CVD apparatus

Details CVD apparatus CVD apparatus

1999-11-04

2001-12-04

Mills, Gregory (Department: 1763)

Coating apparatus

Gas or vapor deposition

With treating means

C118S050100, C118S7230HC, C118S7230DC

Reexamination Certificate

active

06325857

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to Chemical Vapor Deposition (CVD) for forming a desired film on a substrate using a catalyzer More particularly, the invention relates to a CVD apparatus that uses a catalyzer member for applying a catalysis to a CVD reaction or reactions and that is equipped with a cleaning device for cleaning the inside of the reaction chamber after a CVD process or processes is/are completed, and a film formation method using the CVD apparatus.
2. Description of the Prior Art
In the fabrication process sequence of semiconductor devices, for example, Large-Scale Integrated circuits (LSIs) designed for memories, microprocessors, and so on, various thin films need to be formed on a substrate These thin films include dielectric films, such as a silicon nitride (SiN
x
) film which is used for an oxidation-resistant masking film in the isolation-dielectric formation process of Metal-Oxide-Semiconductor (MOS) LSIs, and a silicon dioxide (SiO
2
) film which is used for a passivation film. Furthermore, they include conductive films, such as a polysilicon film which is used for forming gate electrodes and gate wiring lines in MOS LSIs, and a tungsten (W) film which is used for forming contact plugs of multilevel wiring structures
To form the above-described thin films, various CVD processes have been developed and extensively used in the semiconductor device fabrication field In these CVD processes, suitable catalyzers may be used to lower the necessary temperature of the substrate and to improve the quality of the films formed on the substrate. Here, these processes are termed “catalytic CVD processes”.
In a typical catalytic CVD process, a suitable catalyzer member (which is made of, for example, a refractory metal) is placed in a reaction chamber along with a substrate. The substrate and the catalyzer member are heated to specific temperatures, respectively. Then, suitable gaseous source materials are then supplied to the chamber, thereby forming a desired film on the surface of the substrate through a specific CVD reaction or reactions under the catalysis of the catalyzer member. There is a benefit that the thin film thus formed has a satisfactorily good quality even when the temperature of the substrate is comparatively low.
FIG. 1
schematically shows the configuration of a prior-art catalytic CVD apparatus used for performing a catalytic CVD process.
In
FIG. 1
, the CVD apparatus is comprised of a reaction chamber
151
made of quartz and a coil-shaped catalyzer member
152
placed in the chamber
151
. The catalyzer member
152
is formed by a piece of wire made of a refractory metal such as tungsten (W). The catalyzer member
152
is electrically connected to a power supply
153
placed outside the chamber
151
for heating the member
152
to a specific temperature on operation. A substrate stage
155
on which a single-crystal silicon (Si) substrate
154
is placed is fixed in the chamber
151
. The stage
155
is positioned right below the catalyzer member
152
.
A shutter
156
, which is horizontally movable along the horizontal arrow in
FIG. 1
, is provided in the chamber
151
between the catalyzer member
152
and the substrate stage
155
. The shutter
156
can be positioned at a closing position and an opening position. At the closing position, the shutter
156
is located just over the substrate
154
placed on the stage
155
and entirely covers the surface of the substrate
154
. At the opening position, the shutter
156
is located apart from the substrate
154
and entirely exposes the surface of the substrate
154
, allowing active species
159
generated in the vicinity of the catalyzer member
152
to reach the substrate
154
.
A gas inlet
157
is provided at an upper position of the side wall of the reaction chamber
151
. Source or reactant gas or gases SG is/are supplied into the reaction chamber
151
through the gas inlet
157
. A gas outlet
158
is provided at the bottom wall of the chamber
151
. Gaseous substances existing in the chamber
151
are exhausted to the outside of the chamber
151
through the gas outlet
158
.
The above-described prior-art CVD apparatus is used in the following way, in which a thin SiN
x
film used as a dielectric in the semiconductor device is formed on the substrate
154
.
First, the Si substrate or wafer
154
is sent to the inside of the reaction chamber
151
and is placed on the substrate stage
155
. The substrate
154
is then heated up to a specific temperature ranging from 300 to 400° C. and kept at the same temperature by using a heater (not shown) incorporated into the stage
155
.
Next, while the shutter
156
is located at the closing position just over the substrate
154
, the catalyzer member
152
is heated up to a specific high temperature ranging from 1700 to 1800° C. and kept at the same temperature by using the power supply
153
. Thereafter, as the source or reactant gases SG, gaseous monosilane (SiH
4
) and ammonia (NH
3
) are introduced into the chamber
151
through the gas inlet
157
at their specific flow rates. The introduced SiH
4
and NH
3
are decomposed due to the catalysis of the heated catalyzer member
152
, generating the active species
159
in the vicinity of the member
152
. Because of the shutter
156
at the closing position, the active species
159
thus generated do not reach the substrate
154
at this stage.
After the flow rates of the gaseous SiH
4
and NH
3
and the temperature of the catalyzer member
152
become steady, the shutter
156
is horizontally moved to the opening position to thereby expose entirely the surface of the substrate
154
to the active species
159
, as shown in FIG.
1
. Thus, the active species
159
generated from the SiH
4
and NH
3
gases SG begin to be supplied to the surface of the substrate
154
, as shown by the vertical arrows in FIG.
1
. The active species
159
react with the Si atoms of the substrate
154
and deposit SiN
x
on the surface of the substrate
154
. After a specific deposition period passes, the shutter
156
is moved to the closing position again, completing the deposition process. Thus, a desired SiN
x
film (not shown) with a desired thickness is formed on the surface of the Si substrate
154
.
In the prior-art catalytic CVD apparatus shown in
FIG. 1
, thereafter, the substrate
154
with the deposited SiN
x
film is taken out of the reaction chamber
151
and then, a cleaning process is conducted to clean the inside of the chamber
151
, i.e., to removed the unwanted SiN
x
films deposited on the inner walls of the chamber
151
or the like. This cleaning process is carried out by an unillustrated cleaning device or subsystem. A next CVD process is then conducted in the same reaction chamber
151
in the same way as above.
In popular CVD apparatuses, a cleaning subsystem is equipped for the purpose of cleaning the inside of a reaction chamber. Typically, gaseous carbon tetrafluoride (CF
4
) is used as a cleaning gas. After a CVD process is completed, the cleaning gas is introduced into the reaction chamber and then, CF
4
plasma is generated from the gaseous CF
4
using a popular plasma generator. The CF
4
plasma thus generated removes the unwanted SiN
x
films existing in the inside of the reaction chamber by etching.
As seen from the above explanation, the prior-art catalytic CVD apparatus shown in
FIG. 1
has a problem that the catalyzer member
152
itself is etched by the CF
4
plasma during the cleaning process, resulting in breaking or degradation of the coil-shaped catalyzer member
152
. In other words, in the prior-art catalytic CVD apparatus of in
FIG. 1
, there is a problem that the inside of the reaction chamber
151
is difficult to be cleaned.
Moreover, the prior-art catalytic CVD apparatus of
FIG. 1
has another problem that the temperature of the substrate
154
tends to be raised due to the heat radiated from the heated catalyzer member
152
during the deposition process. This is because the catalyzer member
152
is typica

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