JPH0521419A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a favorable via-hole in an InP substrate in a short time. CONSTITUTION:When forming a via-hole 6 in an InP substrate 1 where a semiconductor substrate is made on the surface, a favorable via-hole small in dependency on face orientation and free of surface roughening, etc., can be gotten by performing the etching in mixed liquid of hydrochloric acid, hydrogen peroxide solution, and acetic acid. Moreover, since the etching speed is high, the process can be completed in a short time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming a via hole in an InP substrate such as a field effect transistor for super high frequency using an InP substrate or a heterojunction bipolar transistor.

[0002]

2. Description of the Related Art Since compound semiconductor crystals such as InP have a high electron saturation speed and electron mobility, they have attracted attention as an element material for ultra-high speed and ultra-high frequency, and some studies have been conducted on semiconductor devices using them. . In particular, since a MIS field effect transistor (MISFET) using an InP substrate can obtain a high current and a high breakdown voltage, it is possible to obtain a super high frequency and high output FE.
Potency as T is high. High frequency high power F
In ET, a via hole structure that electrically connects the source electrode and the back surface of the substrate is usually used in order to reduce the parasitic inductance of the FET chip. Also in the microwave monolithic integrated circuit, a via hole is indispensable for conduction with the back surface of the substrate. In the step of forming the via hole, a wet etching method using a mixed solution of sulfuric acid and hydrogen peroxide, a mixed solution of bromine and methanol, or the like is usually used as an etching method.

[0003]

The etching solution used in the step of forming a via hole in an InP substrate is required to have a high etching rate and a small plane orientation dependency. However, when the above-described commonly used etching solution is used to form a via hole in an InP substrate, problems such as low etching rate, large plane orientation dependency, and pit formation occur, and a good via hole is formed. Is difficult to form.

An object of the present invention is to solve the above problems and to provide a method of manufacturing a semiconductor device capable of forming a good via hole in an InP substrate in a short time.

[0005]

The method of manufacturing a semiconductor device according to the present invention uses a mixed solution of hydrochloric acid, hydrogen peroxide solution and acetic acid as an etching solution for forming a via hole in an InP substrate.

[0006]

The via hole normally penetrates through the substrate with a thickness of 30 to 50 .mu.m. As a condition required for the etching solution used for forming such a via hole, as described above, the etching rate must be high first. can give.
Further, in an etching solution having a large plane orientation dependency, if the opening area is small, the via hole may not penetrate, so the plane orientation dependency should be kept as small as possible. Furthermore, it is necessary to reduce the occurrence of etching roughness and pits.

FIG. 2 shows hydrochloric acid, hydrogen peroxide solution according to the present invention,
The liquid temperature of the mixed solution of acetic acid and the etching rate for the InP substrate are shown. By raising the liquid temperature to 30 ° C., an etching rate sufficient for a normal via hole etching process can be obtained. FIGS. 3A and 3B show etching profiles of the InP substrate when using a mixed solution of hydrochloric acid, hydrogen peroxide solution and acetic acid and when using a mixed solution of sulfuric acid and hydrogen peroxide solution. While the sulfuric acid-based etching solution has a large plane orientation dependency, the etching solution of the present invention has a relatively small plane orientation dependency and the etching surface is sharp. From the above, it can be seen that the mixed solution of hydrochloric acid, hydrogen peroxide solution and acetic acid according to the present invention is suitable as an etching solution for forming a via hole of an InP substrate.

The amount of hydrochloric acid in the mixed solution is preferably 5 times or more than that of hydrogen peroxide, and if it is less than that, the etching surface becomes rough. Further, the amount of acetic acid as the buffer solution is preferably equal to or more than the amount of hydrogen peroxide solution, and if it is less than that, the etching rate becomes high and the surface becomes rough.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1A to 1C are cross-sectional views of a semiconductor chip shown in the order of steps for explaining an embodiment of the present invention.

First, as shown in FIG. 1A, FE is formed on the surface.
A pattern for opening a via hole is formed with a photoresist film 5 at a position corresponding to the source electrode 4 on the back surface of the InP substrate 1 on which T has been manufactured. Next, as shown in FIG. 1B, using the photoresist film 5 as a mask, a mixed solution of hydrochloric acid: hydrogen peroxide: acetic acid = 20: 1: 20 at a liquid temperature of 20 to 30 ° C.
The nP substrate 1 is etched to form a via hole 6. Finally, as shown in FIG. 1C, a gold plating layer 7 is formed on the back surface of the InP substrate 1 to complete the conduction step.

[0011]

As is clear from the above description, according to the present invention, it is possible to form a good via hole having a good shape in a semiconductor device using an InP substrate in a short time. .

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor chip for explaining an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a solution temperature of an etching solution and an etching rate in the example.

FIG. 3 is a diagram showing an etching profile of an InP substrate with a conventional etching solution and an etching profile of an etching solution according to the present invention.

[Explanation of symbols]

1 InP substrate 2 drain electrode 3 Gate electrode 4 Source electrode 5 Photoresist film 6 via holes 7 Gold plating layer

Claims (2)

[Claims] 1. A method of manufacturing a semiconductor device, comprising forming a semiconductor element on an InP substrate and then forming a via hole in the InP substrate by a wet etching method, wherein a mixed solution of hydrochloric acid, hydrogen peroxide solution and acetic acid is used as an etching solution. A method for manufacturing a semiconductor device, which is characterized by being used. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the hydrochloric acid in the mixed solution is at least 5 times as much as the hydrogen peroxide solution.