Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2000-11-22
2004-08-24
Pham, Long (Department: 2814)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S622000
Reexamination Certificate
active
06780752
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly, to a metal thin film of a semiconductor device and method for forming the same in which excellent step coverage and surface roughness are maintained.
2. Background of the Related Art
Generally, a method for forming a metal line of a semiconductor device includes two processes such as a tungsten plug+reactive ion etching (RIE) Al process and an Al plug process. In the tungsten plug process, it is possible to even fill a relatively small sized via so as to improve reliability. However, in this case, process steps are relatively complicate and the production cost is high. On the other hand, the Al plug process has advantages that process steps are simple and the production cost is low, but there is a problem that it is difficult for the Al plug process to apply to a microdevice of high packing density.
A related art metal thin film and method for forming a metal line using the same will be described below.
First, a process for forming a metal line using tungsten plug will be described.
FIGS. 1
a
to
1
e
are sectional views of a related art process for forming a metal line using tungsten plug.
As shown in
FIG. 1
a
, an interleaving insulating film
2
is formed on a semiconductor substrate
1
and then selectively etched to form a contact hole
3
.
Subsequently, as shown in
FIG. 1
b
, a thin barrier metal layer
4
is formed on an entire surface of the semiconductor substrate
1
including the contact hole
3
.
As shown in
FIG. 1
c
, blanket tungsten W is deposited on the contact hole
3
on which the barrier metal layer
4
is formed, by chemical vapor deposition (CVD) process to completely fill the contact hole
3
. Thus, a material layer for the formation of plug, i.e., a tungsten layer
5
is formed. At this time, the tungsten layer
5
fills the contact hole
3
and is also formed on the interleaving insulating film
2
.
Afterwards, as shown in
FIG. 1
d
, the tungsten layer
5
is planarized by chemical mechanical polishing (CMP) process or etch-back process to form a plug layer
5
a.
Finally, as shown in
FIG. 1
e
, an anti-reflective coating (ATC) layer
6
and an Al layer
7
are deposited on the entire surface on which the plug layer
5
a
is formed. Thus, a metal line is formed.
The aforementioned process for forming a metal line using tungsten plug has advantages that currently used equipments are used as they are and that the process technology tested and verified by actual mass production is used. However, the production cost is high ($14.36/wf) and a lot of process steps are required, thereby reducing yield. Also, since blanket deposition process is used, it is likely that void occurs if the size of the contact hole becomes smaller.
Now, a process for forming a metal line using Al reflow will be described.
FIGS. 2
a
to
2
d
are sectional views of a related art process for forming a metal line using Al reflow.
As shown in
FIG. 2
a
, an interleaving insulating film
22
is formed on a semiconductor substrate
21
and then selectively etched to form a contact hole
23
. The contact hole
23
has a wine glass type of which corner portions are rounded, so as to improve filling efficiency of a material for the formation of plug.
Subsequently, as shown in
FIG. 2
b
, a barrier layer and a wetting layer
24
are formed on a surface of the interleaving insulating film
22
including bottom and wall of the contact hole
23
. As shown in
FIG. 2
c
, an Al layer
25
is formed by physical vapor deposition (PVD) process. At this time, the Al layer
25
does not completely fill the contact hole
23
but partially fills the contact hole
23
due to characteristic of the PVD process.
Afterwards, as shown in
FIG. 2
d
, the Al layer
25
is reflowed by annealing process at a temperature of 550° C. or greater, and then is planarized to completely fill the contact hole
23
. Thus, a metal line layer
25
a
of plug+main line structure is formed.
The aforementioned process for forming a metal line using Al reflow has an advantage that the production cost is low. However, there are problems that additional process for forming a contact hole having a shape capable of being filled is required, and aspect ratio of the contact hole is limited. Also, there are still problems that high temperature and low vacuum equipment is required, and line resistance may increase due to high temperature process.
Another related art method for forming a metal line using Al cold-hot deposition will be described with reference to
FIGS. 3
a
to
3
d.
FIGS. 3
a
to
3
d
are sectional views of a related art process for forming a metal line using Al cold-hot deposition.
As shown in
FIG. 3
a
, an interleaving insulating film
32
is formed on a semiconductor substrate
31
and then selectively etched to form a contact hole
33
. The contact hole
33
has a greater top width than a bottom width, so as to improve filling efficiency of a material for the formation of plug.
Subsequently, as shown in
FIG. 3
b
, a barrier layer and a wetting layer
34
are formed on a surface of the interleaving insulating film
32
including bottom and wall of the contact hole
33
. As shown in
FIG. 3
c
, a cold Al layer
35
is formed on the barrier layer and the wetting layer
34
.
Afterwards, as shown in
FIG. 3
d
, a hot Al layer
35
a
is formed at a temperature of 400~550° C. to form a metal line layer of plug+main line structure.
The aforementioned process for forming a metal line using Al cold-hot deposition has advantages that no additional equipment is required because the number of process steps is small and thus the production cost is low. However, there is a problem that aspect ratio of the contact hole is limited. Also, there is a problem that line resistance may increase because relatively high temperature process is required.
Another related art method for forming a metal line using CVD/PVD Al will be described with reference to
FIGS. 4
a
to
4
d.
FIGS. 4
a
to
4
d
are sectional views of a related art process for forming a metal line using CVD/PVD Al.
As shown in
FIG. 4
a
, an interleaving insulating film
42
is formed on a semiconductor substrate
41
and then selectively etched by Ar sputtering process to form a contact hole
43
.
Subsequently, as shown in
FIG. 4
b
, a barrier layer and a nucleation layer
44
are formed on an upper surface of the interleaving insulating film
42
including bottom and wall of the contact hole
43
. The barrier layer is formed by depositing Ti TiN or Ti/TiN by ionized PVD or CVD process.
As shown in
FIG. 4
c
, a CVD Al layer
45
is formed on an entire surface on which the barrier layer and the wetting layer
44
are formed, at a thickness of 1000 Å or less by CVD process.
Afterwards, as shown in
FIG. 4
d
, a PVD Al layer
46
is formed on the CVD Al layer
45
by performing PVD process at a temperature of 350~400° C. to form a plug layer and a main line layer. The CVD Al layer
45
is used as the wetting layer required for reflow of the PVD Al layer
46
. Al is deposited on the CVD Al layer
45
at a relatively high temperature and low power of 5 kW or less by PVD process, so that reflow occurs.
To improve accuracy of a subsequent patterning process, an ARC layer may be formed on the PVD Al layer
46
. Ti/TiN may be used as the ARC layer.
IMP Ti/MOCVD TiN is mainly used as a metal for forming the barrier layer during the PVD/CVD Al line process, due to its excellent via filling characteristic.
The metal deposition by CVD process used in the process for forming a metal line has more excellent via filling characteristic than the PVD reflow and thus many researches using CVD have progressed in Al plug process of a next generation device. Particularly, deposition speed of the aforementioned process using PVD/CVD Al is higher than deposition speed by CVD process only, and an alloying element can be added so that a metal line having high productivity and high reliability can be fabricated. However, there is a pro
Hynix / Semiconductor Inc.
Jacobson & Holman PLLC
Pham Long
Trinh (Vikki) Hoa B.
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