Coating processes – Coating by vapor – gas – or smoke – Mixture of vapors or gases utilized
Reexamination Certificate
2000-01-21
2001-11-06
Pianalto, Bernard (Department: 1762)
Coating processes
Coating by vapor, gas, or smoke
Mixture of vapors or gases utilized
C427S585000
Reexamination Certificate
active
06312761
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to the technical field of forming metal nitrides. More particularly, it provides a technique adequate for forming tungsten nitride films.
BACKGROUND OF THE INVENTION
In recent years, aluminum has been replaced by copper as the material mainly employed in metal interconnecting films for semiconductor devices. In the case of aluminum films, titanium nitride films are formed as barrier films at the interface between the aluminum films and silicon substrates. However, these titanium nitride films are poor in it's ability to prevent the diffusion of copper. Thus, W
x
N films (tungsten nitride films) have attracted attention as barrier films against copper films.
It has been a practice to produce W
x
N films at a high temperature (i.e., 500° C. or above) under high pressure (i.e., film-forming pressure: several thousand Pa). However, a large-scale apparatus is employed to sustain such a high pressure; and, in addition, troublesome operations are needed for the maintenance thereof. In a pretreatment apparatus for forming W
x
N films and a film forming apparatus for forming copper film on the W
x
N films, substrates should be treated in vacuum. Thus, there arises an additional problem that these apparatuses are poor in connection properties with a W
x
N film forming apparatus; and thus, the substrates cannot be treated continuously.
Accordingly, it has been required to develop a film forming apparatus by which W
x
N films can be produced in vacuum (under reduced pressure). In FIG.
5
(
a
), a substrate
120
, on which a W
x
N film and a copper film are to be formed, consists of a silicon substrate
150
, a silicon oxide film
152
formed on the silicon substrate
150
and a pore
160
formed in the silicon oxide film
152
.
When a W
x
N film is to be formed on the substrate
120
by using a CVD apparatus
102
of the prior art as shown in
FIG. 6
, a reactor
111
is first evacuated. Then, the substrate
120
is carried thereinto and placed on a holder
114
provided in the bottom side of the reactor
111
.
A shower nozzle
112
is provided in the ceiling side of the reactor
111
. After heating the substrate
120
to a prescribed temperature with a heater contained in the holder
114
, two types of feedstock gases (for example, WF
6
gas and NH
3
gas) are jetted from the shower nozzle
112
toward the substrate
120
as shown by arrows
151
, thereby inducing the following chemical reaction:
4WF
6
+8NH
3
→2W
2
N+24HF+3N
2
.
Thus, a W
x
N film
153
is formed on the surface of the substrate
120
as shown in FIG.
5
(
b
), wherein X is referred tentatively as to 2.
When a prescribed thickness of the W
x
N film is achieved, the substrate
120
is taken out from the reactor
111
. Then, a copper film
154
is formed on the W
x
N film
153
as shown in FIG.
5
(
c
) and followed by the transportation to the subsequent stage, i.e., the patterning of the copper film
154
, etc.
When the W
x
N film
153
and the copper film
154
are formed in a vacuum as described above, the substrate
120
can be continuously treated without exposing to the atmosphere by connecting an apparatus for forming a tungsten film and a apparatus for forming a copper film to a multi-chamber type apparatus.
However, a CVD apparatus of the prior art as described above suffers from the problem of serious dusting. This is because the reaction between WF
6
and NH
3
proceeds even at room temperature, and not W
x
N but WF
6
.4NH
3
etc. are formed at room temperature, different from the above reaction formula, and adhere to the inner wall of the reactor
111
.
When the wall of the reactor
111
is heated to a temperature close to the temperature of the substrate
120
, at least the formation of WF
6
.4NH
3
can be prevented. In this case, however, W
x
N is deposited on the inner wall of the reactor
111
on the contrary and causes dusting.
In addition, the above-described reactor
111
of the prior art suffers from another problem of a low growth speed of the W
x
N film. Thus, it has been required to clarify the cause of this phenomenon and to establish an effective countermeasure.
SUMMARY OF THE INVENTION
The present invention, which has been made to overcome the above-described problems encountered in the prior art, aims at providing a technique for forming a tungsten nitride film without causing dusting, and a technique for forming a tungsten nitride film showing a high growth speed.
In order to achieve these objects, the present invention relates to a film forming apparatus provided with an evacuatable reactor, an adhesion preventive container placed in said reactor, a holder whereby an object on which the film is to be formed is located in said adhesion preventive container, a first gas inlet equipment which faces said holder and constructed so that it can jet a gas into said adhesion preventive container, and a second gas inlet equipment which is constructed so that it can jet a gas between said first gas inlet equipment and said holder.
The present invention relates to the film forming apparatus, which is constructed so that, in said adhesion preventive container, at least the part around said material on which the film is to be formed is maintained at a temperature of 150 to 300° C.
The present invention relates to the film forming apparatus wherein said first gas inlet equipment has a shower nozzle provided with a number of gas jet orifices formed on the almost same plane.
The invention relates to the film forming apparatus wherein said second gas inlet equipment has a nozzle made of a hollow pipe shaped into a ring and a number of gas jet orifices are formed in said hollow pipe.
The present invention relates to a method for producing a tungsten film which comprises jetting a first feedstock gas having a nitrogen atom in its chemical structure and a second feedstock gas having a tungsten atom in its chemical structure into a reactor and reacting said first feedstock gas with said second feedstock gas so as to form a tungsten nitride film on the surface of a material on which the film is to be formed, wherein the distance between the position from which said first feedstock gas is jetted and the surface of said material on which the film is to be formed is different from the distance between the position from which said second feedstock gas is jetted and the surface of said material on which the film is to be formed.
The present invention relates to the method for producing a tungsten film which comprises providing an adhesion preventive container in said reactor and placing said object on which a film is to be formed in the adhesion preventive container; heating, in said adhesion preventive container, at least the part around said material on which the film is to be formed to a temperature of 150 to 250° C.; and jetting said first feedstock gas and second feedstock gas into said adhesion preventive container.
The present invention relates to the method for producing a tungsten film, wherein one of said first feedstock gas and second feedstock gas is jetted downward in the vertical direction toward the surface of said object on which a film is to be formed.
The present invention relates to the method for producing a tungsten film, wherein, between said first feedstock gas and second feedstock gas, the one gas jetted from the lower position is jetted sideways toward the center of said object on which a film is to be formed.
Many other features, advantages and additional objects of the present invention will become apparent to those versed in the art upon making reference to the detailed description which follows and the accompanying sheet of drawings.
REFERENCES:
patent: 5112185 (1992-05-01), Koike
patent: 5470800 (1995-11-01), Muroyama
patent: 5534072 (1996-07-01), Mizuno et al.
patent: 3-255624 (1991-11-01), None
patent: 8-325737 (1996-12-01), None
Copy of European Patent Office Communication for European Patent Application No. 00100937.2 including European Search Report dated May 17, 2000.
Armstrong Westerman Hattori McLeland & Naughton LLP
Pianalto Bernard
ULVAC Inc.
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