Coating apparatus – Gas or vapor deposition
Reexamination Certificate
1998-11-12
2001-03-06
Morris, Terrel (Department: 1771)
Coating apparatus
Gas or vapor deposition
43
Reexamination Certificate
active
06197118
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention of the present application relates to a thin film deposition apparatus that produces a thin film on the surface of a semiconductor wafer substrate, and more specifically it relates to a selective deposition technique that selectively deposits a thin film only in specific regions of the substrate surface.
2. Discussion of Related Art
The deposition of thin films on the surface of semiconductor wafer substrates is frequently performed in the manufacture of various electronic devices. In particular, in the manufacture of integrated circuits such as LSIs, thin films are selectively deposited only on specific regions of the surface of a substrate. For example, a process is sometimes performed wherein a wiring pattern is formed in an insulating film of silicon oxide (SiO
2
) or silicon nitride (Si
3
N
4
) on a silicon substrate, and a silicon film is selectively deposited only on the regions of the substrate surface where the silicon is exposed.
FIG. 5
is a front view outlining the configuration of a conventional thin film deposition apparatus used for this sort of selective deposition of silicon. The thin film deposition apparatus shown in
FIG. 5
has a process chamber
1
equipped with pumping systems
11
and
12
, and a gas introduction means
2
that introduces a process gas into process chamber
1
. A susceptor
3
on which a substrate
9
is positioned and a heater
4
which heats substrate
9
are disposed inside process chamber
1
.
The apparatus shown in
FIG. 5
is a cold-wall apparatus in which the enclosure walls of process chamber
1
are fitted with a cooling mechanism (not illustrated). A first pumping system
11
which pumps down the whole interior of process chamber
1
, and a second pumping system
12
which principally pumps down the region surrounding heater
4
are also provided. First and second pumping systems
11
and
12
both employ ultra-high vacuum pumping systems using turbo-molecular pumps.
Gas introduction means
2
is made to introduce disilane (Si
2
H
6
)—a gaseous silicon hydride—as the process gas.
Susceptor
3
is shaped into a block which is fixed to the bottom surface of process chamber
1
, and substrate
9
is mounted on its upper surface. A lift pin
5
which can be raised and lowered is provided in the interior of susceptor
3
. Lift pin
5
rises and falls through a hole provided in the upper surface of susceptor
3
. When mounting a substrate
9
on susceptor
3
, lift pin
5
is raised up so that it projects from the upper surface of susceptor
3
, and lift pin
5
is lowered after the substrate
9
has been mounted on top of lift pin
5
. Substrate
9
is thereby mounted on the upper surface of susceptor
3
. Susceptor
3
is formed from a material such as silicon, graphite or SiC (silicon carbide), and is made so that it contacts substrate
9
with good thermal conductivity.
A heater
4
is disposed inside susceptor
3
. A heater
4
that heats substrate
9
mainly by radiative heating is used. Specifically, a carbon heater that emits heat by conducting electricity can be used. The heat radiated from heater
4
is conferred to susceptor
3
, and substrate
9
is heated via susceptor
3
. The temperature of substrate
9
is sensed by a thermocouple (not illustrated) and is sent to a heater control unit (not illustrated). The heater control unit performs feedback control of heater
4
according to the sensed result, whereby the temperature of substrate
9
is kept at a set temperature.
Susceptor
3
is made of the same silicon as substrate
9
to avoid contamination of substrate
9
. To avoid contamination of the atmosphere inside process chamber
1
by the release of occluded gas from heater
4
when it becomes hot, second exhaust system
12
pumps down the region surrounding heater
4
.
A cooling mechanism (not illustrated) is also provided at the side parts of susceptor
3
. This is to prevent process chamber
1
from being heated by the conduction of heat from susceptor
3
to process chamber
1
.
A heat-reflecting plate
6
is positioned above the substrate
9
mounted in susceptor
3
so as to be parallel with substrate
9
. Heat-reflecting plate
6
reflects the radiation emitted from substrate
9
and susceptor
3
and returns it to substrate
9
, thereby improving the efficiency with which substrate
9
is heated.
Heat-reflecting plate
6
is made of silicon. By making heat-reflecting plate
6
from the same kind of material as the film deposited on the surface of substrate
9
, the thin film deposited on the surface of heat-reflecting plate
6
can be prevented from peeling away.
The silicon film deposited by thermal decomposition of a gaseous silicon hydride compound as described below is deposited not only on the surface of substrate
9
but also on heat-reflecting plate
6
. If heat-reflecting plate
6
is made of a completely different material other than silicon, the thin film will have poor adhesion and can easily peel away due to internal stress. Parts of the film that peel away will form globular dust particulates that float about inside process chamber
1
. If these particulates adhere to the surface of substrate
9
, they will give rise to defects caused by localized reduction of the layer thickness, which are a cause of faulty products. To prevent the thin film from peeling away, heat-reflecting plate
6
uses the same silicon material as the thin film being formed.
The operation of a conventional apparatus relating to the above configuration is described next.
A substrate
9
is transferred into process chamber
1
via a gate valve
13
, and is mounted on susceptor
3
by raising and lowering lift pin
5
. The interior of process chamber
1
is pumped down in advance to 10
−8
Torr or thereabouts by first and second pumping systems
11
and
12
.
Heater
4
is operated before the film deposition begins, and the substrate
9
mounted on susceptor
3
is heated by the heat from heater
4
and maintained at the desired temperature after reaching thermal equilibrium. After this state has been achieved, gas introduction means
2
is operated and a gaseous silicon hydride compound is introduced into process chamber
1
as the process gas. The process gas diffuses inside process chamber
1
and arrives at the surface of substrate
9
. The gaseous silicon hydride compound then decomposes under the heat at the surface of substrate
9
, whereby a film of polycrystalline silicon is deposited at the surface.
The surface of substrate
9
has a wiring pattern formed in an insulating film of silicon oxide or silicon nitride, so that the surface contains regions of exposed silicon—the material of substrate
9
—and regions where silicon oxide or silicon nitride is formed on the surface. The thermal decomposition reaction rate at the silicon surface is much higher than the thermal decomposition reaction rate at the silicon oxide film surface or silicon nitride film surface. The silicon film is thus selectively deposited only on the silicon surface. Selective deposition of silicon is thereby achieved.
FIGS.
6
(
1
) and (
2
) show the results of experimental selective deposition of silicon using the conventional apparatus shown in FIG.
5
. Specifically, FIGS.
6
(
1
) and (
2
) show photographs of the reflection high energy diffraction (RHEED) pattern observed in film deposition using the apparatus of
FIG. 5
with the temperature of substrate
9
held at 700° C. and with disilane introduced at 6 sccm. FIG.
6
(
1
) shows the state 30 seconds after introduction of the process gas, and FIG.
6
(
2
) shows the state after 300 seconds.
As shown in FIG.
6
(
1
), in the state 30 seconds after introducing the gas, the pattern contains a mixture of bright vertically-extending parts and a diffuse region of brightness. The bright vertically-extending parts represent the diffraction spots from the crystalline lattice, indicating the presence of crystalline silicon at the surface of substrate
9
.
On the other hand, the diffuse region of brightness represents the refl
Anelva Corporation
Burns Doane , Swecker, Mathis LLP
Morris Terrel
Torres-Velazquez Norca L.
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