Semiconductor device manufacturing: process – Chemical etching – Vapor phase etching
Reexamination Certificate
2000-09-12
2002-06-04
Powell, William A. (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Vapor phase etching
C156S345420, C216S058000
Reexamination Certificate
active
06399510
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the field of substrate processing for semiconductor manufacturing and, more specifically, to an apparatus and a method that improve uniformity of deposition or etching of films on the substrate by providing bi-directional gas flow.
BACKGROUND OF THE INVENTION
An important part of integrated circuit manufacturing is the processing of the semiconductor substrate in which active devices such as transistors and capacitors that comprise the integrated circuits are formed. Processing of the substrate includes, for example, growth of an epitaxial silicon or polysilicon layer or film, the formation of a thermal oxide or thermal nitride layer over silicon, or etching of portions of previously deposited layers. These exemplary processes, among others, are typically performed in thermal deposition or etch process chambers. Process chambers typically include a platform such as a susceptor or an edge ring, a substrate support mechanism, a quartz housing or cover, and heat lamps that provide heat energy to the substrate being processed.
Deposition and etching are typically performed in these types of chambers by flowing a process gas through the chamber and over the substrate, which is resting on the platform in the chamber. The substrate and the process gas are heated during the processing. The gas includes the chemical species that react at the wafer surface to deposit or etch the layers of material on the substrate. The process chamber typically includes a gas inlet port and a gas outlet port.
Deposition and etch process chambers are normally designed such that the process gas flows over the substrate and from one side of the chamber to the other. The chemical species react at the wafer surface, which results in a change in gas composition (i.e., depletion of the gas species) in the direction of gas flow. For this reason, some chambers are provided with a mechanism to rotate the wafer holder that carries the substrate so that the reaction rate at the surface of the substrate is averaged out to provide uniformity of deposition or etching along the entire surface. Another technique that is an attempt to achieve greater uniformity of deposition or etching by overcoming the depletion phenomenon is to inject the gas stream into the chamber such that a mixing of the gas occurs which averages out the deposition or etch rate. Another technique is to tilt the wafer support, which allows “fresh” gas to arrive at the wafer surface as the gas travels across the wafer.
FIG. 1A
shows an example of a chamber
100
that can be used to process semiconductor substrates. Chamber
100
includes an enclosure
101
that has a top housing
102
and a bottom housing
104
, which are typically made of quartz. Platform
110
is located within the chamber
100
. Platform
110
typically defines a pocket (not shown) for holding a semiconductor substrate (not shown) to be processed. Lamps
106
are located outside of the top housing
102
and the bottom housing
104
. Lamps
106
are typically arranged in an array (not shown). Lamps
106
provide heat energy to the chamber, and thus to the substrate, during processing of the substrate. Pyrometers
108
a
and
108
b
are positioned above and below enclosure
101
. Pyrometer
108
a
measures the temperature of the substrate being processed, while pyrometer
108
b
measures the temperature of the platform
110
on which the substrate rests. Platform
110
is supported by platform support
112
. Platform support
112
is typically configured so that it can rotate the platform
110
during processing of the substrate. Substrate lift pins
114
are located below the platform
110
and extend upwardly through apertures (not shown) in platform
110
. Substrate lift pins
114
lift the substrate either at its edge or at its bottom surface during loading and unloading of the substrate into and out of the chamber.
As shown in
FIG. 1B
, chamber
100
includes a base ring
103
surrounding enclosure
101
. Base ring
103
can be generally rectangular in shape with the circular enclosure
101
having a dome-shaped top housing
102
mounted within base ring
103
. Referring again to
FIG. 1A
, a gas inlet
150
and a gas outlet
160
are usually provided at diametrically opposed locations on base ring
103
. Arrows
116
illustrate the direction of the gas flow across the platform
110
from gas inlet
150
to gas outlet
160
. A clamp ring
105
can be provided to seal the top housing
102
to the base ring
103
. A second damp ring
107
can be provided to seal the bottom housing
104
to the base ring
103
.
Because the process gas of chamber
100
flows in one direction, the substrate being processed must be rotated to average out the depletion or etch rate of the gas as it travels across the substrate in the direction of arrows
116
. Platform
110
is typically rotated as it carries the substrate. Platform support
112
includes an axle
113
that is connected to a motor (not shown) to provide the rotation. A rotating platform adds complexity and cost to the chamber
100
because the substrate must remain as level as possible as it rotates so as to achieve a uniform deposition or etch rate. Any wobbling or eccentricity of the platform
110
can result in uneven deposition or etching, which can ultimately result in waste of a substrate. Processing chamber
100
can be greatly improved by eliminating sources of potential error in the process such as the mechanisms that rotate the substrate and platform
110
.
SUMMARY OF THE INVENTION
In one embodiment, a semiconductor substrate processing chamber includes an enclosure having a first junction and a second junction. A first gas inlet port is at the first junction. A first gas outlet port is at the second junction. A second gas inlet port is also at the second junction, and a second gas outlet port is at the first junction.
The first gas inlet port and the first gas outlet port cooperate to provide gas flow in a first direction, while the second gas inlet port and the second gas outlet port cooperate to provide gas flow in a second direction.
REFERENCES:
patent: 4048955 (1977-09-01), Anderson
patent: 4563367 (1986-01-01), Sherman
patent: 4738748 (1988-04-01), Kisa
patent: 5945008 (1999-08-01), Kisakibaru et al.
Anderson Roger N.
Comita Paul
Imper Grant D.
Riley Norma B.
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