Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Of specified material other than unalloyed aluminum
Reexamination Certificate
2001-03-07
2004-01-20
Coleman, W. David (Department: 2823)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Of specified material other than unalloyed aluminum
C257S762000, C427S126600
Reexamination Certificate
active
06680540
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device and method of production thereof; and, more particularly, the invention relates to a semiconductor device which has a wiring structure made of copper, a basic wire protective film around said copper wiring, namely, covering the top of the copper wiring, and a barrier film surrounding the side and bottom of said copper wiring.
Improvement of the operation speed of a semiconductor device is required to achieve high integration and advanced operating capabilities. This requirement is accompanied by progress in miniaturization of LSI internal wiring and an increase in the number of layers. Miniaturization of wiring and an increase in the number of layers will cause the wiring resistance and the inter-wiring capacity to be increased and will affect the signal transfer speed in the wiring. Since an increase in the signal transfer speed is subjected to restrictions due to this delay time, the dielectric constant of the inter-layer insulation film is reduced to decrease the inter-wiring capacity. At the same time, the operation speed is improved by reducing the wiring resistance by use of a wiring material of lower resistance.
Therefore, studies have been made on the feasibility of using copper having a low specific resistance of 1.7 &mgr;&OHgr;cm as wiring material. As a technique to form copper wiring, the Dual Damasscene method is attracting attention. An example of this method will be described with reference to FIGS.
10
(
a
) to
10
(
h
).
FIG.
10
(
a
) shows a substrate formed of a lower layer wiring layer
10
a
having a lower layer wiring
2
b
in this example and provided with wire protective film
8
characterized by high insulation on all sides. An insulation film
4
is formed on this substrate, as seen in FIG.
2
(
b
), and a wiring groove
7
to embed wiring and a connection hole
10
to connect between upper and lower wiring are formed in said insulation film
4
, as seen in FIG.
10
(
c
). Since an insulating wire protective film
8
is located between the lower layer wiring layer
10
a
and the insulation film
4
, the wire protective film
8
can be removed from the bottom of the connection hole
10
. After barrier layer
3
has been formed on the surface of both the wiring grooves
7
and the connection hole
10
, as seen in FIG.
10
(
d
), a seed layer
5
is formed thereon, as seen in FIG.
10
(
e
). Then, the wiring grooves
7
and the connection hole
10
are filled with wiring material
6
, as seen in FIG.
10
(
f
). Next, CMP (Chemical Mechanical Polishing) is used to remove the excess portion of the wiring material
6
, and wiring plug
11
in the wiring
2
and connection hole
10
of the upper layer are formed simultaneously, as seen in FIG.
10
(
g
). Then a wire protective film
8
is formed so as to cover the wiring
2
and insulation layer
4
, as seen in FIG.
10
(
h
). This Dual Damasscene method allows the wiring
2
and wiring plug
11
to be formed at one time, thereby ensuring a substantial reduction of the process cost.
Incidentally, copper reacts with insulation film
4
and is diffused in the insulation film. To ensure good wiring reliability, the insulating wire protective film
8
and barrier film
3
must be provided between the copper wiring
2
and the insulation film
4
, as described above. Conventionally, a metal nitride, such as titanium nitride, tantalum nitride and tungsten nitride, which are capable of preventing copper diffusion, metals of high melting point, such as tantalum and tungsten and alloys thereof, have been used as a barrier film
3
. In the meantime, an insulating silicon nitride film (SiN) has been used as the wire protective film
8
on the copper wiring
2
.
However, SiN has a specific dielectric constant of 7.0 to 9.0. It has a dielectric constant twice that of an insulation film of SiO
2
, for example. Hence, it has been hindering reduction in the inter-wiring electric capacity in an extremely fine wiring pattern. To solve this problem, the electric capacity can be reduced by formation of a conductive film serving as a wire protective film on the top surface of the wiring.
U.S. Pat. No. 5,695,810 discloses that a cobalt-tungsten-phosphorus conducting film is formed by electroless plating as a wire protective film. In cobalt-tungsten-phosphorus electroless plating, sodium hypophosphite is commonly used as a reducing agent. Sodium hypophosphite is a known inert reducing agent without reaction occurring on copper which cannot be plated directly on copper (e.g. G. 0. Mallory, J. B. Hajdu, “Electroless Plating—Fundamentals & Applications”, American Electroplaters And Surface Finishers Society, Florida, Page 318, 1990). Hence, a cobalt-tungsten-phosphorus film must be formed by electroless plating after a seed layer, such as palladium, has been applied on the copper wiring. In this case, however, the palladium may react with the copper constituting the wiring layer to increase the copper resistance. Further, palladium may deposit on the insulation other than the wiring, so that a cobalt-tungsten-phosphorus film may be formed on the insulation other than wiring. Therefore, this involves a problem of reducing inter-wiring insulation required when producing fine wiring.
Furthermore, Japanese Official Patent Gazette 16906/1999 discloses the use of cobalt-containing electroless plating as an antioxidant film. However, the cobalt-containing film obtained from said method has an insufficient prevention capacity for a copper diffusion preventive film. If heat treatment is carried out in a semiconductor device forming process or after formation, copper diffuses into the SiO
2
via the cobalt-containing film.
Japanese Official Patent Gazette 120674/1994 discloses that, in the production of the circuit substrate, an intermediate metallic film consisting of tungsten-cobalt-boron alloy as main component is formed on the surface of the wiring board provided with a wiring conductor and is coated with a circuit conductor composed of copper. However, the intermediate metallic film consisting of tungsten-cobalt-boron alloy as a main component is intended to increase the close adhesion between the wiring connector of tungsten or molybdenum on the circuit substrate surface and the circuit conductor of copper formed on the surface thereof; it does not function as a wire protective film between the copper wiring and insulation.
As described above, SiN which has been used as a wire protective film is an insulating material, and it has a high specific dielectric constant. It has been a factor hindering reduction of the inter-wiring electric capacity. To solve this problem, a wiring protective film can be formed with a metallic material allowing electric capacity to be reduced. However, metal nitrides, such as titanium nitride, tantalum nitride and tungsten nitride, which have been used as a wire protective film, and metals having a high melting point, such as tantalum and tungsten and alloys thereof, cannot be formed on the copper wiring alone on a selective basis. To avoid short circuiting between wires, such complicated processes as patterning and etching are required. This will cause deterioration in wiring formation accuracy and reliability. Thus, the following two issues must be solved in order to form a wire protective film with metallic materials:
(i) To ensure copper wiring reliability, it is necessary to form a metallic material capable of preventing copper diffusion without allowing the copper wiring to be oxidized in heat treatment.
(ii) Metallic material specified in (i) must be formed on the copper wiring alone on a selective basis.
A forming method meeting these two requirements must be provided. When a metal nitride, such as titanium nitride, tantalum nitride and tungsten nitride, or a metal having a high melting point, such as tantalum and tungsten or the alloy thereof, is used as a barrier film, a seed layer must be formed in order to provide copper plating because of high resistance. Especially, if the barrier film capable of working as a po
Akahoshi Haruo
Itabashi Takeyuki
Nakano Hiroshi
LandOfFree
Semiconductor device having cobalt alloy film with boron does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Semiconductor device having cobalt alloy film with boron, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Semiconductor device having cobalt alloy film with boron will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3194716