Semiconductor device manufacturing: process – Chemical etching – Vapor phase etching
Reexamination Certificate
2000-03-09
2002-05-07
Powell, William A. (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Vapor phase etching
C216S067000, C216S075000, C216S077000, C438S738000, C438S742000
Reexamination Certificate
active
06383942
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-065046, filed Mar. 11, 1999; and No. 11-068052, filed Mar. 15, 1999, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a dry etching method employed for manufacturing a semiconductor device and, more specifically, to a dry etching method for a stacked film of a metal film containing aluminum as a base metal and metal or a metal compound thin film.
Metal wiring is usually formed on a semiconductor substrate using a dry etching method.
FIG. 1
is a cross-sectional view of a semiconductor substrate on which metal wiring is formed.
As illustrated in
FIG. 1
, an insulation film
102
is formed on a semiconductor substrate
101
. The semiconductor substrate
101
is constituted of a semiconductor such as silicon, while the insulation film
102
is constituted of an insulator such as silicon dioxide (SiO
2
). The surface of the insulation film
102
is planarized. Metal wiring is formed on the planarized surface of the insulation film
102
. The metal wiring is electrically connected to lower wiring (not shown), the semiconductor substrate
101
, the gate (not shown) of a MOS transistor, or the like. The metal wiring is also connected to upper metal wiring (not shown) formed on an insulation film
105
. The insulation film
105
is constituted of an insulator such as silicon dioxide (SiO
2
) and formed on the semiconductor substrate
101
so as to coat the metal wiring.
The metal wiring is a stacked film
103
including a metal film
103
a
and a thin film
103
b
formed on the metal film
103
a
. The metal film
103
a
is constituted of metal including aluminum as a base metal and containing copper and silicon as appropriate. The thin film
103
b
is constituted of metal for protecting the metal film
103
a
and improving its reliability as wiring, a metal compound, or a stacked structure of the above metal and metal compound. Titanium and tungsten are selected as the metal, and titanium nitride and tungsten silicide are selected as the metal compound. An example of the stacked structure is shown in FIG.
1
.
Conventionally the metal wiring of the stacked film
103
is formed by the steps shown in
FIGS. 2A
to
2
D.
First, as shown in
FIG. 2A
, a metal film
103
a
containing aluminum as the base metal, a thin film
103
b
, and a reflection preventing film
103
c
are sequentially stacked on the insulation film
102
on the semiconductor substrate
101
to form a stacked film
103
′. The reflection preventing film
103
c
is constituted of materials for preventing light from being reflected toward photoresist, such as an organic compound film containing carbon.
Then, as illustrated in
FIG. 2B
, photoresist is applied onto the stacked film
103
′ to form a photoresist film. Using an exposure technique, a pattern corresponding to the metal wiring is formed on the photoresist film. This photoresist film is developed to form a photoresist pattern
104
having a metal wiring pattern.
As illustrated in
FIG. 2C
, the stacked film
103
′ is subjected to dry etching using the photoresist pattern
104
as a mask. Thus, the stacked film
103
′ is formed as a metal wiring pattern.
As shown in
FIG. 2D
, the photoresist pattern
104
and reflection preventing film
103
c
are removed. Metal wiring is thus formed of a stacked film
103
of the metal film
103
a
and thin film
103
b.
After that, as shown in
FIG. 1
, an insulation film
105
is deposited on the semiconductor substrate
101
.
The dry etching of the stacked film
103
′ including the reflection protection film
103
c
, thin film
103
b
and metal film
103
a
containing aluminum as the base metal, is performed by a gas system including both chlorine gas (Cl
2
) and boron trichloride (BCl
3
). The gas system is usually used for treating an aluminum film. When the stacked film
103
is etched by the gas system containing chlorine gas and boron trichloride, if the flow rate ratio and mixture ratio of the chlorine gas are increased, the thin film
103
b
is etched vertically as shown in FIG.
3
A. However, the metal film
103
a
is side-etched, and the thin film
103
b
overhangs the metal film
103
a
. If the thin film
103
b
overhangs, a void is likely to be caused between adjacent metal films
103
a
when the insulation film
105
is deposited, as shown in FIG.
4
A.
On the contrary, if the flow rate ratio and mixture ratio of the chlorine gas are decreased, the side-etching of the metal film
103
a
is reduced as illustrated in FIG.
3
B. However, the thin film
103
b
is not etched vertically but tapered, and its bottom portion is increased in size. If the bottom portion of the thin film
103
b
is increased in size, the metal film
103
a
is broadened, and a distance D between adjacent metal films
103
a
is narrowed as shown in
FIG. 4B
, with the result that fine metal wiring becomes difficult.
Therefore, a combination of good sides of the above two cases can be considered. The thin film
103
b
is etched partway by increasing the mixture ratio of the chlorine gas and then the metal film
103
a
is etched by decreasing it. If the mixture ratio is so changed partway, it is possible to obtain the advantages that the thin film
103
b
can be etched vertically and the side-etching of the metal film
103
a
can be prevented.
However, usually, the etching rate of the thin film
103
b
and metal film
103
a
is nonuniform within the plane of the semiconductor substrate. Consequently, the above advantages are difficult to obtain uniformly throughout the semiconductor substrate even though the mixture ratio of the chlorine gas is changed partway.
BRIEF SUMMARY OF THE INVENTION
The present invention has been developed in consideration of the above situation and its principal object is to provide a dry etching method capable of patterning a stacked film of a metal film and a thin film, formed on the metal film and including one of metal and a metal compound, in such a manner that the thin film is formed vertically and the metal film is prevented from being side-etched.
To attain the above object, there is provided a method of dry etching comprising: forming a mask layer on a stacked film above a semiconductor substrate, the stacked film including a metal film formed above the semiconductor substrate and containing aluminum as a base component and a thin film formed on the metal film and containing at least one of metal and a metal compound; and patterning the stacked film using the mask layer as a mask for etching, the patterning including: a first step of dry etching the thin film using a first etching gas having a gas composition for preventing the metal film from being processed; and a second step of dry etching the metal film using a second etching gas having a gas composition other than that of the first etching gas.
Another object of the present invention is to provide a dry etching method capable of patterning a stacked film of a barrier layer and a metal film formed on the barrier layer so as to reduce a pattern transfer difference.
To attain the above another object, there is provided a method of dry etching comprising: forming a mask layer on a stacked film above a semiconductor substrate, the stacked film including a barrier layer formed above the semiconductor substrate and a metal film formed on the barrier layer and containing aluminum as a base component; and patterning the stacked film using the mask layer as a mask for etching, the patterning including a step of dry etching the stacked film using an etching gas containing atoms of oxygen.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinatio
Narita Masaki
Sugiura Hiroshi
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Kabushiki Kaisha Toshiba
Powell William A.
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