JPS63146447A - Formation of soi structure - Google Patents

Abstract

PURPOSE:To obtain a single crystalline silicon film having a thin film thickness and a good crystallizability by a method wherein of single crystalline silicon films formed on a spinel substrate, the interface with the substrate is made of a silicon oxide film. CONSTITUTION:A single crystalline silicon film 2 is grown on a single crystalline magnesia spinel substrate 1. On the silicon film 2, a silicon nitride film 3 is formed by a thermal nitriding reaction. With the substrate 1 temperature being kept at 1050 deg.C, the silicon film 2 is oxidized under a moistened oxygen atmosphere. Then in the interface between the silicon film 2 and the nitride film 3, a silicon oxide film is not formed because the nitride film 3 inhibits the oxygen supply, but oxygen is transported in the substrate 1 and oxidation is performed in the interface between the silicon film 2 and the substrate 1, whereby a silicon oxide film 4 is formed. Accordingly, the silicon film 2 having a good crystallizability and a thin film thickness is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION K) Industrial Application Field The present invention relates to a method for forming a SUE structure, and more particularly to a method for forming a silicon thin film on a magnesia spinel substrate.

(1) Conventional technology The one in which a single-crystal silicon film is grown on a single-crystal insulating substrate is SO5 (Silicon On 5apphine).
) or So I (Silicon On In
It is called sulatiIlgSubstrate) 411 and is known as a device that can achieve higher integration, higher speed, and lower power consumption in semiconductor integrated circuits.

As a single crystal insulating substrate, for example, Applied Ph
ysics Letters 36(9), I May
1980, pp. 741-743, “Growt
h of thinsillicon films
on 5apphire and 5pin
elby molecular beam epira
Sapphire (A/
A substrate made of magnesia spinel (MgOA720) is used.

In this process, a single-crystal silicon film is grown on a spinel substrate heated to 80'0°C by the molecular beam epitaxial method. grows into granular islands near the interface with the spinel substrate, including many defects. For this reason,
A film thickness of 0.5 pm is necessary for the surface of a single crystal silicon film to be flat, but a film thickness of 1.0 .mu.m or more is required for a semiconductor device to exhibit good hole mobility.

Pj Problems that the invention seeks to solveHowever,
When the thickness of the single-crystal silicon film exceeds 1.0 μm, the electrical capacity of the single-crystal silicon film becomes a problem, which has a negative effect on high integration, high speed, and low power consumption, and the advantages of the 501 structure are lost. You will lose it. Furthermore, since the interface state density between the silicon film and the spinel substrate was high, the characteristics as a semiconductor device were worse than those of the silicon substrate.

The present invention has been made in view of these points, and is to form a thin single-crystal silicon film with good crystallinity and a thickness of about 0.3 μm on a spinel substrate.

B) Means for Solving the Problems The present invention comprises a step of forming a single crystal silicon film on a magnesia spinel substrate, a step of forming a silicon nitride film on the single crystal silicon film, and a step of forming a silicon nitride film on the magnesia spinel substrate. This method of forming an SOI structure includes the step of oxidizing the single crystal silicon film on the interface side to form a silicon oxide film.

By forming a silicon oxide film on the interface side with the substrate of a single crystal silicon film formed on a spinel substrate, a thin single crystal silicon film with good crystallinity can be obtained.

(f) Example FIGS. 1A to 1A show schematic process diagrams of an embodiment of the present invention.

First, a single crystal magnesia spinel (MgOklx00 substrate (1) with a thickness of about 200 μm was mirror-polished (100 μm).
) A single crystal silicon film +2++AI with a thickness of 1 μm is epitaxially grown on the surface (%1 Figure A).

This epitaxial growth refers to the silicon molecular beam epitaxial growth method at a substrate temperature of 800°C or the silicon molecular beam epitaxial growth method at a substrate temperature of 1000°C.
This is done by a technique such as a CVD method using SiH4 gas at .degree.

Next, on the grown single crystal silicon film (2), a silicon nitride film (3) of 20 OA is formed by direct thermal nitridation using NHs gas at a substrate temperature of 1050° C. (FIG. 1B).

Then, the single crystal silicon film (2) is oxidized in a humidified oxygen atmosphere while maintaining the substrate temperature at 1050°C. At this time, a silicon oxide film is not formed at the interface with the silicon nitride film (3) of the single crystal silicon film (21) because the silicon nitride film (3) blocks the supply of oxygen. is transported, oxidation occurs at the interface of the single crystal silicon film +21 with the spinel substrate (1), and a silicon oxide film (4) is formed. That is,
A single crystal silicon film with many defects and poor crystallinity near the interface with the spinel substrate (1) is oxidized and becomes an insulating film.

When the silicon oxide film (4) is formed in this way to a thickness of 1.4 Pm, the single crystal silicon film (2) becomes a thin film with a thickness of 0.6 μm on the upper layer side with good crystallinity (FIG. 1C).

Therefore, S with a thin silicon film with good crystallinity
An OI structure can be formed. If the silicon nitride film (1) is removed by dry etching using 31CF4 gas, the single crystal silicon film (2) will be exposed (Fig. 1D).
).

FIG. 2 is a diagram showing the relationship between the silicon film thickness and the hole electron mobility in the 501 structure, where the solid lines are those obtained by the method of the present invention;
The dashed line is from the conventional method. As can be seen from Figure @2, for example, when the silicon film thickness is 0.5 μm, the hole electron mobility is 1 in the conventional SOI structure.
The electrical characteristics were significantly improved to 750 cj/V·S compared to 50 d/V·S by the method of the present invention.

(G1) Effects of the Invention As is clear from the above description, the present invention oxidizes the interface side with the spinel substrate, which has poor crystallinity, of the single crystal silicon film formed on the spinel substrate to form a silicon oxide film. , an SOI structure having a thin silicon film with good crystallinity is formed.The electrical characteristics can also be improved, and a substrate suitable for semiconductor devices can be provided.

[Brief explanation of the drawing]

Figures 1A to 1A are schematic process diagrams of the method of the present invention, and Figure 2 is S
FIG. 3 is a diagram showing the relationship between the film thickness of a silicon film and hole electron mobility in an O1 structure. (1) Magnesia spinel substrate, (2)... single crystal silicon film, (31... silicon nitride film, (4)...
・Silicon oxide film.

Claims (1)

[Claims] (1) Forming a single crystal silicon film on a magnesia spinel substrate, forming a silicon nitride film on the single crystal silicon film, and oxidizing the single crystal silicon film on the interface side with the magnesia spinel substrate. a step of forming a silicon oxide film using
How the structure is formed.