JPS61174649A - Semiconductor device - Google Patents

Abstract

PURPOSE:To realize an IC of higher performance with its charactetistics improved by a method wherein the entire surface of an oxide film is covered by an nitride film and an electrode. CONSTITUTION:An oxide film 2 is formed on the entire surface of an Si substrate 1, to be followed by the formation of a nitride film 3. A desired pattern of a photoresist 4 is provided by application on the nitride film 3, and the photoresist 4 serves as a mask in a process wherein the nitride film 3 is subjected to plasma etching or the like for provision of an opening 5. The photoresist 4 is then removed, another photoresist 6 is provided application, patterning is accomplished to affect the opening 5 well into its depth. Another opening 7 is formed inside the opening 5 with the patterned photoresist 6 serving as a mask, for the provision of an electrode contact window 8. The photoresist 6 is removed, and then an electrode 9 is built in the electrode contact window 8. This results in a semiconductor device A, with its entirety covered by the electrode 9 and nitride film 3, which does not allow any portion of the oxide film 2 to be exposed on the surface.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a semiconductor device in which one surface insulating layer has a two-layer structure of an oxide film and a nitride film.

(Prior Art and Problems) It is well known that various characteristics can be improved by forming the surface insulating layer of a semiconductor device into a two-layer structure of an oxide film and a nitride film.

There are two methods for manufacturing this type of semiconductor device: one is to coat the entire surface of the device with a nitride film before forming the electrode contact window, and the other is to coat the nitride film only on the necessary areas. In view of the number of manufacturing steps, the former method of covering the entire surface with a nitride film is often used.

The problems with this method of covering the entire surface with nitride film are as follows.

When opening the electrode contact window, the nitride film and the oxide film are opened at the same time, as shown in FIG.

This tends to cause an overhang state of the nitride film a.

In FIG. 4, b is an oxide film and C is a silicon substrate.

Various methods can be considered to improve this problem, but in general, as shown in Figure 5, the upper nitride film a of the insulating layer is opened widely, and the lower oxide film is replaced with a nitride film. A so-called step etching method is used in which holes are formed in the openings provided in a. Metal is deposited on the electrode contact window thus formed to form an electrode d, thereby forming a semiconductor device having the structure shown in FIG. 5. As can be seen from this figure, in the conventional semiconductor device, a part of the surface e of the oxide film b is exposed.

(Object of the Invention) An object of the semiconductor device of the present invention is to further improve the above-described semiconductor device and provide a semiconductor device with significantly improved semiconductor characteristics.

(Structure of the Invention) In the semiconductor device of the present invention, the surface insulating layer that insulates the entire surface of the semiconductor layer is composed of two layers of an oxide film and a nitride film, and the upper nitride film has wider pores than the lower oxide film. In this case, the entire surface of the oxide film is covered with the nitride film and the electrode.

(Example) FIG. 1 shows the structure of a semiconductor device itA according to the present invention,
The manufacturing process is shown in FIGS. 2(a) to 2(d).

The semiconductor device A of this example is an NPN type transistor, and an oxide film 2. A nitride film 3 is formed, an electrode 9 is formed in each electrode contact window 8, and the entire surface of the oxide film 2 is covered with the nitride film 3 and the electrode 9.

The semiconductor device A will be described below with reference to FIGS.
The manufacturing process will be explained.

(a) An oxide film (Sint film) 2 is formed on the entire surface of the Si substrate 1 by thermal oxidation or CVD, and then a nitride film (SisNi film) 3 is formed. A photoresist 4 is applied onto the nitride film 3 and formed into a desired pattern, and the nitride film 3 is processed by plasma etching or the like using the patterned photoresist 4 as a mask to form an opening 5 (see FIG. 1). See a)].

(False) Next, after removing the photoresist 4, photoresist 6 is applied again, and the opening of the oxide film 2 is patterned sufficiently inside the opening 5 [see Fig. 2, mountain)]. The dimensions of the opening are determined in consideration of shifts caused by etching in the primary process.

(C) Using this patterned photoresist 6 as a mask, the oxide film 2 is etched with an HF-based etchant, etc., and an opening 7 is formed inside the opening 5 formed in the nitride film 3 for use as an electrode contact. A window 8 is formed (see FIG. 2(C)).

(d) The photoresist 6 is removed and an electrode 9 (usually AI) is formed in the electrode contact window 8 by vapor deposition or the like [see FIG. 2(d)].

Semiconductor device A according to the present invention manufactured by the above steps
In this case, the entire surface of the device is covered with the electrode 9 and the nitride film 3, and the oxide film 2 is not exposed on the surface.

The effect that the oxide film 2 is not exposed on the surface is due to the fact that some NPN transistor characteristics have been experimentally confirmed in Figure 3.
In Figure 0, which shows the collector current dependence of the current amplification factor of the N-th type transistor, the mark Q is the characteristic curve of the semiconductor device A according to the present invention in which the oxide film is covered with the nitride film and does not appear on the surface, x The mark is the characteristic curve of a Structure 6 semiconductor device (shown in Figure 5) in which the oxide film is covered by the nitride film but partially exposed on the surface, and the mark Δ is the characteristic curve where the oxide film is exposed on the entire surface without the nitride film. It is a characteristic curve of a semiconductor device. As can be seen from this figure, a considerable improvement in characteristics can be obtained by simply covering the entire surface with a nitride film.9 In the semiconductor device A of the present invention, the current amplification factor (h□) in the low collector current region does not decrease,
Transistor operating characteristics are further improved.

(Effects of the Invention) As explained above, according to the semiconductor device according to the present invention, the improvement in characteristics obtained by forming a conventional surface insulating layer with a two-layer structure of an oxide film and a nitride film is further promoted. This made it possible to develop higher-performance ICs.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 (a) to (dl show an embodiment of a semiconductor device according to the present invention, and FIG. 1 is a longitudinal cross-sectional view. d) is a vertical cross-sectional view showing the manufacturing process;
The figure is a characteristic diagram of collector current versus current amplification factor (hyz). FIG. 4 is a vertical cross-sectional view showing an overhang state, and FIG. 5 is a vertical cross-sectional view of a conventional semiconductor device.

Claims (1)

[Claims] 1) The surface insulating layer that insulates the entire surface of the semiconductor layer is composed of two layers: an oxide film and a nitride film, and the upper nitride film has holes wider than the lower oxide film to form an electrode contact. 1. A semiconductor device in which a window is formed, wherein the entire surface of the oxide film is covered with the nitride film and the electrode.