U.S. patent application number 09/167269 was filed with the patent office on 2001-07-19 for point-of-use exhaust by-product reactor.
Invention is credited to CARLSON, DAVID K., COMITA, PAUL B., DUBOIS, DALE R., FORSTNER, HALI J.L., RANGANATHAN, REKHA.
Application Number | 20010008618 09/167269 |
Document ID | / |
Family ID | 22606657 |
Filed Date | 2001-07-19 |
United States Patent
Application |
20010008618 |
Kind Code |
A1 |
COMITA, PAUL B. ; et
al. |
July 19, 2001 |
POINT-OF-USE EXHAUST BY-PRODUCT REACTOR
Abstract
A method and an apparatus is provided for removing wafer
processing by-products from gas fluid exhaust systems utilizing an
energy source placed within an exhaust channel either alone or in
combination with a cleaning gas. The placement of the energy source
in an exhaust channel enables emitted energy to react with wafer
processing by-products to convert the by-product residues to more
removable forms. Additionally provided is a cleaning gas source
internal to the exhaust channel to further react with and convert
exiting by-product residues to gaseous fluids.
Inventors: |
COMITA, PAUL B.; (MENLO
PARK, CA) ; RANGANATHAN, REKHA; (CAMBRIDGE, MA)
; CARLSON, DAVID K.; (SANTA CLARA, CA) ; DUBOIS,
DALE R.; (LOS GATOS, CA) ; FORSTNER, HALI J.L.;
(REDWOOD CITY, CA) |
Correspondence
Address: |
PATENT COUNSEL - MS/2061
LEGAL AFFAIRS DEPARTMENT
APPLIED MATERIALS INC
BOX 450A
SANTA CLARA
CA
95052
|
Family ID: |
22606657 |
Appl. No.: |
09/167269 |
Filed: |
October 7, 1998 |
Current U.S.
Class: |
423/210 ;
422/168 |
Current CPC
Class: |
C23C 16/4412
20130101 |
Class at
Publication: |
423/210 ;
422/168 |
International
Class: |
B01D 047/00; B32B
027/02 |
Claims
We claim:
1. An apparatus for removing by-product residues from semiconductor
processing equipment said apparatus comprising an energy generating
means disposed within the exhaust passageway of said semiconductor
processing equipment for energetic excitation of processing
by-products to inhibit the deposition of said processing
by-products and expedite the removal of said by-products from said
exhaust passageway.
2. An apparatus according to claim 1 further comprising a fluid
flow channel connected to said exhaust passageway and aligned with
the energy generating means to direct a reactive fluid onto the
exiting reactor by-products.
3. An apparatus for processing a semiconductor substrate said
apparatus comprising: (a) a reactor chamber; (b) a semiconductor
substrate processing area within said chamber; (c) an exhaust
passageway in communication with the substrate processing area for
removal of semiconductor substrate processing by-products; and (d)
an energy generating means disposed within the exhaust passageway
for excitation of processing by-products to inhibit the deposition
of said processing by-products and expedite the removal of said
by-products from said exhaust passageway.
4. An apparatus according to claim 3 further comprising: (e) a
fluid flow channel connected to said exhaust passageway and aligned
with the energy generating means to direct a reactive fluid onto
the exiting reactor by-products.
5. The apparatus of claim 3 wherein said energy device is selected
from the group consisting of: a resistive heater, an UV lamp, an IR
lamp, a photon generator, a plasma generator and a flame.
6. An apparatus for removing wafer processing by-products from
exhaust conduits said apparatus comprising: (a) a substrate
processing area within a substrate processing chamber; (b) a first
fluid conduit wherein said first fluid conduit is in communication
with said substrate processing area; (c) an energy device wherein
said energy device is internally disposed within a first fluid
conduit; (d) a directional element wherein said directional element
is disposed internal to said first fluid conduit such that fluids
within said first fluid conduit are directed towards said
internally disposed energy device; and (e) a second fluid conduit
wherein said second fluid conduit is in communication with said
first fluid conduit and wherein said second fluid conduit is
coupled to a fluid source.
7. The apparatus of claim 6 wherein said fluids provided by said
fluid source via said second conduit enter said first conduit in
proximity to said internally disposed energy device.
8. The apparatus of claim 6 wherein said substrate processing
chamber further comprises an exhaust manifold wherein said fluids
provided by said fluid source via said second fluid conduit are
provided in proximity to said processing chamber exhaust
manifold.
9. The apparatus of claim 6 wherein said fluids provided by said
fluid source via said second fluid conduit are provided into said
first fluid conduit upstream of said directional element.
10. The apparatus of claim 6 wherein said fluids provided by said
fluid source via said second fluid conduit are provided into said
first fluid conduit downstream of said directional element.
11. A method of removing wafer processing by-products from an
exhaust channel of a wafer processing device comprising the steps
of: (a) imparting sufficient energy from an energy source internal
to an exhaust channel to by-products exiting a wafer processing
device through the exhaust channel to form gaseous by-products; and
(b) removing said by-products from said exhaust channel.
12. The method of claim 11 wherein said energy is heat energy.
13. The method of claim 11 wherein said energy is light energy.
14. A method of removing wafer processing by-products from exhaust
conduits said method comprising the steps of: (a) treating a wafer
processing by-product within a processing chamber exhaust conduit
with an energy source to form a converted by-product; (b) reacting
said converted by-product with a cleaning gas to form a second
converted gaseous by-product; and (c) exhausting said gaseous
by-product from said processing chamber exhaust conduit.
15. The method of claim 14 wherein said cleaning gas is selected
from the group consisting of: Cl.sub.2, HCl, ClF.sub.3, F.sub.2,
NF.sub.3, and O.sub.3.
Description
FIELD OF THE INVENTION
[0001] 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
[0002] 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.
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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.
[0007] 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.
[0008] 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.
[0009] 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.sub.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.
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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 blockages, maximize reactor up-time, and
enables longer time between service for reactor exhaust
systems.
SUMMARY OF THE INVENTION
[0014] In accordance with the present invention, there is disclosed
a method and apparatus for removing wafer processing by-products
from a fluid conduit or exhaust channel which is attached to a
substrate processing area by placing an energy source, such as
heaters or UV lamps, within the exhaust channel. The placement of
this energy source provides energy internal to an exhaust conduit
such that the viscosity of polymeric by-products would be reduced
whereby the by-product material can flow, or partially or fully
vaporize, or recombine or react in the presence of a cleaning gas
to form gaseous by-products. The resulting gaseous by-products can
therefore be more expeditiously and completely removed by gaseous
fluid exhaust systems. More precisely, the present invention is
directed to an improved method and apparatus for adding energy
internal to the exhaust conduit of a wafer processing reactor in
order to minimize condensation and polymerization of deposition and
cleaning by-products as well as promote more thorough removal of
deposition and cleaning by-products from the reactor's exhaust
system.
[0015] In an alternative embodiment of the present invention, a gas
supply feature is provided to a fluid conduit exhaust channel in
proximity to the energy source within the exhaust channel whereby a
cleaning gas or combination of gases such as Cl.sub.2, HCl,
ClF.sub.3, F.sub.2, NF.sub.3 or O.sub.3, can be introduced into the
exhaust channel. In this way, the cleaning gas or mixtures thereof
can react or recombine with or otherwise break down by-products
present within the conduit to form gaseous by-products which are
more easily removed by exhaust treatment systems. With the addition
of the gas supply feature, the cleaning gas or combinations of
cleaning gases utilized in conjunction with the energy provided by
the internal energy source provide an additional process which can
be used to react, recombine, or otherwise break down by-products
present within the exhaust conduit to form gaseous by-products.
[0016] A major objective of the present invention is that the
energy and cleaning gas in the exhaust conduits of the present
invention provide an opportunity to reduce the formation of solid
or highly viscous by-products and convert by-products into less
viscous or gaseous by-products within the gas fluid exhaust
conduits of wafer processing systems. Minimizing by-product
formation and accumulation within chamber exhaust systems leads to
enhanced wafer throughput by reducing or eliminating the necessity
of ceasing chamber operations to dissemble, remove by-product
accumulations and re-install chamber exhaust lines. Wafer
fabrication exhaust treatment system efficiency and ability to
remove and properly dispose of chamber exhaust by-products are
increased by providing methods and apparatuses which result in
gaseous chamber by-product formation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Other objectives, features and advantages of the present
invention will become apparent upon consideration of the
specification and the drawings, in which:
[0018] FIG. 1 is an illustration of a cross-sectional view of a
conventional deposition apparatus and exhaust conduit.
[0019] FIG. 2 is an illustration of a cross-sectional view of a
representative apparatus of the present invention when the
apparatus is a resistive heater which is not in operation.
[0020] FIG. 3 is an illustration of a cross-sectional view of a
representative apparatus of the present invention when the
apparatus is in operation.
[0021] FIG. 4 is an illustration of a cross-sectional view of an
alternative embodiment of the apparatus of the present invention
wherein said embodiment is a radiant energy source.
[0022] FIG. 5 is an illustration of a cross-sectional view of an
alternative embodiment of the apparatus of the present invention
which has eliminated the condensation region CR.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0023] FIG. 2 shows an embodiment of an apparatus for exhaust
by-product removal according to the present invention when said
apparatus is not in operation and exhaust by-products have
accumulated. Referring to FIG. 2, one embodiment of the apparatus
of the present invention is an internal energy device 210 disposed
within the exhaust conduits of a deposition reactor 200. Exhaust
conduits refers to any piping, passageway, or other channel coupled
to a processing reactor for removing process by-products and
by-product residues. Since the method and apparatus of the present
invention are independent of the type of reactor utilized to
generate the by-products, reactor 200 represents a wide variety of
processing reactors such as the prior art thermal CVD reactor 100
but also other processing reactors such as but not limited to
reduced pressure, single or multiple substrate susceptors or batch
furnace type, or plasma deposition reactors. Disposed within
central exhaust conduit 207 is internal energy device 210 which
includes energy source 255 and casing 220. Upper exhaust conduit
203 is coupled to the reactor exhaust manifold 130 and central
exhaust conduit 207. Lower exhaust conduit 335 is coupled to
central exhaust conduit 207 and the wafer fabrication facilities
exhaust system 140. The exhaust system shown in FIG. 2 represents a
typical exhaust configuration for a reduced pressure semiconductor
processing system in which pump 257 is in communication with
chamber 200 via upper, central and lower exhaust conduits 203, 207
and 335 respectively. One of ordinary skill will appreciate that
the method and apparatus of the present invention can also be
practiced on atmospheric pressure semiconductor processing systems.
In an atmospheric pressure system, pump 257 would be removed from
lower exhaust conduit 335 between internal energy device 210 and
wafer fabrication facility exhaust system 140. The exhaust systems
shown in FIGS. 3 and 4 are atmospheric pressure systems.
[0024] An additional conduit 225 is attached to central exhaust
conduit 207 in proximity to internal energy source casing 220 and
downstream of directional insert 260. Downstream refers to the
general flow pattern from reactor 200 to exhaust system 140 while
upstream describes a flow in the opposite direction. Conduit 225 is
in communication with central exhaust conduit 207 and is coupled to
bulk gas supply 230. The bulk gas supply provides cleaning gas or
other reactive gases used to react with and remove exhaust line
by-products. One such cleaning gas is chlorine (Cl.sub.2). One of
ordinary skill will appreciate that the satisfactory results of the
present invention can be achieved by utilizing other cleaning or
reactive gases such as: HCl, ClF.sub.3, F.sub.2, NF.sub.3, and
O.sub.3. Additionally, one of ordinary skill will appreciate that a
plurality of additional conduits similar to conduit 225 and a
plurality of bulk gas supplies similar to bulk gas supply 230 can
be attached in proximity to internal energy device 210 in order to
independently provide multiple cleaning gases according to the
method of the present invention. Gas supplied from bulk gas supply
230 is controlled by flow controlling device 235. One such flow
controlling device is a mass flow controller.
[0025] Casing 220 should be fabricated from material compatible
with energy source 255. An additional material selection criteria
for casing 220 includes the ability to withstand prolonged exposure
to temperatures as low as about 25 C or above about 1000 C in an
oxygen deficient atmosphere and high volumes of semiconductor
deposition and cleaning gases similar to the atmosphere expected in
the exhaust of a semiconductor processing reactor 200. One
representative material for the fabrication of casing 220 is
stainless steel. Other suitable materials include: quartz, Inconel,
Hastelloy, and other low iron content stainless steels such as
Haynes 242. Irrespective of material selected, the size and shape
of casing 220 minimizes any impact on gas flow efficiency within
central exhaust conduit 207. Casing 220 will have a diameter less
than the internal diameter of central exhaust conduit 207 while
allowing sufficient clearance between the outer surface of casing
220 and the inner wall surface of central exhaust conduit 207. In
one representative embodiment central exhaust conduit 207 may be
fabricated from a low iron content stainless steel with an outer
diameter of about 2.0 inches and a wall thickness of about 0.065
inches. Casing 220 may also be fabricated from a low iron content
stainless steel with an outer diameter of approximately about 1.28
inches.
[0026] For simplicity casing 220 has been illustrated with a
generally cylindrical shape having a circular cross section. One of
ordinary skill will appreciate that the cross sectional shape of
casing 220 could be square, rectangular, octagonal or any other
shape which generally conforms with the shape of energy source 255
and does not adversely impact flow efficiencies within exhaust
conduits 203, 207 and 335. One method of minimizing the impact on
flow efficiencies is to have approximately equal cross sectional
flow areas between central exhaust conduit 207 and lower exhaust
conduit 335. For example, in a representative embodiment, central
exhaust conduit 207 has an outer diameter of about 2.0 inches, a
wall thickness of about 0.065 inches with source casing 220 having
an outer diameter of about 1.28 inches which results in a cross
sectional flow area within central exhaust conduit 207 of about
1.46 square inches. A representative lower exhaust conduit 335 with
an outer diameter of 1.5 inches and a wall thickness of 0.065
inches results in a cross sectional flow area of about 1.47 square
inches. One of ordinary skill will appreciate that varying the wall
thickness of exhaust conduits 207 and 335 will alter the
cross-sectional flow area of those exhaust conduits. For example,
given the outer conduit diameters and casing 220 diameter above, a
wall thickness of 0.08 inches results in a cross sectional flow
area of about 1.3722 square inches in central conduit 207 and a
cross-sectional flow area of about 1.4103 square inches in lower
exhaust conduit 335. An exhaust conduit wall thickness of about
0.05 inches results in a central exhaust conduit cross sectional
flow area of about 1.5485 square inches and a lower exhaust conduit
flow area of about 1.5394 square inches. One of ordinary skill will
appreciate that a variety of exhaust conduit outer diameters, wall
thicknesses and source casing 220 diameters may be employed to
maintain an approximately equal cross-sectional flow area or
cross-sectional flow areas whose values are within about 0.04
square inches of each other between central and lower exhaust
conduits 207 and 335.
[0027] As shown in FIG. 2, internal energy source 255 is enclosed
within casing 220 and disposed internal to conduit 207. Energy
source 255 imparts energy to surrounding components but more
specifically to by-products 145 formed on the interior walls of
conduit 207 in order to reduce the viscosity or cause the reaction,
conversion, or degradation of by-products 145 whereby by-product
residues are converted into more removable forms. Energy source 255
could be a resistive heater, a flame, a plasma generator, a photon
generator, UV or IR lamps or any other energy source which reduces
the viscosity of or results in the chemical recombination or
conversion of by-products 145 formed within exhaust conduits 203,
207, and 335. In the specific embodiment of internal energy device
210 of FIG. 2, energy source 255 is a resistive heater. Controller
250 is used to adjust the energy output level from energy source
255.
[0028] In an embodiment of the present invention, energy source
casing 220 is disposed internal to exhaust conduit 207 such that
gas supply outlet 245 is in close proximity to casing tip 240. The
proximity of outlet 245 to tip 240 is advantageous because when
internal energy device 210 is in operation and exhaust by-products
145 come into direct contact with the elevated surface temperature
of casing 220 or otherwise contact the energy provided by internal
energy source 255 said by-products can vaporize, or otherwise react
in proximity to the cleaning or reactive gas exiting fluid flow
channel 225 via outlet 245. As a result of reacting or recombining
with the energy provided by internal energy device 210 in the
presence of a cleaning gas, a by-product could be formed into a
more removable form such as, for example, one which remains gaseous
until removed by the wafer fabrication facility exhaust system 140.
Alternatively, energy from internal energy device 210 alone may be
sufficient to result in the formation of by-products which remain
in the vapor phase or other more removable form until removed by
the wafer fabrication facility exhaust system 140.
[0029] One method of the present invention causes by-products 145
to recombine with a cleaning gas to convert exiting by-products
into a more expeditiously removable and desired gaseous by-product.
This by-product is desirous because it will remain in the vapor
state within the temperature and pressure conditions of upper
exhaust conduit 203 as well as central exhaust conduit 207
surrounding internal energy device 210 and lower exhaust conduit
335 until removed by exhaust treatment systems 140. As an example,
given a representative by-product A.sub.2X.sub.6 where 2 A atoms
are bonded together and 3 X atoms are bonded to each A atom.
Vapor-phase by-product A.sub.2X.sub.6 condenses, polymerizes and
forms (A.sub.2X.sub.6).sub.n chains below, for example, 200 C.
Thus, by-products of A.sub.2X.sub.6 will condense and polymerize
into A.sub.2X.sub.6 chains along the walls of conduit 135 when the
temperature within conduit 135 drops below 200 C. However, in the
presence of cleaning gas R, the A-A bond of the A.sub.2X.sub.6
molecule is broken forming instead AX.sub.4 which can remain in the
vapor phase at or below ambient conditions surrounding exhaust
conduits 203, 207 and 335. Typical ambient conditions would likely
be room temperature of the wafer fabrication facility where the
method and apparatus of the present invention are in use or about
70 F. Chlorosilane polymer by-products, such as
(Si.sub.xCl.sub.y).sub.n produced as a result of various types of
silicon deposition processes, can behave similarly to the
representative by-product A.sub.2X.sub.6 described above when the
chlorosilane by-products are in the presence of chlorine. As a
result of recombining or further reacting by-product
A.sub.2X.sub.6, condensation and polymerization within upper,
central and lower exhaust conduits 203, 207 and 335 is minimized
and the likelihood increased that by-products formed within exhaust
conduits will remain in the vapor phase until removed by exhaust
treatment system 140.
[0030] In an alternative method of the present invention, the
energy provided by internal energy device 210 alone results in the
mechanism described above, specifically, the formation of a gaseous
by-product which remains in the vapor phase until removed by the
wafer fabrication facility exhaust system 140. In another
alternative method of the present invention, processing by-products
recombine as a result of the energy provided by internal energy
device 210 to form a second by-product which then reacts with a
cleaning gas to form a third by-product. The third by-product then
remains in the vapor state until removed by the wafer fabrication
facility exhaust system 140. In another alternative method of the
present invention, processing by-products recombine with a cleaning
gas to form a second by-product. The second by-product reacts or
recombines as a result of the energy provided by internal energy
device 210 to form a third by-product which remains in the vapor
phase until removed by the wafer fabrication facility exhaust
system 140. One of ordinary skill will appreciate that the process
of recombining or reacting by-products with cleaning gas or energy
from internal device 210 could continue for several iterations
resulting in the formation of fourth, fifth or even sixth gaseous
by-products or reduced viscosity by-products depending upon the
type of original by-product formed, the type and level of energy
provided by internal device 210 and the type and amount of cleaning
gas provided.
[0031] Cone shaped directional insert 260 is also disposed internal
to exhaust conduit 135 and is oriented within conduit 135 such that
inlet 265 opens towards chamber 200 and vertex 270 opens towards
internal energy device 210. Upper edge 275 of cone insert 260 is
between about 0.5 and 1.25 inches in diameter or about 0.88 inches
in diameter. Upper edge 275 forms a seal with the interior wall of
upper exhaust conduit 203 such that all material within upper
exhaust conduit 203 flows through cone insert 260. The cone shape
of insert 260 is advantageous because the concave interior surface
280 of cone insert 260 gathers and directs liquefied exhaust
by-products towards vertex 270. A cone shaped directional insert,
similar to insert 260, would be approximately between about 0.25
and 1.25 inches long. The cone's inherent vertex 270 is another
advantage of having a cone shaped directional insert. Concave
interior surface 280 works in conjunction with vertex 270 and upper
edge seal 275 to ensure that all liquefied by-products flow through
directional insert 260 and gather at vertex 270. Vertex 270 has a
circular opening approximately 0.5 inches in diameter.
Alternatively, vertex 270 could have an elliptical shaped opening
with approximately the same diameter.
[0032] One of ordinary skill in the art will recognize the
advantages of a cone shaped directional insert but will also
appreciate that alternative shapes may also provide advantageous
interior surfaces for gathering and directing by-products within
upper exhaust conduit 203. For example, an elongated cylinder
within conduit 203 or a semicircular shape angled within conduit
203 could provide advantageous results as well. Additionally,
directional insert 260 is advantageously situated such that vertex
270 is positioned directly above internal energy device 210. As a
result of this advantageous placement, fluids exiting vertex 270
will be directed so as to impinge on casing 220 at tip 240.
Directional insert 260 can be formed out of a corrosion resistant
material compatible with the material of conduit 135. Materials
suitable for the fabrication of casing 220 are quartz, Inconel,
Hastelloy, and other low iron content stainless steels such as
Haynes 242. An additional consideration for the fabrication of
insert 260 is the compatibility of the material selected with the
type of energy source 255 employed within the apparatus of the
present invention. For example, if energy source 255 is a UV lamp,
then both casing 220 and insert 260 could be formed from quartz or
similar material transparent to UV energy such that UV energy from
the lamp is transmitted through both casing 220 and insert 260 and
into portions of upper exhaust conduit 203 located upstream of
insert 260. Depending upon the type of internal energy source 255
employed as well as other factors such as the volume and
temperature of exhaust from reactor 200, internal energy device 210
and insert 260 should be advantageously placed within the exhaust
conduits such that condensation region or CR is proximate to insert
260 or between insert 260 and casing 220 of device 210.
[0033] Although the use of directional insert 260 has the
advantages described above, one of ordinary skill in the art will
appreciate that the advantageous results of the methods and
apparatus of internal energy device 210 of the present invention
can be obtained without the use of directional insert 260. In such
a case, energy from an embodiment of internal energy source 255
alone or in combination with cleaning gas or gases provided via
outlet 245 is sufficient to recombine or react by-products 145 into
gaseous or less viscous by-products which are more easily removed
by chamber 200 exhaust systems and wafer manufacturing facility
exhaust systems 140.
[0034] FIG. 2 illustrates by product 145 formation within the
apparatus of the present invention when internal energy device 210
is not in operation and no cleaning gas flows from conduit 225. As
described in the prior art, Zone A exists to about 2-3 cm beyond
exhaust manifold 130 where upper exhaust conduit 203 is heated by a
combination of heat sources from reactor 200 and high temperature
exhaust gases from processes conducted within reactor 200. Within
Zone B, upper exhaust conduit 203 and a portion of central exhaust
conduit 207 are heated by exhaust gases from reactor 200. Zone B,
shown between the dashed lines and arrows in FIG. 2, extends from
the downstream boundary of zone A where heat generated by reactor
200 becomes negligible to, depending on the temperature of the
exhaust gas, a point along casing 220 where the temperature of the
casing 220 and the interior of exhaust conduit 135 is about the
same as the ambient temperature surrounding conduit 135. As in the
prior art exhaust lines, a condensation region, CR, exists beyond
which by-product 145 will form within exhaust conduits. When
internal energy device 210 is not in operation, by-product 145 will
form on components within conduits 203 and 207 down stream of CR
such as insert 260, casing 220 and additional exhaust conduit
335.
[0035] FIG. 3 represents an embodiment of a method of the present
invention when an apparatus of the present invention, energy source
255', is in operation. In an embodiment of the present invention,
internal energy source 255' is a resistive heater and casing 220'
is fabricated from non-corrosive stainless steel having a low iron
content such as Hastelloy. In a specific embodiment of the present
invention, internal energy source 255" could be an Inconel
resistive heater such as a "fire-rod" type manufactured by and
commercially available from Watlow, Inc. Typical power ratings for
a resistive heater employed by the apparatus of the present
invention are between about 1.0 and 2.5 kW.
[0036] Zone A exists as described in FIG. 2. Zone B similarly
exists between the dashed lines and arrows indicated but note how
the zone is extended into conduit 335 as a result of the additional
energy provided by the resistive heater 255'. Additionally,
internal energy device 210' will add energy to the region within
Zone B surrounding casing 220' as well as above tip 240. As a
result of energy provided by internal energy device 210', the
temperature of directional insert 260 and exhaust conduit in
proximity to interface 275 is sufficiently high whereby the vapor
only portion of Zone B between the Zone A/Zone B interface and
condensation region CR will be expanded whereby CR is located
closer to inlet 265. Ideally internal energy device 210', insert
260 and outlet 245 of conduit 225 would be advantageously placed
whereby the combination of heat from the hot exhaust gases of
reactor 200 combined with energy from energy source 255' would
result in a CR at or in proximity to inlet 265, or in some
instances, the CR is completely removed. (See FIG. 5 below).
[0037] Internal energy device 210' similarly expands Zone B moving
the Zone B/Zone C boundary such that a portion of conduit 335
remains above the ambient temperatures surrounding conduit 335. The
distance between internal energy device 210' and exhaust system 140
could also be minimized thereby reducing the length of conduit 335
and increasing the likelihood that Zone B would extend to exhaust
system 140. Alternatively, the energy output of device 210' could
be raised wherein sufficient energy is provided into conduit 335
thus expanding Zone B into conduit 335 or to exhaust treatment
systems 140.
[0038] Regardless of specific type of internal energy source 255,
255' or 255" employed, internal energy source 210 is intended to
provide sufficient energy within exhaust conduits 203 and 207 to
break down or react with deposition and cleaning by-products formed
during operation of reactor 200 or similar reactors. By
advantageous placement and operation of the apparatus of the
present invention these by-products are broken down or reacted into
secondary, tertiary and other combinations of by-products which
remain in the vapor phase until removed by exhaust system 140. One
of ordinary skill will appreciate that a variety of methods can be
employed to react, recombine or otherwise remove by-products 145
within the various embodiments of the present invention.
[0039] Referring again to FIG. 3, one method and apparatus of
by-product removal combines the energy supplied by internal energy
device 210' with a cleaning gas provided via conduit 225. Energy
source 255', a resistive heater, heats casing 220', insert 260 and
conduit 203 above insert 260 which results in decreased viscosity
of by-product 145 deposited above insert 260. As a result,
by-product 145 flows toward and is gathered by directional insert
260. Vortex 270, advantageously placed above casing tip 240,
directs fluid or liquid by-product or a steady stream 350 of
by-product 145 onto the surface of casing 220' at tip 240. The
temperature of casing 220', as a result of internal energy source
255', is sufficient to further reduce the viscosity of the
by-product such that the by-product spreads 360 across the tip 240
and sides of casing 220'. A portion of spread by-product 360 will
vaporize, react with cleaning gas provided via outlet 245 and
recombine to form a compound which remains in the vapor phrase
until removed by exhaust treatment system 140.
[0040] The method and apparatus of the present invention provides
for the use of energy to break down, recombine or react the
undesired, highly viscous by-products into exhaustible, gaseous
compounds which remain gaseous until disposed of by exhaust
treatment systems 140. As described above, one method to achieve
such a gaseous by-product utilizes both the energy from internal
energy device 210 as well as cleaning gas supplied by conduit 225
via outlet 245. An alternative method of the present invention
forms exhaustible, gaseous by-products utilizing only the energy
provided by internal energy device 210 to cause recombination of
by-products 145 and the resulting formation of an exhaustible,
vapor-phase by-product.
[0041] In another embodiment of the present invention, by-products
145 break down and recombine to form an exhaustible, gaseous
by-product as a result only of the presence of cleaning gas
provided via outlet 245. In another alternative method of the
present invention, by-products 145 break down and recombine to form
a different, second by-product as a result of reacting with the
cleaning gas provided via outlet 245. This second by-product then
reacts and recombines forming a third by-product as a result of the
energy provided by internal energy device 210. This third
by-product then reacts and recombines with the cleaning gas to form
the desired exhaustible, gaseous by-product which remains gaseous
until removed by exhaust treatment systems 140. Some complex
by-products may repeat several times the above listed cycle of
reacting or recombining as a result of energy from device 210 and
then recombining as a result of reacting or recombining with a
cleaning gas before forming a gaseous, exhaustible by-product.
[0042] FIG. 4 represents an alternative apparatus of the present
invention where internal energy source 255" of internal energy
device 210" is a radiant energy source such as mercury vapor lamps,
quartz halogen lamps, carbon arc lamps or other UV or IR energy
sources. Casing 220" is fabricated from quartz or other material
transparent to the radiant energy of source 255". Directional
insert 260' could also be fabricated from material transparent to
the radiant energy of source 255" to facilitate energy transfer
between energy device 210" and by-products 145 within conduit 203
above insert 260'. Internal energy device 210" functions similarly
to devices 210 and 210' described above in that the energy provided
by internal energy source 255", e.g. radiant or UV energy, is
sufficient alone or in combination with a cleaning gas provided via
outlet 245 to react with and cause recombination of by-products 145
into exhaustible, gaseous by-products. Also as with devices 210 and
210", a cleaning gas provided via outlet 245 alone may be
sufficient to cause the formation of exhaustible, gaseous
by-products. Cleaning gas provided via outlet 245 may also cause
second and third by-product formations which, as described above,
may further react and recombine with a cleaning gas and radiant
energy provided by internal energy device 210" to form exhaustible,
gaseous by-products.
[0043] Turning now to FIG. 5, which as mentioned above, represents
a cross sectional view of an embodiment of the present invention
where internal energy device 210' is coupled sufficiently close to
exhaust manifold 130 such that CR is elimnated. The length of upper
exhaust conduit 203 is minimized such that internal energy device
210' is in close proximity to exhaust manifold 130. As a result,
energy from internal energy device 210' recombines or reacts with
exhaust by-products forming gaseous by-products as they exit
exhaust manifold 130. A representative spacing between internal
energy casing tip 240 and chamber 200 is between about 4 inches and
about 8 inches or about 6.25 inches. FIG. 5 also illustrates the
placement of conduit 255' above directional insert 260.
Representative dimensions for directional insert 260 are about 0.62
inches long with an upstream diameter of about 0.88 inches and a
downstream diameter of about 0.5 inches.
[0044] Like conduit 225, conduit 225' is coupled to bulk gas supply
230. The bulk gas supply provides cleaning gas used to react with
and remove exhaust line by-products. One such cleaning gas is
chlorine (Cl.sub.2). One of ordinary skill will appreciate that the
satisfactory results of the present invention can be achieved by
utilizing other cleaning gases such as: HCl, ClF.sub.3, F.sub.2,
NF.sub.3, and O.sub.3. Additionally, one of ordinary skill will
appreciate that a plurality of additional conduits similar to
conduit 225' and a plurality of bulk gas supplies similar to bulk
gas supply 230 can be attached in proximity to exhaust manifold 130
in order to independently provide multiple cleaning gases according
to the method of the present invention. As with conduit 225, gas
supplied to conduit 225' from bulk gas supply 230 is controlled by
flow controlling device 235. One such flow controlling device is a
mass flow controller. Placing outlet 245' of conduit 225' upstream
of directional insert 260 and directly into exhaust manifold 130
allows a cleaning gas, such as chlorine (Cl.sub.2), to mix with,
recombine or break down cleaning and deposition by-products almost
immediately after said by-products enter exhaust manifold 130.
[0045] The dimensions of internal energy source 210', central and
lower exhaust conduits 207 and 335 are preferentially selected to
minimize interference with gas flow and not result in excessive
back pressure in chamber 200. One method of minimizing gas flow
interference and preventing back pressure is to obtain nearly equal
cross-sectional flow areas between central exhaust conduit 207 and
lower exhaust conduit 335. Representative dimensions of casing 220'
of internal energy device 210' is about 14.5 inches in length, and
about 1.28 inches in diameter. Central exhaust conduit 207 has
representative dimensions of an outer diameter of about 2.0 inches
and a wall thickness of about 0.065 inches. These representative
dimensions result in a cross-sectional flow area within central
exhaust conduit 207 of about 1.46 square inches.
[0046] Representative dimensions of lower exhaust conduit 335 are
an outer diameter of about 1.5 inches and a wall thickness of about
0.065 inches which results in a cross sectional flow area of about
1.47 square inches. Thus, by advantageously selecting the
dimensions of conduits 207 and 335 and casing 220', a nearly
constant cross sectional flow area between central exhaust conduit
207 and lower exhaust conduit 335 is achieved which results in
minimized adverse impact on gas flow and chamber back pressure.
[0047] Thus, it is apparent that there has been provided, in
accordance with the present invention, methods and apparatuses
which minimize or inhibit by-product condensation and polymeric
formation within reactor exhaust conduits that meet the objects and
advantages set forth above. While specific embodiments of the
invention have been shown and described, further modifications and
improvements will occur to those skilled in the art. It is desired
that it be understood, therefore, that this invention is not
limited to the particular forms shown and is intended in the
appended claims to cover all modifications which do not depart from
the spirit and scope of the invention.
* * * * *