JPH04171811A - Semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a semiconductor device having no bend but a flat upper surface on the surface of a grown layer by depositing the first semiconductor grown layer having a coefficient of thermal expansion larger than that of a semiconductor substrate on the substrate and the second grown layer having a coefficient of thermal expansion smaller than that of the first grown layer on the first grown layer. CONSTITUTION:After an Si substrate 11 is placed in an MOCVD device, the substrate 11 is subject to heat treatment in an arsine atmosphere. After the heat treatment, GaAs is grown on the substrate 11 by using trimethylgallium and arsine as a gaseous starting material and a GaAs layer 12 is epitaxially grown. After the layer 12 is formed, an SiO2 layer 13 is formed by using monosilane and O2. Accordingly, a semiconductor device which is extremely reduced in bend and has a substantially flat upper surface is obtained and a large-aperture GaAs substrate, integrated circuit of a GaAs semiconductor device and Si semiconductor device, or inexpensive, high-efficiency, and light- weight solar battery can easily be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a semiconductor device having a multilayer structure in which semiconductor layers having different coefficients of thermal expansion are laminated.

(Prior art) A multilayer structure in which GaAs is epitaxially grown on an 81 substrate can combine the characteristics of Si as a substrate with the electrical and optical characteristics of GaAs.
It is attracting attention because it enables the realization of large-diameter As substrates, integrated circuits of GaAs semiconductor devices and Si semiconductor devices, and inexpensive, highly efficient, and lightweight solar cells.

Conventionally, a two-step growth method using MOCVD or MBE has been proposed as a method for epitaxially growing GaAs on an 81 substrate. This two-step growth method uses GaA
This is an attempt to solve the problem of lattice mismatch between GaAs and Si.
After 50 nm of growth, the temperature is raised to the normal GaAs growth temperature and the growth of the GaAs film is restarted.

However, the thermal expansion coefficient of GaAs is 6.8 Xl0-6/
℃, which is the thermal expansion coefficient of Si, 2.6
It is about 2.5 times that of 6/°C. Therefore, in the conventional method as described above, when the Si substrate is cooled from the GaAS growth temperature to room temperature, the GaAs surface is curved into a concave shape as shown in FIG. Note that in this figure, 1 is a Si substrate, and 2 is a GaAs layer grown on the Si substrate 1 by an epitaxial growth.

This curvature causes various problems in the process of mass producing semiconductor devices using the GaAs layer 2 on the Si substrate 1 as a large diameter substrate.

In other words, due to this curvature, even if the processing conditions are the same,
Different results will be produced between the central part and the peripheral part of the upper surface of the GaAs layer 2 on the Si substrate 1.

For example, in a photolithography process, if the irradiation light is focused on the center, the resolution at the periphery will be extremely reduced.

(Problems to be Solved by the Invention) The present invention provides a semiconductor device having a multilayer structure in which a grown layer of another semiconductor having a coefficient of thermal expansion larger than that of the substrate is deposited on a semiconductor substrate. An object of the present invention is to provide a semiconductor device having a multilayer structure with a flat top surface and no curvature.

(Means for Solving the Problems) In order to solve the above problems, the present invention takes a step of growing a layer having a smaller coefficient of thermal expansion on the semiconductor epitaxial growth layer having a larger coefficient of thermal expansion. Ta.

That is, the present invention deposits a first growth layer of a semiconductor having a coefficient of thermal expansion larger than that of the substrate on a semiconductor substrate, and then, while maintaining this growth temperature, further deposits the first growth layer thereon. a second layer with a smaller coefficient of thermal expansion than the growth layer;
The present invention provides a semiconductor device having a multilayer structure in which grown layers are deposited.

(Function) A first growth layer of a semiconductor having a coefficient of thermal expansion larger than that of the substrate is deposited on a semiconductor substrate, and the first growth layer is further deposited on the semiconductor substrate.
Since a second grown layer having a coefficient of thermal expansion smaller than that of the grown layer is deposited, the interaction between the semiconductor substrate and the first grown layer and the relationship between the first grown layer and the second grown layer are The effects of (1) and (2) are in balance with each other, and the resulting multilayer structure has a flat top surface that is not curved as in the conventional case.

(Example) Hereinafter, the present invention will be explained with reference to illustrated embodiments.

First, a Si substrate 11 with a thickness of 300 μm and a (100) plane that is off-cut by about 5 degrees in the <011> direction is etched, and then this substrate 1 is loaded into an MOCVD apparatus and etched in an arsine (ASH3) atmosphere. Heat treatment was performed at 900°C.

Next, trimethyl gallium (TM
Using Ga) and arsine, GaAs is 2
It was grown to 0 nm. Then, the temperature was raised to 750°C, and GaA
The s-layer 12 was epitaxially grown to a thickness of 2 μm.

After that, while keeping the temperature at 750℃, monosilane (S
A 1 μm 5i02 layer 13 was formed using L'H4) and 02.

When the flatness of the resulting three-layer semiconductor device was measured using a Fizeau laser interferometer, it was found that G
It was found that the curvature was significantly reduced and a substantially flat top surface was formed compared to the case of the two-layer structure of the aAs layer 2i.

Further, when this three-layer structure is used as a substrate of a semiconductor device, the 8102 layer 13 can be used as it is as a part of an insulating layer or the like.

(Effects of the Invention) As described in detail above, according to the present invention, after depositing a first growth layer of a semiconductor having a coefficient of thermal expansion larger than that of the substrate on a semiconductor substrate, the first Since the second growth layer having a coefficient of thermal expansion smaller than that of the growth layer is deposited, it is possible to provide a semiconductor device with a flat top surface without any curvature on the top surface of the growth layer. Therefore, Ga
It becomes possible to easily realize As large diameter substrates, integrated circuits of GaAs semiconductor devices and St semiconductor devices, inexpensive, highly efficient, lightweight solar cells, and the like.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a semiconductor device according to the present invention, and FIG. 2 is a perspective view of a conventional semiconductor device. In the figure, 1...Si substrate, 2...GaAs layer, 11...
=Si substrate, 12...GaAs layer, 13...5i0
2 layers.

Claims (3)

[Claims] (1) Depositing a first growth layer of a semiconductor having a coefficient of thermal expansion larger than that of the substrate on a semiconductor substrate, and further growing a second growth layer thereon having a coefficient of thermal expansion smaller than the first growth layer. A semiconductor device having a multilayer structure in which layers are deposited. (2) The semiconductor substrate is Si, and the first growth layer is Ga.
Claim 1: As, and the second growth layer is SiO_2.
The semiconductor device described. (3) A semiconductor device using the multilayer structure according to claim 1 or 2 as a composite substrate.