Semiconductor device manufacturing: process – Formation of electrically isolated lateral semiconductive... – Grooved and refilled with deposited dielectric material
Reexamination Certificate
1998-06-08
2001-08-21
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Formation of electrically isolated lateral semiconductive...
Grooved and refilled with deposited dielectric material
C438S404000, C438S428000, C438S435000, C438S436000, C438S438000
Reexamination Certificate
active
06277706
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device and more particularly to a method of manufacturing a semiconductor device with circuit-element-isolation trenches on a substrate.
2. Description of the Related Art
With the recent increase of integration and operating speed of semiconductor devices, various technologies have been advanced remarkably to miniature individual circuit elements to be loaded on each semiconductor device, and application of the LOCOS (Local Oxidation of Silicon) isolation using a silicon nitride film for electrically isolating individual circuit elements has increasingly been limited.
Consequently new element isolation technologies utilizing trenches have been developed. For example, Japanese Patent Laid-Open Publication No. Sho60-124840 proposed a technology of forming trenches, filling an insulation film in the trenches and then annealing at a temperature equal to or below a melting point of a substrate.
Another solution was proposed by a paper “An Optimized Densification of the Filled Oxide for Quarter Micron Shallow Trench Isolation” presented in Symposium on VLSI technology Digest Technical Papers 1996 by Han Sim Lee, et al. This technology will now be described with reference to
FIG. 4
of the accompanying drawings of the present specification.
As shown in
FIG. 4
, a number of predetermined trenches
104
are formed on a silicon substrate
101
, and then a thermal oxide film
102
is formed on the inside walls of the trenches
104
, whereupon a silicon oxide film
105
is filled in the trenches
104
by low pressure chemical vapor deposition (hereinafter also called LP-CVD) and is leveled by chemical and mechanical polishing (hereinafter called the CMP process).
In their paper, Lee, et al. disclosed that densification of the silicon oxide film, namely, resistance to wet etching was achieved by annealing at a lower temperature in a water-vapor ambient.
Lee, et al. also pointed out that since the inside walls of the trenches were oxidized, stresses occurred in the trenches to cause crystalline faults.
However, in this conventional technology, since the silicon oxide film used to fill the trenches by CVD was inadequately densified, the wet etching rate was great. Consequently, as shown in
FIG. 4
, after leveling by the CMP method, pits
106
occurred in the film filled in the trenches or a non-illustrated slit occurred centrally in the individual trench.
In the meantime, in order to improve the foregoing inconvenience, as an example, it is necessary to densify the silicon oxide film as by annealing at a high temperature equal to or higher than 1200° C. But if this technique was adopted, large thermal stresses would have occurred in the substrate to cause slippage and/or crystal faults.
Yet in this conventional technology, since densification by annealing is carried out at a low temperature, the inside walls of the trenches are oxidized so that large stresses occur in the trenches, thus causing faults in the substrate.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method of manufacturing a semiconductor device which method adequately densifies a trench-forming film at a low temperature using a high-pressure ambient can reduce occurrences of possible faults and, at the same time, can effectively isolate individual circuit elements from one another.
According to a first aspect of the invention, the above object is accomplished by a method of manufacturing a semiconductor device, comprising the steps of: forming on a substrate an isolation trench for isolating a plurality of semiconductor circuit elements; forming a thermal oxide film on a sidewall of the isolation trench formed in the trench-forming step; forming a silicon oxide film on the substrate by chemical vapor deposition (CVD); and annealing the silicon oxide film along with the substrate in a high-pressure ambient.
Preferably, the annealing of the CVD silicon oxide film and the substrate is carried out in a high-pressure ambient so that the silicon oxide film is densified at a lower temperature compared to normal-pressure ambient.
According to a second aspect of the invention, the above object is accomplished alternatively by a method of manufacturing a semiconductor device, comprising the steps of: forming on a substrate an isolation trench for isolating a plurality of semiconductor circuit elements; forming a thermal oxide film on a sidewall of the isolation trench formed in the trench-forming step; forming a silicon nitride film on the substrate; forming a silicon oxide film on the substrate by chemical vapor deposition (CVD); and annealing said silicon oxide film along with the substrate in a high-pressure ambient.
In the second aspect of the invention, like the first aspect of the invention, the annealing of the silicon oxide film and the substrate is carried out preferably in a high-pressure ambient so that the silicon oxide film is densified at a lower temperature compared to normal-pressure ambient. Also preferably, the high-pressure ambient contains water vapor.
According to a third aspect of the invention, the above object is accomplished yet alternatively by a method of manufacturing a semiconductor device, comprising the steps of: forming on a substrate an isolation trench for isolating a plurality of semiconductor circuit elements; forming a thermal oxide film on a sidewall of the isolation trench formed in the trench-forming step; forming a silicon nitride film on the thermal oxide film formed on the sidewall of the trench; forming a silicon oxide film on the substrate by chemical vapor deposition (CVD); and annealing the entire substrate in a high-pressure ambient.
In the third aspect of the invention, the second aspect of the invention, the annealing of the silicon oxide film and the substrate is carried out preferably in a high-pressure ambient so that the silicon oxide film is densified at a lower temperature compared to normal-pressure ambient. Yet preferably, the high-pressure ambient contains water vapor.
REFERENCES:
patent: 4455325 (1984-06-01), Razouk
patent: 5492858 (1996-02-01), Bose et al.
patent: 5506177 (1996-04-01), Kishimoto et al.
patent: 5817566 (1998-10-01), Jang et al.
patent: 5911109 (1999-06-01), Razouk et al.
patent: 5933748 (1999-08-01), Chou et al.
patent: 60124840 (1985-07-01), None
patent: 1-128527 (1989-05-01), None
patent: 6-252259 (1994-09-01), None
patent: 786393 (1995-03-01), None
Hayes Soloway Hennessey Grossman & Hage PC
NEC Corporation
Nguyen Ha Tran
Niebling John F.
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