JPS596546A - Etching of insulating film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of etching an insulating film that serves as a mask for selective diffusion into an n-type ■-■ group compound semiconductor.

Methods for forming a p-type head region on an n-type m-v group compound semiconductor include a liquid phase epitaxial method and a diffusion method, which are currently widely used in light emitting diodes, lasers, and the like. Compared to the former, the latter has excellent features such as being easier to mass-produce and making it easier to convert the pn junction into a planar one.

When p-type is diffused into an n-type III-V compound semiconductor, p
As the type impurity, a group element such as Zn is used.

Since a silicon oxide film allows Zni to pass through, a silicon nitride film or an alumina film is generally used as a mask for selective diffusion of Zn.

FIG. 1 shows the manufacturing process of this selective diffusion mask. A silicon nitride film or alumina film 2 is formed directly on the n-type III-V group compound semiconductor 1, and a silicon oxide film 3 is further formed on it (FIG. 1(a)). A pattern of the silicon oxide film 3 is formed using a resist or the like (
Figure 1 (k')) o Using this silicon oxide film 3 as a mask, the silicon nitride film or alumina film 2 is etched away to form a window 4 for diffusion (Figure 1 (C)) In etching, it is common to over-etch to avoid insufficient etching. However, the phosphoric acid solution used as an etching solution for silicon nitride films and alumina films is
- It spoils group V compounds. Therefore, excessive etching cannot be performed, and it is extremely difficult to stop the etching process at the interface with the substrate and completely remove the silicon nitride film or alumina film, which is a major cause of poor characteristics.

The present invention solves this problem by forming a silicon oxide film interposed between the l-V compound semiconductor and the silicon nitride film or alumina film. Preventing the surface of the m-v group compound semiconductor from being exposed to the window etching solution,
It is also an object of the present invention to provide a method of etching an insulating film that can form a mask that allows complete selective diffusion.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a process sectional view showing the insulating film etching method of the present invention. First, an n-type [1-V group compound semiconductor substrate 1
A film with a thickness of 1 is deposited on the surface of the
A silicon oxide film 5 of 0.000 mm is formed (Fig. 2(a)
) Next, a silicon nitride film 6 with a thickness of 1,600 thick is formed by thermal solution using silane and ammonia gas, and a silicon oxide film 3 with a thickness of 6,000 thick is formed again. Next, hydrofluoric acid was applied using the usual photoetching method.

The silicon oxide film 3 is removed using an ammonium fluoride mixed solution to form a window 7 (FIG. 2(b)). Then, using this silicon oxide film 3 as a mask, a phosphoric acid solution is used to remove the silicon nitride through the window 7f. A window is opened in the membrane 6 (FIG. 2(C)).

The etching conditions are 160° C. for about 46 minutes, and silicon nitride film 6 is completely selectively removed. In this way, even if the process is performed under excessive etching conditions, the etching speed of the silicon oxide film 6 is slow with the phosphoric acid solution, so the surface of the substrate is coated with the silicon oxide film 6 in the window portion 8, so no damage will occur. . Finally, selective removal of the silicon oxide film 6 and removal of the upper silicon oxide film 3 are simultaneously performed using a mixed solution of hydrofluoric acid and ammonium fluoride (FIG. 1(d)) o This mixed solution is
Since it does not react with II-V group compounds, no damage will occur to the substrate surface of the window portion 9 even if excessive etching conditions are set.In addition, in the above example, an example using a silicon nitride film was described. However, similar effects can be expected in the case of an alumina film.

As described above, the present invention has a double-layer structure in which a first silicon oxide film is formed on the surface of a III-V group compound substrate, and then a second silicon nitride film is formed, thereby forming a silicon nitride film. The silicon oxide film of the first film prevents the etching solution from damaging the substrate surface, and by removing this silicon oxide film with a solution that does not damage the substrate surface, a mask for selective diffusion is formed. , it will not cause any negative impact on the board.

[Brief explanation of the drawing]

FIGS. 1(a) to (C) are process cross-sectional views showing a conventional selective diffusion mask forming method, and FIGS. 2(a) to (d) show an embodiment of the insulating film etching method of the present invention. It is a process sectional view. 1... n-type III-V group compound semiconductor substrate,
3...Silicon oxide film, 6...Silicon oxide film, 6...Silicon nitride film, 7, 8...Window portion, 9... ...Diffusion window. Name of agent: Patent attorney Toshio Nakao Haga1 person-1
9 [-Semi. +-+-, +c-3 Tsuzuka Castle-0θ-197-

Claims (1)

[Claims] A first film and a second insulating film are stacked and formed on the surface of a III-V compound semiconductor substrate, and the second film is selectively etched using a predetermined etching solution, and then an inert etching solution is applied to the second film. A method of etching an insulating film, comprising selectively removing the first film using an etching solution.