Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1999-10-01
2001-07-24
Fourson, George (Department: 2823)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S625000, C438S626000, C438S627000, C438S648000, C438S656000, C438S976000, C438S688000
Reexamination Certificate
active
06265305
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of preventing corrosion of a titanium layer in a semiconductor wafer.
2. Description of the Prior Art
A dielectric layer is normally positioned between the MOS (Metal Oxide Semiconductor) transistor and each of the metal conducting wire in a semiconductor wafer for separating and protecting the components in the semiconductor wafer. In order to successfully connect these components in the MOS to each of the metal conducting wire so as to form a complete electronic device, a contact plug formed in the dielectric layer is necessary to be used as a conducting wire between the MOS and each corresponding metal conducting wire. Therefore, just how to upgrade the quality of process for manufacturing the contact plug and the metal wire layer has become an important subject matter in the study of the process for manufacturing the semiconductor.
Please refer to FIG.
1
and FIG.
2
. FIG.
1
and
FIG. 2
are the prior art's schematic diagrams of the manufacturing process of the contact plug
24
of the semiconductor wafer
10
. The semiconductor wafer
10
comprises a bottom conducting layer
12
and a dielectric layer
14
positioned at the top of the bottom conducting layer
12
. As shown in
FIG. 1
, conventional process for manufacturing the contact plug
24
is first to perform photolithography and etching processes in order to form a contact hole
16
, then to deposit in sequence, on the surfaces of the semiconductor wafer
10
and the contact hole
16
, a titanium layer
18
, a TiN (titanium nitride) layer
20
, and a conducting layer
22
composed of tungsten. Thereafter, as shown in
FIG. 2
, by the use of CMP(Chemical Mechanical Polishing)process to perform a surface treatment on the semiconductor wafer
10
to uniformly remove the conducting layer
22
, the TiN layer
20
, and the titanium layer
18
on the surface of the dielectric layer
14
in order to form a contact plug
24
, and in the mean time, to cut the top of the contact plug
24
to be at the same level as that of the dielectric layer
14
.
Please refer to FIG.
3
and FIG.
4
. FIG.
3
and
FIG. 4
are the prior art's schematic diagrams of the manufacturing process of the metal wire
40
of the semiconductor wafer
10
. After completing the fabrication process of the contact plug
24
, a normal metallization process continues to manufacture the metal wire
40
such that the bottom conducting layer
12
connects to the other components in the semiconductor wafer
10
through the contact plug
24
and the metal wire
40
to gradually form a complete circuit. The conventional way of fabricating the metal wire
40
is first to uniformly deposit, on the surface of the dielectric layer
14
and the top of the contact plug
24
, a titanium layer
26
and a protecting layer
28
composed of TiN, it then to form in sequence, on the protecting layer
28
, an aluminum conducting layer
30
and an anti-reflective coating layer
32
composed of TiN, in the mean time, to define and form the pattern of metal wire
40
by the use of the photolithography and etching processes.
As shown in
FIG. 4
, while fabricating the metal wire
40
, misalignment of the metal wire
40
often occurs due to the limitation of the manufacturing techniques or other factors, that is to say, the patterned photoresist layer
34
used for defining the metal wire
40
is unable to completely cover right at the top of the contact plug
24
even though there is a certain tolerance range in this metal misalignment phenomenon, in other words, only a portion of the metal wire
40
covers on top of the contact plug
24
.
Since only a portion of the metal wire
40
covers on top of the contact plug
24
, a portion of the conducting layer
22
and titanium layer
26
will be exposed on the surface of the semiconductor wafer
10
. And since the tungsten's chemical potential is higher than that of the titanium, the titanium layer
26
on the titanium-tungsten interface
38
is subject to be corroded by the photoresist stripper solution during the upcoming photoresist stripping process of the photoresist layer
34
. As a result, the corrosion situation will decrease the contact area between the metal wire
40
and the contact plug
24
and increase the resistance of the contact plug
24
or increase the contact resistance between the contact plug
24
and the metal wire
40
, or it will even cause a serious result of disconnection of the circuit.
SUMMARY OF THE INVENTION
Therefore, the primary objective of the present invention is to provide a method of preventing corrosion of a titanium layer in a semiconductor wafer to effectively resolve the problem that the joint interface between the metal wire and the contact plug positioned underneath is exposed to the photoresist stripper solution such that the titanium layer is subject to be corroded due to the electrochemical reaction.
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patent: 5776831 (1998-07-01), Padmanabhan et al.
patent: 5846613 (1998-12-01), Neuville
patent: 6051281 (2000-04-01), Kobayashi et al.
patent: 6063703 (2000-05-01), Shinriki et al.
patent: 6069073 (2000-05-01), Kim et al.
patent: 6083825 (2000-07-01), Lin et al.
patent: 6130154 (2000-10-01), Yokoyama et al.
patent: 6136697 (2000-10-01), Wu
patent: 883172 A1 (1997-06-01), None
patent: 8288390 (1996-11-01), None
Chou Yu-Jen
Hu Cheng-Shun
Tsou Shih-Fang
Estrada Michelle
Fourson George
Hsu Winston
United Microelectronics Corp.
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