Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2000-09-08
2004-07-20
Nguyen, Ha Tran (Department: 2812)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S634000, C438S638000, C438S706000, C438S738000
Reexamination Certificate
active
06764939
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a semiconductor device, which uses a carbon-containing layer, such as a fluorine-containing carbon film, as an insulating film, and a method of manufacturing the same.
BACKGROUND ART
In order to achieve the high-density integration of semiconductor integrated circuits, it has been developed to scale down patterns, such as wiring, and to multilayer circuits. As one of such developments, there is a multi-layer metallization technique for constructing multi-layer wiring. In this multi-layer metallization technique, upper and lower wiring layers are connected to each other by a conductive part which is arranged in a predetermined region, and an interlayer dielectric film of an insulating material is arranged to separate the wiring layers from each other in a region other than the conductive part.
Typical materials of the interlayer dielectric films include silicon oxide (SiO
2
). In recent years, in order to more accelerate the operation of integrated circuits, it has been required to lower the relative dielectric constant of the interlayer dielectric films. That is, the relative dielectric constant &egr; of SiO
2
is about 4, and materials having a lower relative dielectric constant than that of SiO
2
have been diligently developed.
As an example of a material having a lower relative dielectric constant than that of SiO
2
, there is a fluorine-containing carbon film comprising carbon and fluorine. This fluorine-containing carbon film can be formed by, e.g., a plasma deposition process using the electron cyclotron resonance (ECR). This method will be described below.
In a deposition system shown in
FIG. 10
, a microwave of 2.45 GHz is first supplied into a plasma producing chamber
801
a
from a high-frequency power supply part
802
via a waveguide
802
a
. At this time, a magnetic field of 875 gausses is applied by magnetic coils
803
and
803
a
, and Ar gas introduced from an introducing pipe
804
is activated as a high-density plasma by the electron cyclotron resonance.
On the other hand, C
4
F
8
gas and C
2
H
4
gas are introduced into a deposition chamber
801
b
from a gas supply part
805
via gas introducing pipes
805
a
and
805
b
to be activated by the high-density plasma to form active-species. By the active-species, a fluorine-containing carbon film
808
having good adhesion and high hardness is formed on the surface of a wafer
807
which is arranged on a supporting table
806
in the deposition chamber
801
b
. The wafer
807
is fixed by an electrostatic chuck
806
a
on the supporting table
806
. The interior of the deposition chamber
801
b
is evacuated to a predetermined degree of vacuum by an evacuating means (not shown) which is communicated with the deposition chamber
801
b
via an exhaust pipe
810
.
By the foregoing, the fluorine-containing carbon film can be formed. However, in order to use the fluorine-containing carbon film as an interlayer dielectric film, it is required to carry out a fine patterning process, such as the formation of a hole portion for arranging a connecting portion for connecting upper and lower wiring layers to each other.
The fine patterning process of the fluorine-containing carbon film will be described below. First, as shown in FIG.
11
(
a
), a fluorine-containing carbon film
902
is formed on a lower wiring layer
901
serving as a substrate as described above. On the fluorine-containing carbon film
902
, an inorganic film
903
of SiO
2
is formed. Then, as shown in FIG.
11
(
b
), a resist pattern
904
having an opening
904
a
at a predetermined place is formed on the inorganic film
903
by a well-known photolithography technique.
The resist pattern
904
is then used as a mask to selectively etch the inorganic film
903
. Thus, as shown in FIG.
11
(
c
), a hard mask
905
having an opening
905
a
at a position corresponding to the opening
904
a
is formed. This etching may be, e.g., a dry etching with the plasma of CF
4
.
The hard mask
905
is then used as a mask to selectively etch the fluorine-containing carbon film
902
. Thus, as shown in FIG.
11
(
d
), a hole portion
906
is formed in the fluorine-containing carbon film
902
. This etching may be, e.g., a dry etching with the plasma of oxygen gas. If oxygen gas is used, the etch-selectivity (the ratio of etch rates) between the fluorine-containing carbon film
902
and the hard mask
905
can be great. If the plasma of oxygen gas is used, the resist pattern
904
can be simultaneously removed.
The fine patterning process of the fluorine-containing carbon film using the hard mask will be described below.
In the fine patterning process, a resist pattern formed by the photolithography technique is generally used as a mask to selectively etch. At this time, the resist pattern must have an etching resistance as a mask for an underlying layer to be processed. When the layer to be processed is thick, the resist pattern must particularly have the etching resistance. This resist pattern is formed by, e.g., exposing and developing a photoresist having photosensitivity, and made of an organic material.
However, when an organic film, such as the above described fluorine-containing carbon film, is fine-patterned, the dry etching with the plasma of oxygen is used. In this case, if a resist pattern of an organic film is used as a mask, the resist pattern is also etched, so that it is not possible to carry out a selective etching.
On the other hand, if a master pattern of an inorganic material, such as SiO
2
, is used when the fluorine-containing carbon film is etched with the plasma of oxygen gas, the master pattern is hardly etched with the plasma of oxygen, so that it is possible to carry out a selective etching For that reason, as described above, a hard mask of SiO
2
or the like is used for fine-patterning the fluorine-containing carbon film.
By the way, in order to form this hard mask, an inorganic film of SiO
2
or the like is patterned. This patterning may use a dry etching with the plasma of CF
4
or C
4
F
8
. In this case, since the resist pattern of the organic film is hardly etched, the resist pattern can be used as a mask to carry out the selective etching to form the hard mask as described above.
However, if a hard mask of SiO
2
or silicon nitride (SiN), which are generally used for patterning organic films, is used for fine-patterning the fluorine-containing carbon film, there are the following problems, so that the reliability of semiconductor devices using a fluorine-containing carbon film as an interlayer film is deteriorated.
First, since SiO
2
and SiN have low adhesion to the fluorine-containing carbon film which is a fluorine-containing organic film, there is a problem in that the hard mask is easily peeled off. As described above, since the hard mask is made of the insulating material, the hold mask is used as a part of an interlayer dielectric film. However, after the fluorine-containing carbon film serving as the interlayer dielectric film is fine-patterned, if a stress in applied in the subsequent process such as forming a metal film for a wiring electrode thereon, the hard mask is sometimes peeled off. If the metal film for the wiring electrode is intended to be flattened by the chemical mechanical polishing method after the metal film is formed, a great stress is applied thereto, so that the hard mask is substantially surely peeled off from the fluorine-containing carbon film.
Next, if the hard mask of SiO
2
or SiN is used for fine-patterning the fluorine-containing carbon film, there is a problem in that the etch-selectivity is lowered as follows, As described above, the dry etching with the plasma of oxygen gas is used for fine-patterning the fluorine-containing carbon film. In view of only this point, a high etch-selectivity should be obtained it the hard mask is made of SiO
2
or SiN.
However, when the fluorine-containing carbon film is etched with the plasma of oxygen gas, the fluorine-containing carbon film is decomposed to produce F (fluorine) and C (carbon) in atmosphere, and
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Nguyen Ha Tran
Tokyo Electron Limited
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