JPS6362235A - Etching method of semiconductor - Google Patents

Abstract

PURPOSE:To etch only a GaAs crystal layer selectively without etching a mixed crystal layer substantially, by using an aqueous solution of hydrogen peroxide containing ammonia water. CONSTITUTION:A mixed crystal layer AlxGa(1-X)As is made to grow on a GaAs substrate crystal, with the molar fraction of aluminum varied with in a range from x = 0 to x = 0.4, and thereafter each mixed crystal is etched with an etching liquid of a hydrogen peroxide aqueous solution containing ammonia water wherein the ammonia water and hydrogen peroxide solution are mixed in the ratio of 1 to 750. As to the mixture ratio of ammonia with the hydrogen peroxide solution a range between 1 to 750 and 1 to 1500 is practi cal, while the temperature of the etching liquid is preferably within a range from 10 deg.C to 35 deg.C. As the result, the GaAs crystal layer alone is etched selective ly, so that a hetero interface may be exposed exactly and with excellent reproducibility. As a result, fine processing of a hetero junction is facilitated, and thus an element having the hetero junction of the AlxGa(1-x)As mixed layer with the GaAs crystal layer can be manufactured in a stable manner.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] This invention relates to GaA, a substrate or layer, and AA! xGa
The present invention relates to a method of selectively etching a GaA semiconductor substrate or layer, in a method of manufacturing a semiconductor device comprising a (1x) A3 mixed crystal layer.

[Prior art and its problems]

In recent years, Z-group compounds have been shown to emit light in the visible or infrared region.
It has attracted attention as a light-receiving device or a solid-state device in the microwave region, and its crystal growth technology has made great progress, and today, multi-element heterojunctions are also realized by epitaxial growth. In particular, a heterojunction grown by an epitaxial growth method in which a klxoa(1-x)As mixed crystal is formed on a GaA crystal, and a GaAS crystal layer is further formed on top of the crystal is a GaA crystal.

Since the lattice constants and thermal expansion coefficients of the crystal, AJxGa(1-x)A, and the mixed crystal match extremely well, semiconductor lasers,
It is attracting attention for its use in solar cells, etc. Even in these fields, there is a need for etching techniques for these crystals to improve the functionality of devices, such as the formation of stripes in semiconductor lasers, and development of etching techniques for forming fine patterns is needed. is strongly desired.

[Purpose of the invention]

This invention was made in view of the above problems, and its purpose is to provide a GaAS substrate or layer and an Aj'x
The present invention provides a method for selectively etching only the GaAs crystal layer without substantially etching the mixed crystal layer when manufacturing a semiconductor device having a Ga(1-x)As mixed crystal layer.

[Key points of the invention]

The present invention achieves its object by using an aqueous solution of hydrogen peroxide containing aqueous ammonia for selective etching of the GaA5F4 crystal layer.

That is, GaA is selectively etched using an aqueous solution of hydrogen peroxide containing aqueous ammonia to form AlxGa(1x)A.
The s-mixed crystal layer is not etched.

[Embodiments of the invention]

Next, embodiments of the present invention will be described based on the drawings. FIG. 2 is a characteristic diagram showing the relationship between the aluminum mole fraction X of the mixed crystal layer kl x G3 (1-x) A and the etching rate, which was determined as follows. GaA.

A mixed crystal layer AlxG3(1-X)As is formed on the substrate crystal at a molar fraction of aluminum of x=0 to x=0.
．． It was grown by varying the range of 4. After growing the mixed crystals, each mixed crystal was treated with an etching solution of a hydrogen peroxide aqueous solution containing ammonia water (28% by weight) and hydrogen peroxide solution (30% by weight) mixed in a ratio of 1:750. Etching was performed at a liquid temperature of 26° C.), and the etching speed was examined. A practical mixing ratio of aqueous ammonia and aqueous hydrogen peroxide is from 1:750 to 1:1,500, and the temperature of the etching solution is preferably from 10°C to 35°C. When a hydrogen peroxide aqueous solution containing aqueous ammonia is used as an etching solution,
As the aluminum mole fraction X of the mixed crystal A/z Ga (1x) A 5 increases, the etching rate rapidly decreases. Applying this fact, GaAs crystal layer and Alx
Microfabrication of the heterojunction of the Ga(1-x)As mixed crystal layer becomes easy.

Next, we will show an experimental example in which the above results are applied to microfabrication of heterojunctions. FIG. 3 is a diagram showing the relationship between etching time and etching depth for heterojunctions of AlxGa(1-X)A, mixed crystal and GaA crystal, and was determined as follows. 0.2μm thick AJo, 4Ga on oaAs substrate crystal
A (0,6)As mixed crystal and a 062 μm thick GaA3 crystal were sequentially grown by epitaxy, and aqueous ammonia at a temperature of 26° C. was etched with an aqueous hydrogen peroxide solution, and the relationship between etching time and etching depth was investigated. The 0.2 μm thick GaA3 layer (corresponding to
It can be seen that the mixed crystal layer of 0,4Ga(0,6)A is exposed, and the chipping does not proceed thereafter, and the heterojunction interface is maintained stably. Furthermore, when etching the AJ O,40a(0,6)As mixed crystal layer, a well-known etching solution such as H20□;
An etching solution containing 3PO4; ethylene glycol = 1; 1; 6 can be used.

Next, the above study results will be applied to the production of a GaA double hetero laser device. In this case AlxGa(1-X)A8
．． GaA to the mixed crystal layer, GaA to the heterojunction of the crystal layer,
The crystal layer was selectively etched to form stripes necessary for laser oscillation. Figure 1 shows SAS (SelfAl
inged 5structure) structure
A is a schematic cross-sectional view of the manufacturing order of the double 5-terror laser device. As shown in FIG. 1(a), an n-type GaA substrate crystal 1
1 μm thick GaA crystal layer (buffer layer) 2,1
．． 5μm thick n-type AA! 0.31Ga(0,69)A.

Mixed crystal layer (cladding layer) 3, 0.1 sn thick GaA3 crystal layer (active layer) 4, 0.2 thin thick PwAlO031Ga (
0,69) After epitaxially growing an As mixed crystal layer (cladding layer) 5, a 0.4 μm thick n-type GaA layer, and a crystal layer (current blocking layer) 6, a photosensitive resin 7 was placed as a corrosion-resistant mask. Using well-known photo-etching technology, the width of 8μ
An opening 8a having a diameter of m is provided. Subsequently, etching was performed for about 5 minutes using a hydrogen peroxide aqueous solution (1; 750) containing aqueous ammonia, and the n-type GaAs crystal layer (current blocking layer) 6 corresponding to the opening 8a was completely removed and the opening was removed. 8b, and the p-type AI0.31Ga(0,69)A and mixed crystal layer (cladding layer) 5 are exposed in the opening 8b (FIG. 1(b)). Considering variations in the film thickness of the epitaxial layer or variations in the etching depth within one surface of the wafer, it is desirable to over-etch for about 1 minute. At that time, this etching solution was AIo,
31Ga(0,69) person, 0.01 a for mixed crystal
Since the etching speed is m/min, the over-etching for one minute has no effect. After forming the openings 8b, the photosensitive resin 7 as a corrosion-resistant mask is removed, and on the n-type GaA layer with the openings 8b, the p-type AlO layer with a thickness of 1.5 μm, and the crystal layer (current blocking layer) 6. 31Ga(0,69)A,
A mixed crystal layer (cladding layer) 5, a p-type GaA layer with a thickness of 0.5 tRn, and a crystal layer (contact layer) 9 are epitaxially grown, and then an AuZn electrode 10 and an AuGeN layer are grown.
The i-electrode 11 is formed by a vapor deposition method and is made of GaAs with an 8A8 structure.
A double hetero laser device was obtained (FIG. 1(C)). As described above, the n-type GaA and predetermined portions of the crystal layer 6 are reliably removed, and the p-type AA! 0.310a(0,69)As
The etching technique that stops etching at the mixed crystal layer 5 is an essential requirement for stably manufacturing a GaAs double hetero laser diode with an SAS structure, taking into account the variation in film thickness due to epitaxial growth, and the present invention solves this essential requirement. It satisfies the following.

The etching technique according to the present invention can be applied not only to laser diodes but also to field effect transistors having a heterojunction Schottky gate structure using GaAS.

〔Effect of the invention〕

l) According to this invention, GaA3 semiconductor AlxGa (1
-x) A5 Since an aqueous solution of hydrogen peroxide containing aqueous ammonia was used to manufacture a semiconductor device formed of a mixed crystal layer, only the GaA and crystal layers were selectively etched, making the hetero interface accurate and reproducible. As a result, the microfabrication of the heterojunction becomes easy, and the AAzGa
It becomes possible to stably manufacture an element having a heterojunction of (1-x)A, mixed crystal 1, GaA, and a crystal layer.

[Brief explanation of the drawing]

FIG. 1 shows GaA having a SAS structure according to an embodiment of the present invention.
, is a schematic cross-sectional view of the fabrication of a double hetero laser diode, (a) is a cross-sectional view at a stage where photoresist is formed on the heterojunction, and (b) is an n-type GaA3 crystal layer formed with an aqueous solution of hydrogen peroxide containing aqueous ammonia. (C) is a cross-sectional view of the completed 8kB structured GaA
, a cross-sectional view of a double hetero laser element, and FIG.
A characteristic diagram showing dependence, FIG. 3 is hl of an embodiment of this invention.
-g G B (1-x) A B mixed crystal layer (x=+
0.4) and GaA, and is a diagram showing the relationship between etching time and etching depth for a heterojunction of a crystal layer. 1-GaA, substrate, 5-p-type Al) (Ga(1”)'s
Mixed crystal layer, 6... n-type GaAs crystal layer, 7... photosensitive resin, 8a... opening, 8b... opening. X (All)xGa(1-x)As) Engineering, 1. +Fern time (min)

Claims (1)

[Claims] 1) GaAs substrate or layer and AlxGa(1-x)As
1. A method for etching a semiconductor, which comprises selectively etching only a GaAs substrate or layer using an aqueous solution of hydrogen peroxide containing aqueous ammonia in the production of a semiconductor device having a mixed crystal layer. 2) In the etching method according to claim 1, an aqueous solution of hydrogen peroxide containing aqueous ammonia and having a ratio of aqueous ammonia to aqueous hydrogen peroxide of 1:750 to 1:1,500 is used. Etching method. 3) A semiconductor etching method according to claim 1, characterized in that the GaAs substrate or layer is etched using an aqueous solution of hydrogen peroxide containing aqueous ammonia at a temperature of 10° C. to 35° C. .