Cleaning and liquid contact with solids – Processes – Including application of electrical radiant or wave energy...
Reexamination Certificate
1999-09-07
2001-08-28
Mills, Gregory (Department: 1763)
Cleaning and liquid contact with solids
Processes
Including application of electrical radiant or wave energy...
C438S238000, C438S382000, C438S751000, C438S754000, C438S705000, C216S087000, C216S101000
Reexamination Certificate
active
06279585
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an etching method particularly for forming a wiring pattern, a barrier metal or the like made of tungsten or its alloy.
2. Description of the Related Art
For example, a thin film resistor made of CrSi or the like adopts a sandwich structure as an electrode structure in which a barrier metal is sandwiched between an Al thin film and a thin film resistor to prevent mutual diffusion therebetween. Accordingly, its characteristics is prevented from deteriorating due to the mutual diffusion.
When such a barrier metal is formed by dry-etching which cannot provide a sufficient selective ratio between the barrier metal and the thin film resistor, the thin film resistor exposed by over-etching is easily etched. Generally, since the thin film resistor has a thin thickness of approximately 10 nm, the etching of the thin film resistor greatly changes characteristics such as a value of resistance thereof. Therefore, the barrier metal needs to be formed by wet-etching which can provide a sufficient etching selective ratio.
The wet-etching of the barrier metal, however, may produce residues which can interrupt the patterning of the thin film resistor and cause short-circuit to a wiring pattern. These problems are more specifically explained referring to
FIGS. 17A
to
17
C, and
18
A to
18
E which show patterning processes of the sandwich structure composed of the Al thin film, the barrier metal, and the thin film resistor. The patterning process shown in
FIGS. 17A
to
17
C are different from that shown in
FIGS. 18A
to
18
E.
FIGS. 17A
to
17
C shows a case where the thin film resistor is patterned after the barrier metal is patterned, while
FIGS. 18A
to
18
E shows a case where the thin film resistor is patterned before the barrier metal is patterned.
When the process shown in
FIGS. 17A
to
17
C is adopted, first, as shown in
FIG. 17A
, a CrSi film
102
for forming the thin film resistor and a TiW film
103
for forming the barrier metal are deposited on an insulation film
101
in sequence. After that, as shown in
FIG. 17B
, the TiW film
103
is patterned using a resist
104
as a mask to form the barrier metal. At that time, a residue
103
a
of TiW remains on the CrSi film
102
. As shown in
FIG. 17C
, when the thin film resistor is patterned by, for example, chemical dry-etching to have a defined shape, the residue
103
a
adversely affects the patterning.
Meanwhile, when the process shown in
FIGS. 18A
to
18
E is adopted, first, as shown in
FIG. 18A
, a 1st Al
202
is formed on an insulation film
201
, and a thin film resistor
204
is formed adjacently to the 1st Al
202
through an insulation film
203
. After that, as shown in
FIG. 18B
, a TiW film
205
for forming the barrier metal and an Al thin film
206
are deposited in sequence. As shown in
FIG. 18C
, the Al thin film layer
206
is patterned using a resist
207
as a mask. Further, as shown in
FIG. 18D
, the TiW film
205
is patterned to form the barrier metal. At that time, a residue
205
a
of TiW remains on the thin film resistor
204
and on the insulation film
203
. Therefore, as shown in
FIG. 18E
, when a wiring pattern
209
is formed through an insulation film
208
, the wiring pattern
209
may be short-circuited by the residue
205
a.
It is not easy to remove the residues
103
a
,
105
a
by lengthening the etching time and/or by changing etching conditions such as a temperature of etching solution. For example, when the etching time is lengthened, the resist as the patterning mask is separated to deteriorate a patterning accuracy.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above problems. An object of the present invention is to completely remove a specific portion of a thin film including tungsten without remaining a residue thereof. Another object of the present invention is to provide a method for manufacturing a semiconductor device, in which a thin film resistor is stably performed and a wiring pattern is not short-circuited by eliminating effects caused by a residue produced when an electrode material is patterned.
According to a first aspect of the present invention, a specific region of a thin film including tungsten is removed by an alkaline solution after the specific region is oxidized. As a result, the specific region can be completely removed.
According to a second aspect of the present invention, after an electrode material including tungsten is patterned to produce a residue, the residue is oxidized and then is removed.
According to a third aspect of the present invention, in a method for forming a semiconductor device, a residue, which is produced when a barrier metal film for forming a barrier metal is patterned, is removed after the oxidation thereof. Accordingly, the residue can be completely removed. A thin film resistor film underlying the barrier metal film may be patterned for forming a thin film resistor before the barrier metal film is patterned. Otherwise, the thin film resistor film may be patterned after the residue is removed. In this case, the patterning of the barrier metal film can be stably performed without being adversely affected by the residue.
Preferably, the barrier metal film is patterned by wet-etching to produce the residue. The barrier metal film can be patterned through a resist provided on the barrier metal film and serving as a mask. In this case, the resist and the residue can be removed at the same time, resulting in a simplified manufacturing process. The resist may be removed separately from the residue.
An insulation film can be formed to cover the barrier metal and the thin film resistor after the residue is removed, and a wiring pattern can be formed on the insulation film to communicate with the barrier metal through a contact hole in the insulation film. In this case, because the residue does not remain, the wiring pattern is not short-circuited by the residue.
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patent: 5043295 (1991-08-01), Ruggerio et al.
patent: 5334332 (1994-08-01), Lee
patent: 5382916 (1995-01-01), King et al.
patent: 5420063 (1995-05-01), Maghsoudnia et al.
patent: 5503878 (1996-04-01), Suzuki et al.
patent: 5525831 (1996-06-01), Ohkawa et al.
patent: 5989970 (1999-11-01), Ohkawa et al.
patent: 2-058259 (1990-02-01), None
patent: 7-202124 (1995-08-01), None
patent: 7-335831 (1995-12-01), None
patent: 8-250462 (1996-09-01), None
patent: 10-022452 (1998-01-01), None
patent: 10-144866 (1998-05-01), None
Ohkawa Makoto
Shiraki Satoshi
Denso Corporation
Goudreau George
Mills Gregory
Pillsbury & Winthrop LLP
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