U.S. patent application number 09/790769 was filed with the patent office on 2001-11-22 for molecular contamination control system.
Invention is credited to Comer, Wayland, Eglinton, Robert B., Genco, Robert M., Mundt, Gregory K., Roberson, Glenn A. JR..
Application Number | 20010042439 09/790769 |
Document ID | / |
Family ID | 24865973 |
Filed Date | 2001-11-22 |
United States Patent
Application |
20010042439 |
Kind Code |
A1 |
Roberson, Glenn A. JR. ; et
al. |
November 22, 2001 |
Molecular contamination control system
Abstract
The system and method for molecular contamination control
permits purging a SMIF pod to desired levels of relative humidity,
oxygen, or particulates. The SMIF pod includes an inlet port
including a check valve and filter assembly for supplying a clean,
dry gaseous working fluid to maintain low levels of moisture,
oxygen, and particulate content around materials contained in the
SMIF pod. The SMIF pod outlet port, which also includes a check
valve and filter assembly, is connected with an evacuation system.
Flow of purge gas inside the SMIF pod can be directed with one or
more nozzle towers to encourage laminar flow inside the pod, and
one or more outlet towers, having a function similar to that of the
inlet tower, may also be provided. The purge gas can be dried by
exposure to a desiccant, heated to temperatures between about
100.degree. C. and about 120.degree. C., and can be tested for
baseline constituent levels prior to or after introduction into a
SMIF pod. Multiple SMIF pods can also be purged by a single
contamination control base unit.
Inventors: |
Roberson, Glenn A. JR.;
(Hollister, CA) ; Genco, Robert M.; (Atlanta,
GA) ; Eglinton, Robert B.; (Carmel, CA) ;
Comer, Wayland; (Salinas, CA) ; Mundt, Gregory
K.; (Duluth, GA) |
Correspondence
Address: |
FULWIDER PATTON LEE & UTECHT, LLP
HOWARD HUGHES CENTER
6060 CENTER DRIVE
TENTH FLOOR
LOS ANGELES
CA
90045
US
|
Family ID: |
24865973 |
Appl. No.: |
09/790769 |
Filed: |
February 21, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09790769 |
Feb 21, 2001 |
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09460616 |
Dec 14, 1999 |
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6221163 |
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09460616 |
Dec 14, 1999 |
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09240254 |
Jan 29, 1999 |
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6042651 |
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09240254 |
Jan 29, 1999 |
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08713396 |
Sep 13, 1996 |
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5879458 |
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Current U.S.
Class: |
95/8 ; 55/385.2;
55/417; 55/420; 95/138; 95/90; 96/108; 96/111; 96/147 |
Current CPC
Class: |
H01L 21/67769 20130101;
Y10S 414/135 20130101; H01L 21/67393 20130101; H01L 21/67389
20130101; H01L 21/67017 20130101; H01L 21/67775 20130101 |
Class at
Publication: |
95/8 ; 95/90;
95/138; 96/108; 96/111; 96/147; 55/385.2; 55/417; 55/420 |
International
Class: |
B01D 053/02 |
Claims
What is claimed is:
1. A system for purging an environment for semiconductor
manufacturing materials, to desired levels of relative humidity,
oxygen and particulates, comprising: a modular isolation capsule
having a housing defining a chamber for semiconductor manufacturing
materials, said housing including a base; an inlet port disposed in
said base for admitting a gaseous working fluid to said modular
isolation capsule for purging said modulation isolation chamber
with said gaseous working fluid, said inlet port including a check
valve and filter assembly for permitting one-way flow of said
gaseous working fluid into said modular isolation capsule and for
filtering said gaseous working fluid being admitted to said modular
isolation capsule; an outlet port disposed in said base for
removing said gaseous working fluid from said modular isolation
capsule, said outlet port including a check valve assembly for
permitting one-way flow of said gaseous working fluid being removed
from said modular isolation capsule; a source of gaseous working
fluid for purging said modular isolation capsule; and a molecular
contamination control base assembly having a gaseous working fluid
supply port connected in fluid communication with said source of
gaseous working fluid, said base assembly gaseous working fluid
supply port being adapted to mate in sealed fluid communication
with said modular isolation capsule inlet port, and said molecular
contamination control base assembly having a base assembly exhaust
port adapted to mate in sealed fluid communication with said
modular isolation capsule outlet port.
2. The system of claim 1, wherein said inlet port comprises an
inlet tower having a plurality of spaced apart orifices.
3. The system of claim 2, wherein said spaced apart orifices
comprise a series of nozzles that are graduated in size.
4. The system of claim 1, wherein said inlet port comprises an
inlet tower having a plurality of spaced apart radial slotted
ports.
5. The system of claim 1, wherein said outlet port comprises an
outlet tower having a plurality of spaced apart orifices.
6. The system of claim 1, wherein said outlet port comprises an
outlet tower having a plurality of spaced apart radial slotted
ports.
7. The system of claim 1, wherein said molecular contamination
control base assembly further comprises a vacuum pump in fluid
communication with the base assembly exhaust port for removing said
gaseous working fluid, particulate contaminants, oxygen, and
humidity entrained in said gaseous working fluid from said modular
isolation capsule.
8. The system of claim 1, wherein said molecular contamination
control base assembly comprises a plurality of pairs of said base
assembly gaseous working fluid supply ports and said base assembly
exhaust ports for matingly receiving a plurality of said modular
isolation capsules.
9. The system of claim 1, wherein said molecular contamination
control base assembly comprises a desiccant chamber containing a
desiccant for drying said gaseous working fluid being supplied to
said modular isolation capsule.
10. The system of claim 1, wherein said molecular contamination
control base assembly comprises a heater for heating said gaseous
working fluid being supplied to said modular isolation capsule to a
temperature between about 100.degree. C. and about 120.degree.
C.
11. The system of claim 1, wherein said molecular contamination
control base assembly comprises a sensor for monitoring relative
humidity of said gaseous working fluid being supplied to said
modular isolation capsule.
12. The system of claim 1, wherein said molecular contamination
control base assembly comprises a sensor for monitoring oxygen
content of said gaseous working fluid being supplied to said
modular isolation capsule.
13. The system of claim 1, wherein said molecular contamination
control base assembly comprises a sensor for monitoring particulate
content of said gaseous working fluid being supplied to said
modular isolation capsule.
14. The system of claim 1, wherein said molecular contamination
control base assembly comprises a sensor for monitoring relative
humidity of said gaseous working fluid exiting from said modular
isolation capsule.
15. The system of claim 1, wherein said molecular contamination
control base assembly comprises a sensor for monitoring oxygen
content of said gaseous working fluid exiting from said modular
isolation capsule.
16. The system of claim 1, wherein said molecular contamination
control base assembly comprises a sensor for monitoring particulate
content of said gaseous working fluid exiting from said modular
isolation capsule.
17. A method for purging an environment in a modular isolation
capsule for semiconductor manufacturing materials, to desired
levels of relative humidity, oxygen and particulates within the
modular isolation capsule, the modular isolation capsule having a
base including an inlet port disposed in said base for admitting a
gaseous working fluid to said modular isolation capsule for purging
said modulation isolation chamber, an outlet port disposed in the
base for removing said gaseous working fluid from said modular
isolation capsule, a source of gaseous working fluid for purging
said modular isolation capsule, and a molecular contamination
control base assembly having a base assembly gaseous working fluid
supply port being adapted to mate in sealed fluid communication
with said modular isolation capsule inlet port and a base assembly
exhaust port adapted to mate in sealed fluid communication with
said modular isolation capsule outlet port, the steps of the method
comprising: supplying a flow of gaseous working fluid to the
modular isolation capsule for purging the modulation isolation
chamber of moisture, oxygen and particulates; maintaining the flow
of said gaseous working fluid at a laminar flow velocity to
encourage laminar flow inside the pod; and withdrawing the gaseous
working fluid with the moisture, oxygen and particulates entrained
therein from the modular isolation capsule.
18. The method of claim 17, wherein said step of maintaining the
flow of said gaseous working fluid at a laminar flow velocity
comprises maintaining the flow of said gaseous working fluid at a
laminar flow velocity that is below sonic flow velocity.
19. The method of claim 17, further comprising the step of drying
said gaseous working fluid being supplied to said modular isolation
capsule.
20. The method of claim 17, further comprising the step of heating
said gaseous working fluid being supplied to said modular isolation
capsule to a temperature between about 100.degree. C. and about
120.degree. C.
21. The method of claim 17, further comprising the step of
monitoring oxygen content of said gaseous working fluid being
supplied to said modular isolation capsule.
22. The method of claim 17, further comprising the step of
monitoring particulate content of said gaseous working fluid being
supplied to said modular isolation capsule.
23. The method of claim 17, further comprising the step of
monitoring relative humidity of said gaseous working fluid being
supplied to said modular isolation capsule.
24. The method of claim 17, further comprising the step of
monitoring relative humidity of said gaseous working fluid exiting
from said modular isolation capsule.
25. The method of claim 17, further comprising the step of
monitoring oxygen content of said gaseous working fluid exiting
from said modular isolation
26. The method of claim 17, further comprising the step of
monitoring particulate content of said gaseous working fluid
exiting from said modular isolation capsule.
Description
BACKGROUND OF THE INVENTION
[0001] 1.Field of the Invention
[0002] This invention relates generally to systems and methods for
semiconductor fabrication, and more particularly concerns systems
and methods for purging a modular isolation chamber such as a
standard mechanical interface box or pod used for storing or
transporting semiconductor manufacturing materials, to desired
levels of relative humidity, oxygen, or particulates.
[0003] 2.Description of Related Art
[0004] A modular isolation chamber such as a standard mechanical
interface (SMIF) box, or pod, typically provides a microenvironment
to isolate and control the environment surrounding a wafer,
cassette of wafers or substrates used in manufacturing integrated
circuits, during storage, transport and processing of the
materials. Processing of such materials traditionally has been
carried out in a particulate free environment generally known as a
"clean room". However, maintenance of such "clean rooms" in a
contaminant free state can require a great deal of care and effort,
particularly during processing of the materials.
[0005] In one conventional system in which a SMIF system is used to
replace a traditional clean room, filtered air is circulated in the
SMIF box, and still air is used to achieve cleanliness in the SMIF
box. A particle-free dockable interface for linking together two
spaces each enclosing a clean air environment includes interlocking
doors on each space that fit together to trap particles which have
accumulated from the dirty ambient environment on the outer
surfaces of the doors.
[0006] A processing apparatus and technique is also known for
thermal processing in the manufacture of semiconductor devices, to
prevent outside air from entering a reaction tube. Loading and
unloading an object to be processed is typically effected by an
insertion jig outside a heating section, to prevent outside air
from entering the heated processing chamber.
[0007] While such systems can control the level of particulates in
a SMIF box, the presence of oxygen can also degrade the surface of
semiconductor materials. In one conventional process for preventing
the formation of native oxides on the surface of semiconductor
materials, silicon nitride layers are formed on silicon substrates.
Purge systems are also known, such as one in which a movable
cantilevered purge system provides for a wafer load position, a
wafer purge position, and a wafer process position. A purge
injector and return exhaust tube are provided in an elephant tube
which provides for access to wafer loads. In another known system,
the manufacturing materials are subjected to cold nitrogen purge
cycles, and particles and particle-generated defects during gas
phase processing such as during deposition are decreased by
controlling particle transport mechanisms, such as by applying low
level radiant energy during cold nitrogen purge cycles.
[0008] The presence of humidity in a SMIF box can also be
undesirable. One conventional method and apparatus for cleaning
integrated circuit wafers utilizes dry gases. At least one of the
gases is excited by passing the gas through a microwave plasma
generator or by heating the wafer, exciting the gases near the
surface of the wafer, causing chemical reactions similar to those
induced by ionization of nongaseous cleaning materials in water.
After an etching period, the etching chamber is purged by inert
gas, such as nitrogen, which helps carry away the remaining reacted
contaminants, which can include vaporous halogens or radicals that
can be present after conventional processes, such as chlorine,
bromine, arsine, silane, and the like.
[0009] However, there remains a need for a system and method of
purging SMIF pods to consistently maintain desired levels of
relative humidity, oxygen, or particulates while the pods are
otherwise not required, such as while waiting for a next production
station or step in a fabrication facility. These periods have been
estimated to be about six minutes to several hours long. Ideally,
the SMIF pod should be completely purged to desired levels of
relative humidity, oxygen, or particulates in a period of about 6
minutes or less. The present invention meets these needs.
SUMMARY OF THE INVENTION
[0010] Briefly, and in general terms, the present invention
provides for an improved system and method for purging a SMIF pod
to desired levels of relative humidity, oxygen, or particulates. In
one preferred embodiment, the SMIF pod includes an inlet port and
an outlet port, each including a check valve filter assembly, for a
clean, dry gaseous working fluid that is used to provide controlled
low levels of moisture, oxygen, and particulate content around the
materials contained in the SMIF pod. The SMIF pod inlet port is
connected with a gaseous working fluid source, and the outlet port
is connected with an evacuation system. The integral directional
flow check valves operate at very low pressure differentials (such
as less than 10 millibar).
[0011] The method of the invention also provides for improvements
to a purge process by drying of purge gas by exposure to a
desiccant; heating the purge gas to temperatures above 100.degree.
C., but below the thermal sensitivity of the pod, i.e., 105 to
120.degree. C.; and testing the pre-treated gaseous working fluid
for baseline constituent levels prior to introduction into a SMIF
Pod. In another aspect of the invention, an improved inlet flow of
the purge gas is provided, by maintaining the purge gas velocity
throughout the gas stream in the pod at a laminar flow velocity,
below sonic flow velocity, to prevent formation of undesirable
vortices that may trap moisture or particles, and to encourage
laminar flow inside the pod. In another embodiment, flow of purge
gas inside the SMIF pod is directed towards the product using one
or more nozzle towers to encourage laminar flow inside the pod. One
or more outlet towers, having a function similar to that of the
inlet tower, may also be provided to encourage laminar flow inside
the pod. In another embodiment, integrated towers are provided to
direct and disperse flow of the gaseous working fluid throughout
the pod envelope. A molecular contamination control base unit on
which the SMIF pod can be mounted can also include features for
improvement of the purging of the environment in the pod. In
another aspect of the method of the invention, mass flow control
can be used to ramp the gas flow rate up and down in a controlled
manner to avoid generation of particles due to "rattling" of the
wafers in the SMIF pod.
[0012] These and other aspects and advantages of the invention will
become apparent from the following detailed description, and the
accompanying drawings, which illustrate by way of example the
features of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1A is a schematic diagram of a single SMIF pod mounted
to a molecular contamination control base unit for purging of the
SMIF pod according to the invention;
[0014] FIG. 1B is a schematic diagram of an alternative embodiment
of a single SMIF pod mounted to a molecular contamination control
base unit for purging of the SMIF pod according to the
invention;
[0015] FIG. 2 is a partial sectional view illustrating the mounting
of a SMIF pod to a base plate of a molecular contamination control
base unit of FIG. 1A and 1B;
[0016] FIG. 3A is an enlarged sectional view of a mechanical
interface of a check valve port with a fluid line of the base plate
of a molecular contamination control base unit of FIG. 1A and
1B;
[0017] FIG. 3B is an enlarged sectional view of an alternative
embodiment of a mechanical interface of a check valve port with a
fluid line of the base plate of a molecular contamination control
base unit of FIG. 1A and 1B;
[0018] FIG. 4 is a perspective view of an improved SMIF pod
according to the invention;
[0019] FIG. 5 is an exploded perspective view of an inlet tower of
the SMIF pod of FIG. 4;
[0020] FIG. 6 is an exploded perspective view of an alternate
embodiment of an inlet tower for the SMIF pod of FIG. 4;
[0021] FIG. 7A is an alternate embodiment of a SMIF pod having
inlet towers integrated into wafer support arms of a SMIF pod,
showing a circled portion in section;
[0022] FIG. 7B is an enlargement of the sectional view of the
circled portion of FIG. 7A;
[0023] FIG. 8A is a perspective view of a single SMIF pod mounted
to a molecular contamination control base unit for purging of the
SMIF pod according to the invention;
[0024] FIG. 8B is a perspective view of an alternative embodiment
of a single SMIF pod mounted to a molecular contamination control
base unit for purging of the SMIF pod according to the
invention;
[0025] FIG. 9A is a front elevational view of a series of several
SMIF pods mounted to base plates connected in parallel to gaseous
working fluid supply and exhaust lines of a molecular contamination
control base unit for purging of the SMIF pods according to the
invention;
[0026] FIG. 9B is a front elevational view of an alternative
embodiment of a series of several SMIF pods mounted to base plates
connected in parallel to gaseous working fluid supply and exhaust
lines of a molecular contamination control base unit for purging of
the SMIF pods according to the invention;
[0027] FIG. 10 is a front elevational view of several SMIF pods
mounted in a tower to base plates connected in parallel to gaseous
working fluid supply and exhaust lines of a molecular contamination
control base unit for purging of the SMIF pods according to the
invention; and
[0028] FIG. 11 is a schematic diagram of the mounting of multiple
SMIF pods to a molecular contamination control base unit for
purging of the SMIF pods according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] Since particulates, humidity and oxygen can contaminate and
degrade the surface of semiconductor manufacturing materials, it is
important to adequately purge and maintain the local manufacturing
environment for such materials free of such contaminants.
Contaminants in the atmosphere can include water vapor, oxygen, and
particulates, and contaminants produced during conventional
manufacturing processes can include vaporous halogens or radicals,
such as chlorine, bromine, arsine, and silane, for example. As is
illustrated in the drawings, the invention provides for
improvements in a system and methods for purging a SMIF pod to
desired levels of relative humidity, oxygen, or particulates.
[0030] With reference to FIGS. 1A, 1B, 2 and 2A, in a preferred
embodiment of the molecular contamination control system 10 of the
invention, a standard mechanical interface (SMIF) box, or pod 12
having a housing 13 forming a chamber, is adapted to be mounted for
operation in combination with a molecular contamination control
base unit 14 providing a source 15 of gaseous working fluid, such
as nitrogen gas, argon gas, or other similar inert gas or
combination of gases, at a pressure of about 80 psi, for example,
in fluid communication with the SMIF pod for purging the SMIF pod.
Pressurized nitrogen gas and other inert gases are typically
available at pressures from about 65 to about 125 psi. Currently,
nitrogen gas is preferred, and the pressure of the working gas
within the system is controlled using a point-of-use regulator,
limiting feed-pressure to the inlet of the SMIF pod to a maximum of
about 10 psi, while working pressures within the SMIF pod are
typically about 1 psi. A vacuum pump 16 is also preferably provided
in fluid communication with the SMIF pod for removing the gaseous
working fluid, particulate and other contaminants, oxygen, and
humidity from the SMIF pod.
[0031] As is shown in FIG. 1A, the gaseous working fluid being
supplied to the SMIF pod can also be heated by a heater 18, and can
be dried by a desiccator 20. The gaseous working fluid, or purge
gas, can be dried, for example, by exposure of gas flowing from a
nitrogen or other inert gas source to the SMIF pod to a desiccant
in the desiccator that will chemically react with any residual
moisture in the purge gas, and that will introduce no undesirable
constituents to the purge gas. In a presently preferred embodiment,
the purge gas can also be heated to temperatures above 100.degree.
C., but below the thermal sensitivity of the pod, such as, for
example, between 105.degree. C. to 120.degree. C. As is illustrated
in FIGS. 1A and 1B, mass flow control valve 21 is also preferably
provided in fluid communication between the source of gaseous
working fluid and one or more inlets of the SMIF pod for
controlling the supply flow of gaseous working fluid to the SMIF
pod. Mass flow control is preferably used to ramp the gas flow rate
up and down in a controlled manner to avoid generation of particles
caused by "rattling" of the wafers in the SMIF pod. Purge gas
velocity throughout the gas stream in the pod is also preferably
maintained at a laminar flow velocity, below sonic flow velocity,
to prevent formation of undesirable vortices that may trap moisture
or particles, and to encourage laminar flow inside the pod.
[0032] With reference to FIGS. 1A to 3B, in a presently preferred
embodiment of the invention, check valve assemblies 22 and 24 are
incorporated into each of the one or more inlet ports 26 and the
one or more outlet ports 28 located in the base 30 of the SMIF pod.
The inlet port of the SMIF pod base is adapted to be connected in
fluid communication with a supply or feed line 32, and the outlet
port of the SMIF pod base is adapted to be connected in fluid
communication with an exhaust or outlet line 34, respectively, of a
base plate 36 of a molecular contamination control base unit 14, to
which the SMIF pod can be mounted. The SMIF pod base 30 serves as a
door to the SMIF pod, and is sometimes referred to as the SMIF pod
door.
[0033] As is illustrated in FIGS. 3A and 3B, the check valve
assembly of the inlet port includes a check valve 40 allowing
one-way flow of the gaseous working fluid into the SMIF pod, and a
filter 42 to remove particulate matter. The check valve assembly of
the outlet port typically only need include a check valve 44
allowing one-way flow of the gaseous working fluid out of the SMIF
pod, but can also include a filter as in the inlet port check valve
and filter assembly. The integral directional flow check valves are
preferably activated at very low pressure differentials, typically
less than 10 millibar. The feed line 32 and exhaust line 34
typically extend from the base plate of the molecular contamination
control base unit and include o-ring seals 46, 48, that are sized
to sealingly mate the supply line and exhaust line in the inlet and
outlet ports, respectively.
[0034] The check valve assemblies of the inlet and outlet ports
help to insure that only a clean, dry gaseous working fluid enters
the SMIF pod, to provide a controlled environment around the
contents of the SMIF pod with an ultra low moisture content, a very
low oxygen content, and a very low particulate content. With a
gaseous working fluid of substantially 100% nitrogen or other inert
gas to purge the SMIF pod, the atmospheric content of the SMIF pod
typically can reach a relative humidity level of about 0.1%, and
substantially no oxygen, in approximately five minutes, for
example. Ideally, a SMIF Pod can be completely purged to desired
levels of relative humidity, oxygen, or particulates in a period of
about 6 minutes or less.
[0035] As is shown in FIG. 1A, in one embodiment, the gaseous
working fluid exhaust line in the molecular contamination control
base unit can also include a flow meter 50 for monitoring the flow
of gaseous working fluid through the SMIF pod and a pair of valves
52, 54, for diverting flow of the working gas from the SMIF pod
directly from the supply line to the exhaust line, for monitoring
by sensors 56 for humidity, oxygen, and particulates, as well as
temperature, for example. In one presently preferred embodiment,
the valves can comprise an electronically controlled solenoid valve
52 controlling flow of gaseous working fluid from the supply to the
exhaust line, and an electronically controlled solenoid valve 54
controlling flow of gaseous working fluid from the SMIF pod through
the exhaust line. By closing the connecting valve 52 and opening
exhaust line valve 54, contaminant levels in gaseous working fluid
exiting from the SMIF pod can be monitored by sensors 56; by
opening the connecting valve 52 and closing exhaust line valve 54,
for testing the pre-treated gaseous working fluid by sensors 56 for
baseline constituent levels prior to introduction of the gaseous
working fluid into a SMIF pod. In an alternative preferred
embodiment illustrated in FIG. 1B, since the purity of the working
gas can typically be controlled at the source, such as by
certification from a vendor of the working gas, or by testing prior
to use at the facility or laboratory, for example, monitoring of
the condition of the working gas is not required, and monitoring of
the gas exiting the SMIF pod by a sensor at 56, such as a
hygrometer, for example, included in the exhaust line, can be
provided for optionally monitoring contaminant levels in gaseous
working fluid exiting from the SMIF pod.
[0036] Referring to FIGS. 4 and 5, in a presently preferred
embodiment of the invention, flow of the gaseous working fluid or
purge gas inside a SMIF pod can be directed toward and away from
wafer or substrate manufacturing materials 60 housed in the SMIF
pod using one or more uniquely configured towers 62 connected by a
mounting member 64 to the inlet port 26 or to the outlet port 28.
Orifices are provided in each tower, preferably in the form of a
series of spaced apart nozzles 66 that are graduated in size. When
used as an inlet tower, the effect of the graduation of size of the
nozzles is to generate a uniform velocity field near the inlet
tower, thereby vectoring the gas currents around the inside of the
SMIF pod. The gaseous working fluid will sweep the SMIF pod and its
contents, picking up residual moisture and encouraging movement of
particulates toward the exhaust port. In one preferred alternate
embodiment, illustrated in FIG. 6, the tower configuration can be
in the form of a tower 68 with a series of spaced apart, radial
slotted ports 70. One or more vent towers are also preferably
connected to the outlet port or ports, having a structure and
function similar to that of the inlet towers, to direct flow to the
outlet valve for exhausting to the instrument suite, and to the
local environment. The outlet towers thus preferably have the
configuration as illustrated in FIG. 5, or in an alternate
embodiment, as illustrated in FIG. 6. When used as an outlet tower,
the nozzle openings encourage increased gaseous working fluid
velocities from the slower gaseous working fluid velocities in the
pod, to more rapid flow velocities in the exhaust line.
[0037] In another preferred alternative embodiment shown in FIG. 7A
and 7B, inlet towers 72 can be integrated into wafer support arms
74 of the SMIF pod, in the tubular vertical element 76, to direct
and disperse flow of the gaseous working fluid throughout the pod
envelope. On an opposing side of the SMIF pod, one or more similar
outlet or exhaust towers (not shown) can be provided to draw off
purge gas laden with residues for discharge. The integrated inlet
and outlet towers do not compromise the operation of the base plate
"door" of the SMIF pod, and do not impose constraints on supporting
robotic apparatus used in wafer processing.
[0038] The system and method of the invention are planned for use
while the SMIF pods are otherwise not required, i.e., while waiting
for the next production station or step in the fabrication
facility. These periods have been estimated to be about six minutes
to more than one hour long. Ideally, the SMIF pod is completely
purged to desired levels of relative humidity, oxygen, or
particulates in a period of about 6 minutes or less. Relative
humidity levels of about 0.1% or less have been achieved in about 5
minutes. Flow of the gaseous working fluid or purge gas is
typically provided in the SMIF pod at up to 20 SCFH, and at a
pressure of from about zero to about 5 psi. Pressurized nitrogen
gas and other inert gases are typically available at pressures from
about 65 to about 125 psi, and the pressure of the working gas
within the system is typically controlled using a point-of-use
regulator, limiting feed pressure to the inlet of the SMIF pod to a
maximum of about 10 psi. Working pressures within the SMIF pod are
typically about 1 psi. The gaseous working fluid or purge gas is
filtered to remove particulates as small as 0.10-2.0 microns at an
efficiency of about 99.999%.
[0039] As illustrated in one preferred embodiment of the system and
method of the invention in FIG. 8A and in an alternative preferred
embodiment in FIG. 8B, a single SMIF pod 80 can be mounted,
typically manually, to a base plate 82 of a molecular contamination
control module base unit 84 providing a supply of gaseous working
fluid to and from the SMIF pod, as described above. In alternate
preferred embodiments of the system and method of the invention
illustrated in FIGS. 9A, 9B, 10 and 11, a single contamination
control module base unit 84 can provide supply of gaseous working
fluid to and from a plurality of SMIF pods 80. As shown in FIG. 9,
a series of several SMIF pods can be mounted to base plates 82
connected in parallel to gaseous working fluid supply and exhaust
lines 86, or as shown in FIG. 10, a series of several SMIF pods 80
can be mounted in a tower to base plates 82 connected in parallel
to gaseous working fluid supply and exhaust lines 86.
[0040] As illustrated in FIG. 11, similar to the configuration of
FIGS. 1A and 1B for a single SMIF pod, in the multiple pod
configurations of FIGS. 9A, 9B and 10, the molecular contamination
control module base unit 84 generally provides a supply 85 of the
gaseous working fluid, which can typically be nitrogen or other
inert gas supplied at a pressure of 80 psi, for example. The
molecular contamination control base unit can also include a filter
88 for filtration of the gaseous working fluid to remove particles
as small as 0.10-2.0 microns at an efficiency of about 99.999%. The
molecular contamination control base unit preferably contains a
purge control assembly 90 typically including a mass control valve
21 controlling the supply of gaseous working fluid to the SMIF
pods. In a presently preferred embodiment, the purge control
assembly also provides a desiccant chamber 20 for receiving and
drying the gaseous working fluid or purge gas by exposure to a
desiccant such as activated alumina, calcium chloride, silica gel,
or zinc chloride, for example, that can chemically react with and
remove any residual moisture in the purge gas being supplied to the
SMIF pod, and that will introduce no undesirable constituents to
the purge gas. Other desiccants that will introduce no undesirable
constituents to the purge gas may also be suitable.
[0041] In a presently preferred embodiment, the purge control
assembly also provides a heater 18 for heating the purge gas to
temperatures above 100.degree. C., but below the thermal
sensitivity of the pod, i.e., 105 to 120.degree. C. For multiple
pod configurations, a manifold 92 is typically provided for
distributing an even flow of gaseous working fluid to the SMIF
pods. As described above in connection with FIG. 1A, in a presently
preferred embodiment, the purge control unit also can also provide
sensors 56 in the outlet line from the SMIF pods, with a connection
to the supply line, to monitor relative humidity, oxygen and
particulate content of gaseous working fluid exiting from the
purged SMIF pods, and to permit testing the pretreated gaseous
working fluid for baseline constituent levels prior to introduction
into a SMIF pod. Other types of sensors can also be provided for
monitoring other types of contaminants such as vapor-borne halogens
or radicals that can be present after conventional processes, such
as chlorine, bromine, arsine, silane, for example. As in FIGS. 1A
and 1B, a vacuum pump 16 is also preferably provided in fluid
communication with one or more outlets of the SMIF pods for
removing the gaseous working fluid or purge gas, and any particle
contaminants, other types of vaporous contaminants such as from the
manufacturing processes, oxygen, and humidity entrained in the
gaseous working fluid or purge gas from the SMIF pod.
[0042] It will be apparent from the foregoing that while particular
forms of the invention have been illustrated and described,various
modifications can be made without departing from the spirit and the
scope of the invention. Accordingly, it is not intended that the
invention be limited, except as the appended claims.
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