Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Coating moving substrate
Reexamination Certificate
1999-04-22
2001-06-05
Wong, Edna (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Coating moving substrate
C205S157000, C205S159000, C205S205000, C205S224000, C205S118000, C205S123000
Reexamination Certificate
active
06241869
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus for electroplating and a method for electroplating, and particularly it relates to an apparatus for electroplating and a method for electroplating, in-which copper is formed into a film in a semiconductor device by electroplating.
BACKGROUND OF THE INVENTION
With high integration of an LSI (large scale integrated) circuit, internal interconnection is becoming minute and multi-layered. Along with such a tendency, development of a flattening technique on formation of interconnection, and a processing technique for minute interconnection, and maintenance of reliability become important problems. As one of the solutions to these problems, embedded interconnection technique has been investigated. In particular, a copper embedded interconnection technique aiming at high speed operation and low consumption power is receiving attention.
Formation of a copper film by an electroplating method receives attention as a recent method of copper embedding. In this method, a barrier metal layer is formed in a groove or a connecting hole, and then a copper film is formed by an electroplating method using a copper sulfate solution. In this case, a copper film is often formed by a sputtering method or a CVD (chemical vapor deposition) method on the barrier metal layer and used as a glue layer. The electroplating method realizes embedding in a high aspect structure at room temperature.
However, the conventional technique described above involves the following problems. The process of embedding copper in a groove or a connecting hole by electroplating of copper is described below. As shown in
FIG. 1A
, a concave part
112
comprising the groove and the connecting hole is formed in an interlayer insulating film
111
by an ordinary RIE (reactive ion etching) method. As shown in
FIG. 1B
, a barrier metal layer
113
is formed on the inner wall of the concave part
112
and on the interlayer insulating film
111
by forming, for example, a titanium film and a titanium nitride film, as a laminated film, in this order from the lower layer, for example, by a sputtering method, and then a glue layer
114
is further formed thereon. At this time, the barrier metal layer
113
and the glue layer
114
are formed at the opening parts of the concave part
112
in the form of overhang.
As shown in
FIG. 1C
, because the coverage of the barrier metal layer
113
and the glue layer
114
on the concave part
112
does not become 100%, the resistance of the barrier metal layer
113
and the glue layer
114
is increased at these parts. Under the circumstances, when electroplating is conducted by immersing in a copper electroplating solution
121
, current concentration occurs at the opening part (shown by arrows in the figure). The rate of the film formation is thus increased at the part at which current concentration occurs. A bubble
115
is formed inside the concave part
112
. As a result, a copper film
116
is formed with a void
115
forming inside the concave part
112
, as shown in FIG.
1
D. In
FIG. 1C
, the figure is drawn with the upper surface of the interlayer insulating film
111
being downward on the contrary to the other figures.
FIG. 2
is a schematic cross sectional view showing the voids actually formed on producing a copper film by electroplating. As shown in
FIG. 2
, it has been found that the copper film
116
is grown in the condition that the voids
115
are formed over the interior to the upper part of the concave parts (grooves)
112
formed in the interlayer insulating film
111
.
In the electroplating apparatus
120
for a wafer currently available as shown in
FIG. 3
, in order to prevent the back surface of the wafer
110
from contacting with a plating solution (containing copper ions)
121
, a face-down structure is employed in that the front surface of the wafer
110
faces the plating solution
121
. The plating solution is stored in a plating bath
122
, and an anode
123
is provided in the plating solution
121
.
In the method described above, there is a case where the plating solution
121
cannot be spread into minute parts formed on the surface of the wafer
110
as shown in FIG.
4
A. That is, there is a case where a bubble
117
remains inside the concave part (for example, a groove)
112
. When electroplating is conducted under such conditions, the copper film
116
is grown in the condition in that the bubble
117
remains and a void
115
is formed inside the concave part
112
, as shown in FIG.
4
B.
It has been reported by Y. Harada, et al. in
Preprints of
58
th Shuki Gakujutu Koenkai of the Japan Society of Applied Physics
, 3p-E-4, p. 776 (1997) that the void thus formed is avoided by subjecting to a heat treatment at about 400° C. However, a void generated by forming a film by electroplating contains air as different from a void generated by sputtering under high vacuum. Since the air contains about 20% of oxygen, there is a possibility that the surroundings of the void are oxidized, and increase in resistance and deterioration of reliability may occur.
SUMMARY OF THE INVENTION
The invention relates to an apparatus for electroplating and a method for electroplating that solve the problems described above, and in the apparatus for electroplating, a plating bath is provided in a non-oxidative atmosphere, such as a rare gas atmosphere, a nitrogen gas atmosphere and a hydrogen gas atmosphere.
Because the plating bath is provided in a non-oxidative atmosphere in the apparatus for electroplating, even when a bubble invades into the minute part, such as a groove and a connecting hole, of the article to be plated on immersing the article into a plating solution in the plating bath, so as to form a plated layer with the bubble becoming a void, the void contains a non-oxidative gas but does not contain oxygen. Therefore, the plated layer is not oxidized when the gas contained in the void is absorbed by the plated layer by subjecting the plated layer to the heat treatment to disappear the void. Thus, increase in resistance and deterioration of reliability in the plated layer do not occur.
In the method for electroplating according to the invention, an article to be plated is immersed in a plating solution through a non-oxidative atmosphere, such as a rare gas atmosphere, a nitrogen gas atmosphere and a hydrogen gas atmosphere.
Because the article to be plated is immersed in the plating solution through the non-oxidative atmosphere, even when a bubble invades into the minute part, such as a groove and a connecting hole, of the article to be plated on immersing the article into a plating solution, so as to form a plated layer with the bubble becoming a void, the void does not contain oxygen. Therefore, the plated layer is not oxidized when the gas contained in the void is absorbed by the plated layer by subjecting the plated layer to the heat treatment to cause the void to disappear. Thus, increase in resistance and deterioration of reliability in the plated layer do not occur.
REFERENCES:
patent: 5273642 (1993-12-01), Crites et al.
patent: 5763953 (1998-06-01), Iijima et al.
patent: 4-131395 (1992-05-01), None
Kananen Ronald P.
Rader Fishman & Grauer
Sony Corporation
Wong Edna
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