atmosphere to carbonize the silicon layer. 1. A method for manufacturing a semiconductor device, comprising the step of processing. (2) Hydrocarbon gas is introduced into a vacuum container containing a single crystal silicon substrate heated to a first temperature (T_1), and then the silicon substrate is heated to a second temperature (T_2;>T
A first step of heating the silicon substrate to a temperature of _1) to form a silicon carbide layer on the surface of the silicon substrate, and heating the silicon substrate to a third temperature (T_3; T_2 after stopping the introduction of the hydrocarbon gas into the vacuum vessel). ≧T
_3>T_1) and depositing a silicon layer on the silicon carbide layer, and heating the silicon substrate on which the silicon layer is deposited to a fourth temperature (T_4; T_4< a third step of holding the silicon substrate at a temperature T_3), and introducing a hydrocarbon gas into the vacuum container in which the silicon substrate held at the fourth temperature (T_4) is held, and holding the silicon substrate at a fifth temperature T_3); Temperature (T_5; T_
5≧T_3) to convert the silicon layer into a single-crystal silicon carbide layer. (3) The method for manufacturing a semiconductor device according to claim 2, wherein the second to fourth steps are repeated.