Method of etching a layer

Details Method of etching a layer Method of etching a layer

1999-03-10

2001-09-18

Utech, Benjamin L. (Department: 1765)

Semiconductor device manufacturing: process

Chemical etching

Vapor phase etching

C438S905000, C438S906000, C438S963000, C134S001000

Reexamination Certificate

active

06291360

ABSTRACT:

This application claims the benefit of Korean Patent Application No. 98-10465, filed on Mar. 26, 1998, which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a thin film transistor in a liquid crystal display and, more particularly, to a method of precisely etching a layer when fabricating a thin film transistor in liquid a crystal display.
2. Discussion of the Related Art
FIG. 1A
to
FIG. 1C
show cross-sectional views of a method of etching a layer according to a related art.
Referring to
FIG. 1A
, a layer
13
is formed by depositing a material, for example amorphous silicon, polycrystalline silicon, metal, silicon oxide, silicon nitride or the like on a substrate
11
by conventional fabrication processes, for example by chemical vapor deposition (CVD) or sputtering. The substrate
11
may be one of a number of materials, for instance transparent glass, a wire or an insulating layer on glass. The layer has an exposed surface
12
opposite the surface in contact with the substrate
11
.
The surface
12
of the layer
13
is coated with photoresist, and a photoresist pattern
15
is defined by exposure and development to cover a predetermined portion of the surface of the layer. Commonly, an etch-resistant residue
17
is left on the surface
12
of the layer
13
outside the predetermined region. The residue
17
can be an undesireable by-product of the photoresist definition process, or it may result from adhesion of materials not intentionally introduced into the process, such as organic material present in the atmosphere.
Referring to
FIG. 1B
, a patterned layer
19
is formed by pattering the surface of the layer not covered by photoresist. Patterning processes include wet etch and dry etch, also called plasma etch. In each case, the photoresist pattern
15
acts as an etch mask.
Referring to
FIG. 1C
, the photoresist pattern
15
remaining on the now-patterned layer
19
and the residue
17
are removed.
Unfortunately, the related art is unable to provide a precisely patterned layer, e.g., a layer where all regions of the layer outside the predetermined region have been etched away. The presence of the unetched residue acts as an unintentional etch mask, causing undesired layer pattern artifacts to occur. Accordingly, there is a need for a method of precisely and completely etching a layer which prevents unintentional pattern artifacts from occuring due to the presence of undesired residues.
SUMMARY OF THE INVENTION
The present invention is directed to a method of precisely and completely etching a layer that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a substantially residue-free etch surface in the area not intentionally covered by photoresist to allow precise etching of the desired pattern.
Additional features and advantages of the invention will be set forth in the description which follows and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as in the appended drawings.
To achieve the objects and in accordance with the purpose of the invention, as embodied and broadly described herein, a method of etching a layer on a substrate includes the steps of defining a photoresist pattern on a predetermined region of the layer surface, wherein an etch-resistant residue is left on at least a portion of the layer surface outside the predetermined region, removing the residue by plasma ashing, and patterning the layer with an etchant where the photoresist pattern acts as an etch mask.
In another aspect of the invention, the method includes the steps of defining a photoresist pattern on a predetermined region of the layer surface, wherein an etch-resistant residue is left on at least a portion of the layer surface outside the predetermined region, removing the residue by plasma ashing in a system having a pressure lower than atmospheric pressure, and patterning the layer by plasma etching where the photoresist pattern acts as an etch mask. In this embodiment, the ash and etch steps are performed sequentially in the same pump-down in a plasma ash/etch system.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.


REFERENCES:
patent: 5356478 (1994-10-01), Chen et al.
patent: 5674357 (1997-10-01), Sun et al.
patent: 6033993 (2000-03-01), Love, Jr. et al.

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