Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Halogenous component
Reexamination Certificate
1998-10-07
2002-04-09
Griffin, Steven P. (Department: 1754)
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Halogenous component
C423S325000, C423S344000, C423S439000, C423S462000
Reexamination Certificate
active
06368567
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of an apparatus for minimizing or eliminating by-product accumulation in the exhaust lines of reactors used for electronic device fabrication.
BACKGROUND OF THE INVENTION
Many of the films used in electronic device fabrication today are formed in deposition reactors similar to reactor
100
shown in FIG.
1
. In deposition reactor
100
, lamps
105
provide radiant heat to wafer
110
which is supported within reactor
100
by rotating susceptor
115
. Process and cleaning gases are provided via gas inlet conduit
120
and inlet manifold
125
. Gases are exhausted via exhaust manifold
130
and exhaust conduit
135
. Exhaust conduit
135
is in communication with reactor
100
and the remaining exhaust systems
140
located within the wafer fabrication facility. Exhaust systems
140
may contain scrubbers, filtration units as well as other exhaust treatment systems.
During deposition and cleaning processes conducted with reactor
100
, lamps
105
, or alternative heat sources utilized by other types of semiconductor processing reactors, heat not only rotating susceptor
115
and wafer
110
but also gas inlet
125
and exhaust manifold
130
. As a result, lamps
105
or other chamber heat sources also heat approximately 2-3 cm of exhaust conduit
135
located directly adjacent to exhaust manifold
130
.
Additionally, hot gases exhausted by reactor
100
also heat conduit
135
. Generally, as the processing temperature within reactor
100
increases the length of conduit
135
heated by hot exhaust gases increases. For example, in a deposition reactor
100
depositing silicon film by thermal CVD at, for example, 600 C., as much as about 2 to 3 feet of conduit
135
could be heated above room temperature or about 70 F. by exhausting deposition gases. Additionally, conduit
135
could be heated because of the cleaning processes used to clean reactor
100
after deposition. One representative cleaning process for the silicon deposition process described above is to raise reactor
100
above about 900 C. and inject HCl into reactor
100
. The exhaust from such a high temperature cleaning process could be expected to raise the temperature of about 3-6 feet of conduit
135
.
Referring to
FIG. 1
, that portion of exhaust conduit
135
heated by a combination of reactor heat sources, such as lamps
105
, and heated reactor exhaust is labeled Zone A. Zone A is that portion of exhaust conduit
135
between exhaust manifold
130
and the dashed line, representing 2-3 cm beyond exhaust manifold
130
, where hot exhaust gases as well as chamber heating sources, such as lamps
105
, contribute to the heating of conduit
135
.
Zone B of
FIG. 1
, shown between the dashed lines, represents that portion of conduit
135
heated by the hot exhaust gases of reactor
100
. The temperature of conduit
135
within Zone B remains above the ambient temperature surrounding conduit
135
. Zone B could include several feet of conduit
135
depending upon the temperature and flow rate of the exhausting gases. Zone C represents that portion of conduit
135
where the temperature is essentially the same as the surrounding ambient conditions.
Although conduit
135
within Zone B remains above the surrounding ambient temperature, at some point the temperature within conduit
135
decreases below the condensation points of the vapors contained in the exhaust of reactor
100
. This condensation region, labeled CR on
FIG. 1
, delineates where gaseous by-products may condense to form deposits along the internal walls of conduit
135
. Upstream of CR towards reactor
100
, conduit
135
contains mostly vapor while downstream of CR conduit
135
contains a mixture of vapor and condensing by-products
145
. Condensation continues within conduit
135
beyond condensation region CR so long as the temperature within conduit
135
remains below the condensation temperature of by-products
145
. After condensation, many by-products will further polymerize along the interior walls of conduit
135
. Reference number
145
indicates condensed, polymerized by-products formed along the interior walls of conduit
135
.
Deposition processes conducted within reactor
100
result in desired deposits on substrate
110
as well as undesired film formation on internal surfaces and components of reactor
100
. Additionally, some source gases, such as SiH
4
or chlorinated silanes from the previous example, exhaust unreacted from deposition reactor
100
. As unreacted source gases exit reactor
100
, temperatures within exhaust manifold
130
and exhaust conduit
135
within Zone A are typically high enough such that the unreacted gases can remain in the vapor phase. However, beyond the condensation region CR, unreacted source gases can also condense, polymerize and contribute to the accumulation of by-products
145
along the interior walls of conduit
135
.
During the cleaning process, cleaning gases are introduced into reactor
100
to remove unwanted deposits from internal reactor components. As these deposits are removed from reactor
100
and are exhausted via exhaust manifold
130
into exhaust conduit
135
, the unwanted deposit/cleaning gas mixture can behave similarly to the unreacted source gas. Within Zone A, a portion of the unwanted deposit/cleaning gas mixture remains gaseous, does not form deposits, condense or polymerize on the interior walls of exhaust conduit
135
. As a result of the higher temperatures used during cleans, temperatures within Zone A and some of Zone B will be high enough such that a portion of the unreacted cleaning gas exhausting from reactor
100
will remain active. Thus, within that region where the unreacted cleaning gas remains active, the unreacted cleaning gas will be able to react with and remove by-products
145
deposited within that active cleaning gas area of conduit
135
.
However, like the exhaust from the deposition process, the exhaust from the cleaning process will eventually cool within the condensation region CR, to a temperature where it is likely that most of the cleaning gas or gases will be inactive. Beyond CR, exhaust from the cleaning process will also contribute to the accumulation and further polymerization of by-products
145
. Thus, within Zone A, reactor heating sources and high exhaust gas temperatures can result in sufficient temperatures within conduit
135
where most deposits formed will likely be removed by unreacted but still active cleaning gases. Within Zone B however, temperatures will likely not be high enough for any remaining unreacted cleaning gas to remain active. As described above, downstream of the condensation region, conditions within conduit
135
are such that the mixture of cleaning gas/by-product removed from Zone A, and the mixture of cleaning gas/deposits removed from reactor
100
can condense, polymerize and contribute to the accumulation of by-products
145
within conduit
135
.
The problem currently faced by many types of reactors is the condensation and polymerization of unreacted source gas, cleaning gas/by-product mixture and cleaning gas/unwanted deposition mixture which result in the constant, gradual formation of highly viscous liquid or solid by-product
145
along the interior walls of exhaust conduit
135
. As a result of this by product build up, exhaust conduit
135
becomes partially blocked thereby reducing reactor exhaust flow efficiencies and, in the case of reduced pressure systems, reducing vacuum pump performance. On a regularly occurring basis, by-product accumulation within conduit
135
becomes so substantial that the reactor
100
must stop production, exhaust conduit
135
, or the blocked portion therein, must be disconnected from reactor
100
and the accumulated by-product removed.
These and other disadvantages of the prior art are overcome by the present invention directed to a method and an apparatus which can inhibit or eliminate by-product condensation and polymeric formation within exhaust lines. Such an apparatus minimizes exhaust line bloc
Carlson David K.
Comita Paul B.
DuBois Dale R.
Forstner Hali J. L.
Ranganathan Rekha
Applied Materials Inc.
Blakely & Sokoloff, Taylor & Zafman
Griffin Steven P.
Medina Maribel
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