JPS61284913A - Selective epitaxial growth method for gaas - Google Patents

Abstract

PURPOSE:To make GaAs layer to epitaxially grow on a substrate with good selectivity by using a mask composed of a composite film of SiO2 and tungsten. CONSTITUTION:A GaAs layer 9 can be formed on a substrate 1 by corresponding to a window 7 on the selective epitaxial growth basis without rising a substrate temperature, making thick the SiO2 film and narrowing a pattern width of the mask, unlike the conventional case where using the mask of SiO2, by the epitaxial growth of GaAs with MO CVD using the mask pattern 8 of the double-layer structure of the tungsten pattern 5 and SiO2 pattern 6. As a result, good GaAs layer can be formed on the selective epitaxial growth basis without deterioration of crystallization of GaAs layer, generation of defect to the interface between the mask pattern and the substrate and without drop of a degree of freedom of element design.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for selective epitaxial growth of GaAs, and in particular, to a method for selective epitaxial growth of GaAs, and in particular to a method for selective epitaxial growth of GaAs.
This invention relates to improvements in selective epitaxial growth methods for aAs.

[Technical background of the invention and its problems]

In the production of devices such as GaAs high-speed device ICs and optical devices, the so-called selective epitaxial growth technique, which forms a high-quality epitaxial layer on the necessary portions of a substrate, is as important a technique as the ion implantation method.

By the way, conventionally, as a method for selectively epitaxially growing a GaAs layer on a GaAs substrate, a SiO2 film is formed on the GaAs substrate by electron beam evaporation, the SiO2 film is patterned by photoetching, and after cleaning with an organic agent, It is known to perform epitaxial growth on a substrate by step etching with H2O2/H2SO4, followed by MO-CVD to expose the GaAs layer. However, this epitaxial growth method has a problem in that the GaAs layer is deposited not only on the exposed GaAs substrate but also on the mask made of SiO2, that is, the so-called selectivity is poor.

For this reason, when selectively epitaxially growing a GaAs layer using a mask made of 5102, it is necessary to: (1) increase the substrate temperature to avoid Ga adhering onto the SiO2 mask;
To promote the migration of atoms so that they are incorporated into the exposed part (window part); ■ To prevent the migration of Ga atoms from the GaAs layer side by increasing the thickness of 3i02; ■ To increase the pattern width of the mask. It has been considered to make it narrower so that Ga atoms can easily reach GaAs1l.

However, in the method of raising the substrate temperature in (2) above, G
This results in decomposition of aAs, deterioration of crystallinity of the GaAs layer, and autodoping of impurities. S as a mask for ■ above
In the method of increasing the thickness of iO2, the GaAs layer may take on an overhanging shape, or the difference in thermal expansion coefficient between the substrate and SiO2 may become significant, and the resulting stress may cause defects at the interface between them. In the method of narrowing the width of the mask pattern described in (■) above, G
The width of the aAs layer is restricted, reducing the degree of freedom in device design.

On the other hand, a method can be considered in which a GaAs layer is selectively epitaxially grown on a GaAs substrate using tungsten (W) as a mask instead of the Si2. However, in this method, W as a mask reacts with GaAs during the epitaxial growth of the GaAs layer, so if the mask is removed with H202 after selective epitaxial growth of the GaAs layer, the substrate surface that was in contact with the mask becomes rough. There is a problem.

[Purpose of the invention]

The present invention provides a method for selective epitaxial growth of GaAs that allows selective epitaxial growth of a GaAs layer on a substrate without increasing the substrate temperature, increasing the mask thickness, or narrowing the width of the mask pattern. This is what we are trying to provide.

[Summary of the invention]

The present invention provides a method for selectively epitaxially growing a GaAs layer on the surface of a GaAs substrate by organometallic pyrolysis.
This method is characterized by using a mask made of a composite film of SiO2 and tungsten that is selectively provided from the surface side of the substrate.

According to the present invention, as described above, GaAs can be used with good selectivity.
Layers can be epitaxially grown on the substrate.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to FIGS. 1 to 6.

First, a 3i02 film 2 is formed on a GaAs substrate 1 by electron beam evaporation, and a tungsten I film 2 is formed on this SiO2 film 2.
! 13 is formed by sputtering (as shown in FIG. 1).

Next, a resist pattern 4 is formed by a photoetching process (as shown in FIG. 2). Subsequently, using the resist pattern 4 as a mask, the tungsten film 3 was selectively etched away using H2O2 to form a tungsten pattern 5 (as shown in FIG. 3). Subsequently, using the same resist pattern 4 as a mask, S! was etched using a hydrofluoric acid buffer. 021[12 is etched away and 5i0
I want to form two patterns 6 and open a window 7 (as shown in FIG. 4). Through this process, a mask pattern 8 having a two-layer structure of W/SiO2 was formed.

Next, the raw material is ・Trimethyl gallium (TMG)
and arsine (・~5H3) and TMG at 5.2c
c/+nin, arsine (ASH3) to ASH3/T
A GaAs layer 9 was selectively epitaxially grown on the GaAs substrate 1 corresponding to the window 7 between the mask patterns 8 by MO-CVD using an MG ratio of 8 (as shown in FIG. 5). Thereafter, the tungsten pattern 5 constituting the mask pattern 8 is removed with H2O2, and the Sr02 pattern 6 is removed with a hydrofluoric acid etching solution (as shown in FIG. 6).

According to the present invention, GaA
By epitaxially growing s, conventional Si
GaAs is deposited on the substrate 1 corresponding to the window 7 without increasing the substrate humidity, increasing the thickness of the SiO2 film, or narrowing the pattern width of the mask, unlike when using a mask made of O2. Layer 9 can be selectively epitaxially grown.

As a result, a good GaAs layer can be selectively epitaxially grown without deteriorating the crystallinity of the GaAs layer, causing defects at the interface between the mask pattern and the substrate, or reducing the degree of freedom in device design.

In addition, since the mask pattern is composed of W/S i 02, reactants are generated at the contact area between W and the GaAs substrate, such as in selective epitaxyl growth that masks W, and when the W mask is removed. This eliminates the inconvenience of the substrate surface becoming rough.

〔Effect of the invention〕

As described in detail above, according to the present invention, a GaAs layer can be epitaxially grown on a substrate with high selectivity without increasing the substrate temperature, increasing the mask thickness, or narrowing the width of the mask pattern. A method for selective epitaxial growth of GaAs can be provided.

[Brief explanation of the drawing]

1 to 6 are cross-sectional views showing the process of selective epitaxial growth of GaAs in an embodiment of the present invention. 1... GaAs substrate, 2... SiO2 film, 3...
Tungsten film, 4... resist pattern, 5...
Tungsten pattern, 6...S i 02 pattern, 7... Window, 8... Mask pattern, 9... Ga
As layer. Figure 2 6rEJ

Claims (1)

[Claims] A method for selective epitaxial growth of a GaAs layer on the surface of a GaAs substrate by organometallic pyrolysis, characterized in that a mask consisting of a composite film of SiO_2 and tungsten is selectively provided from the surface side of the substrate.
Selective epitaxial growth method for aAs.