Method to prevent the formation of a thinner portion of...

Details Method to prevent the formation of a thinner portion of... Method to prevent the formation of a thinner portion of...

2000-05-31

2002-03-12

Smith, Matthew (Department: 2825)

Active solid-state devices (e.g., transistors, solid-state diode

Physical configuration of semiconductor

Groove

C257S302000, C257S330000, C257S328000, C257S374000, C257S397000, C438S424000, C438S425000

Reexamination Certificate

active

06355974

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for fabricating semiconductor devices, and more particularly to a method to prevent the formation of a thinner portion of gate oxide at the junction between the side walls and the bottom insulator of a trench type semiconductor device.
2. Description of the prior art
As the design rule continues to shrink, a trench type semiconductor device, for example metal-oxide-semiconductor transistor, has been provided to economize the wafer area.
Referring to
FIGS. 1A through 1C
, the cross-sectional side views of a conventional method for fabricating a gate oxide within a trench are depicted in sequence.
Referring now to
FIG. 1A
, a cross-sectional view of the first step is schematically shown.
FIG. 1A
shows a silicon substrate
10
having a trench
12
. A silicon nitride layer
11
is formed overlaying the silicon substrate
10
.
Next, as shown in
FIG. 1B
, a bottom oxide
16
is deposited on the lower portion of the trench
12
by high density plasma chemical vapor deposition (HPCVD).
Referring now to
FIG. 1C
, a gate oxide layer
18
, or example silicon oxide having a thickness of about 500 angstroms, is grown on the side walls of the trench
12
.
However, the gate oxide layer
18
is naturally thinner at the junction
20
between the side walls and the bottom oxide
16
. This thinner portion will cause junction leakage problems.
SUMMARY OF THE INVENTION
In view of the above disadvantages, an object of the invention is to provide a method to prevent the formation of a thinner portion of oxide layer at the junction between the side walls and the bottom oxide.
It is a further object of the invention to provide a method to avoid junction leakage.
The above objects are attained by providing a method to prevent the formation of a thinner portion of insulating layer suitable for a semiconductor substrate having a trench comprising the steps of: (a) forming a pad insulating layer on the side walls and the bottom of said trench; (b) forming a bottom insulator over said pad insulating layer, said bottom insulator filled within said trench; (c) etching the upper portion of said bottom insulator to form a bottom insulator having a concave surface; and (d) forming an insulating layer on the side walls of said trench.
The above objects are also attained by providing a method to prevent the formation of a thinner portion of oxide layer suitable for a semiconductor substrate having a trench comprising the steps of: (a) forming a bottom insulator having a concave surface on the bottom of said trench; and (b) forming an oxide layer on the side walls of said trench.
An aspect of the invention is to provide a method to prevent the formation of a thinner portion of insulating layer in which said insulating material is oxide material.
Another aspect of the invention is to provide a bottom insulator (oxide) which has a specially shaped surface, especially concave shaped, for growing a conformal gate oxide layer.


REFERENCES:
patent: 4992390 (1991-02-01), Chang
patent: 6071794 (2000-06-01), Lin et al.

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