JPH02296352A - Semiconductor device - Google Patents

Abstract

PURPOSE:To restrain crystal defect in the vicinity of an isolation trench which generates in a semiconductor substrate, by filling the trench with an oxide film, a polycrystalline silicon film, and a nitride film which are formed in order in the trench formed in the semiconductor substrate, and adjusting the thickness of said films. CONSTITUTION:An insulating film 2 is selectively formed on the surface of a semiconductor substrate 1; by using the insulating film 2 as a mask, a trench 3 is formed to a necessary depth: an oxide film 4 is formed on the inner surface of the trench 3. In the trench 3 a polycrystalline silicon film 5 is grown, and further in the inside, a nitride film 6 is grown, thereby filling the trench 3. Thus an isolation trench is formed. The thermal expansion coefficients of the oxide film 4, the polycrystalline silicon film 5 and the nitride film 6 are averaged in accordance with the thickness ratio of the films, and the whole part is adjusted so as to be equal to the thermal expansion coefficient of the semiconductor substrate 1. Thereby crystal defect in the vicinity of the isolation trench which generates in the semiconductor substrate can be restrained.

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 a recessed groove, that is, a wrench isolation groove for separating semiconductor elements.

[Prior Art] In recent years, trench isolation grooves have been adopted in semiconductor devices aimed at high integration as an isolation structure for insulating and isolating elements formed on a semiconductor substrate. Conventionally, this type of trench isolation trench is formed by forming a trench with a narrow width in the depth direction from the surface of a semiconductor substrate, forming an oxide film on the inner surface of this trench, and then forming a multilayer film inside the trench. It has a structure in which a material such as crystalline silicon is buried.

(Problems to be Solved by the Invention) In the conventional double trench isolation groove, the oxide film formed on the inner surface of the groove is thin, and the inside of the groove is mostly filled with polycrystalline silicon. For this reason, stress is generated in the semiconductor substrate due to the difference in thermal expansion coefficient between polycrystalline silicon and the semiconductor substrate during the heat treatment process after forming the trench isolation groove, and this stress causes many crystal defects on the surface of the semiconductor substrate. There is a problem in that this adversely affects the characteristics of the semiconductor device.

An object of the present invention is to provide a semiconductor device in which the occurrence of crystal defects in a semiconductor substrate is suppressed.

[Failure to solve the problem]

In the semiconductor device of the present invention, an oxide film is formed on the inner surface of a trench formed in an element isolation region of a semiconductor substrate, and a polycrystalline silicon film and a nitride film are sequentially formed in this trench to bury the trench. .

[Function] In this configuration, by adjusting the film thicknesses of the oxide film, polycrystalline silicon film, and nitride film, the coefficient of thermal expansion of the entire material buried in the 1-trench groove is made approximately equal to that of the semiconductor substrate, thereby reducing stress generation. suppress.

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

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention.

A trench 3 with a width of 2 μm is formed in the semiconductor substrate 1 by selectively forming an insulating film 2 on the surface of a semiconductor substrate 1 made of silicon, and performing anisotropic etching using the insulating film 2 as a mask.
is formed to the required depth.

Then, a 0.2 μm silicon oxide film 4 is formed on the inner surface of this trench 3. Also, in trench 3, 0.5
A polycrystalline silicon film 5 with a thickness of .mu.m is grown, and a silicon nitride film 6 with a thickness of 0.3 .mu.m is grown inside the polycrystalline silicon film 5 to fill the trench 3 and form a trench isolation groove.

That is, silicon oxide film 4. The film thickness of each of the polycrystalline silicon film 5 and the silicon nitride film 6 is 1. ．． 15t, ratio of 2:
The ratio is 5:3.

With this configuration, the silicon oxide film 4. Polycrystalline silicon film 5. The coefficient of thermal expansion of each silicon nitride film 6 is averaged according to the ratio of the film thicknesses, and the coefficient of thermal expansion of the silicon nitride film 6 as a whole is adjusted to be close to that of silicon constituting the semiconductor substrate 1. Therefore, the stress generated in the semiconductor substrate in the vicinity of the I-wrench isolation trench can also be reduced by the heat treatment step after the formation of the I-wrench isolation trench, and crystal defects can be suppressed.

When the present inventor actually applied the above-described I-wrench isolation groove to a semiconductor device formed on a silicon substrate, crystal defects were reduced to 1/2 to 1/3 of the conventional level.

FIG. 2 is a longitudinal sectional view of a second embodiment of the invention.

In this embodiment, a trench 3 with a width of 2 μm is formed in a semiconductor substrate 1.
After forming, a 0.21 zm thick silicon oxide film 4 and a 0.3 μm thick polycrystalline silicon film 5.0.3 μm are formed on the inner surface.
A thick silicon nitride film 6 and a 0.2 μm thick polycrystalline silicon film 7 are sequentially formed to fill the trench 3.

In this embodiment as well, the ratio of the film thicknesses 14 and 16 of at least the silicon oxide film 4 and the silicon nitride film 6 is set to 2:3.
- The overall coefficient of thermal expansion of the buried material H in the wrench groove can be made close to that of silicon, and the occurrence of crystal defects in the semiconductor substrate 1 due to the occurrence of stress can be suppressed.

〔Effect of the invention〕

As explained above, in the present invention, an oxide film, a polycrystalline silicon film, and a nitride film are sequentially formed in a trench provided in a semiconductor substrate to bury the l~trench, and by adjusting the thickness of these films, This has the effect of making the thermal expansion coefficient of the entire material buried in the trench substantially equal to that of the semiconductor substrate, and reducing crystal defects around the trench caused by heat treatment.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a first embodiment of the present invention, and FIG. 21 is a longitudinal cross-sectional view of a second embodiment of the present invention.

Claims (1)

[Claims] 1. A semiconductor device characterized in that an oxide film is formed on the inner surface of a trench formed in an element isolation region of a semiconductor substrate, and a polycrystalline silicon film and a nitride film are sequentially formed in this trench to bury the trench. .