JPS6140034A - Chemical etching method for semiconductor device - Google Patents

Abstract

PURPOSE:To realize 3 flattened surface by a method wherein an epitaxial lamination wherein a layer built of GaAs is positioned just under the topmost layer built of GaAlAs is exposed to an etchant composed of H2SO4+H2O2+H2O. CONSTITUTION:On a GaAs substrate 1, an N type clad layer 2, activation layer 3 and P type clad layer 4 are formed in that order, all the three made of AlGaAs respectively composed as prescribed. A P type GaAs cap 5 is provided to cover the top surface. A mask 6 is provided and the GaAs cap 5 only is subjected to etching. The mask 6 is provided again. Etching is effected by using an etchant composed of H2SO4+H2O2+H2O until the GaAs substrate 1 is affected for the formation of flat mirror-like walls vertical to the P-N junction. The etchant should be composed of 10-96wt% of H2SO4 and 5-50wt% of H2O2+ H2O. The ratio in volume of H2SO4 against H2O2+H2O should be 10<-2>-10. With the etching rate being well under control within this range, etching results in a mirror surface. Such a product is of great use because it needs no cleavage when it is incorporated into a semiconductor laser device.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for chemically etching semiconductor devices comprising GaAs and AI GaAs.

Conventional configurations and their problems Semiconductor lasers generally have a cavity surface formed by the open method, but attempts are being made to monolithically integrate semiconductor lasers and elements such as detectors and drive circuits, such as in optical ICs. In this case, the spread method cannot be used at all. For this purpose, wet etching methods such as chemical etching methods and dry etching methods such as active ion etching (RIE) are being studied. Chemical etching is superior in terms of mass production and reliability, and because of its ease, various methods have been tried to fabricate the cavity surface.

Hereinafter, a conventional example will be explained with reference to the drawings. As shown in FIG. 1(a), n-type GaA s (100
) n-type Aj on substrate 1! 0.4Ga0.6As cladding layer 2, Ag002Gao, 8As active layer 3, p-type Ag
0.4Ga0.6As cladding layer 4 and p-type Ga A
scan 1 layer 5 was grown continuously.

Thereafter, as shown in FIG. 1, a striped photomask 6 was formed along the 011> direction, and the substrate was etched through this mask.

The etchant used was sulfuric acid with a concentration of 64% by weight and 30% by weight.
The volume ratio with hydrogen peroxide solution having a concentration of 30% by weight.

When etching is carried out using the above-mentioned etchant, the end face that becomes the cavity surface is curved, and the degree of bending is extremely low for a cavity surface of a semiconductor laser. The reason why the etched surface is curved is because the etchant acts as a diffusion rate-limiting thread.

Due to these problems, lasers fabricated by conventional chemical etching methods have a higher threshold current density than the interosseous method, making continuous oscillation extremely difficult.

Purpose of the Invention In view of the above-mentioned drawbacks, the present invention provides a structure in which the uppermost layer is ALG a Am
The present invention provides a method for chemically etching a semiconductor device, which can form a flat etched surface in a multilayer epitaxially grown layer with a GaAm layer underneath.

Structure of the Invention In order to achieve this object, the method of chemically etching a semiconductor device of the present invention uses sulfuric acid and hydrogen peroxide.

Using an etching solution consisting of G and water, G a A
Aj on top of m layer! It consists of etching a semiconductor layer provided with a GaAs layer.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 2(a), n-type GaAs (
100) n-type Ajl on substrate 1; , 4Ga0.6As
Cladding layer 2, A11o, 2 Gao, 8As active layer 3, p-type jVo, 4Gao, eA8 cladding layer 4
and a p-type GaAs cap layer 5 were continuously grown. Thereafter, as shown in FIG. 2), a striped photomask 6 is formed along the <011) direction, and G a A ! is passed through the mask. ! Only the cap layer 5 was selectively etched. Furthermore, as shown in FIG. 3(C), after removing the 7□ odd mask 6, the exposed p-type A2o, 4G
A striped photomask 6 was formed on the a0.6As cladding layer 4 along the <011> direction, and etching was performed to the substrate through this mask.

The etchant used was 64% by weight of sulfuric acid and 3% by weight.
When etching was performed using the above-mentioned etchant having a -volume ratio of 0 to hydrogen peroxide, the end face serving as the cavity face was perpendicular to the pn junction surface and had a flat mirror surface.

After forming a positive electrode 7 on the Ueno cap layer 5 obtained in FIG. 2 and forming a negative electrode 8 on the substrate side, it breaks at the etched groove, as shown in FIG. 3. A semiconductor laser device was obtained.

This semiconductor laser device has been obtained with extremely high yield through continuous oscillation, and the typical oscillation threshold is 72 mA (Jj9
70mA in the open method), and the differential quantum efficiency is 29% per side.
(30% for the interosseous method), which was almost the same as the interosseous method.

In the above embodiments, the etchant used was one in which the volume ratio of 64% by weight sulfuric acid to 30% by weight hydrogen peroxide was -, but the present invention is not limited thereto. 10-96 as sulfuric acid
It is good if it is % by weight, and the hydrogen peroxide solution should be 6 to 50% by weight, and the volume ratio of sulfuric acid and hydrogen peroxide solution should be 10-2 to 10. good.

If the etchant is prepared within these ranges, the etching will be rate-limiting or dominant, and the etched surface will have a flat mirror surface.

Effects of the Invention Disappointing In the chemical etching method for semiconductor devices of the invention, the uppermost layer is an ARGaAm layer, and the lowermost layer is an ARGaAm layer.
By chemically etching a multifaceted epitaxially grown layer, a flat etched surface can be formed. When used in semiconductor laser devices, the interosseous method is not required, and it is an essential technology for the practical application of optical ICs, and its practical effects are significant.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a method for manufacturing a cavity surface by conventional etching, FIG. 2 is a diagram showing a method for manufacturing a cavity surface by etching according to the present invention, and FIG. 3 is a diagram showing a method for manufacturing a cavity surface by etching according to the present invention. FIG. 1... N-type GaAs (100) substrate, 2...
... type fill(), 4 Gao, cs A
B cladding layer, 3...-Al1o, 2Ga0.8A
s active layer, 4----p-type AItO, 4"0.6"
Cladding layer, 5...p-type Ga As cap layer, 6... photomask, 7... positive electrode, 8... negative electrode.

Claims (2)

[Claims] (1) The top layer is an AlGaAs layer, and the AlGaAs
A semiconductor characterized in that when chemically etching a multilayer epitaxially grown layer in which the layer below the s-layer is a GaAs layer with an etching liquid, the etching liquid is a mixture of sulfuric acid, hydrogen peroxide, and water. Chemical etching method for equipment. (2) Sulfuric acid with a concentration of 10-96% by weight and 5-50% by weight
2. The method of chemically etching a semiconductor device according to claim 1, characterized in that an etching solution having a volume ratio of 10^-^2 to 10 with respect to a hydrogen peroxide solution at a concentration of 10 to 10 is used.