JPS6235267B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method suitable for manufacturing a semiconductor device having a trench-like element isolation region.

2. Description of the Related Art Conventionally, a so-called grooved isolation technique is known in which an isolation region between elements in a semiconductor device is formed in a groove shape.

For example, as shown in FIG. 1, a trench 2 with a depth of, for example, 3 [μm] and a width of, for example, 1 [μm] is formed in a silicon semiconductor substrate 1, and the entire surface is heated to a thickness of, for example, [Å]. An oxide film 3 is formed, and a silicon dioxide film 4 is further formed on the entire surface by chemical vapor deposition (CVD).

Since the element isolation region formed by this technique occupies a small area when viewed in plan, it is effective for highly integrating semiconductor devices.

However, the device isolation region has serious drawbacks. As can be seen in the figure,
When the silicon dioxide film 4 is formed by the CVD method, voids 4' are likely to be generated inside. If such a hole 4' exists, when it is necessary to etch the silicon dioxide film 4 on the surface in a later step, if a part of the hole 4' is exposed due to the etching, the hole 4' will be further removed. The purpose of filling the groove 2 with the silicon dioxide film 4 by enlarging it into a cavity cannot be achieved.

Additionally, if heat treatment is performed in the subsequent semiconductor device manufacturing process with the 4′ present,
Accidents may also occur in which the gas trapped in the cap 4' expands thermally and causes an explosion, destroying the device.

In order to eliminate the above-mentioned drawbacks, an element isolation region having the configuration shown in FIG. 2 has been proposed. That is, in this conventional example, the side walls of the groove 2 are tapered. In this way, the possibility that cavities will be formed in the silicon dioxide film 4 is reduced. However, it is not easy to form grooves 2 having tapered side walls with good reproducibility and controllability. That is, this type of groove is usually formed by applying the reactive ion etching (RIE) method, but in order to create the taper as described above,
The component ratio of the etching gas, the pressure of the etching gas, the high frequency power, etc. must be specially controlled, and the reproducibility is not good.

The present invention makes it possible to easily form an isolation region between elements without a cavity in an insulator buried in a trench, and this will be described in detail below.

3 to 7 are sectional side views of essential parts of a semiconductor device at key points in the process for explaining one embodiment of the present invention, and the following description will be made with reference to these figures.

Refer to Fig. 3 (1) For example, a thermal oxidation method is applied to the silicon semiconductor substrate 11 to form a silicon dioxide film having a thickness of, for example, about 4000 [Å], and then it is processed using, for example, X-ray lithography technology or electron beam lithography. Patterning is performed using an appropriate technique such as A technique, and the width is 1 [μ
m].

(2) Etching the silicon semiconductor substrate 11 by FIE method using the silicon dioxide film as a mask,
A groove 12 having a width of about 1 [μm] and a depth of, for example, about 1 [μm] is formed.

(3) After removing the silicon dioxide film, if etching is performed by applying an isotropic plasma etching method, isotropic chemical wet etching method, etc., the surface corner of the groove 12 will have a circular shape 12 as shown in the figure. ′
is attached. At this time, since almost no reactive atoms are supplied to the deep part of the groove 12, almost no etching is performed.

See Figure 4 (4) For example, by applying the thermal oxidation method, the thickness of
An oxide film 13 of about [Å] is grown.

Refer to FIG. 5 (5) A phosphosilicate glass (PSG) film 14 having a thickness of, for example, about 3500 [Å] is formed by applying a chemical vapor deposition (CVD) method.

Refer to FIG. 6 (6) For example, heat treatment is performed at a temperature of 1100 [° C.] for about 30 [minutes] to melt the PSG film 14. As a result, the PSG on the surface melts and flows into the groove 12, filling the void to some extent.

Refer to Figure 7 (7) When the PSG film is grown again using the CVD method and then melted by heat treatment, the inside of the groove 12 is densely filled with the PSG film 14 as shown in the figure, and the surface is flat. I will be in charge.

As can be seen from the above description, according to the present invention, a semiconductor substrate is reactive sputter etched to form a groove having substantially vertical sidewalls, and then isotropic etching is performed to form the groove. The corners of the surface are rounded, a thin insulating film is formed, and the glass film is repeatedly formed and melted several times to fill the grooves densely with the glass and flatten the surface. No cavities or cavities occur in the glass within the groove. Therefore, no explosion occurs even after the subsequent heat treatment process, and it is possible to easily manufacture a semiconductor device that can maintain reliability over a long period of time.

[Brief explanation of the drawing]

1 and 2 are side cross-sectional explanatory views of main parts of a semiconductor device at key points in the process for explaining the conventional technology;
3 to 7 are side cross-sectional views of essential parts of a semiconductor device at key points in the process for explaining one embodiment of the present invention. In the figure, 11 is a substrate, 12 is a groove, 12' is a circle, 13 is an oxide film, and 14 is a PSG film.

Claims (1)

[Claims] 1. Forming a groove having substantially perpendicular side walls in a semiconductor substrate, and then rounding the groove surface corners,
A semiconductor device comprising the steps of: next forming an insulating film; then forming a glass film and melting it; repeating this process multiple times to densely fill the groove with glass; manufacturing method.