Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1999-11-03
2001-10-30
Bowers, Charles (Department: 2812)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S637000, C438S638000, C438S645000, C438S668000, C438S672000, C438S685000, C438S687000, C438S688000, C438S692000, C438S700000
Reexamination Certificate
active
06309961
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a method of polishing a metal film which is used for forming damascene wirings or conductors by polishing a metal film formed on an insulating film having trenches thereon by using a CMP (Chemical Mechanical Polishing) method. More particularly, the present invention relates to a method of polishing a metal film in which excess polishing, that is, dishing, of buried conductors having large area occurring when the metal film is polished by the CMP method can be restrained.
BACKGROUND OF THE INVENTION
Recently, in a manufacturing process of a semiconductor device, damascene wirings or buried wirings are often fabricated by forming a metal film on an insulating film having trenches thereon such that the trenches are filled with the material of the metal film and by polishing the metal film by using the CMP method.
FIG.
4
A through
FIG. 4C
are schematic cross sectional views illustrating a conventional method of polishing a metal film to form such a damascene wiring.
In this method, as shown in
FIG. 4A
, a groove or a trench
33
is formed in an insulating film
32
, such as an oxide film and the like, formed on a semiconductor substrate
31
by using photolithography and etching, and the like. In the drawings, only one trench is shown for the sake of simplicity. However, in practice, it is possible to form many trenches and, therefore, many damascene wirings simultaneously. Then, as shown in
FIG. 4B
, a metal film
36
is formed on the insulating film
32
such that the trench
33
is filled with the material of the metal film
36
. Thereafter, as shown in
FIG. 4C
, the metal film
36
is polished by the CMP method until the insulating film
32
is exposed. Thereby, a buried wiring, that is, the damascene wiring
37
, which comprises a portion of the metal film
36
remaining in the trench
33
is formed.
However, in the above-mentioned conventional method, as the width of the trench
33
becomes large, the portion of the metal film
36
buried in the trench
33
is overpolished in the vicinity of the central portion of the trench
33
. Thereby, as shown in
FIG. 4C
, a recessed portion is produced on the upper surface of the damascene wiring
37
.
Japanese patent laid-open publication No. 9-8039 discloses a method of forming a buried wiring which can improve the disadvantage of the above-mentioned conventional method of forming a damascene wiring.
FIG.
5
A through
FIG. 5C
illustrate a method of forming a buried wiring disclosed in Japanese patent laid-open publication No. 9-8039. First, as shown in
FIG. 5A
, trenches
43
are formed in an insulating film
42
formed on a semiconductor substrate
41
by using photolithography and etching. In this case, island patterns
44
comprising portions of the insulating film
42
are left in the trenches
43
.
Then, as shown in
FIG. 5B
, a metal film
45
is formed on the insulating film
42
such that the trenches
43
are filled by the material of the metal film
45
. Thereafter, as shown in
FIG. 5C
, the metal film
45
is polished by the CMP method until the insulating film
42
is exposed. Thereby, a buried wiring, that is, a damascene wiring,
46
is formed in each of the trenches
43
. By using this method, since the island patterns
44
exist in each of the trenches
43
, it is possible to avoid overpolishing, that is, dishing, which occurs when a buried wiring pattern having large area is formed.
However, in the method disclosed in Japanese patent laid-open publication No. 9-8039 and described above, the volume of each buried wiring
46
decreases by the amount of the volume of the island patterns
44
. Therefore, it is impossible to obtain good electrical characteristic, such as electrical resistance and the like, of the buried wiring
46
. Also, because of the existence of the island patterns
44
, there is a possibility that the electrical characteristic becomes even worse. Further, when the buried wiring
46
is to be coupled, for example, to any other conductor portion by using a via hole and the like, it is necessary to consider locations and sizes of the island patterns
44
. Therefore, design of connection in a semiconductor device becomes complicated. These disadvantages are caused by forming the island patterns
44
in each of the trenches
43
.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to obviate the disadvantages of the above-mentioned prior art.
It is another object of the present invention to provide a method of polishing a metal film in which excess polishing, that is, dishing, of buried conductors having large area occurring when the metal film is polished by the CMP method can be restrained, thereby providing damascene wirings or conductors each having planar top surface.
It is still another object of the present invention to provide a method of polishing a metal film in which excess polishing, that is, dishing, of buried conductors having large area occurring when the metal film is polished by the CMP method can be restrained without forming island patterns in each trench, thereby providing damascene wirings or conductors having large cross sections and high reliability.
According to an aspect of the present invention, there is provided a method of polishing a metal film used for forming a damascene wiring, the method comprises: providing a substrate on which an insulating film is formed; forming a trench in the insulating film; forming a buried metal film portion in the trench whose width is equal to or larger than 1 micrometer; forming a first metal film on the insulating film such that the buried metal film portion is covered by the first metal film; and polishing a surface of the first metal film by using a CMP method.
In this case, it is preferable that a lower portion of the buried metal film portion is buried in the trench whose width is equal to or larger than 1 micrometer, and at least a part of an upper portion of the buried metal film portion is located higher than the top surface of the insulating film.
It is also preferable that, in the polishing the surface of the first metal film by using the CMP method, the first metal film and the buried metal film portion are polished.
It is advantageous that each of the buried metal film portion and the first metal film includes an alloy including at least one metal selected from a group consisting of tungsten, aluminum, copper and titanium.
It is also advantageous that the forming a buried metal film portion in the trench whose width is equal to or larger than 1 micrometer comprises: forming a second metal film on the insulating film such that the trench is filled with the material of the second metal film; and selectively removing the second metal film, and forming the buried metal film portion comprising a portion of the second metal film remaining in the trench whose width is equal to or larger than 1 micrometer.
Also, it is preferable that, in the selectively removing the second metal film, and forming the buried metal film portion comprising a portion of the second metal film remaining in the trench whose width is equal to or larger than 1 micrometer, a portion of the second metal film in the trench whose width is equal to or larger than 1 micrometer is left and another portion of the second metal film is removed.
It is possible to form the first and second metal films by a reflow sputtering method.
It is also possible to form the first and second metal films by a CVD method.
Further, it is possible to form the first and second metal films by a plating method.
It is preferable that the forming a buried metal film portion in the trench whose width is equal to or larger than 1 micrometer comprises: forming a second metal film on the insulating film such that the trench is filled with the material of the second metal film; forming a resist film on the second metal film; patterning the resist film to form patterned resist film which covers the second metal film on the trench whose width is equal to or larger than 1 micrometer; by using the pattern
Bowers Charles
Gurley Lynne A.
McGinn & Gibb PLLC
NEC Corporation
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