U.S. patent application number 12/110831 was filed with the patent office on 2008-08-28 for transmission of ultrasonic energy into pressurized fluids.
This patent application is currently assigned to AIR PRODUCTS AND CHEMICALS, INC.. Invention is credited to Wayne Thomas McDermott, Richard Carl Ockovic, Dean Van-John Roth.
Application Number | 20080202550 12/110831 |
Document ID | / |
Family ID | 34750470 |
Filed Date | 2008-08-28 |
United States Patent
Application |
20080202550 |
Kind Code |
A1 |
McDermott; Wayne Thomas ; et
al. |
August 28, 2008 |
Transmission of Ultrasonic Energy into Pressurized Fluids
Abstract
Ultrasonic probe comprising an elongate body having a first end
and a second end, an ultrasonic transducer attached to the probe at
or adjacent the first end, and an enlarged support section
intermediate the ultrasonic transducer and the second end, wherein
the enlarged support section has an equivalent diameter greater
than an equivalent diameter of the body at any location between the
enlarged support section and the ultrasonic transducer. The probe
may be used to introduce ultrasonic energy into ultrasonic cleaning
systems.
Inventors: |
McDermott; Wayne Thomas;
(Fogelsville, PA) ; Roth; Dean Van-John; (Center
Valley, PA) ; Ockovic; Richard Carl; (Northampton,
PA) |
Correspondence
Address: |
AIR PRODUCTS AND CHEMICALS, INC.;PATENT DEPARTMENT
7201 HAMILTON BOULEVARD
ALLENTOWN
PA
181951501
US
|
Assignee: |
AIR PRODUCTS AND CHEMICALS,
INC.
Allentown
PA
|
Family ID: |
34750470 |
Appl. No.: |
12/110831 |
Filed: |
April 28, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10785298 |
Feb 24, 2004 |
|
|
|
12110831 |
|
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Current U.S.
Class: |
134/1 ;
134/147 |
Current CPC
Class: |
B06B 3/00 20130101; B08B
3/12 20130101 |
Class at
Publication: |
134/1 ;
134/147 |
International
Class: |
B08B 3/12 20060101
B08B003/12 |
Claims
1. An ultrasonic probe comprising an elongate body having a first
end and a second end, an ultrasonic transducer attached to the
probe at or adjacent the first end, and an enlarged support section
intermediate the ultrasonic transducer and the second end, wherein
the enlarged support section has an equivalent diameter greater
than an equivalent diameter of the body at any location between the
enlarged support section and the ultrasonic transducer.
2. The probe of claim 1 wherein the ultrasonic transducer is a
piezoelectric transducer or a magnetostrictive transducer.
3. The probe of claim 1 wherein the ultrasonic transducer is a
magnetostrictive transducer formed by an electrical coil wrapped
around a section of the probe between the first end and the
enlarged support section.
4. The probe of claim 1 comprises a metal or metal alloy.
5. The probe of claim 1 wherein the probe has a circular cross
section at any location between the first end and the second end,
the cross section being defined as a section perpendicular to an
axis defined by the first end and the second end.
6. The probe of claim 5 wherein at least a portion of the probe
between the enlarged support section and the second end is
cylindrical, and wherein the diameter of the probe decreases
discontinuously in this portion.
7. The probe of claim 5 wherein the probe has a circular cross
section at all locations between the enlarged support section and
the second end, and wherein the diameter of the probe decreases
continuously between the enlarged support section and the second
end.
8. The probe of claim 1 wherein the ratio of the distance between
the first end and the enlarged support section to the distance from
the enlarged support section to the second end is between 1:10 and
10:1
9. The probe of claim 1 which further comprises a detachable tip
attached to the second end of the probe.
10. An ultrasonic probe comprising (a) an elongate planar body
having a first end, a second end opposite the first end, a third
end intersecting the first and second ends, a fourth end opposite
the third end and intersecting the first and second ends, a first
side intersecting the first, second, third, and fourth ends, and a
second side opposite the first side and intersecting the first,
second, third, and fourth ends; (b) attachment means on the first
end adapted for attaching the first end to one or more transducer
assemblies; (c) a first longitudinal shoulder support section
projecting from the first side, extending linearly between the
third and fourth ends, and having an outer edge; and (d) a second
longitudinal shoulder support section projecting from the second
side, extending linearly between the third and fourth ends, and
having an outer edge, wherein the second longitudinal shoulder
support section is disposed opposite the first longitudinal
shoulder support section; wherein the distance between the outer
edge of the first longitudinal shoulder support section and the
outer edge of the second longitudinal shoulder support section is
greater than the thickness of the planar body at any location
between the longitudinal shoulder supports and the first end, the
thickness of the planar body being defined as the perpendicular
distance between the first and second sides.
11. A method of providing ultrasonic energy to a pressurized fluid
comprising (a) providing an ultrasonic pressure vessel system
including (1) an ultrasonic probe assembly including (1a) a seal
assembly comprising a seal body having a first end and a second
end, an axis passing through the first end and the second end, and
a coaxial cylindrical passage disposed between the first end and
the second end; (1b) An ultrasonic probe comprising an elongate
body having a first end and a second end, an ultrasonic transducer
attached to the probe at or adjacent the first end, and a
cylindrical collar support section intermediate the ultrasonic
transducer and the second end, wherein the probe is cylindrical
between the ultrasonic transducer and the collar support section,
the collar support section has a diameter greater than diameter of
the cylinder between the collar support section and the ultrasonic
transducer, the cylindrical section of the probe is disposed
coaxially within the cylindrical passage of the seal body such that
the shoulder support section is adjacent the second end of the seal
body, and the diameter of the cylindrical shoulder section is
greater than the diameter of the cylindrical passage at the second
end of the seal body; and (1c) an elastomeric torroidal seal ring
disposed coaxially between, and forming a seal between, the collar
support section of the ultrasonic probe and the second end of the
seal body; (2) a pressure vessel having an interior, an exterior,
and at least first and second openings between the interior and the
exterior; and (3) first sealing means associated with the second
end of the seal assembly and second sealing means associated with
the first opening in the pressure vessel, wherein the first and
second sealing means are adapted to form a seal between the seal
assembly and the pressure vessel, wherein the elastomeric torroidal
seal ring is compressed between the collar support section and the
second end of the seal body to form a seal between the interior and
the exterior of the pressure vessel, and wherein the second end of
the ultrasonic probe is disposed in the interior of the pressure
vessel; (b) introducing a pressurized fluid via the second opening
into the interior of the pressure vessel; (c) providing electrical
power to the ultrasonic transducer to generate ultrasonic energy;
and (d) transmitting the ultrasonic energy through the ultrasonic
probe to the pressurized fluid in the interior of the pressure
vessel.
12. The method of claim 11 wherein the pressure of the pressurized
fluid in the interior of the pressure vessel is in the range of
10.sup.-3 to 680 atma.
13. The method of claim 11 wherein the ultrasonic energy is
provided in a frequency range of 20 KHz to 2 MHz.
14. The method of claim 11 wherein the ultrasonic energy is
provided at a power density in the range of 0.1 to 10,000
W/in.sup.2.
15. The method of claim 11 wherein the pressurized fluid comprises
one or more components selected from the group consisting of carbon
dioxide, nitrogen, methane, oxygen, ozone, argon, hydrogen, helium,
ammonia, nitrous oxide, hydrogen fluoride, hydrogen chloride,
sulfur trioxide, sulfur hexafluoride, nitrogen trifluoride,
monofluoromethane, difluoromethane, tetrafluoromethane,
trifluoromethane, trifluoroethane, tetrafluoroethane,
pentafluoroethane, perfluoropropane, pentafluoropropane,
hexafluoroethane, hexafluoropropylene, hexafluorobutadiene,
octafluorocyclobutane, and tetrafluorochloroethane.
16. The method of claim 15 wherein the pressurized fluid further
comprises one or more processing agents selected from a group
consisting of an acetylenic alcohol, an acetylenic diol, a dialkyl
ester, hydrogen fluoride, hydrogen chloride, chlorine trifluoride,
nitrogen trifluoride, hexafluoropropylene, hexafluorobutadiene,
octafluorocyclobutane tetrafluorochloroethane,
fluoroxytrifluoromethane (CF.sub.4O), bis(difluoroxy)methane
(CF.sub.4O.sub.2), cyanuric fluoride (C.sub.3F.sub.3N.sub.3),
oxalyl fluoride (C.sub.2F.sub.2O.sub.2), nitrosyl fluoride (FNO),
carbonyl fluoride (CF.sub.2O), perfluoromethylamine (CF.sub.5N), an
ester, an ether, an alcohol, a nitrile, a hydrated nitrile, a
glycol, a monester glycol, a ketone, a fluorinated ketone, a
tertiary amine, an alkanolamine, an amide, a carbonate, a
carboxylic acid, an alkane diol, an alkane, a peroxide, a water, an
urea, a haloalkane, a haloalkene, a beta-diketone, a carboxylic
acid, an oxine, a tertiary amine, a tertiary diamine, a tertiary
triamine, a nitrile, a beta-ketoimine, an ethylenediamine
tetraacetic acid and derivatives thereof, a catechol, a
choline-containing compound, a trifluoroacetic anhydride, an oxime,
a dithiocarbamate, and combinations thereof.
17. The method of claim 15 which further comprises providing a
sealable opening in the pressure vessel adapted to insert and
withdraw one or more articles, inserting one or more contaminated
articles into the pressure vessel prior to (b), cleaning the one or
more contaminated articles during (c) and (d), depressurizing the
pressure vessel by withdrawing a contaminated fluid therefrom, and
withdrawing one or more cleaned articles therefrom.
18. The method of claim 11 wherein the fluid comprises at least one
component which undergoes a chemical reaction that is promoted by
the ultrasonic energy introduced into the pressure vessel.
19. The method of claim 11 wherein the shoulder support section of
the ultrasonic probe is located at a vibrational node between the
first and second ends of the ultrasonic probe.
20. A method for cleaning a contaminated wafer comprising: (a)
providing an ultrasonic pressure vessel system including (1) an
ultrasonic probe assembly including (1a) an elongate planar body
having a first end, a second end opposite the first end, a third
end intersecting the first and second ends, a fourth end opposite
the third end and intersecting the first and second ends, a first
side intersecting the first, second, third, and fourth ends, and a
second side opposite the first side and intersecting the first,
second, third, and fourth ends; (1b) attachment means on the first
end adapted for attaching the first end to one or more transducer
assemblies; (1c) a first longitudinal shoulder support section
projecting from the first side, extending linearly between the
third and fourth ends, and having an outer edge; and (1d) a second
longitudinal shoulder support section projecting from the second
side, extending linearly between the third and fourth ends, and
having an outer edge, wherein the second longitudinal shoulder
support section is disposed opposite the first longitudinal
shoulder support section; wherein the distance between the outer
edge of the first longitudinal shoulder support section and the
outer edge of the second longitudinal shoulder support section is
greater than the thickness of the planar body at any location
between the longitudinal shoulder supports and the first end, the
thickness of the planar body being defined as the perpendicular
distance between the first and second sides; (2) a reactor vessel
having an interior, an exterior, and at least first and second
openings between the interior and the exterior; and (3) first
sealing means associated with the first and second longitudinal
shoulder support sections and second sealing means associated with
the first opening in the pressure vessel, wherein the first and
second sealing means are adapted to form a seal between the
ultrasonic probe and the pressure vessel, wherein the second end of
the ultrasonic probe is disposed in the interior of the pressure
vessel; (b) introducing the contaminated wafer into the interior of
the pressure vessel; (c) introducing a pressurized fluid via the
second opening into the interior of the pressure vessel, thereby
pressurizing the vessel; (d) providing electrical power to the
ultrasonic transducer to generate ultrasonic energy; and (e)
transmitting the ultrasonic energy through the ultrasonic probe to
the pressurized fluid in the interior of the pressure vessel while
moving the wafer past the second end of the ultrasonic probe.
21. The method of claim 20 wherein the wafer defines a first plane
and the ultrasonic probe defines a second plane, and wherein the
included angle between the first plane and the second plane is
between 10 degrees and 90 degrees.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. Ser. No. 10/785,298
filed on Feb. 24, 2004.
BACKGROUND OF THE INVENTION
[0002] Ultrasonic energy is used to promote mass transfer and
chemical reactions in fluid systems for a wide variety of
applications. One of these applications is ultrasonic cleaning, in
which articles are immersed in a fluid bath while ultrasonic energy
is introduced into the bath to enhance the cleaning process.
Ultrasonic cleaning systems range from small countertop units used
in dental offices and laboratories to large industrial units used
in the food and chemical process industries. Ultrasonic cleaning
systems also are used in the fabrication of electronic components
to remove residues from parts and components following
manufacturing steps such as lithography, etching, stripping, and
chemical mechanical planarization. In another application,
ultrasonic energy is used in sonochemical reactor systems to
promote chemical reactions in fluid reaction media.
[0003] Many ultrasonic cleaning systems use a fluid bath at
atmospheric pressure for immersing articles during cleaning. Other
ultrasonic cleaning systems are operated at elevated pressures
using pressurized liquids, condensing pressurized vapors, dense
fluids, or supercritical fluids to effect cleaning of the articles
in a pressurized vessel. Such pressurized ultrasonic cleaning
systems are used, for example, in the electronics manufacturing
industries to remove residues from parts and components during
various fabrication steps. Pressurized ultrasonic processing
systems may be used in the chemical industry to promote chemical
reactions in sonochemical reaction systems.
[0004] Ultrasonic energy can be introduced into fluids by several
methods. In one method, ultrasonic generators are submerged in the
fluid and operated in situ to generate and transmit ultrasonic
energy directly to the fluid. In another method, ultrasonic
generators are attached to the outer surface of the vessel walls
and the ultrasonic energy is transmitted through the vessel walls
and into the fluid. In yet another method, ultrasonic energy is
transmitted from external ultrasonic transducers via ultrasonic
probes or horns passing through the vessel wall, wherein the
ultrasonic energy is dissipated from the horns into the fluid.
[0005] The successful operation of high-pressure fluid processes
with ultrasonic energy will require careful design of the
ultrasonic probes that transmit the ultrasonic energy from an
external transducer into the pressurized process fluid in a
pressure vessel. There is a need in the art for new and improved
designs for these ultrasonic probes and for appropriate seals to
secure these probes in pressure vessel walls during pressurized
operation.
BRIEF SUMMARY OF THE INVENTION
[0006] These design requirements for ultrasonic probes and seals
are met by the embodiments of the present invention. In one
embodiment, a specifically designed ultrasonic probe comprises an
elongate body having a first end and a second end, an ultrasonic
transducer attached to the probe at or adjacent the first end, and
an enlarged support section intermediate the ultrasonic transducer
and the second end, wherein the enlarged support section has an
equivalent diameter greater than an equivalent diameter of the body
at any location between the enlarged support section and the
ultrasonic transducer. This ultrasonic probe may be installed in a
seal assembly which in turn may be installed in the wall of a
pressure vessel.
[0007] The seal assembly comprises a seal body having a first end
and a second end, an axis passing through the first end and the
second end, and a coaxial cylindrical passage within the seal
assembly between the first end and the second end. An elastomeric
sealing ring is placed around the probe adjacent the enlarged
support section and the ultrasonic probe is inserted in the passage
in the seal assembly, wherein the elastomeric sealing ring is
disposed between the enlarged support section of the probe and the
second end of the seal assembly. When the seal assembly is
installed in the wall of a pressurized vessel, the outward axial
force on the probe caused by the pressure differential across the
seal compresses the elastomeric sealing ring between the enlarged
support section and the second end of the seal assembly. This forms
a seal and also prevents the probe from being forced out of the
seal body by the pressure differential.
[0008] An embodiment of the invention includes an ultrasonic probe
comprising an elongate body having a first end and a second end, an
ultrasonic transducer attached to the probe at or adjacent the
first end, and an enlarged support section intermediate the
ultrasonic transducer and the second end, wherein the enlarged
support section has an equivalent diameter greater than an
equivalent diameter of the body at any location between the
enlarged support section and the ultrasonic transducer. The
ultrasonic transducer may be a piezoelectric transducer or a
magnetostrictive transducer. When the ultrasonic transducer is a
magnetostrictive transducer, it may be formed by an electrical coil
wrapped around a section of the probe between the first end and the
enlarged support section. The probe may comprise a metal or metal
alloy.
[0009] The probe may have a circular cross section at any location
between the first end and the second end, the cross section being
defined as a section perpendicular to an axis defined by the first
end and the second end. At least a portion of the probe between the
enlarged support section and the second end may be cylindrical,
wherein the diameter of the probe decreases discontinuously in this
portion. Alternatively, the probe may have a circular cross section
at all locations between the enlarged support section and the
second end, wherein the diameter of the probe decreases
continuously between the enlarged support section and the second
end. The ratio of the distance between the first end and the
enlarged support section to the distance from the enlarged support
section to the second end may be between 1:10 and 10:1 Optionally,
the probe may further comprise a detachable tip attached to the
second end of the probe.
[0010] A related embodiment of the invention includes an ultrasonic
probe comprising an elongate body having a first end and a second
end, an ultrasonic transducer attached to the probe at or adjacent
the first end, a cylindrical collar support section intermediate
the ultrasonic transducer and the second end, wherein the probe is
cylindrical between the first end and the collar support section,
and wherein the collar support section has a diameter greater than
diameter of the cylinder between the collar support section and the
ultrasonic transducer.
[0011] An alternative embodiment relates to an ultrasonic probe
comprising [0012] (a) an elongate planar body having a first end, a
second end opposite the first end, a third end intersecting the
first and second ends, a fourth end opposite the third end and
intersecting the first and second ends, a first side intersecting
the first, second, third, and fourth ends, and a second side
opposite the first side and intersecting the first, second, third,
and fourth ends; [0013] (b) attachment means on the first end
adapted for attaching the first end to one or more transducer
assemblies; [0014] (c) a first longitudinal shoulder support
section projecting from the first side, extending linearly between
the third and fourth ends, and having an outer edge; and [0015] (d)
a second longitudinal shoulder support section projecting from the
second side, extending linearly between the third and fourth ends,
and having an outer edge, wherein the second longitudinal shoulder
support section is disposed opposite the first longitudinal
shoulder support section.
[0016] The distance between the outer edge of the first
longitudinal shoulder support section and the outer edge of the
second longitudinal shoulder support section may be greater than
the thickness of the planar body at any location between the
longitudinal shoulder supports and the first end, the thickness of
the planar body being defined as the perpendicular distance between
the first and second sides.
[0017] In another embodiment of the invention, an ultrasonic probe
assembly comprises [0018] (a) a seal assembly comprising a seal
body having a first end and a second end, an axis passing through
the first end and the second end, and a coaxial cylindrical passage
within the seal assembly between the first end and the second end;
[0019] (b) An ultrasonic probe comprising an elongate body having a
first end and a second end, an ultrasonic transducer attached to
the probe at or adjacent the first end, and a cylindrical collar
support section intermediate the ultrasonic transducer and the
second end, wherein the probe is cylindrical between the ultrasonic
transducer and the collar support section, the collar support
section has a diameter greater than diameter of the cylinder
between the collar support section and the ultrasonic transducer,
the cylindrical section of the probe is disposed coaxially within
the cylindrical passage of the seal body such that the shoulder
support section is adjacent the second end of the seal body, and
the diameter of the cylindrical shoulder section is greater than
the diameter of the cylindrical passage at the second end of the
seal body; and [0020] (c) an elastomeric torroidal seal ring
disposed coaxially between the collar support section of the
ultrasonic probe and the second end of the seal body.
[0021] The cylindrical section of the ultrasonic probe typically
extends beyond the first end of the seal body; the ultrasonic probe
assembly may further comprise a compression fitting adapted to grip
the ultrasonic probe and the first end of the seal body to maintain
the ultrasonic probe in a coaxial position in the cylindrical
passage of the seal assembly. The ultrasonic probe and the seal
body may comprise a metal or metal alloy. The ultrasonic probe
assembly may further comprise a transducer assembly attached to the
first end thereof.
[0022] The elastomeric torroidal seal ring may comprise an
elastomer selected from the group consisting of
tetrafluoroethylene, chlorotrifluoroethylene, polyvinylidene
fluoride, perfluoroalkoxy, polyethylene, unplasticized polyvinyl
chloride, acrylonitrile butadiene styrene, acetal, cellulose
acetate butyrate, nylon, polypropylene, polycarbonate,
polyphenylene oxide, polyphenylene sulfide, polysulfone, polyamide,
polyimide, thermosetting plastic, natural rubber, hard rubber,
chloroprene, neoprene, styrene rubber, nitrile rubber, butyl
rubber, silicone rubber, chlorosulfonated polyethylene,
polychlorotrifluoroethylene, polyvinyl chloride elastomer,
cis-polybutadiene, cis-polyisoprene, ethylene-propylene rubbers,
carbon, and graphite.
[0023] The compression fitting may include a torroidal elastomeric
ferrule comprising an elastomer typically selected from the group
consisting of tetrafluoroethylene, chlorotrifluoroethylene,
polyvinylidene fluoride, perfluoroalkoxy, polyethylene,
unplasticized polyvinyl chloride, acrylonitrile butadiene styrene,
acetal, cellulose acetate butyrate, nylon, polypropylene,
polycarbonate, polyphenylene oxide, polyphenylene sulfide,
polysulfone, polyamide, polyimide, thermosetting plastic, natural
rubber, hard rubber, chloroprene, neoprene, styrene rubber, nitrile
rubber, butyl rubber, silicone rubber, chlorosulfonated
polyethylene, polychlorotrifluoroethylene, polyvinyl chloride
elastomer, cis-polybutadiene, cis-polyisoprene, ethylene-propylene
rubber, carbon, and graphite.
[0024] Another embodiment of the invention includes an ultrasonic
processing system comprising [0025] (a) An ultrasonic probe
assembly including [0026] (1) a seal assembly comprising a seal
body having a first end and a second end, an axis passing through
the first end and the second end, and a coaxial cylindrical passage
disposed between the first end and the second end; [0027] (2) An
ultrasonic probe comprising an elongate body having a first end and
a second end, an ultrasonic transducer attached to the probe at or
adjacent the first end, and a cylindrical collar support section
intermediate the ultrasonic transducer and the second end, wherein
the probe is cylindrical between the ultrasonic transducer and the
collar support section, the collar support section has a diameter
greater than diameter of the cylinder between the collar support
section and the ultrasonic transducer, the cylindrical section of
the probe is disposed coaxially within the cylindrical passage of
the seal body such that the shoulder support section is adjacent
the second end of the seal body, and the diameter of the
cylindrical shoulder section is greater than the diameter of the
cylindrical passage at the second end of the seal body; and [0028]
(3) an elastomeric torroidal seal ring disposed coaxially between
the collar support section of the ultrasonic probe and the second
end of the seal body; [0029] (b) a pressure vessel having an
interior, an exterior, and at least one opening between the
interior and the exterior; and [0030] (c) first sealing means
associated with the second end of the seal assembly and second
sealing means associated with the at least one opening in the
pressure vessel, wherein the first and second sealing means are
adapted to form a seal between the seal assembly and the pressure
vessel; wherein the elastomeric torroidal seal ring is compressed
between the collar support section and the second end of the seal
body to form a seal between the interior and the exterior of the
pressure vessel, and wherein the second end of the ultrasonic probe
is disposed in the interior of the pressure vessel.
[0031] The cylindrical section of the ultrasonic probe typically
extends beyond the first end of the seal body and the ultrasonic
probe assembly may further comprise a compression fitting adapted
to grip the ultrasonic probe and the first end of the seal body to
maintain the ultrasonic probe in a coaxial position in the
cylindrical passage of the seal assembly. The ultrasonic probe
assembly may further comprise a transducer assembly attached to the
first end thereof.
[0032] The pressure vessel may further comprise an inlet for
introducing a fresh cleaning fluid into the pressure vessel and an
outlet for withdrawing a contaminated cleaning fluid from the
pressure vessel. The pressure vessel may further comprise an inlet
port for introducing one or more contaminated articles into the
pressure vessel and an outlet port for withdrawing one or more
cleaned articles from the pressure vessel.
[0033] Another related embodiment of the invention includes a
method of providing ultrasonic energy to a pressurized fluid
comprising [0034] (a) providing an ultrasonic pressure vessel
system including [0035] (1) an ultrasonic probe assembly including
[0036] (1a) a seal assembly comprising a seal body having a first
end and a second end, an axis passing through the first end and the
second end, and a coaxial cylindrical passage disposed between the
first end and the second end; [0037] (1b) An ultrasonic probe
comprising an elongate body having a first end and a second end, an
ultrasonic transducer attached to the probe at or adjacent the
first end, and a cylindrical collar support section intermediate
the ultrasonic transducer and the second end, wherein the probe is
cylindrical between the ultrasonic transducer and the collar
support section, the collar support section has a diameter greater
than diameter of the cylinder between the collar support section
and the ultrasonic transducer, the cylindrical section of the probe
is disposed coaxially within the cylindrical passage of the seal
body such that the shoulder support section is adjacent the second
end of the seal body, and the diameter of the cylindrical shoulder
section is greater than the diameter of the cylindrical passage at
the second end of the seal body; and [0038] (1c) an elastomeric
torroidal seal ring disposed coaxially between, and forming a seal
between, the collar support section of the ultrasonic probe and the
second end of the seal body; [0039] (2) a pressure vessel having an
interior, an exterior, and at least first and second openings
between the interior and the exterior; and [0040] (3) first sealing
means associated with the second end of the seal assembly and
second sealing means associated with the first opening in the
pressure vessel, wherein the first and second sealing means are
adapted to form a seal between the seal assembly and the pressure
vessel, wherein the elastomeric torroidal seal ring is compressed
between the collar support section and the second end of the seal
body to form a seal between the interior and the exterior of the
pressure vessel, and wherein the second end of the ultrasonic probe
is disposed in the interior of the pressure vessel; [0041] (b)
introducing a pressurized fluid via the second opening into the
interior of the pressure vessel; [0042] (c) providing electrical
power to the ultrasonic transducer to generate ultrasonic energy;
and [0043] (d) transmitting the ultrasonic energy through the
ultrasonic probe to the pressurized fluid in the interior of the
pressure vessel.
[0044] The pressure of the pressurized fluid in the interior of the
pressure vessel may be in the range of 10.sup.-3 to 680 atma. The
ultrasonic energy typically is provided in a frequency range of 20
KHz to 2 MHz. The ultrasonic energy may be provided at a power
density in the range of 0.1 to 10,000 W/in.sup.2.
[0045] The pressurized fluid may comprise one or more components
selected from the group consisting of carbon dioxide, nitrogen,
methane, oxygen, ozone, argon, hydrogen, helium, ammonia, nitrous
oxide, hydrogen fluoride, hydrogen chloride, sulfur trioxide,
sulfur hexafluoride, nitrogen trifluoride, monofluoromethane,
difluoromethane, tetrafluoromethane, trifluoromethane,
trifluoroethane, tetrafluoroethane, pentafluoroethane,
perfluoropropane, pentafluoropropane, hexafluoroethane,
hexafluoropropylene, hexafluorobutadiene, octafluorocyclobutane,
and tetrafluorochloroethane. The pressurized fluid may further
comprise one or more processing agents selected from a group
consisting of an acetylenic alcohol, an acetylenic diol, a dialkyl
ester, hydrogen fluoride, hydrogen chloride, chlorine trifluoride,
nitrogen trifluoride, hexafluoropropylene, hexafluorobutadiene,
octafluorocyclobutane tetrafluorochloroethane,
fluoroxytrifluoromethane (CF.sub.4O), bis(difluoroxy)methane
(CF.sub.4O.sub.2), cyanuric fluoride (C.sub.3F.sub.3N.sub.3),
oxalyl fluoride (C.sub.2F.sub.2O.sub.2), nitrosyl fluoride (FNO),
carbonyl fluoride (CF.sub.2O), perfluoromethylamine (CF.sub.5N), an
ester, an ether, an alcohol, a nitrile, a hydrated nitrile, a
glycol, a monester glycol, a ketone, a fluorinated ketone, a
tertiary amine, an alkanolamine, an amide, a carbonate, a
carboxylic acid, an alkane diol, an alkane, a peroxide, a water, an
urea, a haloalkane, a haloalkene, a beta-diketone, a carboxylic
acid, an oxine, a tertiary amine, a tertiary diamine, a tertiary
triamine, a nitrile, a beta-ketoimine, an ethylenediamine
tetraacetic acid and derivatives thereof, a catechol, a
choline-containing compound, a trifluoroacetic anhydride, an oxime,
a dithiocarbamate, and combinations thereof.
[0046] The method may further comprise providing a sealable opening
in the pressure vessel adapted to insert and withdraw one or more
articles, inserting one or more contaminated articles into the
pressure vessel prior to (b), cleaning the one or more contaminated
articles during (c) and (d), depressurizing the pressure vessel by
withdrawing a contaminated fluid therefrom, and withdrawing one or
more cleaned articles therefrom. The fluid may comprise at least
one component which undergoes a chemical reaction that is promoted
by the ultrasonic energy introduced into the pressure vessel. The
shoulder support section of the ultrasonic probe typically is
located at a vibrational node between the first and second ends of
the ultrasonic probe.
[0047] Another embodiment of the invention includes method for
cleaning a contaminated wafer comprising: [0048] (a) providing an
ultrasonic pressure vessel system including [0049] (1) an
ultrasonic probe assembly including [0050] (1a) an elongate planar
body having a first end, a second end opposite the first end, a
third end intersecting the first and second ends, a fourth end
opposite the third end and intersecting the first and second ends,
a first side intersecting the first, second, third, and fourth
ends, and a second side opposite the first side and intersecting
the first, second, third, and fourth ends; [0051] (1b) attachment
means on the first end adapted for attaching the first end to one
or more transducer assemblies; [0052] (1c) a first longitudinal
shoulder support section projecting from the first side, extending
linearly between the third and fourth ends, and having an outer
edge; and [0053] (1d) a second longitudinal shoulder support
section projecting from the second side, extending linearly between
the third and fourth ends, and having an outer edge, wherein the
second longitudinal shoulder support section is disposed opposite
the first longitudinal shoulder support section; [0054] wherein the
distance between the outer edge of the first longitudinal shoulder
support section and the outer edge of the second longitudinal
shoulder support section is greater than the thickness of the
planar body at any location between the longitudinal shoulder
supports and the first end, the thickness of the planar body being
defined as the perpendicular distance between the first and second
sides; [0055] (2) a reactor vessel having an interior, an exterior,
and at least first and second openings between the interior and the
exterior; and [0056] (3) first sealing means associated with the
first and second longitudinal shoulder support sections and second
sealing means associated with the first opening in the pressure
vessel, wherein the first and second sealing means are adapted to
form a seal between the ultrasonic probe and the pressure vessel,
wherein the second end of the ultrasonic probe is disposed in the
interior of the pressure vessel; [0057] (b) introducing the
contaminated wafer into the interior of the pressure vessel; [0058]
(c) introducing a pressurized fluid via the second opening into the
interior of the pressure vessel, thereby pressurizing the vessel;
[0059] (d) providing electrical power to the ultrasonic transducer
to generate ultrasonic energy; and [0060] (e) transmitting the
ultrasonic energy through the ultrasonic probe to the pressurized
fluid in the interior of the pressure vessel while moving the wafer
past the second end of the ultrasonic probe.
[0061] The wafer may define a first plane and the ultrasonic probe
may define a second plane, and the included angle between the first
plane and the second plane may be between 10 degrees and 90
degrees.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
[0062] Embodiments of the present invention are illustrated by the
following drawings, which are not necessarily to scale.
[0063] FIG. 1 is a side view of a cylindrical ultrasonic probe
according to an embodiment of the invention.
[0064] FIG. 2 is a side view of another cylindrical ultrasonic
probe according to an alternative embodiment of the invention.
[0065] FIG. 3 is a sectional view of a cylindrical ultrasonic probe
and seal assembly.
[0066] FIG. 4 is an illustration of a cylindrical ultrasonic probe
and seal assembly in a pressurized vessel for the ultrasonic
cleaning of articles.
[0067] FIG. 5 is an illustration of multiple cylindrical ultrasonic
probe and seal assemblies in a pressurized vessel for the
ultrasonic cleaning of articles.
[0068] FIG. 6 is a side sectional view of the system of FIG. 5.
[0069] FIG. 7 is a sectional end view of a planar ultrasonic probe
and seal assembly installed in the wall of a pressure vessel.
[0070] FIG. 8 is a partial sectional view of a system including a
planar ultrasonic probe, seal assembly, and pressure vessel for
cleaning wafers or other articles with a gate-type door assembly
for inserting and withdrawing the wafers or other articles.
[0071] FIG. 9 is an exploded view of an alternative system
including a planar ultrasonic probe, seal assembly, and pressure
vessel for cleaning wafers or other articles with a gate-type door
assembly for inserting and withdrawing the wafers or other
articles.
DETAILED DESCRIPTION OF THE INVENTION
[0072] The design of an ultrasonic probe for use in transmitting
ultrasonic energy from an external transducer into a process fluid
in a pressurized vessel must meet several important criteria.
First, an appropriate seal assembly is required to seal the probe
at the vessel wall to prevent leakage of the pressurized fluid from
the vessel interior. Second, because the probe is vibrating at very
high frequencies, it must be mounted in the seal assembly such that
the high-frequency vibrations do not destroy the seal where the
probe passes through the vessel wall. Third, the seal assembly
design must ensure that the probe is held in place and is not
subject to blowout because of a large pressure differential between
the pressurized vessel interior and the surrounding atmosphere. In
addition, the probe and seal assembly must be readily removable for
seal maintenance and replacement of components when required. The
various embodiments of the present invention address these design
criteria as described below.
[0073] A first embodiment of an ultrasonic probe is shown in FIG.
1. The probe is an elongate body comprising four main parts: main
probe body 1, ultrasonic transducer 3, enlarged support section or
collar support section 5, and horn 7. All parts of the probe may be
cylindrical or alternatively any portion of the probe may have a
non-circular cross section. When any part of the probe has a
non-circular cross section, the non-circular part may be
characterized by an equivalent diameter defined as the diameter of
a circular cross section having the same area as the non-circular
cross section. The generic term "equivalent diameter" as used
herein thus refers to the diameter of a circular cross section when
the part is cylindrical and refers to the equivalent diameter when
the part has a non-circular cross section, and therefore the term
equivalent diameter includes both cylindrical and non-cylindrical
parts. When the part is cylindrical, the terms diameter and
equivalent diameter have the same meaning and are
interchangeable.
[0074] Main probe body 1 is fitted at one end thereof (which is the
first end of the probe) with ultrasonic transducer 3 in attached to
the probe at junction or connection point 9. Ultrasonic transducer
3 may be joined or connected to the end of main probe body 1 at
point 9 by any appropriate means to ensure proper ultrasonic
contact. For example, the ultrasonic transducer may be bolted to
the end of main probe body 1 by any type of bolt or bolt assembly
(not shown) as is known in the art. The term ultrasonic contact is
defined herein as any method of joining the transducer and probe
body such that vibrational energy generated by the transducer is
transmitted directly to the probe without significant energy loss
or dissipation and without any significant change in the frequency
and intensity of the ultrasonic vibrations. The term "without
significant energy loss" as used here means that at least 75% of
the sonic energy generated by the transducer is transferred to the
end of main probe body 1 at point 9.
[0075] Horn 7 operates as a booster to increase the amplitude of
the ultrasonic waves generated by transducer 3 and transmitted by
main probe body 1. The amplitude increases as the waves travel into
progressively narrower sections of horn 7, and this focuses the
ultrasonic energy for increased power density. For a stepped horn
design illustrated by FIG. 1, the gain in ultrasonic wave amplitude
provided by the decrease in cross-sectional area is typically equal
to 0.8 times the ratio of the larger cross-sectional area to the
smaller cross-sectional area. The acoustic or ultrasonic power
transmitted into the fluid by the tip of horn 7 is proportional to
the vibrational amplitude of the horn tip, and thus the horn can
focus a high acoustic power to a selected area or volume within a
pressurized fluid.
[0076] The equivalent diameter of collar support section 5 is
greater than the equivalent diameter of main probe body 1 for
reasons described later. Horn 7 may be stepped as shown wherein the
diameter of the horn decreases discontinuously between collar
support section 5 and the second end of the probe. Alternatively,
the diameter of the horn may decrease continuously between collar
support section 5 and the second end of the probe. Other horn
configurations may be used and typically the diameters of all
sections of the horn are less than the diameter of main probe body
1.
[0077] Ultrasonic transducer 3, which is shown schematically, may
be a piezoelectric crystal or crystal assembly activated by
alternating current supplied via conductors 11 and 13. These
crystals oscillate at ultrasonic frequencies in the range of 20 KHz
to 2 MHz and are commercially available in many different
configurations. Alternatively, ultrasonic transducer 3 may be a
magnetostrictive transducer assembly comprising iron or nickel
surrounded by an electromagnetic coil attached to conductors 11 and
13 wherein the alternating magnetic field induces ultrasonic
vibrations in the transducer.
[0078] An alternative embodiment of the probe is shown in FIG. 2
wherein the core of a magnetostrictive transducer is an integral
part of main probe body 1. As shown, a section of the main probe
body adjacent to the first end is surrounded by electrically
insulated electromagnetic coil 203 that is energized by alternating
current supplied via conductors 205 and 207. The end of the main
probe body within coil 203 may be the same metal as that of the
rest of the probe or may be a different metal or alloy joined or
attached to the probe by any appropriate method. As in the probe of
FIG. 1, the diameter of enlarged support section or collar 209 is
greater than the diameter of main probe body 201 for reasons
described later.
[0079] The ultrasonic probes described above are designed to fit
into a seal assembly for mounting the probe in the wall of a
pressure vessel. An axial section of an exemplary seal assembly and
probe is illustrated in FIG. 3. The ultrasonic probe of FIG. 1
(without the ultrasonic transducer) is shown in FIG. 3 and includes
main probe body 1, collar support section 5, and horn 7. In this
illustration, the probe parts are all cylindrical but as mentioned
earlier any part may have a non-circular cross section. The end of
probe body 1 has threaded stud 301 for attachment of an ultrasonic
transducer. The seal assembly comprises seal body 303, first end
305 with a tapered throat 307 to receive ferrule 309, second end
311 having a generally flat face, and a cylindrical bore between
the first and second ends. Main probe body 1 of the probe is
inserted coaxially into the cylindrical bore of the seal assembly
wherein the inner diameter of the bore is greater than the outside
diameter of the main probe body. Seal body 303 has center section
313 and may have at least two opposite parallel flat sections to
fit a wrench; center section 313 may have a hexagonal outer cross
section. Seal body 303 also has threaded sections 315 and 317 on
either side of center section 313.
[0080] Threaded section 317 is designed to be sealably inserted
into a threaded opening in the wall of a pressure vessel (not
shown). Alternatively, instead of using threaded section 317, the
seal body may be flanged at second end 311 and the flange designed
to seal to a corresponding flanged opening in the wall of the
pressure vessel. In another alternative, end 311 of seal body 303
may be welded directly to the opening in the pressure vessel. The
outer diameters of seal ring 319 and collar support section 5
typically are smaller than the inner diameter of the threaded or
flanged opening in the wall of the pressure vessel so that the
probe can pass through the opening in the pressure vessel during
installation.
[0081] Seal ring 319 is disposed between and collar support section
5. This torroidal seal ring may have a thin front section which
fits into the annulus between the outer surface of probe body 1 and
the inner surface of the bore in seal body 303. The seal ring may
have a thicker rear section which fits between second end 311 and
an inner surface of. The dimensions of collar support section 5
should be designed appropriately for the anticipated differential
operating pressure across the seal (i.e., the pressure difference
between the interior of the pressure vessel and atmospheric
pressure) formed by seal ring 319, collar support section 5, and
the face of second end 311 of seal body 303. The radial height of
collar support section 5, which is the distance that the collar
support projects outward radially from, should be sufficient to
avoid failure of the collar support section by compression. The
axial thickness of collar support section 5 should be sufficient to
avoid collar failure due to the axial shear caused by the pressure
differential. The ratio of the distance between the end of probe
body 1 and collar support section 5 to the distance from collar
support section 5 to the end of horn 7 may be between 1:10 and
10:1
[0082] Ferrule 309 forms a packing gland in combination with
follower ring 321 and threaded compression nut 323. Seal body 303,
tapered throat 307, ferrule 309, follower ring 321, threaded
compression nut 323, seal ring 319, second end 311, and collar
support section 5 work in combination to locate main probe body 1
firmly and coaxially within the bore of seal body 303 such that the
outer surface of main probe body 1 does not contact the inner
surface of the bore in seal body 303. In addition, second end 311,
seal ring 319, and collar support section 5 work in combination to
seal main probe body 1 to seal body 303. These elements provide the
sealing and centering functions for main probe body 1 by forcing
collar support 5 axially against seal ring 319 and forcing seal
ring 319 against second end 311, while simultaneously tightening
compression nut 323 on threads 315 to push follower ring 321
against ferrule 309 and push ferrule 309 into tapered throat 307.
The seal assembly then may be sealably threaded into a threaded
opening in the wall of a pressure vessel. Alternatively, if seal
body 303 is flanged at second end 311 instead of using threaded
section 317, the flange is sealed to a corresponding flanged
opening in the wall of the pressure vessel.
[0083] When the probe assembly is sealed into the pressure vessel
and the vessel is pressurized with a high pressure fluid, the
pressure differential between the vessel interior and the
surrounding atmosphere forces collar support 5 axially against seal
ring 319 and forces seal ring 319 against second end 311, thereby
forming a pressure-activated seal. Thus increasing the pressure in
the vessel will increase the force of collar support 5 axially
against seal ring 319 and the force of seal ring 319 against second
end 311.
[0084] The probe may be ultrasonically vibrated by means of an
ultrasonic transducer attached to threaded stud 301 as described
later. Ferrule 309 and seal ring 319 preferably are elastomeric
materials which serve to isolate the vibrating probe body 1 from
the fixed seal body 303. In addition, as described above, seal ring
319 seals probe body 1 to seal body 303 at end 311. Ferrule 309 and
seal ring 319 may comprise any elastomeric material and may be
selected from the group consisting of tetrafluoroethylene,
chlorotrifluoroethylene, polyvinylidene fluoride, perfluoroalkoxy,
polyethylene, unplasticized polyvinyl chloride, acrylonitrile
butadiene styrene, acetal, cellulose acetate butyrate, nylon,
polypropylene, polycarbonate, polyphenylene oxide, polyphenylene
sulfide, polysulfone, polyamide, polyimide, thermosetting plastic,
natural rubber, hard rubber, chloroprene, neoprene, styrene rubber,
nitrile rubber, butyl rubber, silicone rubber, chlorosulfonated
polyethylene, polychlorotrifluoroethylene, polyvinyl chloride
elastomer, cis-polybutadiene, cis-polyisoprene, ethylene-propylene
rubber, carbon, and graphite.
[0085] The various elements of the probe and seal assembly of FIG.
3, other than ferrule 309 and seal ring 319, may be fabricated from
a metal or metals appropriate for the required service. Such metals
may include, for example, titanium, carbon steel, iron, copper,
brass, bronze, nickel, and alloys thereof. The metals also may
include aluminum, aluminum alloys, stainless steel alloys, and
other commercially-available alloys such as Hastelloy.RTM.,
Inconel.RTM., and Monel.RTM..
[0086] The end of horn 7 may have a detachable tip of any shape. In
one embodiment, the detachable tip may have the same diameter as
the end of horn 7. In other embodiments, the detachable tip may
have other geometries that are designed to direct or radiate
ultrasonic energy in a particular manner for a given
application.
[0087] Main probe body 1 and horn 7 vibrate or oscillate as
ultrasonic waves pass from an ultrasonic generator attached to
threaded stud 301 to the tip of horn 7. The amplitude of the
axially-directed oscillations varies along the length of the main
probe body and horn and is a function of the probe and horn
geometry. The amplitude reaches maxima at the vibrational antinodes
and reaches minima at the vibrational nodes. The seal assembly of
FIG. 3 will constrain the vibrational motion of main probe body 1
while simultaneously providing pressure seals at ferrule 309 and
seal ring 319. If the sealing points of this assembly were rigid
connections, there could be a resulting vibrational energy loss at
these points, which could lead to localized overheating, mechanical
damage, and eventual fluid leakage. In addition, if the probe body
were constrained too rigidly at the seals, the combined probe body
and horn could become acoustically detuned, and this in turn could
reduce the efficiency of the transducer/probe assembly and cause to
damage to the assembly.
[0088] The probe and seal assembly of FIG. 3 should be designed
such that the seals at ferrule 309 and seal ring 319 are located at
vibrational nodes of the probe. The combination of this design
feature, the use of elastomeric materials for ferrule 309 and seal
ring 319, and the function of ferrule 309 and seal ring 319 to
prevent metal-to-metal contact between main probe body 1 and seal
body 303, should minimize or eliminate these problems. The
dimensions between the ultrasonic transducer, end 305 of seal body
303, and end 311 of seal body 303 should be selected carefully in
combination with the operating parameters of the ultrasonic
transducer to ensure that the vibrational nodes of the assembly
occur at the seals formed by ferrule 309 and seal ring 319.
[0089] The probe and seal assembly of FIGS. 1 and 3 may be
installed in a pressure vessel as illustrated in FIG. 4. In this
schematic illustration, probe 401 is inserted through seal body 403
attached to top 405 of pressure vessel body 407. Seal body 403 is
shown here in phantom and represents the seal body 303 of FIG. 3.
Ultrasonic transducer 409 is attached to the end of probe 401.
Heaters 402 may be used to maintain the vessel at an elevated
temperature. Pressure sensor 404 and temperature sensor 406 enable
the monitoring of the pressure and temperature in the vessel. Fresh
cleaning fluid 411, for example a supercritical fluid, flows into
the vessel via inlet line 413. Contaminated cleaning fluid 415
exits the vessel via line 415. In this illustration, the system
comprising the probe, transducer, seal body, and pressure vessel is
used for the cleaning of article 411 located on support 413. This
article may be, for example, a semiconductor device or component
previously subjected to manufacturing steps such as lithography,
etching, stripping, and chemical mechanical planarization.
[0090] The pressure vessel of FIG. 4 may be utilized, for example,
as a test system for studying methods of cleaning a single article
or a small number of articles. In a typical test, the pressure
vessel components are disassembled, article 411 to be cleaned is
placed on holder 411, top 405 (with seal body 403 and probe 401
having been installed previously) is sealed to pressure vessel body
407, a pressurized cleaning fluid is introduced into the sealed
vessel, and the ultrasonic transducer is operated at a selected
frequency and power level to generate ultrasonic waves 415 in the
pressurized fluid. Upon completion of the cleaning step, the system
is depressurized, the vessel is opened, and the cleaned article is
withdrawn. The pressure vessel of FIG. 4 alternatively may be used
for supercritical fluid extraction or as a sonochemical chemical
reactor, wherein the extraction and chemical reactions are enhanced
by the ultrasonic energy.
[0091] Larger and more complex pressure vessel systems may be
required for commercial ultrasonic cleaning applications. An
example of an advanced ultrasonic cleaning system using the
ultrasonic probe and seal assembly systems described above is
illustrated in FIG. 5, which is an exemplary system designed for
the cleaning of large-diameter flat articles such as silicon wafers
using a flow of pressurized cleaning fluid. Pressure vessel 501
comprises vessel lid 503, cylindrical wall 505, and detachable
vessel bottom 507. Wafer 509, for example a 300 mm diameter wafer,
is placed on a rotating table (not visible in this view) driven by
shaft 513 via a magnetic coupling (not visible) installed on
detachable vessel bottom 507.
[0092] Multiple probe and seal assemblies are mounted in vessel lid
503. In this illustration, four assemblies are installed in a
radial configuration to expose the rotating wafer to uniform
ultrasonic energy waves 514. The four assemblies include ultrasonic
transducers 515, 517, 519, and 521 and probes 523, 525, 527, and
529, wherein each probe includes main probe body 1, collar support
section 5, and horn 7 as illustrated in FIG. 3. Alternatively, a
single ultrasonic transducer attached to probes 523, 525, 527, and
529 may be used instead of individual transducers 515, 517, 519,
and 521. Seal assemblies 531, 533, 535, and 537 (shown here in
phantom) are installed in vessel lid 503 and each comprise tapered
throat 307, ferrule 309, follower ring 321, threaded compression
nut 323, seal ring 319 as illustrated in FIG. 3.
[0093] Pressurized fluid for the cleaning process is introduced
through inlet line 539 at the center of vessel lid 503, flows
radially through the interior of the vessel, under circular baffle
541, and exits via multiple outlet lines 543 located around the
outer edge of the vessel. The pressurized fluid alternatively may
be introduced via a shower head, multiple inlet tubes, or other
inlet devices known in the art. The flow of cleaning fluid
continuously sweeps contaminants, reactants, and undesirable
contaminants from the surface of the wafer and out through the
multiple outlets. The internal volume of vessel 501 should be
minimized to minimize processing time and materials
requirements.
[0094] In order to expose the surface of wafer 509 to a uniform
level of ultrasonic energy, the power settings of the transducers
may be maintained at different levels at the different radial
locations such that transducer 515 has the highest setting and
transducer 521 has the lowest setting. The tangential velocity of
the wafer is lower near the center and higher near the periphery,
and the power settings for transducers 515, 517, 519, and 521 may
be selected to provide a relatively uniform time-integrated
exposure to ultrasonic energy across the entire wafer surface.
[0095] A schematic sectional side view of the system of FIG. 5 is
shown in FIG. 6. Pressurized fluid 601 enters inlet 539, fluid 603
flows uniformly over the surface of wafer 509, under baffle 541,
and exits via outlets 543. The wafer requires at least one full
rotation in order to complete the cleaning process, and the cycle
time thus is set by the rotation rate of rotating table 605.
Heaters 607 may be used to maintain the system at an elevated
temperature. The pressure and temperature in the vessel may be
monitored by pressure probe 609 and temperature probe 611.
Additional transducer/probe assemblies may be installed to reduce
processing time in this type of system. For example, two additional
radial rows of four assemblies may be installed for a total of
three radial rows located 120 degrees apart. In this alternative,
wafer processing time would be reduced by 67%. In another
alternative, the multiple transducers in a row of radial
transducer/probe assemblies may be replaced by a single linear
transducer driving all four probes.
[0096] An alternative probe geometry may be used in which the probe
is planar rather than cylindrical as described in FIGS. 1-3. This
alternative probe geometry is shown in the sectional illustration
of FIG. 7. Planar probe 701 comprises an elongate planar body
having first end 703, second end 705, first longitudinal shoulder
support 707, and oppositely-located and parallel second
longitudinal shoulder support 709. Threaded stud 704 may be used to
attach an ultrasonic transducer to first end 703 of planar probe
701. Horn 711 is formed between second end 705 and the two shoulder
supports 707 and 709. Main probe body 713 is formed between first
end 705 and the two shoulder supports 707 and 709. Probe 701 has a
first side comprising planar surface portion 715 of horn 711 and
planar surface portion 717 of main probe body 713. Probe 701 has a
second side comprising opposite second planar surfaces (not seen in
this drawing) that are parallel to planar surface portion 715 of
horn 711 and planar surface portion 717 of main probe body 713,
respectively.
[0097] Planar probe 701 may be installed in pressure vessel wall
719 by means of two parallel seal assemblies 721 and 723, which are
sealed or welded to pressure vessel wall 719 at parallel joints 725
and 727 formed between the seal assembly and the vessel wall. Seal
assemblies 721 and 723 are mirror images of each other, and the
following description of the elements of seal assembly 721
therefore applies to the corresponding elements of seal assembly
723. Seal assembly 721 comprises seal body 729, seal cap 731, seal
bolt 732, seal bolt washer 733, seal nut 735, follower 737,
elastomeric packing gland 739, and elastomeric shoulder seal
741.
[0098] Seal body 729, seal cap 731, seal bolt 732, seal bolt washer
733, seal nut 735, follower 737, packing gland 739, shoulder
support 709, and shoulder seal 741 work in combination to locate
main probe body 713 firmly between seal assemblies 721 and 723. The
outer surface of main probe body 713 does not contact the inner
surfaces of seal cap 731, follower 737, and seal body 729.
Likewise, the opposite parallel surface (not visible) of main probe
body 713 does not contact the corresponding seal cap, follower, and
seal body of seal assembly 723. A gap is formed between the outer
side of main probe body 713 and the inner surfaces of seal cap 731,
follower 737, and seal body 729. Likewise, a similar gap is formed
on the opposite side of main probe body 713. Shoulder seal 741 has
a thin upper section which fits into the gap between the lower
portion of seal body 729 and planar surface portion 717 of main
probe body 713. The shoulder seal has a thicker lower section which
fits between shoulder support 709 and the bottom of seal body
729.
[0099] The functions of these elements for sealing and locating
planar probe 701 are provided by forcing shoulder support 709
against shoulder seal 741, thereby forcing shoulder seal 741
against the bottom of seal body 729 and into the gap between seal
body 729 and planar surface portion 717 of main probe body 713.
Seal bolt 732 and seal nut 735 are tightened to compress packing
gland 739 between follower 737 and the lower part of seal body 729,
thereby forcing packing gland 739 against and planar surface
portion 717 of main probe body 713. The same procedure is used for
the corresponding elements in seal assembly 723 on the opposite
side of planar probe 701. Shoulder support 709 and shoulder seal
741 ensure that planar probe 701 cannot slip out of seal assembly
721 when high pressures occur on the interior of pressure vessel
wall 719.
[0100] The probe may be ultrasonically vibrated by means of one or
more ultrasonic transducers (not shown) attached to first end 703.
Main probe body 713 and horn 711 vibrate or oscillate as ultrasonic
waves pass from the ultrasonic generator to second end 705 of
planar probe 701. The amplitude of the axially-directed
oscillations varies along the length of the main probe body and
horn, and the amplitude is a function of the probe and horn
geometry. The amplitude reaches maxima at the vibrational antinodes
and reaches minima at the vibrational nodes. The seal assemblies
721 and 723 of FIG. 7 will constrain the vibrational motion of main
probe body 701 while simultaneously providing pressure seals at
shoulder seal 741 and packing gland 739. If the sealing points of
this assembly were rigid connections, there could be a resulting
energy loss at these points, which could lead to localized
overheating, mechanical damage, and eventual fluid leakage. In
addition, if the probe body were constrained too rigidly at the
seals, the combined probe body and horn could become acoustically
detuned, and this in turn could reduce the efficiency of the
transducer/probe assembly and cause to damage to the assembly.
[0101] The second end 705 of horn 711 may have a detachable tip of
any shape. In one embodiment, the detachable tip may have the same
shape as the end of horn 711. In other embodiments, the detachable
tip may have other geometries that are designed to direct or
radiate ultrasonic energy in a particular manner for a given
application.
[0102] The elastomeric materials of packing gland 739 and shoulder
seal 741 serve to isolate the vibrating planar probe 701 from seal
body 703 and follower 737. In addition, as described above, packing
gland 739 and shoulder seal 741 seal planar probe 701 to seal body
729, thereby sealing the interior of the vessel from the external
atmosphere. Packing gland 739 and shoulder seal 741 may comprise
any elastomeric material and may be selected from the group
consisting of tetrafluoroethylene, chlorotrifluoroethylene,
polyvinylidene fluoride, perfluoroalkoxy, polyethylene,
unplasticized polyvinyl chloride, acrylonitrile butadiene styrene,
acetal, cellulose acetate butyrate, nylon, polypropylene,
polycarbonate, polyphenylene oxide, polyphenylene sulfide,
polysulfone, polyamide, polyimide, thermosetting plastic, natural
rubber, hard rubber, chloroprene, neoprene, styrene rubber, nitrile
rubber, butyl rubber, silicone rubber, chlorosulfonated
polyethylene, polychlorotrifluoroethylene, polyvinyl chloride
elastomer, cis-polybutadiene, cis-polyisoprene, ethylene-propylene
rubber, carbon, and graphite.
[0103] The various elements of the probe and seal assembly of FIG.
7, other than packing gland 739 and shoulder seal 741, may be
fabricated from a metal or metals appropriate for the required
service. Such metals may include, for example, titanium, carbon
steel, iron, copper, brass, bronze, nickel, and alloys thereof. The
metals also may include aluminum, aluminum alloys, stainless steel
alloys, and other commercially-available alloys such as
Hastelloy.RTM., Inconel.RTM., and Monel.RTM..
[0104] The probe and seal assembly of FIG. 7 should be designed
such that the seals at packing gland 739 and shoulder seal 741 are
located at vibrational nodes of the probe. The combination of this
design feature, the use of elastomeric materials for packing gland
739 and shoulder seal 741, and the function of packing gland 739
and shoulder seal 741 to prevent metal-to-metal contact between
main probe body 701 and seal body 729, should minimize or eliminate
these problems. The dimensions between the ultrasonic transducer,
packing gland 739, and shoulder seal 741 should be selected
carefully in combination with the operating parameters of the
ultrasonic transducer to ensure that the vibrational nodes of the
assembly occur at the seals formed by packing gland 739 and
shoulder seal 741.
[0105] The dimensions of planar probe 701 should be designed
appropriately for the anticipated differential operating pressure
across the seal (i.e., the pressure difference between the interior
of pressure vessel 719 and atmospheric pressure) formed by shoulder
seal 741, seal body 729, and shoulder support 709. The thickness of
shoulder support 709, which is the distance that the shoulder
support projects outward perpendicularly from planar probe 701,
should be sufficient to avoid failure of the collar support section
by compression. The axial thickness of shoulder support 709 should
be sufficient to avoid collar failure due to shear parallel to the
plane of planar probe 701 caused by the pressure differential.
[0106] An example of an advanced ultrasonic cleaning system using
the ultrasonic probe and seal assembly systems described above is
illustrated in FIG. 8, which is an exemplary system designed for
the cleaning of large-diameter flat articles such as silicon wafers
using a flow of pressurized cleaning fluid. Pressure vessel 801
comprises vessel lid 803, cylindrical wall 805, and vessel bottom
807. Wafer 809, for example a 300 mm diameter wafer, is placed on a
rotating table (not visible in this view) driven by shaft 813 via a
magnetic coupling (not visible) installed on vessel bottom 807.
[0107] A probe and seal assemblies similar to those of FIG. 7 are
mounted in vessel lid 803. In this illustration, planar probe 815
is mounted in seal device 817, which is shown here in phantom and
includes all of the seal elements described with reference to FIG.
7, and the probe is driven by single transducer 819. The planar
probe of this embodiment may provide a more uniform radial
distribution of ultrasonic waves across the surface of wafer 809 as
compared with the multiple probe system of FIGS. 5 and 6 described
above.
[0108] Pressurized fluid for the cleaning process may be introduced
through inlet line 821 at the center of vessel lid 803, flows
radially through the interior of the vessel, under circular baffle
823, and exits via multiple outlet lines 825 located around the
outer edge of the vessel. The pressurized fluid alternatively may
be introduced via a shower head, multiple inlet tubes, or other
inlet devices known in the art. The flow of cleaning fluid
continuously sweeps contaminants, reactants, and undesirable
contaminants from the surface of the wafer and out through the
multiple outlets. The internal volume of vessel 801 should be
minimized to minimize processing time and materials requirements.
The pressure and temperature in the vessel may be monitored by
pressure and temperature probes 826 and 828, respectively.
[0109] FIG. 8 also shows an exemplary apparatus for loading and
unloading a wafer from pressure vessel 801. Gate valve or door
assembly 827 comprises front gate guide 829, rear gate guide 831,
gate seal assembly 833, gate opening 835, and gate drive assembly
837. Gate opening 835 is in flow communication with and is sealed
to pressure vessel 801, and opens into the interior of the vessel.
A valve gate (not seen in this view) is moved upward by gate drive
assembly 837 through gate seal assembly 833 to seal a wafer into
the pressure vessel and the gate is moved downward to open the
vessel for insertion and removal of the wafer. A wafer may be
inserted and withdrawn through the gate valve assembly by manual
means or by robotic wafer handlers as known in the silicon wafer
processing art. Thus the seals provided by gate seal assembly 833
(when the gate is closed) and by seal device 817 allow leak-free
pressurization of the interior of pressure vessel 801 during the
cleaning process.
[0110] An alternative wafer cleaning system which uses the probe
and seal assembly of FIG. 7 is illustrated in an exploded view in
FIG. 9. This exemplary system utilizes linear motion of the wafer
during cleaning, in contrast with the rotational motion in the
systems of FIGS. 5, 6, and 8. The system comprises reactor 901,
wafer carrier system 903, and optional loadlock chamber 905.
Reactor 903 includes front loading opening and flange 907 that
joins with wafer carrier seal plate 930 to form a pressure seal, a
corresponding rear loading opening 909, ultrasonic probe opening
911, heaters 912, and cleaning fluid vent 913. Temperature and
pressure may be monitored by temperature sensor 914 and pressure
sensor 916. Fresh cleaning fluid may be introduced via inlet 920.
Optional loadlock chamber 905 includes front loading opening 915,
front gate valve or door assembly 917, rear opening 919, rear gate
valve or door assembly 921, and wafer lifting pin 923.
[0111] Wafer carrier system 903 comprises wafer carrier 922 mounted
on carrier rod 925 and wafer carrier 922 has a recessed surface 924
for holding a wafer. Carrier rod 925 is adapted to move wafer
carrier forward or backward linearly along the axis of reactor 901
by rack and pinion linear actuator 927 and stepping motor 929
mounted on wafer carrier seal plate 930.
[0112] FIG. 9A, which is an inset of FIG. 9, shows a side view of
reactor 901 including front loading opening 907, corresponding rear
loading opening 909, ultrasonic probe opening 911, and cleaning
fluid vent 913. Fresh cleaning fluid 918 enters via inlet line 920
and contaminated cleaning fluid 926 (FIG. 9) exits via fluid vent
913.
[0113] Ultrasonic probe assembly 931, which uses components similar
to those of the planar ultrasonic probe assemblies in FIGS. 7 and
8, fits sealably into ultrasonic probe opening 911. The probe
assembly comprises ultrasonic transducer 933, probe 935, and seal
device 937 (shown in phantom). Seal device 937 includes all the
seal components described with reference to FIG. 7. The plane of
ultrasonic probe opening 911 may form an included angle of 10
degrees to 90 degrees with the plane of reactor 901, and a typical
angle may be 45 degrees. As a wafer in recessed surface 924 moves
with wafer carrier 922 through reactor 901 during a cleaning step,
the included angle between the plane of ultrasonic probe 931 and
the plane of the wafer may be between 10 degrees to 90 degrees.
[0114] In one method of operation, reactor 901, wafer carrier
system 903, ultrasonic probe assembly 931, front gate valve or door
assembly 917, rear gate valve or door assembly 921, and wafer
lifting system 923 are joined and sealed together to provide a
pressurizable reactor system. The six components 901, 903, 905,
917, 921 and 931 of this system are operated in a programmed
sequence of twenty one steps. In step 1, the system is in its
initial status: ultrasonic transducer 931 is off, pressurized
cleaning fluid flow inlet 920 is closed, the pressure of the
reactor chamber 901 is set at an initial low pressure, and wafer
carrier 922 is retracted into isolated cleaning chamber 901. The
wafer lifting pins 923 are down, the loadlock/wafer loader gate
valve 921 is open, and there is no wafer in the loadlock 901.
[0115] At this point in the sequence a wafer loader robot (not
shown) or operator (not shown) delivers a contaminated wafer (not
shown) into the loadlock chamber 905 for cleaning. The wafer is
placed onto the lowered lifting pins by the robot or operator, and
the pins are then raised. In the next six steps of the operating
sequence, the wafer loading is completed. The steps proceed as
follows: (2) the loadlock/wafer loader gate valve 921 closes; (3)
the pressure in the loadlock chamber 905 is equalized with that of
the cleaning chamber 901 by opening a valve in a bypass line (not
shown) around cleaning chamber/loadlock gate valve 917; (4) the
pressurized flow inlet is opened, allowing pressurized cleaning
fluid to enter the cleaning chamber 901, and the loadlock chamber
pressurizes as cleaning fluid flows continuously through the
cleaning chamber and passes to the chamber's outlet line; (5)
cleaning chamber/loadlock gate valve 917 then opens; (6) carrier
block 922 is then extended to a position under the wafer by
actuating stepping motor 929; and (7) the wafer is lowered onto
carrier block 922 using wafer lifting mechanism 923.
[0116] In step 8, stepping motor 929 is again actuated, but in the
reverse direction, and carrier block 922 begins to move back into
cleaning chamber 901 and carry the wafer into the cleaning chamber.
In step 9, ultrasonic transducer 933 is activated and ultrasonic
energy begins to pass into the cleaning fluid, exposing the wafer
to the cleaning process. The stepping motor then reverses direction
in step 10, exposing the wafer to the second pass under the
ultrasonically-activated probe.
[0117] In the next five steps the wafer is returned to loadlock
chamber 905. The steps proceed as follows: (11) the ultrasonic
transducer is de-activated; (12) the pins lift the wafer off the
carrier block 922; (13) carrier block 922 retracts into the
cleaning chamber; and (14) cleaning chamber/loadlock chamber gate
valve 917 is closed as (15) the pressurized cleaning fluid inlet is
closed.
[0118] In the next four steps, the loadlock chamber is further
de-pressurized and, if necessary, is evacuated. The steps proceed
as follows: (16) the cleaning chamber and loadlock chamber pressure
falls as the pressurized cleaning fluid exits the cleaning chamber,
and this venting process produces a set low pressure in the
cleaning chamber and loadlock chamber; then, (17) the valve in the
bypass line (not shown) around cleaning chamber/loadlock gate valve
917 is closed. In some cases, the loadlock may be evacuated further
in order to equilibrate the loadlock pressure with that of an
attached robotic wafer loading system (not shown). If further
loadlock evacuation is necessary, then (18) the vent valve in a
vacuum line (not shown) extending from the loadlock chamber is
opened to complete evacuation of the loadlock chamber. Following
this evacuation of the loadlock chamber, (19) this vent line valve
is closed, and the loadlock chamber is left in an evacuated
condition.
[0119] In the final two steps of the operating sequence, the
cleaned wafer is unloaded. In step 20 the wafer is lowered by
lowering the lifting pins of wafer lifter 923. Finally, in step 21
loadlock/wafer loader gate valve 921 is opened and the wafer is
removed by the loader robot or operator. At this point the system
has returned to its initial (step 1) status.
[0120] The estimated time required to complete the steps is as
follows: steps 1 to 7 (loading), approximately 10 seconds; steps 8,
9 and 10 (cleaning), approximately 48 seconds; steps 11 to 21
(unloading), approximately 20 seconds; total time required to
complete the sequence, approximately 78 seconds. Steps 8, 9 and 10
may be accomplished in less time in an optimized cleaning
process.
[0121] The ultrasonic cleaning systems described above may use a
wide variety of pressurized cleaning fluids and optional processing
agents mixed with the cleaning fluids. A cleaning fluid may be in
the form of a pressurized condensing vapor, a pressurized saturated
or subcooled liquid, a dense fluid, or a supercritical fluid. The
pressurized cleaning fluid may comprise one or more components
selected from the group consisting of carbon dioxide, nitrogen,
methane, oxygen, ozone, argon, hydrogen, helium, ammonia, nitrous
oxide, hydrogen fluoride, hydrogen chloride, sulfur trioxide,
sulfur hexafluoride, nitrogen trifluoride, monofluoromethane,
difluoromethane, tetrafluoromethane, trifluoromethane,
trifluoroethane, tetrafluoroethane, pentafluoroethane,
perfluoropropane, pentafluoropropane, hexafluoroethane,
hexafluoropropylene, hexafluorobutadiene, octafluorocyclobutane,
and tetrafluorochloroethane. The pressurized fluid may further
comprise one or more processing agents selected from a group
consisting of an acetylenic alcohol, an acetylenic diol, a dialkyl
ester, hydrogen fluoride, hydrogen chloride, chlorine trifluoride,
nitrogen trifluoride, hexafluoropropylene, hexafluorobutadiene,
octafluorocyclobutane tetrafluorochloroethane,
fluoroxytrifluoromethane (CF.sub.4O), bis(difluoroxy)methane
(CF.sub.4O.sub.2), cyanuric fluoride (C.sub.3F.sub.3N.sub.3),
oxalyl fluoride (C.sub.2F.sub.2O.sub.2), nitrosyl fluoride (FNO),
carbonyl fluoride (CF.sub.2O), perfluoromethylamine (CF.sub.5N), an
ester, an ether, an alcohol, a nitrile, a hydrated nitrile, a
glycol, a monester glycol, a ketone, a fluorinated ketone, a
tertiary amine, an alkanolamine, an amide, a carbonate, a
carboxylic acid, an alkane diol, an alkane, a peroxide, a water, an
urea, a haloalkane, a haloalkene, a beta-diketone, a carboxylic
acid, an oxine, a tertiary amine, a tertiary diamine, a tertiary
triamine, a nitrile, a beta-ketoimine, an ethylenediamine
tetraacetic acid and derivatives thereof, a catechol, a
choline-containing compound, a trifluoroacetic anhydride, an oxime,
a dithiocarbamate, and combinations thereof.
[0122] Typical operating parameters for the systems described above
may include fluid pressures in the range of 10.sup.-3 to 680 atma,
temperatures in the range of ambient to 95.degree. C., ultrasonic
energy frequencies in the range of 20 KHz to 2 MHz, and ultrasonic
power densities in the range of 0.1 to 10,000 W/in.sup.2. Articles
being cleaned may be exposed to ultrasonic energy for 30 to 120
seconds. Frequency sweeping may be used in which the frequency is
varied during the cleaning period according to a predetermined
frequency profile.
[0123] The following Examples illustrate embodiments of the present
invention but do not limit the invention to any of the specific
details described therein.
EXAMPLE 1
[0124] A probe as described with reference to FIG. 3 was fabricated
from titanium with the following dimensions: total length including
main probe body 1, collar support section 5, and horn 7, 6.86 inch;
combined length of probe body 1 and collar support section 5, 3.10
inch; total length of horn 7, 3.76 inch; length of larger diameter
horn section, 1.76 inch; length of smaller diameter horn section,
2.00 inch; diameter of main probe body 1, 0.50 inch; diameter of
smaller diameter horn section, 0.125 inch, and diameter of larger
diameter horn section, 0.250 inch. The axial thickness of collar
support section 5 is 0.125 inch and the diameter is 0.650 inch. The
end of the horn adjacent collar support section 5 has a smooth
radius transition from 0.500 inch diameter to 0.250 inch diameter
and the smaller horn section adjacent the junction with larger horn
section has a smooth radius transition from 0.250 inch diameter to
0.125 inch diameter.
EXAMPLE 2
[0125] A planar probe as described with reference to FIG. 7 is
fabricated from titanium with the following dimensions: total
length of planar probe 701 having first end 703 and second end 705,
6.86 inch; combined length of upper, thicker portion of planar
probe 701 and shoulder supports 707 and 709, 3.10 inch; total
length of horn 711, 3.76 inch; thickness of main probe body 713,
0.50 inch; and thickness of horn 711, 0.125 inch. The axial
thickness of shoulder supports 707 and 709 is 0.125 inch and the
width of shoulder supports 707 and 709 perpendicular to the plane
of planar probe 701 is 0.650 inch. The end of the horn adjacent
shoulder supports 707 and 709 has a smooth radius transition from
0.250 inch diameter to 0.125 inch diameter.
EXAMPLE 3
[0126] A 3.8 cm.times.3.8 cm silicon wafer test fragment containing
silicon debris particles was cleaned in a small scale reactor
similar to that of FIG. 4. The probe body was constructed of
Hastelloy.RTM. C-276 and had a diameter of 0.25 in at the seal
location, a diameter of 0.5 inch between the seal and the
transducer, and a diameter of 0.125 in between the seal and the
probe tip. The tip of the ultrasonic probe was positioned 6 mm
above the wafer surface, the reactor was sealed, and the sealed
reactor was charged with carbon dioxide at 3000 psig and
104.degree. F. The ultrasonic transducer was operated at 20 KHz and
a power density of approximately 100 W/cm.sup.2 for 60 seconds. The
system was depressurized and disassembled, and the wafer test
fragment was removed and observed. It was seen that more than 90%
of the super-micron sized and sub-micron-sized silicon debris
particles were removed from the entire chip surface by the
ultrasonic cleaning process.
EXAMPLE 4
[0127] The procedure of Example 1 was repeated but without the use
of ultrasonic energy. It was observed that the silicon debris
particles were not removed from the wafer test fragment.
* * * * *