JPS6386450A - Manufacture of substrate for formation of semiconductor element - Google Patents

Abstract

PURPOSE:To prevent an SOI substrate to be formed from warping and to contrive to prevent the generation of crack by a method wherein an amorphous Si layer is previously formed on the rear of the insulative substrate and thereafter, an Si layer is epitaxially grown on the substrate. CONSTITUTION:An amorphous Si layer 12 is previously formed on the side of the rear of a sapphire substrate 11 by a vapor phase growth method of low temperature in the roughly same thickness as that of an Si epitaxial layer 13 which is formed on the surface of the substrate 11. After the amorphous Si layer 12 is formed in such a way, the thermal expansion coefficient of this amorphous Si layer 12 comes to have the same thermal expansion coefficient as that of the single crystal Si epitaxial layer 13 by the heat treatment at the time the single crystal Si layer 13 is formed on the surface of the insulative substrate 11. Therefore, cracks are prevented from generating in the Si epitaxial layer 13 to be formed in such a way that the substrate 11 is not warped by the heat treatment at the time of this epitaxial growth.

Description

[Detailed Description of the Invention] [Summary] A monocrystalline silicon (Si) layer is formed on an insulating substrate such as a sapphire substrate or a magnetic spinel substrate.
ilicon-ON-Insulator (hereinafter SO
A method for forming a Sol substrate in which a substrate (referred to as I) is formed and a semiconductor element is formed on this Si layer, in which an amorphous Si layer is formed in advance on the back side of an insulating substrate, and then an St epitaxial layer is formed on the surface of this substrate. By forming a layer, S
i Prevent the insulating substrate from warping due to heat treatment during epitaxial layer formation.

[Industrial application field]

The present invention relates to a method of manufacturing a substrate for forming semiconductor elements, and particularly to a method of manufacturing an SOI substrate.

A single-crystal Si layer is formed on an insulating substrate such as a sapphire substrate or a magnetic spinel substrate to form a substrate for forming a semiconductor element with an SO■ structure, and when a semiconductor element is formed on this Si layer, it is possible to Recently, it has been increasingly used in the formation of semiconductor devices such as high-voltage, highly integrated ICs because it has advantages such as facilitating the separation process and reducing the stray capacitance of the formed elements. .

[Conventional technology]

Conventionally, when forming a substrate for forming a semiconductor element having such a Sol structure, as shown in FIG.
Silane (5iH4) gas is thermally decomposed on an insulating substrate of μ-free sapphire or magnetic spinel at a growth temperature of 950°C to 1050°C, and single-crystal Si epitaxial N2 is grown at a rate of about 0.1 to 10 μI. It was formed to a thickness of .

[Problem that the invention seeks to solve]

By the way, the coefficient of thermal expansion of the above-mentioned sapphire substrate is 4.
At 6 Xl0-'/°C, the coefficient of thermal expansion of single crystal Si is:
2.5 Xl0-'/''C, each having a different coefficient of thermal expansion.

Therefore, a single crystal Si layer is placed on the substrate surface at 850°C to 10°C.
When the substrates are cooled to room temperature after being formed at a growth temperature of 00°C, there is a problem that the two substrates warp in a convex shape toward the surface.
There was a problem in that crank 3 occurred in the single crystal Si layer formed on this substrate.

This problem of substrate warping tends to become more pronounced as the thickness of the formed Si layer increases and as the insulating substrate becomes thinner.

When such a substrate is used and a semiconductor element is formed thereon, there is a problem that the characteristics of the element deteriorate.

It is an object of the present invention to provide a novel method for manufacturing a substrate for forming semiconductor elements, which eliminates the above-mentioned problems and prevents the formed SOR substrate from warping.

[Means for solving problems]

In the method of manufacturing a substrate for forming a semiconductor element of the present invention, amorphous silicon is previously formed on the back surface of an insulating substrate, and then a silicon layer is epitaxially grown on the substrate.

[Effect]

The method of manufacturing a substrate for forming a semiconductor element of the present invention uses a low-temperature vapor phase growth method to previously form an amorphous Si layer on the back side of the substrate to a thickness approximately the same as that of the Si etaxial layer formed on the surface of the substrate. Form. In this way, amorphous S
After forming the i-layer, heat treatment is performed when forming a single-crystal Si layer on the surface of the insulating substrate, so that the coefficient of thermal expansion of this amorphous Si layer is similar to that of the single-crystal Si epitaxial layer. Therefore, cranks are prevented from occurring in the Si epitaxial layer formed by preventing the substrate from warping during the heat treatment during epitaxial growth.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, an amorphous Si layer 12 is formed on the back side of a single crystal sapphire substrate 11 with a thickness of 50 to 500 μm by plasma CVD at a growth temperature of 30 to 200°C.
form.

Here, the growth temperature should be as close to room temperature as possible.
This is preferable in order to prevent the substrate from being subjected to thermal strain when the substrate is subsequently taken out from the growth apparatus and cooled to room temperature.

The thickness of this amorphous Si layer 12 is approximately the same as that of the single crystal Si layer formed on the substrate surface.

Next, as shown in FIG. 2, a single-crystal Si layer 13 having a thickness of 0.1 to 10 .mu.m is formed on the front surface of the substrate using the CVD method at a growth temperature of 850 DEG C. to 1000 DEG C..

In this way, when forming a single-crystal Si epitaxial layer on the substrate surface, the amorphous Si layer adhering to the back side of the insulating substrate 11 due to the temperature rise will be
The crystal structure of the polycrystalline Si layer is shifted to that of the polycrystalline Si layer, and almost no stress is applied to the substrate to prevent its thermal expansion.

Furthermore, after the single crystal Si epitaxial layer is formed, the amorphous Si layer on the back side becomes polycrystalline or single crystal, and the single crystal Si layer formed on the front side of the substrate becomes polycrystalline or single crystal.
Since the thermal expansion coefficient is almost the same as that of the layer, it is possible to suppress warping of the substrate.

In this way, even if a single-crystal Si epitaxial layer for semiconductor element formation is formed on the surface, the formed SOI substrate will not warp and cracks will not occur in the substrate, resulting in high reliability. A Sol substrate is obtained.

〔Effect of the invention〕

As described above, according to the method of manufacturing a substrate for forming a semiconductor element of the present invention, a highly reliable SOI substrate can be obtained without causing warpage in the formed SOI substrate, and elements can be formed on such a substrate. By forming this, a highly integrated semiconductor device can be obtained.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views showing the method of the present invention in the order of steps, and FIG. 3 is a cross-sectional view for explaining the conventional method of forming a SOR substrate. In the figure, 11 is a sapphire substrate, 12 is an amorphous St layer, 4th ε Hu's A U seven cases S1 type V engineering 1 Figure 1 Osaki Hishishi seven five Hayabusa familiar J'BSi layer J Jizu” to the stone 2nd
Mukuro/l sot guide? Completed form of precepts
figure

Claims (1)

[Claims] In a method of forming a substrate by epitaxially growing a silicon layer on the surface of a single-crystal insulating substrate (11), an amorphous silicon layer (12) is formed in advance on the back side of the insulating substrate (11). ) is formed, and then a single crystal silicon layer (13) is epitaxially grown on the substrate (11).