Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Reexamination Certificate
1998-09-04
2001-01-30
Duda, Kathleen (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
C430S396000, C216S041000, C438S706000
Reexamination Certificate
active
06180321
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for patterning a thin film layer; and, more particularly, to an improved method for patterning a thin film layer by exposing a partial depth of a photoresist layer to a light beam to reduce a minimum line width in the patterned thin film layer.
DESCRIPTION OF THE PRIOR ART
In
FIGS. 1A and 1B
, there are provided schematic cross sectional views illustrating a prior art method for patterning a thin film layer formed on a substrate.
As shown in
FIG. 1A
, the method for patterning the thin film layer
120
begins with the formation of the thin film layer
120
and a photoresist layer
130
on top of a substrate
110
, successively. The thickness of the photoresist layer
130
is determined by the thickness of the thin film layer
120
and a ratio of etching rates between the photoresist layer
130
and the thin film layer
120
. The notation “D” in
FIG. 1A
represents the thickness of the photoresist layer
130
.
The thin film layer
120
made of, e.g., a dielectric material, is deposited on top of the substrate
110
by using, e.g., a chemical vapor deposition(CVD) method; and the photoresist layer
130
made of, e.g., a positive photoresist, is formed on top of the thin film layer
120
by using, e.g., a spin coating method. After the photoresist layer
130
is formed, a photomask
140
is aligned with the photoresist layer
130
at a distance of “S”, wherein the notation “S” in
FIG. 1A
represents a distance between the photomask
140
and the top surface of the photoresist layer
130
. The photomask
140
includes a transmitting region
142
and a non-transmitting region
144
, wherein the transmitting region
142
is made of a light transmitting material, and the non-transmitting region
142
is made of a light non-transmitting material, e.g., Cr. When exposed to a light beam, a portion of the photoresist layer
130
under the transmitting region
142
becomes soluble in an appropriate solution and the remaining portion
132
of the photoresist layer
130
remains insoluble.
The portion of the photoresist layer
130
under the light transmitting region
142
of the photomask
140
is removed by using the appropriate solution, thereby allowing the remaining portion
132
of the photoresist layer
130
to serve as a mask for patterning the thin film layer
120
. Subsequently, a part of the thin film layer
120
which is not covered by the remaining portion
132
of the photoresist layer
130
is removed, by using e.g., an ion milling or a reactive ion etching (RIE), to thereby produce a patterned thin film layer
122
as depicted in FIG.
1
B. In this case, a minimum line width “W” which can be replicated in the patterned thin film layer
122
is given by:
W
=
3
2
λ
(
S
+
D
2
)
wherein &lgr; is the wavelength of the light beam; S, the distance between the photomask
140
and the top surface of the photoresist layer
130
; and D, the thickness of the photoresist layer
130
.
One of the major shortcomings of the above-described method is that it is difficult to decrease the minimum line width “W” when the photoresist layer
130
becomes very thick due to a ratio of etching rates between the photoresist layer
130
and the thin film layer
120
. As shown in the above-described equation, the minimum line width “W” is proportional to the square root of “D”. Therefore, as the “D” increases, the larger the minimum line width “W” becomes larger due to the diffraction of the light beam.
Further, the interface between the photoresist layer
130
and the thin film layer
120
reflects the light beam transmitted through the photoresist layer
130
to the portion
134
of the photoresist layer
130
. Therefore, the portion
134
of the photoresist layer
130
is exposed to the reflected light beam. The portion
134
, which need not be removed, is removed during the process for removing the portion of the photoresist layer
130
under the transmitting region
142
of the photomask
140
, which will, in turn, increase the minimum line width “W”.
SUMMARY OF THE INVENTION
It is, therefore, a primary object of the present invention to provide a method for patterning a thin film layer into a predetermined configuration with a narrow minimum line width.
In accordance with the present invention, there is provided a method for patterning a thin film layer into a predetermined configuration for use in the manufacture of a semiconductor device, the method comprising the steps of: (a) preparing a substrate with the thin film layer, an intermediate layer and a photoresist layer formed thereon, successively; (b) exposing a light beam to a partial depth of the photoresist layer; (c) removing the portion of the photoresist layer exposed to the light beam by using a solution to thereby obtain a patterned photoresist layer; (d) etching the intermediate layer by using the patterned photoresist layer as a mask; and (e) etching the thin film layer into the predetermined configuration by using the etched intermediate layer as a mask.
REFERENCES:
patent: 5905019 (1999-05-01), Obszarny
patent: 2198149 (1988-06-01), None
patent: 2292831 (1996-03-01), None
Daewoo Electronics Co. Ltd.
Duda Kathleen
Pennie & Edmonds LLP
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