JPS6273737A - Semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a semiconductor device which has high reliability and high performance by burying a polycrystalline silicon in a 3-layer film made of a silicon oxide film, a silicon nitride film and a silicon oxide film along the inner wall of a groove, and forming a silicon oxide film on the polycrystalline silicon. CONSTITUTION:An oxide film 106 and a silicon nitride film 107 superposed on the film 106 are formed on a substrate 101 to form a 2-layer film. Then, a photoresist mask is formed, and a 2-layer film of a groove forming region and a silicon substrate are etched to form a groove. Subsequently, with the 2-layer film as a mask an oxide film 105 is formed only on the inner wall of the groove, the film 107 is removed, a nitride film 104 is newly grown, and an oxide film 103 is formed on the film 104. Then, a polycrystalline silicon is vapor-phase grown, and further etched back to allow the polycrystalline silicon to remain only in the groove. Thereafter, the film 103 is etched with buffered fluoric acid, a buried polycrystalline silicon 102 is oxidized to form an oxide film 103 on the surface. Then, the films 104, 106 of an element region are removed to form an element. Thus, the oxide film formed on the buried polycrystalline silicon is not contracted at a place near the wall of the groove.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device, and more particularly to a semiconductor device having trench isolation.

[Conventional technology]

Conventionally, when element isolation is performed using a trench filled with polycrystalline silicon, the buried polycrystalline silicon is oxidized to form a full silicon oxide film on the top of the trench with polycrystalline silicon buried inside the trench. In order to prevent this silicon oxide film from digging into the element region, a structure in which the inner wall of the trench has a two-layer film of a silicon oxide film and a silicon nitride film has been used. Third
The figure is a cross-sectional view of a conventional semiconductor device having an insulating isolation region with a two-layer film structure. In the figure, 101 is a silicon substrate;
105 and 104 are a silicon oxide film and a silicon nitride film forming a two-layer film. Further, 102 is polycrystalline silicon that fills the groove inside the two-layer film, and 203 is a silicon oxide film above the groove formed by oxidizing polycrystalline silicon.

[Problem that the invention seeks to solve]

In the conventional method described above, when the buried polycrystalline silicon is oxidized to form an oxide film on the top of the trench, the oxide film becomes thinner at the part where it contacts the silicon nitride film on the inner wall of the trench. There is a problem in that the oxide film on the surface is partially removed and the polycrystalline silicon is exposed, resulting in a short circuit in the wiring system and a decrease in the threshold voltage VT2.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the problems of the prior art and provide a structurally stable semiconductor device having a sub-element isolation groove.

[Means for solving problems]

The semiconductor device of the present invention has a groove buried in a dielectric film and polycrystalline silicon on a semiconductor substrate, and in the semiconductor device in which insulation isolation between elements is performed by the groove, the inner wall of the groove is A three-layer film consisting of a first silicon oxide film, a silicon nitride film, and a second silicon oxide film is formed along the line, polycrystalline silicon is buried inside the three-layer film, and a third layer is formed on the polycrystalline silicon. A silicon oxide film of No. 3 is formed, and the third silicon oxide film is formed.
The silicon oxide film is connected to the second silicon oxide film without being constricted at the connecting portion.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a cross-sectional view of one embodiment of the present invention, and FIG. 2 ta+ to ffl are cross-sectional views shown in the order of steps to fully explain the manufacturing method of the ninth embodiment shown in FIG.

First, the manufacturing method for the plow will be explained with reference to FIGS. 2(a) to +f).

First, as shown in FIG.
A silicon oxide film 106 is formed thereon, and a silicon nitride film 107 (fc) is formed over the silicon oxide film 106 to form a first two-layer film.

Next, the photoresist mask is released using photolithographic technology.
Using this photoresist mask, the first two-layer film in the groove forming region is etched, and the silicon substrate is further etched to form a groove.

Next, as shown in FIG. 2(b), a silicon oxide film 105 is formed only on the inner wall of the trench as a first two-layer mask, and then the silicon nitride film 107 is removed and a new silicon nitride film is formed. Grow 104. Next, polycrystalline silicon is left only inside the trench by sputtering a silicon oxide film using a vapor phase growth method or a sputtering method.

Next, as shown in FIG. 2 (dl), the silicon oxide film 103 ft is etched with a 1 buffer hydrofluoric acid solution. At this time, the etching time is set so that the upper end of the silicon oxide film 103 is lower than the upper surface of the buried polycrystalline silicon. Adjust.

Next, as shown in Figure 2 (el), the buried polycrystalline silicon 1
02t - Oxidize to form silicon oxide films 103a to 103f on the surface.

Next, as shown in Figure 2), the silicon nitride film 104 and silicon oxide film 106 in the element region are removed, and the element is formed through a post-process.

As shown in FIG. 1, the semiconductor device realized in the above embodiment has a first silicon oxide film 1 along the inner wall of the trench.
05, silicon nitride film 104. A three-layer film of a second silicon oxide film 103 is formed, polycrystalline silicon 102 is buried inside the three-layer film, a third silicon oxide film 1oaa is formed on the polycrystalline silicon, and the third silicon oxide film 103 is formed. The silicon oxide film 103a of No. 3 is the second silicon oxide film 103
It has a structure in which it is connected without constricting at the connecting part.

Therefore, it is possible to create a structure in which the oxide film on the upper part of the trench is not constricted by the trench wall portion, compared to the conventional example, which is only a two-layer film consisting of the silicon oxide film 105 and the silicon nitride film 104 shown in FIG.

〔Effect of the invention〕

As explained above, in the present invention, since the silicon oxide film is formed on the silicon nitride film formed on the trench wall, the oxide film formed on the buried polycrystalline silicon is There is no constriction, and the problems with conventional structures can be solved.
Furthermore, the thicker dielectric film on the trench wall compared to the conventional structure has the effect of reducing the coupling capacitance between elements.
By using the groove of this structure, a highly reliable and high performance semiconductor device can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention, and FIG. 2 is a sectional view of an embodiment of the present invention.
f) is a cross-sectional view shown in order of steps to explain the manufacturing method of the embodiment shown in FIG. 1, and FIG. 3 is a cross-sectional view of an example of a conventional semiconductor device. 101...Silicon substrate, 102...
Polycrystalline silicon, 103...Silicon 11 oxide 1
1L 103 a...Silicon oxide film, 104
...Silicon nitride film, 105...Silicon oxide film, 106...Silicon oxide film, 10
7...Silicon nitride film, 203...Silicon oxide film. Agent Patent Attorney Shinma Uchihara 21st Kozuman Han 21 Kaya Zaku

Claims (1)

[Claims] In a semiconductor device having a trench buried in a dielectric film and polycrystalline silicon on a semiconductor substrate, and insulating and isolating between elements in the trench, a first silicon oxide layer is formed along the inner wall of the trench. A three-layer film consisting of a silicon nitride film and a second silicon oxide film is formed, polycrystalline silicon is buried inside the three-layer film, and a third silicon oxide film is formed on the polycrystalline silicon. A semiconductor device characterized in that the third silicon oxide film is connected to the second silicon oxide film without being constricted at the connection portion.