U.S. patent application number 09/737676 was filed with the patent office on 2001-10-18 for apparatus and method for cleaning a vertical furnace pedestal and cap.
Invention is credited to Guldi, Richard L., Poag, Frank D., Pressnall, William.
Application Number | 20010029681 09/737676 |
Document ID | / |
Family ID | 26870117 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010029681 |
Kind Code |
A1 |
Pressnall, William ; et
al. |
October 18, 2001 |
Apparatus and method for cleaning a vertical furnace pedestal and
cap
Abstract
A system (10) is disclosed for cleaning a vertical furnace (12)
pedestal (34) and cap (36) including at least one inlet conduit
(40) in fluid communication with a pressurized cleaning medium
source (46). The system also includes at least one exhaust conduit
(42) in fluid communication with a negative pressure source (48). A
boat assembly (30) may be positioned such that the at least one
conduit (40) is operable to direct cleaning medium at the boat
assembly (30) to dislodge contaminate particles associated with the
boat assembly. The exhaust outlet (42) then evacuates the cleaning
medium and any dislodged contaminate particles. The system may
operate automatically within a closed processing environment and
after each process cycle.
Inventors: |
Pressnall, William;
(Richardson, TX) ; Poag, Frank D.; (Plano, TX)
; Guldi, Richard L.; (Dallas, TX) |
Correspondence
Address: |
TEXAS INSTRUMENTS INCORPORATED
P O BOX 655474, M/S 3999
DALLAS
TX
75265
|
Family ID: |
26870117 |
Appl. No.: |
09/737676 |
Filed: |
December 14, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60174324 |
Jan 4, 2000 |
|
|
|
Current U.S.
Class: |
34/409 ; 134/21;
134/37; 15/345; 34/516 |
Current CPC
Class: |
H01L 21/67028 20130101;
Y10S 438/905 20130101 |
Class at
Publication: |
34/409 ; 134/21;
134/37; 15/345; 34/516 |
International
Class: |
B08B 005/02; F26B
005/04 |
Claims
What is claimed is:
1. A vertical furnace system for semiconductor processing
comprising: a boat assembly having a pedestal operable to be
disposed in a vertical furnace; at least one inlet conduit operable
to communicate a cleaning medium from a pressurized cleaning medium
source; the at least inlet conduit further operable to direct the
pressurized cleaning medium at the pedestal to dislodge impurities
associated with the pedestal; and at least one exhaust conduit in
fluid communication with a negative pressure source, operable to
evacuate the directed cleaning medium and any dislodged
impurities.
2. The system of claim 1 wherein the cleaning medium comprises
inert gas.
3. The system of claim 1 wherein the cleaning medium comprises
nitrogen.
4. The system of claim 1 wherein the cleaning medium comprises
clean dry air.
5. The system of claim 1 further comprising an elevator assembly
coupled to the boat assembly operable to transfer the boat assembly
from the vertical furnace to a cleaning position spaced from the
vertical furnace.
6. The system of claim 1 further comprising: an elevator assembly
operable to transfer the boat assembly from the vertical furnace to
a cleaning position spaced from the vertical furnace; a shroud
assembly operable to surround the pedestal when the boat assembly
is placed in the cleaning position; and the shroud assembly shaped
for directing the cleaning medium from the at least one inlet
conduit to the at least one exhaust conduit.
7. The system of claim 1 wherein the boat assembly further
comprises: a boat for securing at least one substrate wafer; the
pedestal comprising a plurality of disks disposed in a
substantially horizontal position spaced from one another, the
pedestal coupled to the boat such that the pedestal supports the
boat; and a cap coupled to the pedestal distal the cap, the cap
operable to form a seal when disposed adjacent to a bottom portion
of the vertical furnace.
8. The system of claim 1 further comprising: a plurality of inlet
conduits operable to communicate the cleaning medium from the
cleaning medium source; and the plurality of inlet conduits further
operable to direct the cleaning medium at the pedestal.
9. The system of claim 1 further comprising a plurality of exhaust
conduits in fluid communication with the negative pressure source
positioned for receiving the cleaning medium exiting the at least
one inlet conduit.
10. The system of claim 1 further comprising: a process chamber
housing the vertical furnace, the boat assembly, the at least on
inlet conduit, and the at least one exhaust conduit; and the
process chamber operable to regulate the environment within the
process chamber.
11. A system for cleaning a vertical furnace used to process
semiconductor devices comprising: at least one inlet conduit in
fluid communication with a pressurized cleaning medium source
operable to direct a pressurized cleaning medium at a boat
assembly; at least one exhaust conduit in fluid communication with
a negative pressure source; and the exhaust conduit positioned to
receive the cleaning medium exiting the at least one inlet
conduit.
12. The system of claim 11 wherein the cleaning medium is an inert
gas.
13. The system of claim 11 wherein the inlet conduit further
comprises a nozzle coupled to the inlet conduit for directing the
cleaning medium at the boat assembly.
14. The system of claim 11 further comprising: a shroud assembly
associated with the at least one inlet conduit and the at least one
exhaust conduit operable to direct the flow of cleaning medium
around a pedestal disposed within the shroud assembly; and the
shroud assembly shaped for directing the cleaning medium exiting
the at least one inlet conduit to the at least one exhaust
conduit.
15. The system of claim 11 further comprising: at least one flow
control device disposed between the pressurized cleaning medium
source and the at least one inlet conduit; and the flow controller
operable to selectively allow at least one pulse of pressurized
cleaning medium to exit the pressurized cleaning medium source and
communicate with the at least one inlet conduit.
16. A method for cleaning a vertical furnace boat assembly during
semiconductor processing comprising: placing the boat assembly in a
cleaning position; directing a pressurized cleaning medium at the
boat assembly to dislodge impurities associated with the boat
assembly; and evacuating the pressurized cleaning medium and any
dislodged impurities through an exhaust conduit in fluid
communication with a negative pressure source.
17. The method of claim 16 wherein the cleaning medium comprises an
inert gas.
18. The method of claim 16 further comprising directing the
pressurized cleaning medium at a pedestal supporting the boat
assembly.
19. The method of claim 16 further comprising: moving the boat
assembly to a loading position; loading at least one substrate
wafer onto the boat assembly; placing the boat assembly in an
interior cavity of a vertical furnace; processing the at least one
substrate wafer within the vertical furnace; moving the boat
assembly to the loading position; unloading the at least one
substrate wafer; and repeating the placing the boat assembly in a
cleaning position, directing the cleaning medium, and evacuating
the cleaning medium.
20. The method of claim 16 wherein said directing further comprises
directing at least one pressurized pulse of cleaning medium.
Description
TECHNICAL FIELD
[0001] This invention relates in general to the field of electronic
devices. More specifically this invention relates to an apparatus
and method for cleaning a vertical furnace pedestal and cap.
BACKGROUND OF THE INVENTION
[0002] Semiconductor fabrication environments are typically
required to maintain high levels of cleanliness. Impurities
associated with wafers, processing equipment, and operators may
lead to defects in the semiconductor devices manufactured, often
rendering them unusable for their intended purpose. These defects
often have serious negative effects on product yield and
profitability. Semiconductor fabrication typically takes place in
so-called clean room environments where operators wear non-linting
garments, overshoes, gloves, and masks to limit the introduction of
contaminate particles into the fabrication environment.
Semiconductor substrate wafers are often processed during
fabrication to remove contaminates and impurities.
[0003] Vertical furnaces are often used to facilitate high
temperature processing of multiple semiconductor substrate wafers.
Often, a heated process fluid enters the vertical furnace through
an inlet at a bottom portion of the vertical furnace. Process fluid
then flows through the vertical furnace before exiting through an
exhaust outlet. The vertical furnace typically has an interior
cavity sized to allow a wafer carrier assembly, often referred to
as a boat assembly, to be loaded inside the cavity and an automated
elevator apparatus to insert and remove the boat assembly in and
out of the furnace cavity. However, some vertical furnaces may be
loaded manually.
[0004] The boat assembly supports multiple substrate wafers during
processing within a vertical furnace. The boat assembly typically
includes a wafer carrier or boat, and a pedestal and a cap that
support the boat. The pedestal often includes insulating quartz
baffles. Because process fluid typically enters the vertical
furnace adjacent to the baffles, impurities and contaminates often
collect on the pedestal. Impurities also collect on the pedestal
and cap because it may located beneath wafer loading equipment and
because particles within the vertical furnace often fall within the
interior of the furnace, where the pedestal and cap are located
during processing. These impurities can later dislodge and
contaminate the substrate wafers being treated within the vertical
furnace.
[0005] The pedestal and cap can be cleaned manually to remove
accumulated contaminate particles. However, this cleaning
interrupts fabrication processes, consuming valuable time and
resources. Often, manual cleaning is periodic, taking place only
after several process runs and after impurities and contaminate
particles have built up on the pedestal. Also, manual cleaning
within a controlled process environment can disturb the process
environment by introducing dislodged impurities and cleaning medium
therein.
SUMMARY OF THE INVENTION
[0006] In accordance with teachings of the present invention, a
system and method for cleaning a vertical furnace pedestal and cap
are described which substantially eliminate or reduce disadvantages
and problems associated with prior systems and methods. The system
includes at least one inlet conduit in fluid communication with a
pressurized cleaning medium source. The system also includes at
least one exhaust conduit in fluid communication with a negative
pressure source. A boat assembly may be positioned such that the at
least one conduit is operable to direct a cleaning medium at the
boat assembly to dislodge contaminate particles associated with the
boat assembly. The exhaust outlet then evacuates the cleaning
medium and any dislodged contaminate particles. The system may
operate automatically within a closed processing environment.
Additionally the system may clean the boat after each process
cycle. The exhaust conduit acts to remove the cleaning medium and
any dislodged particles to maintain a desired level of cleanliness
within the process environment.
[0007] In one aspect of the present invention the vertical furnace
system includes a boat assembly with a pedestal. The boat assembly
is operable to be disposed within a vertical furnace. The system
also includes at least one inlet conduit that communicates a
cleaning medium from a pressurized cleaning medium source and
directs the pressurized cleaning medium at the pedestal to dislodge
impurities associated with the pedestal. At least one exhaust
conduit is in fluid communication with a negative pressure source
and is operable to evacuate the cleaning medium and any dislodged
impurities.
[0008] More specifically, the boat assembly further includes a boat
for securing at least one substrate wafer. The pedestal supports
the boat and preferably includes an insulating baffle or disks
disposed in a substantially horizontal position spaced from one
another. A cap may be coupled to the pedestal distal the boat. The
cap is preferably operable to form a seal when disposed adjacent to
a bottom portion of the vertical furnace.
[0009] In another aspect of the present invention, the system
includes at least one inlet conduit and at least one exhaust
conduit. The at least one inlet conduit is in fluid communication
with a pressurized cleaning medium source operable to direct a
pressurized cleaning medium at a boat assembly. The at least one
exhaust conduit is in fluid communication with a negative pressure
source and is positioned to receive the cleaning medium exiting the
at least one inlet conduit.
[0010] More specifically at least one flow control device may be
disposed between the pressurized cleaning medium source and the at
least one inlet conduit. The flow controller may selectively allow
a pulse or series of pulses of pressurized cleaning medium to exit
the pressurized cleaning medium source and communicate to the at
least one inlet conduit.
[0011] In yet another aspect of the present invention a method for
cleaning a boat assembly during semiconductor processing includes
placing the boat assembly in a cleaning position. A pressurized
cleaning medium is then directed at the boat assembly to dislodge
impurities associated with the boat assembly. The pressurized
cleaning medium and any dislodged impurities are then evacuated
through an exhaust conduit in fluid communication with a negative
pressure source. More specifically, the method includes directing a
pressurized pulse of cleaning medium at the boat assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] A more complete understanding of the present embodiments and
advantages thereof may be acquired by referring to the following
description taken in conjunction with the accompanying drawings, in
which like reference numbers indicate like features, and
wherein:
[0013] FIG. 1 is a schematic diagram of a semiconductor fabrication
apparatus including a vertical furnace and boat assembly
incorporating teachings of the present invention; and
[0014] FIG. 2 is a schematic diagram of a semiconductor fabrication
apparatus including a loading station incorporating teachings of
the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0015] Preferred embodiments and their advantages are best
understood by reference to FIGS. 1 and 2 wherein like numbers are
used to indicate like and corresponding parts. FIG. 1 is a
schematic diagram of a semiconductor fabrication apparatus
indicated generally at 10 including vertical furnace 12 and boat
assembly 30 incorporating teachings of the present invention.
Vertical furnace 12 includes interior cavity 13, a substantially
cylindrical cavity defined by the interior walls of vertical
furnace 12. Opening 20 allows boat assembly 30 to be inserted into
interior cavity 13. Furnace inlet 22 acts to communicate process
fluids into interior cavity 13 for heat treatment processing.
Furnace inlet 22 communicates process fluid into a bottom portion
of interior cavity 13. Process fluids travel through the interior
cavity, around quartz tubes 16 and exits vertical furnace 12
through furnace outlet 26.
[0016] Vertical furnace 12 also includes liner 18 and heater
element 14. Liner 18 is located radially spaced from interior
cavity 13. Heater element 14 is located radially spaced from liner
18. Heater element 14 acts to heat vertical furnace 12 for
processing and may be a heating wire wrapped circumferentially
around vertical furnace 12 or another suitable heater device. Liner
18 may be a silicon carbide liner.
[0017] Boat assembly 30 is preferably coupled to elevator assembly
44. Elevator 44 is operable to raise and lower boat 30 such that
boat assembly 30 can be raised into interior cavity 13 or lowered
from vertical furnace 12. In an alternative embodiment, elevator
assembly 44 may transfer boat assembly to other positions as shown
in FIG. 2.
[0018] Boat assembly 30 preferably includes boat 32 having a
plurality of slotted rods 33 operable to support semiconductor
devices (not expressly shown) for processing within vertical
furnace 12. Boat 32 extends from pedestal 34. Pedestal 34 includes
a baffle assembly 35 in the present embodiment. The baffle assembly
35 is typically made up of a plurality of quartz disks positioned
substantially horizontally and spaced from one another. Pedestal 34
is preferably attached to and supported by cap 36. Cap 36 is
further coupled to elevator assembly 44. When elevator assembly 44
raises boat assembly 30 into interior cavity 13 of vertical furnace
12, cap 36 preferably contacts opening 20 forming a seal with
pedestal 34. Pedestal 34 is preferably positioned adjacent to
furnace inlet 22. In the present embodiment the seal between
opening 20 and cap 36 may be an air tight seal.
[0019] Elevator assembly 44 may selectively lower boat assembly 30
into a cleaning position as shown in FIG. 1. While in this cleaning
position, pedestal 34 and cap 36 are substantially surrounded by a
cowling or shroud assembly 38. Shroud assembly 38 includes inlet
conduits 40 which are preferably in fluid communication with
cleaning medium source 46. Cleaning medium source 46 preferably is
a pressurized cleaning medium source. Shroud assembly 38 further
includes exhaust outlet 42. Exhaust outlet 42 is preferably in
fluid communication with negative pressure source 48. Shroud
assembly 38 is preferably shaped for directing cleaning medium from
inlet conduits 40 to exhaust outlet 42.
[0020] In operation, elevator assembly 44 raises boat assembly 30
into interior cavity 13 for desired heat treatment processing.
After the heat treatment processing, the boat assembly is
preferably removed from vertical furnace 12 and semiconductor
devices such as semiconductor substrate wafers are removed from
boat assembly 30. Boat assembly 30 is preferably moved into the
cleaning position such that inlet conduits 40 may direct cleaning
medium from cleaning medium source 46 to pedestal 34 and cap
36.
[0021] When cleaning medium is released from cleaning medium source
46, it travels to inlet conduits 40. Cleaning medium directed from
inlet conduit 40 interacts with pedestal 34 and cap 36 to dislodge
any impurities or contaminant particles associated with pedestal 34
and cap 36. As cleaning medium is released from cleaning medium
source 46 exhaust outlet 42 communicates negative pressure from
negative pressure source 48. As cleaning medium interacts with
pedestal 34, cleaning medium is preferably drawn into exhaust
outlet 42 by negative pressure from negative pressure source 48.
Negative pressure source 48 acts to evacuate cleaning medium and
any dislodged impurities or contaminate particles. Cleaning medium
is preferably an inert gas such as nitrogen. In an alternative
embodiment, cleaning medium may be clean dry air.
[0022] In the present embodiment a pair of inlet conduits 40 are
shown. In alternative embodiments, a single inlet conduit may be
employed. In further alternative embodiments a plurality of inlet
conduits or an array of inlet conduits may be employed to clean
pedestal 34. For embodiments in which multiple inlet conduits are
used, the inlet conduits may be spaced for selective introduction
of cleaning medium from cleaning medium source 46.
[0023] The present embodiment discloses a single exhaust outlet 42.
In an alternative embodiment, multiple exhaust outlets may be used
to evacuate cleaning medium and any dislodged particles or
impurities from pedestal 34.
[0024] In an alternative embodiment, inlet conduits 40 may be
selectively positioned for selectively directing cleaning medium at
pedestal 34. In this alternative embodiment inlet conduits may
employ flexible tubing or directable nozzles for selectively
directing the cleaning medium.
[0025] FIG. 2 is a schematic diagram of a semiconductor fabrication
apparatus 10a including a loading station 64 according to the
teachings of the present invention. The system 10A includes process
chamber 66 housing vertical furnace 12, boat assembly 30 and
loading assembly 64. A control system (not expressly shown) may be
associated with process chamber 66 to selectively regulate the
environment within process chamber 66. Vertical furnace 12 includes
furnace inlet 22 in fluid communication with vertical furnace 12
and a process fluid source (not expressly shown). Furnace inlet 22
allows for selective introduction of process fluid into vertical
furnace 12 for processing. Exhaust conduit 26 is preferably in
fluid communication with vertical furnace for allowing process
fluids to exit vertical furnace 12.
[0026] Boat assembly 30 is preferably coupled to elevator 44.
Elevator 44 is operable to raise, lower and rotate pedestal 34
between different positions within process chamber 66. Elevator 44
may raise boat assembly 30 into an interior cavity 13 of vertical
furnace 12. Elevator 44 is operable to lower boat assembly 30 into
the cleaning position. Elevator 44 is further operable to move boat
assembly 30 into a loading position such that loading assembly 64
may load semiconductor devices such as substrate wafers 65 onto
boat assembly 30 to process within vertical furnace 12.
[0027] Shroud assembly 38 includes inlet conduits 40 in fluid
communication with flow controller 62. Flow controller 62 is
preferably in fluid communication with cleaning medium source 46
(as shown in FIG. 1). Flow controller 62 is operable to selectively
allow cleaning medium to flow from cleaning medium source to inlet
conduits 40. Flow controller 62 may be operable to selectively
allow a pulse or a plurality of pulses to flow from cleaning medium
source 46. Flow controller 62 may be associated with a system
controller (not expressly shown) having software operable to
selectively operate flow controller 62. Nozzles 60 are preferably
coupled to inlet conduits 40 for directing cleaning medium exiting
inlet conduits 40 to pedestal 34. Exhaust conduit 42 is positioned
to receive cleaning medium exiting inlet conduits 40.
[0028] Exhaust outlet 42 is preferably in fluid communication with
negative pressure source 48 (as shown in FIG. 1). Exhaust
controller 63 is preferably in fluid communication with exhaust
outlet 42 and negative pressure source 48. Exhaust controller 63 is
preferably operable to selectively communicate negative pressure to
exhaust outlet 42. Exhaust controller 63 may be associated with a
system controller (not expressly shown) having software operable to
selectively operate exhaust controller 63.
[0029] In operation, elevator 44 moves boat assembly 30 into a
loading position operable for loading assembly 64 to load substrate
wafers 65 onto boat 32. Elevator 44 then rotates boat assembly 30
to a position directly beneath vertical furnace 12. Elevator 44
then raises boat assembly 30 such that boat assembly 30 is inserted
into interior cavity 13 within vertical furnace 12 and cap 36
contacts and forms a seal with a bottom portion of vertical furnace
12. After processing within vertical furnace 12, elevator 44 lowers
boat assembly 30 from vertical furnace 12.
[0030] Elevator 44 moves boat assembly 30 to a position adjacent
loading assembly 64 such that loading assembly 64 can unload the
processed semiconductor devices from boat assembly 30. Boat
assembly 30 is then preferably moved to a cleaning position such
that pedestal 34 is positioned generally adjacent to inlet conduits
40. Flow controller 62 then allows cleaning medium to be
communicated to inlet conduits 40. Flow controller 62 may allow
single pulse or a series of pulses of cleaning medium to
communicate to inlet conduits 40. Cleaning medium travels through
inlet conduits 40 and through nozzles 60.
[0031] Cleaning medium exiting nozzles 60 interacts with pedestal
34 and cap 36 such that cleaning medium acts to dislodge
contaminate particles and impurities from pedestal 34 and cap 36.
When flow controller 62 operates to allow cleaning medium to flow
to inlet conduits 40, exhaust controller 63 allows exhaust conduit
42 to communicate with negative pressure source 48 (as shown in
FIG. 1). Exhaust controller 63 can allow the negative pressure
source to communicate with exhaust outlet 42 before flow controller
62 opens or after. Cleaning medium and any dislodged particles are
evacuated through exhaust conduit 42.
[0032] In the present embodiment, elevator 44 acts to raise or
lower boat assembly 30 or rotate boat assembly 30 into a position
for loading. In an alternative embodiment, any suitable transfer
mechanism or transfer assembly may be used to move boat assembly 30
from within vertical furnace 12 to loading assembly 64 and to a
cleaning position.
[0033] Although the disclosed embodiments have been described in
detail, it should be understood that various changes,
substitutions, and alterations can be made to the embodiments
without departing from their spirit and scope.
* * * * *