JPH02192126A - Epitaxial deposition - Google Patents

Abstract

PURPOSE:To manufacture wafers having no interfacial transition layer in excellent reproducibility by a method wherein the substrate surface is exposed to a yellow ammonium sulfide solution and then heat-treated successively. CONSTITUTION:A semiinsulating GaAs substrate 11 is etched away by adopting a standard processing means of GaAs. Next, the residual natural oxide film on the surface after etching process is removed by immersing the whole body in HCl solution for around one minute and then immediately washed and dried up by N2 blowing process. Next, the surface is sulfurized. For the sulphatization, the substrate 1 is immersed in (NH4)2Sx solution prepared in a vessel capable of being sealed to be sealed up and left as it is. Later, a sulfide in around monoatomic layer degree is deposited on the substrate surface by heat-treating the surface at the temperature exceeding 100 deg.C. Later, the semiinsulating GaAs substrate 11 is mounted on an ordinary epitaxial device so as to form an epitaxial deposition layer 12. Through these procedures, wafers having no layers in abnormal carrier concentration on the interface between the epitaxial deposition layer and the GaAs substrate can be manufactured in excellent reproducibility.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for epitaxial growth of semiconductors.

[Prior Art] In the half-half technique, a technique of epitaxial growth on a substrate is widely used. For example, AR1 with QaAS as a substrate
-x Fabrication of GaxAs/GaAs double hetero lasers and other GaAS field effect transistors (hereinafter referred to as
It is well known that it is used to fabricate high electron concentration layers under the source and drain electrodes of MESFETs.

[Problems to be Solved by the Invention] A problem that often arises in such epitaxial growth is that a so-called interfacial transition layer, which has a carrier concentration different from the desired one, occurs at the interface between the substrate crystal and the epitaxial layer. Can be mentioned. For example, as shown in FIG. 1, when a GaAs layer 12 is epitaxially grown on a GaAs substrate 11, the carrier distribution in the thickness direction of the epitaxially grown layer 12 is as shown by the broken line 1 in FIG. It becomes like this. In other words, as can be seen from the figure, a region 21 in which the carrier concentration is significantly reduced is seen near the GaAS substrate 11, and this is called an interfacial transition layer. The cause of this is not yet fully understood, but it is believed to be due to impurities that constitute deep levels existing in the substrate, stoichiometric defects in compound semiconductors, oxides on the surface, or impurities attached to the substrate surface. There is a theory that Both theories can occur depending on the case, but the great problem is that the significant drop in carrier concentration near the substrate interface is caused by the generation of heat due to the increase in series resistance in the case of double hetero lasers. In the case of MESFEH, this increases the resistance between the source and the train, which impedes high frequency characteristics.

An object of the present invention is to provide an epitaxial growth method that is effective in preventing the formation of an interfacial transition layer near the interface between a substrate crystal and an epitaxial layer.

[Means for Solving the Problems] The present invention exposes the surface of a substrate on which epitaxial growth is to be performed to a yellow ammonium sulfide solution, and then
This epitaxial growth method is characterized in that epitaxial growth is performed on the surface of the substrate after heat treatment at 0° C. or higher.

In the present invention, the substrate on which epitaxial growth is to be performed is GaAs, InP, and InAs.

Garb, and many other materials can be mentioned, which are of great help in improving the production yield of, for example, l r+QaAs/I nP-based heterostructure avalanche photodiodes.

[Function] Hereinafter, the function of the present invention will be explained by taking epitaxial growth onto a GaAs substrate-L as an example.

It is known that in the process of exposing the GaAs substrate surface to a yellow ammonium sulfide solution, the GaAs surface is etched 3.9 times per hour.
By heat treatment at C or higher, about one atomic layer of sulfide is present on the substrate surface.

At this time, there is no Qa or ΔS chemically bonded to oxygen, and even if such a surface is exposed to the air, the detected oxygen will not be easily eliminated by heating it in a vacuum to 100°C or higher. The baby was born using photoelectron spectroscopy.

The GaAs substrate before epitaxial growth is exposed to H2 at approximately 60°C.
In the usual surface treatment method of etching with a solution of 804:H202:H20=3:1:1 (volume ratio), oxides of Qa and As exist on the surface after etching, and it is necessary to remove these oxides. Approximately 550 min in vacuum
This is a big difference compared to the need to raise the temperature to about ℃. That is, in the present invention, no oxidation state exists on the surface of the wafer that has been subjected to heat treatment.

For this reason, the growth layer epitaxially grown on the GaAs substrate after heat treatment has a carrier concentration distribution as shown by solid line 2 in FIG. can be manufactured with good reproducibility.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

As an example, semi-insulating GaAs as shown in FIG.
A case where an n-type epitaxial growth layer 12 with an electron concentration of 1016 cm-3 is formed to a thickness of 0.5 cm on the substrate 11 is not shown.

First, the semi-insulating GaAs substrate 11 is etched using standard GaAs processing means. That is, GaAs
The substrate 11 is heated to about 60'C H2SO4:H202:H20
Etch for 1 minute with an etching solution of =3: 1: 1 (volume ratio) and wash with water.Next, remove the natural oxide film remaining on the surface after etching by immersing it in HCl solution for about 1 minute, and then rinse immediately. Wash with water and dry with N2 blow.

Next, the surface is sulfurized. For this purpose, the substrate is immersed in a (NH4) 2 S x solution prepared in a sealable container, and the container is left sealed. In this example, after leaving it for 1 to 10 days, the substrate surface was exposed to (N H4) 2 by N2 blowing.
Remove the S X liquid. Next, the substrate surface temperature was set to 200'C in a simple vacuum container and left for about 5 minutes.

After this, semi-insulating GaAs was fabricated in a normal epitaxial device.
A substrate 11 is installed and epitaxial growth begins. In the example, the epitaxial growth layer 12 was formed by molecular beam epitaxial growth.

The carrier concentration of the epitaxially grown layer 12 epitaxially grown as described above takes a constant value in the thickness direction, as shown by the solid line 2 in FIG. 2, and there is no abnormal layer as in the conventional example. there were.

[Effects of the Invention] As described above, according to the present invention, a wafer without an interfacial transition layer at the interface between the substrate crystal and the epitaxial growth layer can be manufactured with good reproducibility. Using this technology eliminates the problem of interfacial transition layers in the epitaxial layer in contact with the substrate, and in the case of double hetero lasers, heat generation due to increased series resistance and even increased threshold current occur. The problem disappears. In particular, the manufacturing yield of double hetero laser wafers with irregularities on the substrate surface is significantly increased. In addition, in the case of MESFET, the problem of increased resistance between the source and the train can be avoided,
It is possible to fabricate a device with good stability and excellent high frequency characteristics.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an example of an epitaxially grown layer obtained by the method of the present invention, and FIG. 2 is a conventional example of the relationship between the distance from the substrate and the carrier concentration of an example of the epitaxially grown layer obtained by the method of the present invention. It is a characteristic diagram shown in comparison with the case according to. 11.G a As substrate 12...Epitaxial growth layer

Claims (1)

[Claims] (1) The surface of the substrate on which epitaxial growth is to be performed is exposed to a yellow ammonium sulfide solution, and then the surface of the substrate is heated to 100°C.
An epitaxial growth method characterized in that after the above heat treatment, epitaxial growth is performed on the surface of the substrate.