JPS5842254A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a metal electrode and wiring of semiconductor device having always favorable ohmic contact by a method wherein the heat treatment is performed after a glass film containing impurities is formed on a mask layer having the extremely lower etching rate than the glass film containing impurities. CONSTITUTION:The silicon nitride film 7 is made to grow applying the chemical vapor phase growth method. After then, the phospho silicate glass (PSG) film 4 is made to grow applying the CVD method, and moreover patterning of the PSG film 4 is performed applying usual photolithography to form an electrode contact window. Then the heat treatment is performed at about 950- 1,100 deg.C to make the PSG film 4 to be molten and to be softened. Accordingly the PSG film 4 is made to have the smooth shape having roundness wholly. Then the whole surface is etched applying the plasma etching method using carbon tetrafluoride (CF4) as the etchant. Etching thereof is continued till the mask film 7 is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a modification of a method for manufacturing a semiconductor device having a protective film made of impurity-containing glass.

Conventionally, in an IT field effect semiconductor device (for example, an insulating film), impurity-containing glass films,
A phosphosilicate glass film (hereinafter referred to as a P2O film) is often formed on the substrate.After forming a PSG film, heat treatment is performed to melt and soften the P2O film, thereby forming it on the surface of a semiconductor substrate. A method has been used to prevent wire breakage when metal wiring is formed by smoothing the stepped steps, but in this case, the following problems occur. This will be explained using FIGS. 1 and 2.

FIG. 1 is a cross-sectional view of a contact part in a conventional structure, where 1 is an N@ silicon semiconductor substrate, 2 is a silicon dioxide film, 3 is a P@ impurity doped region, 4 is a P2O film, and 5 is an electrode contact window. It is. In this state, after forming P80Il[4t-, 31, PaG film 4 and silicon dioxide film 2 are subjected to first heat treatment as shown in FIG. By P
The 8G film 4 is melted and softened to have a rounded and smooth shape. However, as a result of this heat treatment, phosphorus is diffused out from the fiP8G film 4 (OUT DIFFUSION), and it is diffused into the P-type impurity exposed in the contact window 5 for the electrode or strip wiring, and into the surface of the region 3. A type impurity region 6 is formed, and an ICP-N junction is generated on the silicon substrate surface of the contact portion 5, as shown in FIG. 2, and in this state, when a metal electrode is formed It is not possible to make good contact with the user.

In addition, when forming the electrode contact window 5t, it is sufficient to perform this heat treatment with the contact processing limited to only the t-P8G film and the underlying silicon dioxide film 2 remaining.
However, currently, in such cases, P8G film 4
It is impossible to selectively etch the silicon dioxide 11121, and there is no choice but to etch the silicon dioxide 11121.

The object of the present invention is to overcome the above-mentioned drawbacks of the prior art.

A feature of the present invention is, for example, when an impurity region having conductivity is formed on the surface of a semiconductor substrate, the impurity-containing glass film is etched using a different etchant and the etchant is not etched at the same time, or the impurity-containing glass film is A process of forming a mask layer made of a material with a significantly low ching rate, forming this impurity-containing glass film on the mask layer, and opening a contact window with the impurity region only in the impurity-containing glass film. A semiconductor device comprising the steps of: further performing heat treatment to smooth the entire surface of the impurity-containing glass film; and using the impurity-containing glass film as an etching mask to open a contact window in the mask layer, and then forming electrode wiring. It is in the manufacturing method.

That is, in the present invention, even if an electrode contact window is formed on an impurity-containing glass film such as P801i and then heat treatment is performed, a p-n junction as described above is formed. This makes it possible to obtain a semiconductor device having electrodes, and this will be explained in detail below.

FIGS. 3(7) to 3) are process explanatory diagrams of an embodiment of the present invention, and the following description will be made with reference to these diagrams.

FIG. 3 (7): Applying a conventional technique, a field silicon dioxide film 2, a P-type impurity doped region 3 serving as a source region or a drain region, are formed on an n-type silicon semiconductor substrate l.
A state in which a gate oxide film 8 and a composite gate 9 are formed is shown.

FIG. 3 ((A): Chemical vapor deposition is further applied to grow the silicon nitride film 7t to a thickness of, for example, 500 to 100 OA.

Figure 3 (After fjI coating, the CVD method is applied to grow the P8G film 4 to a thickness of, for example, 7,000λ to 15,000λ, WIL, and then the PSGS film is pattern-engraved by applying normal photolithography'fc to form electrode contacts. form a window.

(See FIG. 3); Next, heat treatment is performed at a temperature of about 950°C to 1100°C to melt and soften the P2O3[4.

As a result, the entire PSGS deposited film has a rounded and smooth shape. Even if phosphorus diffuses outward from the P8G film 4 in this step, since the mask film 7 is present on the impurity-introduced region 3, there is no fear that the phosphorus will enter the region 3 and form a pn junction.

Figure 3 t! 6: Next, carbon tetrafluoride (C
F4) using Plas Y @ engineering, applying the ching method to obtain all f
fi't etching. This etching is continued until the mask film 7 is removed. Since the etching rate in this case is P2O:silicon nitride=1:100 degrees, the mask film 7 can be removed before the PSGS deposited film is hardly etched. Through this process, the electrode contact window sFi is completed, and the silicon surface is exposed inside the window.

Thereafter, conventional techniques are applied to form metal electrodes, such as aluminum, and wiring to complete the device.

As can be seen from the above explanation, according to the present invention, even if an electrode contact window is formed on an impurity-containing glass film and then the surface is smoothed by clearing and softening, outward diffusion Since there is no possibility that the impurities introduced into the semiconductor substrate are incorporated into the semiconductor substrate and form unnecessary junctions, it is possible to obtain a semiconductor device having metal electrodes and wiring with good ohmic contact at all times.

In this example, a silicon nitride film was used as the impurity-containing glass film, but as the mask film, impurity-containing glass, that is, PEG in this example, was used, but unless it is etched by the process or chant, the etching rate will be extremely high. It may be a film of a low i material, and is not limited to silicon nitride.

[Brief explanation of the drawing]

w, Figures 1 and 2 are explanatory views of the conventional example, and Figures 3 (7) to (4) are process explanatory views of the embodiment according to the present invention. In the figure, 1... Semiconductor substrate, 2... Silicon dioxide film, 3... Impurity introduced region, 4...
- Impurity-containing glass film, 5... electrode contact window, 6... conduction ff opposite to impurity introduction region 3
Impurity introduced region shown as 1t, 7...Mask film, 8
. . . Gate oxide film, 9 . . . Silicon gate electrode, t, respectively. Figure 1 Figure 2 63 Figure 3

Claims (1)

[Claims] A step of forming an impurity-containing glass film on a substrate, etching a chant tube, and etching the chant tube at the same time, or forming a mask layer made of a material whose etching rate is significantly lower than that of the impurity-containing glass film. forming the impurity-containing glass film on the mask layer, forming an opening only in the impurity-containing glass film, and further performing heat treatment to smooth the surface of the impurity-containing glass film;
A method of manufacturing a semiconductor device, comprising the steps of forming an opening in the mask layer using the impurity-containing glass film as an etching mask, and then forming an electrode wiring.