Fabricating process for polysilicon gate

Details Fabricating process for polysilicon gate Fabricating process for polysilicon gate

1999-10-28

2001-03-13

Pham, Long (Department: 2823)

Semiconductor device manufacturing: process

Coating with electrically or thermally conductive material

Insulated gate formation

C438S299000

Reexamination Certificate

active

06200886

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fabrication process for an integrated circuit. More particularly, the present invention relates to a fabrication process for a polysilicon gate.
2. Description of the Related Art
In general, a gate is formed with polysilicon or other similar types of material. During gate definition, however, polysilicon tends to reflect the light used for the photolithography process and leads to photolithography errors. In the fabrication process of a semiconductor device, an anti-reflection layer is typically formed on the polysilicon layer before defining the gate to avoid the reflection of the light by the polysilicon layer. The anti-reflection layer is usually formed with a silicon oxynitride material and is removed after the gate is defined. Methods to remove the antireflection layer include etching with a hot phosphoric acid solution. The polysilicon, however, is easily corroded by the hot phosphoric acid, resulting in an incomplete gate structure or even a peeling of the gate.
FIGS. 1A
to
1
D are schematic, cross-sectional views showing the manufacturing of a gate structure according to the conventional practice.
Referring to
FIG. 1A
, a substrate
100
is provided, followed by a formation of a layer
101
on the substrate
100
. Since the polysilicon easily reflects the photolithography light and results in photolithography errors in the subsequent definition of the polysilicon gate, a silicon oxynitride anti-reflection layer
103
is normally formed on the polysilicon layer
101
to prevent the reflection of light by the polysilicon layer
101
before defining the polysilicon gate. A photoresist pattern
106
is thereafter formed on the anti-reflection layer
103
.
As shown in
FIG. 1B
, with the photoresist pattern
106
serving as a mask, the anti-reflection layer
103
(as shown in
FIG. 1A
) and the polysilicon layer
101
(as shown in
FIG. 1A
) are etched to form a polysilicon gate
102
on the substrate
100
. The anti-reflection layer after the etching is designated by reference number
104
.
Referring to
FIG. 1C
, the photoresist pattern
106
(as shown in
FIG. 1B
) is removed, exposing the anti-reflection layer
104
.
Referring to
FIG. 1D
, the anti-reflection layer
104
above the polysilicon gate
102
is removed by a hot phosphoric acid solution to complete the formation of the polysilicon gate. The etching rate of the hot phosphoric acid to polysilicon is, however, relatively high, and the sidewall of the polysilicon gate is thereby easily corroded by the hot phosphoric acid, leading to a peeling of the gate.
SUMMARY OF THE INVENTION
Based on the forgoing, the present invention provides a fabrication process for a polysilicon gate. A substrate is provided, and a polysilicon layer and an anti-reflection layer are sequentially formed on the substrate in which the anti-reflection layer is preferably a silicon oxynitride. The anti-reflection layer and the polysilicon layer are then patterned to form a polysilicon gate. After this, thermal oxidation is conducted to form a silicon dioxide layer on the surface of the silicon substrate, the sidewalls of the polysilicon gate and the surface of the anti-reflection layer. Using the anti-reflection layer as an etching stop, the silicon dioxide layer on the anti-reflection layer is etched back and removed, with only enough anti-reflection layer to cover the sidewalls of the polysilicon gate and the surface of the polysilicon substrate. The anti-reflection layer is further removed by the hot phosphoric acid.
The silicon dioxide layer generated in the present invention can provide protection to the sidewall of the polysilicon gate and the silicon substrate during the removal of the anti-reflection layer.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.


REFERENCES:
patent: 5656519 (1997-08-01), Mogami
patent: 5920095 (1999-07-01), Davies et al.
patent: 5956584 (1999-09-01), Wu

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