JPH03232221A - Vapor growth method for compound semiconductor - Google Patents

Abstract

PURPOSE:To reduce growth temperature, to conduct an epitaxial growth operation on the selected region only, and to make it possible to arbitrarily adjust the quantity of carbon doping on an epitaxial growth layer by a method wherein the vapor of a metal organic compound, containing both methyl group and ethyl group, is fed to a reaction chamber, and a vapor epitaxial growth operation is conducted at the prescribed substrate temperature. CONSTITUTION:Dimethylethylgallium or ethyldimethylgallium is used as a metal organic compound containing both methyl group and ethyl group, and the vapor of the above-mentioned metal organic compound is fed to a reaction chamber, and a vapor epitaxial growth operation is conducted. The substrate temperature at that time is set lower than the temperature of the epitaxial growth using the material of metal organic compound containing methyl group only. When C is doped as P-type impurities, dimethylgallium is used when it is doped in a large quantity, and methyldiethylgallium is used when it is doped in a small quantity. Also, when a fine adjustment is conducted, dimethylethylgallium and methyldiethylgallium are used by properly mixing them.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to vapor phase epitaxial growth of compound semiconductors such as GaAs, and includes a lower temperature growth method in MOVPE, a selective growth method that does not deposit on a mask film, and a carbon doping method. MOVP in the present invention aims to realize a growth method that can control the amount.
In the E treatment, vapor of a metal organic compound having both methyl groups and ethyl groups is supplied to the reaction chamber, and the substrate temperature is lowered to a temperature lower than the epitaxial growth temperature using the metal organic compound having only methyl groups as a raw material. While holding, vapor phase epitaxial growth of a compound semiconductor is performed.

[Industrial Application Field] The present invention relates to the vapor phase epitaxial growth of compound semiconductors, and particularly to the composition of metal-organic compound materials used in MOVPE.

■-■ When performing vapor phase epitaxial growth of a compound such as GaAs by the MOVPE method, TMG is used as a raw material for Ga.
It is usual to use organic compounds such as (trimethyl gallium) and TEG (triethyl gallium), and to use arsine (A s H3) as the raw material for As.

[Conventional technology]

TMG and TEG are liquids at normal temperature and pressure, and their vapors are sent to the reaction chamber by bubbling hydrogen (H2) as a carrier gas. On the other hand, arsine, which is a gas under normal pressure, is diluted with hydrogen and sent to the reaction chamber. The composition of the source gas is adjusted by adding doping impurity gas and carrier gas as necessary.

When the raw material gas reaches the heated substrate surface, the raw material is thermally decomposed and deposited as a compound on the substrate.

The deposited layer is grown as an epitaxial single crystal by appropriately selecting the substrate temperature, the supply rate of the source gas, and the pressure within the reaction chamber. If the substrate surface is partially masked with a SiO□ film or the like, growth will occur selectively only on the substrate surface.

In such a MOVPE method, selective growth is possible when TMG is used as a raw material, and the carbon content in the growth layer can be increased, but since the thermal decomposition temperature of TMG is relatively high, It is difficult to lower the growth temperature.

On the other hand, when TEG is used, it is possible to lower the growth temperature, but if selective growth is performed, reaction products may also be deposited on the mask film, or the boundary between the mask region and the growth region may be ridge grow
h) Problems such as abnormal growth occur.

Furthermore, it is difficult to intentionally incorporate carbon into the growth layer.

Other methods used in practice for epitaxial growth of compound semiconductors include chloride VPE and molecular beam epitaxy (MBE), which use constituent elemental halides (mainly chlorides) as raw material gas, but the former is a , it is difficult to obtain a sharp impurity distribution, and the growth layer becomes non-uniform on large-diameter substrates, and selective growth is not possible in the latter case.

[Problem to be solved by the invention]

When using TMG, the lowest temperature at which epitaxial growth will proceed is about 400"C, while for TEG it is about 300"C.
It is °C. As the growth temperature increases, thermal distortion and defects due to it are more likely to occur, which adversely affects the characteristics of devices formed using epitaxial growth. The temperature of 400'C in TMG is the lowest temperature at which epitaxial growth is possible, and in reality it is performed at a higher temperature, so epitaxial growth may be performed at a lower temperature to form high-speed operation devices. desirable.

In addition, a mask such as a SiOz film formed on a substrate
If a pattern can be used multiple times as a mask for etching or ion implantation, it will be advantageous in terms of improving the accuracy of mask alignment in lithography processing, which is required as device shapes become smaller.Similarly, selective growth will also be possible. desirable. Furthermore, there may be cases where selective growth is essential in the element formation process.

When considering the characteristics of an element formed in an epitaxially grown layer, consideration must also be given to the amount of carbon (C) contained in the epitaxial layer. Traditionally, C has been regarded as an impurity that inhibits crystallinity, and a low content has been considered advantageous, but recently, carbon has been actively utilized as an impurity that imparts P-type conductivity. Proposed.

From this standpoint, it is desirable that the C content in the epitaxial growth layer can not only be simply decreased or increased, but also controlled to a desired value.

An object of the present invention is to provide a growth method in MOVPE at a lower temperature, a selective growth method that does not deposit on a mask film, and a growth method in which the amount of carbon doping can be controlled. The objective is to improve the characteristics of the active elements used.

[Means to solve the problem]

In order to achieve the above object, in the vapor phase growth method of the present invention, vapor phase epitaxial growth is performed by supplying vapor of a metal organic compound having both a methyl group and an ethyl group to a reaction chamber.

The substrate temperature at this time is set lower than the epitaxial growth temperature using the organic compound of the metal having only methyl groups as a raw material. Further, the metal organic compound having both a methyl group and an ethyl group is dimethylethyl gallium or ethyldimethyl gallium in the examples.

[For production]

The chemical formula of TMG is Ga(CH)l and that of TEG is Ga(CzHs)t. All of them have only a methyl group or an ethyl group, and the difference in behavior when used as a raw material for MOVPE is caused by the difference in chemical properties of the methylated product and the ethylated product. Dimethylethylgallium (Ga(CH)zCzHs) and methyldiethylgallium (GaCH.

Compounds having both methyl and ethyl groups, such as (CzHs)z), exhibit chemical properties intermediate between T, MG and TEG, and therefore, in MOVPE using these as raw materials, growth temperature, appropriateness of selective growth, All of the C doping amounts are TM
It is thought that it will be intermediate between MOVPE by G and MOVPE by TEG.

As a result of the present inventor actually growing GaAs by MOVPE using dimethylethylgallium and methyldiethylgallium, it became clear that this prediction was correct. These substances are not commercially available at the time of filing of the present invention, but are specially prepared and have their chemical structures identified by nuclear magnetic resonance.

When the above two types of organic gallium compounds, TMG, and TEG are used as raw materials, the respective growth initiation temperatures (lowest temperature at which epitaxial growth proceeds continuously) are as shown in Table 1. Table 1 DMEC; is dimethyl ethyl gallium, MDEG is methyl diethyl gallium. As shown here, the growth initiation temperature of the intermediate composition compound is significantly lower than that of TMG, and especially when methyldiethylgallium is used, epitaxial growth is possible at a temperature between that of TEG.

Moreover, FIG. 1 is a schematic diagram showing the difference in surface shape during selective growth, in which 1 is a CraAs substrate and 2 is a 5iozll! that partially covers the surface. , 3 are GaAs epitaxially grown layers made of the respective raw materials. The shape of selective growth with dimethylethylgallium and methyldiethylgallium is shown in the same figure (a), and as with the case with TMG, crystal growth is observed only on the substrate surface, and SiO□
It does not deposit on the membrane. Furthermore, no abnormal growth occurs at the boundary. On the other hand, in the selective growth by TEG, as shown in FIG. 2(b), many small island-like deposits 4 occur on the SiO□ film 2, and abnormal growth 5 also occurs at the boundary portion.

Regarding the C doping amount, C doping amount is determined by MOVPE using TMG.
It is generally accepted that a large amount of C is doped because of the methyl groups, and the above experimental results also show that the amount of C increases or decreases depending on the number of methyl groups contained in the organometallic compound used as the raw material. was recognized.

When doping C as a p-type impurity, use dimethylethylgallium when doping in a large amount, and methyldiethylgallium when doping in a small amount.Also, if you want to make fine adjustments, mix dimethylethylgallium and methyldiethylgallium as appropriate. If necessary, it may be mixed with TMG or TEG.

〔Example〕

The above experiment was conducted under the following conditions. That is, all the organic gallium compounds used as raw materials were kept in a constant temperature bath at 3°C.
Bubble with 50 sccm H2. Arsine, which is a raw material for AS, is diluted to 10% with H2 and is supplied at a rate of 200 sec+w. Furthermore,
H2 is added so that the total amount of H2 becomes 2000 sec+w.

The pressure inside the reaction chamber was 20 Torr, the substrate temperature was 500°C in the selective growth experiment, and 2°C in the growth start temperature experiment.
Various substrate temperatures from 50 to 450'C were tried.

(Effects of the Invention) As explained above, according to the epitaxial growth method of the present invention, in crystal growth of a compound semiconductor by MOVPE, it is possible to lower the growth temperature, perform epitaxial growth only in a selected region, and perform epitaxial growth. It becomes possible to arbitrarily adjust the amount of carbon doped in the layer.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the effect of the present invention on selective growth, in which 1 is a GaAs substrate, 2 is a SiO film, 3 is an epitaxial growth layer, 4 is an island-like deposition layer, and 5 is a This is abnormal growth.

Claims (3)

[Claims] (1) A method for vapor phase growth of a compound semiconductor, characterized in that vapor phase epitaxial growth is performed by supplying vapor of an organic compound of a metal having both a methyl group and an ethyl group to a reaction chamber. (2) In the vapor phase growth method according to claim (1), vapor phase epitaxial growth is performed while maintaining the substrate temperature at a temperature lower than the epitaxial growth temperature using an organic compound of the metal having only methyl groups as a raw material. A method for vapor phase growth of compound semiconductors, characterized by the following. (3) The vapor phase growth method of claim (1) or claim (2), wherein the organic compound of the metal is dimethylethyl gallium or ethyldimethyl gallium. How to grow.