JPH0342818A - Compound semiconductor device and its manufacture - Google Patents

Abstract

PURPOSE:To prevent generation of warpage and crack of a compound semiconductor by forming a porous layer on an Si substrate and by enabling Si to grow on it. CONSTITUTION:A porous layer 2 is formed on the surface of an Si substrate 1 and then the substrate is subjected to Si homoepitaxial growth 3 by the organic metal vapor growth method. Then, growing Si and then an As coated surface on Si, a GaAs low-temperature layer 4 is formed and then GaAs growth is performed successively, thus achieving improved surface flatness and crystallinity as compared with a GaAs epitaxial layer which is directly allowed to grow on the surface of Si substrate. Also, no cracks occur even if the film thickness of GaAs exceeds 4mum.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention provides a high-quality compound semiconductor device on a Si substrate in which warpage and cracking of the substrate are extremely suppressed compared to those of the prior art, and its manufacture. It is about the method.

(Prior Art) ■-■ group compound semiconductors represented by GaAs are used in high-speed devices and optical devices because they are direct transitions and have higher electron mobility than Sl, which is currently the mainstream. However, the above ■-v represented by GaAs
W1 group compound semiconductors are mechanically fragile and cannot be formed over a large area, so they are expensive. In order to solve such problems,
The above ■-■ is mounted on an SI substrate that is inexpensive and has excellent mechanical and thermal properties.
Attempts have been made to epitaxially grow group compound semiconductors and form devices thereon.

(Problem to be Solved by the Invention) However, taking the above-mentioned GaAs as an example, it has a mismatch with Si of about 4% in lattice constant and about twice the coefficient of thermal expansion, so it cannot be grown directly on a Si substrate. It's tough.

To solve this problem, a two-step growth method is currently available in which several hundred low-temperature GaAs layers are formed on the Si substrate at a growth temperature of 300 to 400°C, and then a GaAs layer is formed at a growth temperature of 600 to 800°C. Good crystallinity has been obtained. Furthermore, by performing thermal annealing in addition to the above method, it is possible to form a GaAs epitaxial layer with even further improved crystallinity and surface flatness on the Si substrate.

However, as mentioned above, there is a difference in thermal expansion coefficient of approximately twice that between the Si and the GaAs, so a very large tensile stress acts during the cooling process to room temperature after the GaAs is heated. The GaAs epitaxial layer has an upwardly convex curved shape, and the film thickness is 3/! a
There was a problem that cracks would occur if the temperature was exceeded.

(Objective of the Invention) The present invention was proposed to improve the above-mentioned drawbacks. It is an object of the present invention to provide a compound semiconductor device and a method for manufacturing the same in which warping and cracking occurring in the semiconductor device are significantly suppressed compared to conventional methods.

(Means for Solving the Problem) In order to achieve the above object, the present inventors have conducted various experiments and found that the surface of the Si substrate is made into a porous shape and Si is homogenized on the porous Si surface. By epitaxially growing GaAs on the substrate, the warpage of the substrate can be significantly reduced, and cranks also occur when the GaAs growth exceeds 3μ in the conventional method, but according to the present invention, 3n can be reduced. I discovered that the crank did not occur even when I crossed it.

In order to achieve the above object, the present invention includes a Si substrate, a porous layer formed on the Si substrate, a homoepitaxial layer formed on the porous layer, and a porous layer formed on the homoepitaxial layer. The gist of the invention is a compound semiconductor device characterized by comprising a compound semiconductor layer.

Furthermore, the present invention is characterized in that the step of forming a compound semiconductor on a Si substrate includes the steps of forming porous Si on the surface of the Si substrate, and growing Si epitaxially on the surface of the porous Si. The gist of the invention is a method for manufacturing a compound semiconductor device.

(Function) The present invention makes the surface of the Si substrate porous and deposits S on this surface.
i is homoepitaxially grown, and GaA is further grown on top of this.
Since s is epitaxially grown, the warpage of the substrate can be significantly reduced.

(Example) Next, an example of the present invention will be described. It should be noted that the embodiments are merely illustrative, and it goes without saying that various changes and improvements may be made without departing from the spirit of the present invention.

Embodiments of the present invention will be described below, taking as an example a case where GaAs is epitaxially grown on a Si substrate using a metal organic chemical vapor deposition method (hereinafter referred to as MOCVD method).

Figure 1 is a cross-sectional view of a GaAs epitaxial layer formed on a Si substrate according to the present invention.
2 is a porous Si substrate, 3 is a Si homoepitaxial layer, and 4 is a GaAs epitaxial layer.

The substrate is a P-type Sl with a resistivity of 0.01 Ωam or less and a thickness of 300 nm, with a plane orientation slightly deviated from <100>.
A substrate was used. In order to make the Si substrate surface porous, anodization was carried out in an HF solution at a current density of 0.1 after normal cleaning.
A/c+w'' for 20 minutes to form a porous layer with a thickness of 1.6 nm.Then, the substrate was introduced into the above MOCVD apparatus, and the substrate was heated at 1000'C for 110 minutes in an H8 atmosphere to coat the surface of the Si substrate. I did some cleaning.

Then, the substrate temperature was set at 900°C, 5I84 was introduced into the reactor, and In homoepitaxial growth of Sl was performed. After introducing Si and forming an As-coated surface on the Si, the substrate temperature was set at 400°C and a GaAs low-temperature layer was applied for 150 times, and then the substrate temperature was lowered to 70°C.
GaAs growth was performed at a temperature of 50°C.

As a result of evaluating the surface flatness and crystallinity of the GaAs epitaxial layer on the Si substrate manufactured according to the above process by the X-ray double crystal method, it was found that
In order to investigate the warpage of the zero-order substrate, which was found to be comparable to a GaAs epitaxial layer grown directly on the substrate surface, a GaAs epitaxial layer was grown using a flatness tester.
The curvature of a substrate of As1ll thickness 2n was measured. The results are shown in Table 1. In the conventional method, the curvature measured by the flatness tester was 6.4 m, whereas in the present invention, the curvature measured by the flatness tester was 15 m, which shows that the warpage is significantly reduced. . Furthermore, in the conventional method, cracks began to occur when the GaAs film thickness exceeded 3 nm, but according to the present invention, no cracks occurred even when the thickness exceeded 4 μ.

In the examples shown in Table 1 and above, GaA is used as the ■-V group compound semiconductor.
s is used as an example, but it goes without saying that the above effect can be obtained even if InAs, GsP, InP, etc. are used as the = V group compound semiconductor. In addition, in this example, a semiconductor device made of GaAs on a Si substrate is used. (2) In forming the V group compound semiconductor, epitaxial growth is performed using the MOCVD method, but this example is just an example, and it goes without saying that other crystal growth methods can be applied.

For example, when forming GaAs on a Si substrate by molecular beam epitaxial (hereinafter referred to as MBE) method, the Si substrate on which a porous layer has been formed is introduced into the above MBE apparatus, and the substrate is heated at 100°C for 110 minutes in an ultra-high vacuum. Heating is performed, the surface of the Si substrate is cleaned, and the substrate temperature is increased to 500°C.
, and evaporate Si using an electron beam evaporation source.
Perform 1n homoepitaxial growth of Si, and
Using a grown Knudsen cell, ^S is evaporated and Si
After forming the ^3 coating surface on top, the substrate temperature is set to 400°C to form 150 GaAs low temperature layers, and then the substrate temperature is set to 750°C to perform GaAs growth.

(Effects of the Invention) As explained above, according to the present invention, by making the surface of a Si substrate porous and growing Si on it, warping and cracking that occur in compound semiconductors can be reduced compared to conventional methods. It has now become possible to significantly reduce this. Therefore, it becomes possible to design devices with high precision in the lithography process, resulting in significant economic effects such as improved manufacturing yield and improved device performance.

[Brief explanation of drawings]

Figure 1 shows G formed on a Si substrate with a plane orientation of <100>.
FIG. 3 is a diagram showing a cross section of an aAs epitaxial layer. 1...Si substrate 2...Porous Si 3...Si homoepitaxial layer 4...GaAs epitaxial layer Fig.

Claims (2)

[Claims] (1) A Si substrate, a porous layer formed on the Si substrate, a homoepitaxial layer formed on the porous layer, and a compound semiconductor layer formed on the homoepitaxial layer. A compound semiconductor device characterized by: (2) a step of forming a compound semiconductor on a Si substrate, a step of forming porous Si on the surface of the Si substrate;
A method for manufacturing a compound semiconductor device, comprising the step of epitaxially growing Si on the porous Si surface.