JPH052742B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an etching solution for indium aluminum arsenide.

[Conventional technology]

Indium aluminum arsenide In _1-x Al _x As, (0
<X<1), especially Ino _0.52 Al _0.48 As is In _0.53 Ga _0.47 As
It is attracting attention as a material for use in optical communication devices and high-performance microwave devices, especially as a heterojunction structure with. However, there have been few reports on etching solutions for In _1-x Al _x As, and it has been difficult to control etching, which is an important process in device manufacturing.

[Problem that the invention seeks to solve]

A well-known compound semiconductor etching solution is a mixture of sulfuric acid, hydrogen peroxide, and water. However, when etching is performed using such a mixed solution, there is a problem that the etching rate is high and it is difficult to control the amount of etching. For example, the mixing ratio of sulfuric acid, hydrogen peroxide, and water is 3:1:1.
When using a mixed solution with (volume ratio), at a solution temperature of 25°C, etching occurs by more than 5.5 μm per minute.
It is impossible to control the thickness below 1000 Å, and process steps that normally require control of several hundred Å have the problem of decreasing yield.

An object of the present invention is to provide an etching solution that can control InAlAs up to several thousand Å per minute.

[Means for solving problems]

The indium aluminum arsenide etching solution of the present invention is a mixed solution consisting of aqueous ammonia, aqueous hydrogen peroxide, and water.

[Effect]

Aqueous ammonia and hydrogen peroxide are used to etch semiconductors, and water is a softening agent. Furthermore, etching can be explained by the mechanism of oxidizing with hydrogen peroxide solution, which is an oxidizing agent, and removing it with aqueous ammonia. Further, since water is a moderating agent, the etching rate can be lowered as the amount thereof increases.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows In _0.52 according to the first embodiment of the present invention.
FIG. 4 is a characteristic diagram showing the relationship between etching time and etching depth of Al _0.48 As.

This example consists of ^30cm3 of ammonia water (29%) and 70cm3 of ammonia water (29%)
It is a mixture of cm ³ of hydrogen peroxide (30%) and 50 cm ³ of water.

Figure 1 shows the results of etching In _0.52 Al _0.48 As at room temperature (approximately 20°C) using this mixed solution. There is a nearly linear relationship between etching time and etching depth. It can be seen that the etching depth can be controlled by This means that etching can be controlled very easily.

FIG. 2 shows In _0.52 according to the second embodiment of the present invention.
FIG. 4 is a characteristic diagram showing the relationship between etching depth and etching time of Al _0.48 As.

This example consists of ^60cm3 of ammonia water (29%) and 40cm3 of ammonia water (29%).
It is a mixture of ³ cm3 of hydrogen peroxide (30%) and 50 cm of water.

Figure 2 shows the results of etching In _0.52 Al _0.48 As at room temperature (approximately 20°C) using this mixed solution. There is a nearly linear relationship between etching time and etching depth. It can be seen that the etching depth can be controlled by

FIG. 3 is a characteristic correlation diagram showing the relationship between the composition of the etching solution of the present invention and the etching rate.

These data were obtained by changing the ratio by keeping the sum of the volumes of ammonia water (29%) and hydrogen peroxide water (30%) constant at 100 ^cm3 , and adding 50 ^cm3 of water as a relaxing agent to make the total volume 150 ^cm3 . The results were obtained using various etching solutions prepared. The horizontal axis represents the volume of ammonia water in 150 cm ³ of the etching solution (cm ³ ), and the vertical axis represents the etching rate (μm/min). By changing the composition, the etching rate can be changed by about one order of magnitude. It can also be seen that the etching rate is maximum when the amount of ammonia water is about the same to twice as much as that of hydrogen peroxide. Further, regardless of the composition of the etching solution, a mirror surface was obtained on the etched surface, and no unevenness due to etching was observed.

Next, an application example of the present invention will be described.

FIGS. 4a to 4c are cross-sectional views of a semiconductor chip shown in order of steps to explain a method of manufacturing a light receiving element using the etching solution of the present invention.

First, as shown in FIG. 4a ^{, an} n ^-
−In _0.53 Ga _0.47 As layer (impurity concentration 1×10 ¹⁵ cm ^-3 )2
A layer of n-In _0.52 Al _0.48 As (impurity concentration 1×10 ¹⁶ cm ⁻³ ) 3 was successively grown to a thickness of 0.5 μm. After that, as shown in Figure 4b, CVD-
A mask 4 consisting of a SiO ₂ film of 3000 Å is formed, and Zn is selectively diffused to form a p ⁺ region 5 of 0.5 µm in the n ^- -InGAs layer 2.
It was formed to a depth of m. At this time, due to the heat caused by diffusion, a thermally degraded layer 6 is formed on the surface of the n ^- -In Al As layer 3. If this thermally degraded layer 6 is left, a large amount of dark current will flow, making it unusable, so it will be etched. It will be necessary to remove it.

Next, as shown in FIG. 4c, the mask 4 was removed and the thermally degraded layer 6 was removed using the etching solution of the present invention. The etching solution used was the same as in the first embodiment: 30 cm ³ of ammonia water, 70 cm ³ of hydrogen peroxide solution, and water.
The thermally degraded layer 6 was removed by etching for 10 seconds at a composition of 50 cm ³ and at room temperature to remove about 500 Å. In this way, etching of only a few hundred Å can be performed with good controllability. Such precise control could not be achieved with the conventional sulfuric acid-hydrogen peroxide-water etching solution.

Although the above explanation was made using In _0.52 Al _0.48 As, the present invention can generally be applied to In _1-x Al _x As (0<x<1).

〔Effect of the invention〕

As explained in detail above, according to the present invention,
Etching amount can be easily controlled and a mirror surface can be obtained.
This has the effect that an etching solution of In _1-x Al _x As (0<x<1) can be obtained.

[Brief explanation of the drawing]

FIGS. 1 and 2 are characteristic diagrams showing the relationship between etching time and etching depth of In _0.52 Al _0.48 As according to the first and second embodiments of the present invention, respectively, and FIG. A characteristic correlation diagram showing the relationship between composition and etching rate, and FIGS. 4a to 4c are cross-sectional views of a semiconductor chip shown in the order of steps to explain the method of manufacturing a light receiving element using the etching solution of the present invention. 1... n-InP substrate, 2... n ^- -InGaAs layer,
3...n ^-- InAlAs layer, 4...mask, 5...p ⁺
Area 6...Thermal deterioration layer.

Claims (1)

[Claims] 1. An etching solution for indium aluminum arsenide, which is a mixed solution consisting of ammonia water, hydrogen peroxide solution, and water.