Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of... – Multiple layers
Reexamination Certificate
2000-09-08
2003-09-16
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
Multiple layers
C438S624000, C438S738000, C438S763000, C438S778000
Reexamination Certificate
active
06620739
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to a method of manufacturing a semiconductor device using a fluorine-containing layer, such as a fluorine-containing carbon layer, as an insulating layer.
BACKGROUND ART
In the recent semiconductor integrated circuit producing industry, technical developments, such as the scale down of wiring patterns and the multilayering of wiring, have been made in order to achieve the high density integration. For example, in the wiring multilayering technique, there is used a wiring structure wherein a plurality of wiring layers are stacked via interlayer dielectric films and wherein adjacent two of the wiring layers are connected to each other by a conductive portion arranged in a through hole formed in each of the interlayer dielectric films.
In this case, a silicon oxide (SiO
2
) film capable of being easily formed on a silicon substrate, which comes into widest use as a semiconductor substrate, is generally used as the interlayer dielectric film. However, SiO
2
has a relatively large relative dielectric constant ∈ of about 4, which is an obstacle to develop more rapid semiconductor integrated circuits.
In order to solve such a problem, there is proposed a fluorine-containing carbon film which has a smaller relative dielectric constant than that of SiO
2
and which comprises carbon (C) and fluorine (F). The fluorine-containing carbon film can be formed by a plasma process using the electron cyclotron resonance (ECR).
This film-forming method will be described. First, a film-forming system shown in
FIG. 3
is used. This film-forming system comprises a plasma producing chamber
501
a
of manufacturing plasma, and a film-forming chamber
501
b
communicated therewith. A microwave of 2.45 GHz is supplied to the plasma producing chamber
501
a
from a high-frequency power supply unit
502
via a waveguide
502
a
to produce plasma. In the film-forming chamber
501
b
, a supporting table
506
is arranged, and a wafer
507
to be processed is fixed thereon by an electrostatic chuck
506
a
. The interior of each of the plasma producing chamber
501
a
and film-forming chamber
501
b
is evacuated to a predetermined degree of vacuum by an evacuating means (not shown) which is communicated thereto via an exhaust pipe
510
.
Such a film-forming system is used for forming a fluorine-containing carbon film on the wafer
507
as follows. First, the microwave of 2.45 GHz is supplied to the plasma producing chamber
501
a
from the high-frequency power supply unit
502
via the waveguide
502
a
. Then, together therewith, a magnetic field of 875 gausses is applied by magnetic coils
503
and
503
a
to activate argon (Ar) gas, which has been introduced from an introducing pipe
504
, by the electron cyclotron resonance to be high-density plasma. On the other hand, C
4
F
8
and C
2
H
4
gases are introduced into the film-forming chamber
501
b
from a gas supply part
505
via gas introducing pipes
505
a
and
505
b
to activate these gases by the high density plasma to form active species (radicals and so forth). Then, by the active species, a fluorine-containing carbon film
508
having good adhesion and high hardness is formed on the wafer
507
which is fixed on the supporting table
506
arranged in the film-forming chamber
501
b.
By the way, as described above, in order to construct a semiconductor device, upper and lower wiring layers are connected to each other by the conductive portion, which is arranged in a through hole formed in an interlayer dielectric film, so that it is required to carry out a fine pattern process, such as the formation of a through hole in an interlayer dielectric film. Thus, it is necessary to carry out a fine pattern process, such as the formation of a through hole in the fluorine-containing carbon film used as an interlayer dielectric film.
However, the fluorine-containing carbon film is an organic material, so that the patterning technique for an SiO
2
film which is an inorganic film can not be used as it is. The reason for this is as follows. First, in the fine pattern process, a resist pattern having formed generally by the photolithography technique is used as a mask to carry out a selective etching. At this time, the resist pattern must have an etching resistance as a mask against an underlying layer to be patterned. If the layer to be patterned is thick, the etching resistance of the resist pattern is particularly required. This resist pattern is formed by, e.g., exposing and developing a photoresist having photosensitivity, and is made of an organic material.
However, when an organic film, such as the above described fluorine-containing carbon film, is fine-patterned, a dry etching using the plasma of oxygen gas (O
2
) is used. In this case, if the resist pattern being the organic film is used as a mask, the resist pattern is also etched, so that it is not possible to carry out any selective etching processes. Thus, if the photoresist is used as a master pattern as conventional methods, it is not possible to carry out any selective etching processes, and the master pattern is also etched. Therefore, the dimension of the master pattern and so forth vary, so that it is not possible to precisely fine-pattern the fluorine-containing carbon film.
On the other hand, if a master pattern of an inorganic insulating material, such as SiO
2
, is used when the fluorine-containing carbon film is etched with the plasma of O
2
, the master pattern is hardly etched with the plasma of O
2
. Therefore, it is possible to carry out a selective etching, so that it is possible to carry out a fine pattern process while maintaining a high dimensional precision.
For that reason, in the fine pattern process of the fluorine-containing carbon film, a hard mask of SiO
2
or the like is used. If the hard mask is made of an inorganic insulating material, it is possible to obtain a high etch selectivity to the fluorine-containing carbon film, so that the hard mask may be thin.
Therefore, if the fluorine-containing carbon film is used as the interlayer dielectric film, there is no problem from the point of view of insulation performance even if the hard mask remains, and there is no serious problem with respect to the relative dielectric constant if the thickness is small. For that reason, if the fluorine-containing carbon film is used as the interlayer dielectric film, the hard mask having used for the pattern lithography is designed to remain without being removed, since the number of steps increases if the hard mask is removed.
The fine pattern process of the fluorine-containing carbon film using such a hard mask will be described below.
First, as shown in FIG.
4
(
a
), a fluorine-containing carbon film
602
is formed on a bottom wiring layer
601
serving as a substrate as described above. Then, an inorganic insulating film
603
of SiO
2
is formed on the fluorine-containing carbon film
602
by a chemical vapor deposition (CVD) method using SiH
4
or the like as a raw material, which is a well-known technique. The silicon (Si) containing inorganic insulating layer, such as SiO
2
, is a generally used insulating material since it has good adhesion to metallic materials used as materials of wiring layers and since its raw material is inexpensive and its deposition technique is established so that it can be easily handled.
Then, as shown in FIG.
4
(
b
), a resist pattern
604
having an opening portion
604
a
at a predetermined position is formed on the inorganic insulating film
603
by a well-known photolithography technique.
Then, the resist pattern
604
is used as a mask for selectively etching the inorganic insulating film
603
. Thus, as shown in FIG.
4
(
c
), a hard mask
605
having an opening portion
605
a
at a position corresponding to the opening portion
604
a
is formed. In this etching, a dry etching using, e.g., the plasma of CF
4
or C
3
F
8
, may be used.
Then, the hard mask
605
is used as a mask for selectively etching the fluorine-containing carbon film
602
. Thus, as shown in FIG.
4
(
d
),
Kato Yoshihiro
Kobayashi Takashi
Yoshitaka Hikaru
Finnegan Henderson Farabow Garrett & Dunner LLP
Malsawma Lex H.
Smith Matthew
Tokyo Electron Limited
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