JPS634621A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To keep the finished width of a via-hole and the variation of the finished width of the via hole in a small range by a method wherein two steps are alternately repeated which are a step of forming a damaged layer in the part on a GaAs substrate surface where the via-hole is to be formed through the aperture of a mask pattern or by a converged ion beam and a step of removing the damaged layer by etching. CONSTITUTION:After a mask pattern 3 made of metal which has a high density, i.e. a high ion blocking capability, is formed on the surface of a GaAs substrate 1, high energy ions of a relatively large mass number are selectively implanted into a required part of the GaAs substrate 1 surface through the aperture of the mask pattern 3 so as to form a damaged layer 1a. Then only the damaged layer 1a is selectively etched with acid. After that, the ion implantation process and the etchinn process are alternately repeated to obtain a substrate piercing part (via-hole 4).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a GaAs (gallium arsenide) integrated circuit having via holes.

[Conventional technology]

FIGS. 2(a) to 2(c) are cross-sectional views showing the main steps of conventional via hole formation in GaAs integrated circuits. In these figures, 1 is a GaAs substrate, 2 is a glass plate,
3 represents a mask pattern, and 4 represents an ear hole.

FIG. 2(a) shows a GaAs substrate 1 bonded to a glass plate 2 using wax. After this state, mask-cut turns 3 are formed by photolithography, etc., as shown in Figure 2 (b).
)') Then, via hole 4 is formed by wet etching using a mixed solution of acid and oxidizing agent (
Figure 2 (C)).

In the wet etching of the GaAs substrate 1 shown in FIG. 2(C), the oxidizing agent (hydrogen peroxide, etc.) in the etchant is
As is oxidized and the product of the above oxidation reaction is treated with an acid (sulfuric acid,
The process progresses by dissolving tartaric acid, etc.). Furthermore, gluing the GaAs substrate 1 to the glass plate 2 has the effect of preventing the surface of the GaAs substrate 1 on the side where the mask pattern 3 is not provided from being etched by the etchant in the wet etching process.

[Problem that the invention seeks to solve]

In the conventional semiconductor device manufacturing method, when the via hole 4 is formed by wet etching using a mixed solution of acid and oxidizing agent as an etchant, the side etching is large and the etching progresses almost isotropically. Hall 4
The finished width is approximately twice as wide as the depth. Therefore, in order to penetrate the GaAs substrate 1, the finished width of the via hole must be designed to be approximately twice the thickness of the substrate.

Figures 3(a) and 3(b) are cross-sectional views showing an example of problems in the conventional manufacturing method.
The same reference numerals as those in (C) represent the same parts.

Wet etching as described above has poor controllability compared to dry etching, so in deep etching such as via hole etching, the amount of etching tends to vary within the substrate surface. If there is variation within the hole, there will be holes that are through and holes that are not through, as shown in Figure 3(a). When additional etching is performed to penetrate the unpierced holes, the finished width of the holes that were penetrated in the state shown in FIG. (Fig. 3(b)).

As described above, according to the conventional semiconductor device manufacturing method,
There was a problem in that the finished width of the via hole 4 became large, which not only became an obstacle to miniaturization of one circuit pattern, but also that the finished width varied within one surface of the GaAs substrate.

This invention was made in order to solve the above-mentioned problems, and it is possible to reduce the finished width of the via hole,
Another purpose is to prevent variations in the finished width of the via hole within the surface of the GaAs substrate.

[Means for solving problems]

A method for manufacturing a semiconductor device according to the present invention includes: passing through an opening of a mask pattern formed on a surface of a GaAs substrate;
Alternatively, GaA using focused ion beam (FIB)
s selectively implanting ions with a relatively large mass number at high energy into the portion where the via hole is to be formed on the substrate surface,
The layer damaged by ion implantation is etched with acid.

[Effect]

In this printing, via holes on the surface of the GaAs substrate are selectively implanted with high energy to damage the ion-implanted area and form an amorphous layer (damaged layer), making etching possible with only acid.

〔Example〕

FIGS. 1(a) to 1(e) are cross-sectional views showing the main manufacturing steps in a method for manufacturing a semiconductor device according to an embodiment of the present invention. In these figures, 1 is a GaAs substrate, and 1a is a damaged layer caused by ion implantation. , 3 indicates the mask pattern,
The arrow represents the direction of incidence of ions to be implanted.

Next, the manufacturing process will be explained.

As shown in FIG. 1(a), a metal with a high density, that is, a high ion-stopping ability (for example, Al
After forming a mask pattern 3 of (U, Pt, W, etc.), as shown in FIG. ion) with a relatively large mass number (
For example, Ar, Xe, etc.) are selectively implanted at high energy to form a damaged layer 1a by ion implantation. Next, as shown in FIG. 1(C), only the damaged layer 1a of the GaAs substrate 1 is implanted. is selectively etched with acid. Thereafter, the ion implantation process as shown in FIG. 1(b) and the etching process as shown in FIG. 1(C) are repeated alternately to form the final ion implantation process shown in FIG. Through an implantation process and a final etching process, a substrate penetrating portion (via hole 4) is obtained.

When a semiconductor device is manufactured through the steps described above, the depth and width of the damaged layer 1a of the GaAs substrate 1 are appropriately controlled by ion implantation (especially while keeping the width expansion small). It is possible to selectively etch only. In addition, as shown in the conventional method, GaA
Of course, the process of gluing the glass plate 2 to the glass plate 2 for the purpose of protecting the back surface of the s-substrate 1 (FIG. 2(b)) is unnecessary.

In the above embodiment, ions were selectively implanted into the GaAs substrate 1 through the opening of the mask pattern 3, but maskless implantation using a focused ion beam (FIB) may also be used.

〔Effect of the invention〕

As explained above, this invention enables GaAs to be produced through the openings of a mask pattern or by a focused ion beam.
This process involves repeating the process of selectively implanting ions with high energy into the area on the substrate surface where the via hole is to be formed to form a damaged layer, and the process of removing this damaged layer by etching. Since etching can be suppressed and the amount of etching can be easily controlled, the finished width of the via hole and the variation in the finished width can be kept small.

[Brief explanation of drawings]

1(a)-(e) are cross-sectional views showing the main steps of an embodiment of the method for manufacturing a semiconductor device of the present invention, and FIG. 2(a)-(e)
(C) is a cross-sectional view showing the main steps of the conventional manufacturing method;
Figures (a) and (b) are cross-sectional views for explaining problems in the conventional manufacturing method. In the figure, 1 is a GaAs substrate, 1a is a damaged layer due to ion implantation, and 3 is a mask pattern. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Masuo Oiwa (and 2 others) Figure 1 Figure 2

Claims (1)

[Claims] In a method for manufacturing a semiconductor device having a via hole,
A damaged layer is formed by implanting ions with a relatively large mass number at high energy through the opening of a mask pattern formed on the surface of the gallium arsenide substrate or by using a focused ion beam into the portion where the via hole is to be formed. By repeating the step and the step of selectively etching the damaged layer caused by the ion implantation with acid,
A method for manufacturing a semiconductor device, comprising the step of forming a via hole in the gallium arsenide substrate.