Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2002-12-26
2004-07-06
Gurley, Lynne (Department: 2812)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S627000, C438S629000, C438S631000, C438S633000, C438S636000, C438S637000, C438S638000, C438S643000, C438S645000, C438S648000, C438S653000, C438S656000, C438S672000, C438S687000, C438S692000, C438S700000, C438S906000, C438S952000, C438S959000
Reexamination Certificate
active
06759322
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming a wiring structure in a semiconductor device.
As a conventional method for forming a wiring structure, there has been used one disclosed in, e.g., Japanese Laid-Open Patent Publication No. HEI 10-214834. Referring to the drawings, the conventional method for forming a wiring structure will be described by using, as an example, the case where plugs are formed in holes formed in an insulating film.
FIGS. 9A
to
9
C are cross-sectional views illustrating the individual process steps of the conventional method for forming a wiring structure.
First, as shown in
FIG. 9A
, a silicon dioxide film
12
having a thickness of about 1 &mgr;m is deposited as an insulating film on a silicon substrate
11
. Then, holes
13
each having a diameter of about 0.8 &mgr;m are formed by lithography and dry etching in specified regions of the silicon dioxide film
12
to extend therethrough.
Next, a titanium film
14
having a thickness of 30 nm and serving as a lower-layer conductive film and a titanium nitride film
15
having a thickness of 100 nm and serving as an interlayer conductive film are deposited successively by PVD (physical vapor deposition) over the entire surface of the silicon dioxide film
12
including the holes
13
. Thereafter, a tungsten film
16
having a thickness of 1 &mgr;m and serving as an upper-layer conductive film is deposited by CVD (chemical vapor deposition) over the entire surface of the titanium nitride film
15
, whereby a conductive film having a three-layer structure is deposited. In the three-layer conductive film, each of the titanium film
14
and the titanium nitride film
15
is a barrier metal.
Next, the respective portions of the tungsten film
16
and the titanium nitride film
15
deposited on regions outside the holes
13
are removed by chemical mechanical polishing (CMP) using an abrasive agent, as shown in FIG.
9
B. This completely exposes the portions of the titanium film
14
deposited on the regions outside the holes
13
.
Next, the portions of the titanium film
14
deposited on the regions outside the holes
13
are removed by CMP using another abrasive agent, as shown in FIG.
9
C. This forms plugs
17
composed of tungsten in the holes
13
and exposes the silicon dioxide film
12
.
Although the formation of tungsten plugs has been described above by way of example, it is also possible to form, e.g., copper wires in wiring grooves formed in an insulating film by the same method.
With the scaling down of a wiring pattern, the spacing between adjacent wires (wire-to-wire spacing) has been reduced increasingly so that an anti-reflection layer (hereinafter referred to as ARL) has been used in a lithographic step for forming wiring grooves, via holes, and the like.
However, the formation of wires using an ARL film based on the foregoing conventional method for forming a wiring structure has the problem that a short circuit occurs between wires.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to prevent a short circuit between wires buried in an insulating film and in an ARL film on the insulating film.
To attain the object, the present inventors have examined causes for the short circuit occurring between the wires in the conventional method for forming a wiring structure and made the following finding.
In forming wires in accordance with the conventional method for forming a wiring structure, a barrier metal under polishing locally peels off to form a foreign matter. Since the foreign matter is hard, if an ARL film composed of a material more fragile than an insulating film present between wires has been formed on the insulating film, the foreign matter causes a microcrack in a surface of the ARL film. In the case where the microcrack extends from one wire to another wire adjacent thereto, if a metal (the barrier metal or a conductive film) is buried in the microcrack during the formation of wiring, a short circuit occurs between the wires.
Since the spacing between wires is reduced as the wiring structure is scaled down, the microcrack mentioned above is more likely to extend between the adjacent wires so that the metal buried in the microcrack is more likely to form a pseudocross-linking structure between the wires. As a result, a short circuit is more likely to occur between the wires.
FIG. 10
is a plan view showing the metal buried in the microcrack caused in the ARL film between the wires. As shown in
FIG. 10
, a plurality of copper wires
22
are buried in an ARL film
21
in such a manner as to extend in parallel with each other. A crack
23
has been formed in the ARL film
21
between the copper wires
22
in such a manner as to extend therebetween. Copper was buried in the crack
23
during the formation of the copper wires
22
so that a short circuit occurs between the copper wires
22
.
The present invention has been achieved in view of the foregoing finding. Specifically, a method for forming a wiring structure according to the present invention comprises: a groove forming step of forming an anti-reflection film on an insulating film and then forming, in each of the anti-reflection film and the insulating film, a first groove and a second groove adjacent to the first groove; a film depositing step of depositing a barrier metal film and a conductive film on the anti-reflection film such that each of the first and second grooves is filled therewith; a first polishing step of removing the portion of the conductive film outside the first and second grooves by polishing; a second polishing step of removing, after the first polishing step, the portion of the barrier metal film outside the first and second grooves by polishing; a foreign matter removing step of removing a foreign matter adhered to a surface to be polished after the second polishing step in the second polishing step therefrom; and a third polishing step of polishing, after the foreign matter removing step, a surface of the anti-reflection film.
In the method for forming a wiring structure according to the present invention, the barrier metal film and the conductive film are buried in the grooves formed in the insulating film and in the anti-reflection film on the insulating film and then the respective portions of the conductive film and the barrier metal film outside the grooves are removed by polishing. Thereafter, the foreign matter adhered to the surface to be polished during polishing is removed and then the surface of the anti-reflection film is polished. This achieves the following effects if a microcrack is formed in the surface of the anti-reflection film present between the grooves (i.e., between wires) during the polishing of the barrier metal film and a metal is buried in the microcrack. Since final polishing is performed with respect to the surface of the anti-reflection film after the foreign matter adhered to the surface to be polished during the polishing of the barrier metal film or the like is removed therefrom, it is possible to remove the metal buried in the microcrack, while preventing new damage caused by the foreign matter to the surface of the anti-reflection film. This allows the situation in which the metal buried in the microcrack causes cross-linking between the wires to be circumvented and thereby reduces the frequency of short circuits occurring between the wires. As a result, high-performance wiring can be formed.
Preferably, the method for forming a wiring structure according to the present invention further comprises, between the second and third steps, the step of removing a foreign matter adhered to a polishing pad used in the second polishing step therefrom.
The arrangement more reliably prevents damage to the surface of the anti-reflection film if the polishing pad used in the second polishing step (polishing of the barrier metal film) is used in the third polishing step (polishing of the anti-reflection film). In this case, if the step of removing the foreign matter adhered to the polishing pad therefrom includes the step
Hamanaka Masashi
Harada Takeshi
Ueda Tetsuya
Yoshida Hideaki
Gurley Lynne
McDermott & Will & Emery
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