U.S. patent application number 10/456995 was filed with the patent office on 2004-08-19 for method and apparatus for removing organic layers.
This patent application is currently assigned to P.C.T. Systems, Inc.. Invention is credited to Matthews, Robert R., Montierth, Garry L..
Application Number | 20040159335 10/456995 |
Document ID | / |
Family ID | 33490277 |
Filed Date | 2004-08-19 |
United States Patent
Application |
20040159335 |
Kind Code |
A1 |
Montierth, Garry L. ; et
al. |
August 19, 2004 |
Method and apparatus for removing organic layers
Abstract
Embodiments in accordance with the present invention provide
methods and apparatuses for heating a substrate with radiation
during processing of substrates. Radiation in the radio or
microwave portion of the electromagnetic spectrum is applied to a
substrate housed within a processing chamber to promote desirable
chemical reactions involving the substrate. Processing in
accordance with embodiments of the present invention may utilize
pressurization of the processing chamber in conjunction with the
application of microwave, RF, IR, or UV radiation, or
electromagnetic induction, to heat the substrate or a component of
the processing chemistry present within the chamber. Alternative
embodiments of the present invention may use combinations of these
energy types for more effective processing. For example, UV
radiation may be introduced into the chamber in conjunction with
microwave heating in order to generate reactive species from the
processing chemistry.
Inventors: |
Montierth, Garry L.;
(Fremont, CA) ; Matthews, Robert R.; (Richmond,
CA) |
Correspondence
Address: |
TOWNSEND AND TOWNSEND AND CREW, LLP
TWO EMBARCADERO CENTER
EIGHTH FLOOR
SAN FRANCISCO
CA
94111-3834
US
|
Assignee: |
P.C.T. Systems, Inc.
Fremont
CA
|
Family ID: |
33490277 |
Appl. No.: |
10/456995 |
Filed: |
June 6, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10456995 |
Jun 6, 2003 |
|
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10150748 |
May 17, 2002 |
|
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60387155 |
Jun 6, 2002 |
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Current U.S.
Class: |
134/10 |
Current CPC
Class: |
B08B 7/0021 20130101;
G03F 7/423 20130101; H01L 21/67115 20130101; H01L 21/6708 20130101;
H01L 21/67051 20130101; G03F 7/425 20130101; G03F 7/42 20130101;
B08B 3/08 20130101; C23F 1/16 20130101; B08B 7/005 20130101; B08B
7/0057 20130101; H01L 21/32134 20130101; H01L 21/02052 20130101;
H01L 21/31133 20130101; H01L 21/31111 20130101 |
Class at
Publication: |
134/010 |
International
Class: |
C23G 001/36 |
Claims
What is claimed is:
1. A method for performing processing of a substrate comprising:
providing a processing chamber; inserting a substrate into the
processing chamber; introducing a processing chemistry into the
processing chamber; pressurizing the processing chamber by at least
one of introducing a component of the processing chemistry into the
processing chamber and introducing a gas into the processing
chamber; and applying radiation to heat at least one of a layer of
the substrate and a component of the processing chemistry, thereby
promoting reaction between the substrate and the processing
chemistry, wherein the pressurizing step occurs at least one of
before, after, and simultaneously with radiation application
step.
2. The method of claim 1 wherein the applied radiation comprises at
least one of microwave, UV, IR, RF and electromagnetic
induction.
3. The method of claim 1 further comprising applying ultraviolet
radiation into the chamber to generate a reactive species from the
processing chemistry.
4. The method of claim 3 further comprising evacuating the
processing chamber prior to pressurizing the processing chamber to
a level greater than an evacuation pressure in order to prolong the
lifetime of the reactive species generated from the processing
chemistry.
5. The method of claim 3 wherein: a wavelength of the ultra-violet
radiation comprises one of 254 nm, 222 nm, 172 nm; and the
processing chemistry comprises one of ozone, hydrogen peroxide,
oxygen and N.sub.2O.
6. The method of claim 1 wherein microwave radiation is applied to
the chamber to heat at least one of one layer of the substrate, the
substrate-contacting member, and a component of the processing
chemistry.
7. The method of claim 6 wherein the microwave radiation is applied
to the chamber in a single mode configuration.
8. The method of claim 6 wherein the microwave radiation is applied
to the chamber in a multi-mode configuration.
9. The method of claim 6 wherein at least part of the chamber walls
are coated with a microwave absorbing material to reduce
reflections within the chamber.
10. The method of claim 1 wherein at least one layer of the
substrate is heated by electromagnetic inductive heating.
11. The method of claim 1 wherein the radiation source emits
radiation varying in at least one of frequency, power, wave form,
and pulse duration.
12. The method of claim 1 wherein a temperature in the processing
chamber changes during processing.
13. The method of claim 1 wherein at least one component of the
chemistry changes concentration during processing.
14. The method of claim 1 wherein the processing chemistry
comprises at least one of a gas, a liquid, a droplet, a mist, a
vapor, and a solid.
15. The method of claim 1 wherein at least part of the substrate
surface is contacted with the processing chemistry.
16. The method of claim 1 wherein the substrate comprises at least
one layer.
17. The method of claim 1 wherein the substrate moves relative to
at least one of the chamber and the processing chemistry during at
least part of the processing.
18. The method of claim 1 wherein the radiation is directed towards
the substrate at least one of parallel, perpendicular and at an
angle between parallel and perpendicular.
19. The method of claim 1 wherein the processing chemistry
comprises at least one of an acid, a base, an oxidant, a reducing
agent, deionized (DI) water, and an organic solvent.
20. The method of claim 19 wherein the acid comprises an inorganic
acid.
21. The method of claim 19 wherein the acid comprises an organic
acid.
22. The method of claim 21 wherein the organic acid is selected
from the group consisting of acetic acid, formic acid, butyric
acid, propionic acid, citric acid, oxalic acid, and sulfonic
acid.
23. The method of claim 19 wherein the oxidant is selected from the
group consisting of ozone, oxygen, a peroxide, and oxide of
nitrogen.
24. The method of claim 19 wherein the base is selected from the
group consisting of NH.sub.3, NH.sub.4OH, NaOH, TMAH, and KOH.
25. The method of claim 19 wherein the organic solvent is selected
from the group consisting of NMP, photresist stripper, semi-aqueous
stripper, and methylene chloride.
26. The method of 19 wherein the reducing agent comprises
hydrogen.
27. The method of claim 1 wherein the processing chemistry
comprises ozone in a concentration range of between about 100 and
400,000 ppm.
28. The method of claim 1 wherein the processing chemistry contacts
both sides of the substrate simultaneously.
29. The method of claim 1 wherein at least one component of the
processing chemistry is selectively heated by the radiation.
30. The method of claim 1 wherein the processing chemistry
comprises at least one of the list of the standard RCA chemistries
including H.sub.2SO.sub.4, H.sub.2O.sub.2, H.sub.2SO.sub.5, HF,
NH.sub.4OH, and HCl.
31. The method of claim 1 wherein the processing chemistry
comprises one of a surfactant and a chelating agent.
32. The method of claim 1 wherein a first processing chemistry
contacts one side of the substrate and then a second processing
chemistry contacts another side of the substrate.
33. The method of claim 1 wherein the radiation is directed towards
a back side of the substrate.
34. The method of claim 1 wherein the radiation is directed toward
a front side of the substrate.
35. The method of claim 1 wherein multiple processing chemistries
are used.
36. The method of claim 1 wherein the processing of a substrate
comprises multiple processing steps performed in at least one of
the same and different processing chambers.
37. The method of claim 1 wherein the substrate is selected from
the group consisting of silicon, GaAs, SiGe, Si, GaAs, GaInP, and
GaN quartz, borosilicate glass, a flat panel display, a substrate
bearing microelectro-mechanical (MEMS) devices, a hard disk
substrate, a biomedical slide, a substrate for DNA and genetic
markers, an optical device, a mirror, a lens, a waveguide, and a
liquid crystal display (LCD).
38. The method of claim 1 wherein the substrate comprises a
patterned layer of a dielectric, metallic, organic, or
organo-metallic material.
39. The method of claim 1 wherein the processing comprises at least
one of removing material from a substrate, adding material to a
substrate, and modifying a substrate.
40. The method of claim 1 wherein the radiation is directed to the
chamber and wafer through a reflecting/focusing network comprising
lenses and mirrors.
41. The method of claim 1 wherein the processing chemistry
comprises at least one of F.sub.2, Cl.sub.2, HF, HCl,
H.sub.2SO.sub.4, H.sub.2CO.sub.3, HNO.sub.3, H.sub.3PO.sub.4, Aqua
Regia, chromic and sulfuric acid mixtures, sulfuric and ammonium
persulfate mixtures, and various combinations thereof.
42. The method of claim 1 wherein the substrate comprises at least
one layer of radiation absorbing material.
43. The method of claim 1 wherein during application of radiation
the substrate is in contact with a member comprising a
radiation-absorbing material.
44. The method of claim 1 wherein the substrate comprises at least
one silicon wafer.
45. The method of claim 1 wherein the substrate heats up at a rate
of between 10 and 10,000.degree. C./min.
46. The method of claim 1 further comprising cooling the heated
substrate at a rate of between 10 and 10,000.degree. C./min.
47. The method of claim 1 wherein pressurizing the process chamber
results in a pressure greater than atmospheric pressure.
48. The method of claim 47 wherein pressurizing results in a
pressure of between about one and 100 ATM during the
processing.
49. The method of claim 48 wherein pressurizing results in a
pressure of between about one and 10 ATM during the processing.
50. The method of claim 1 wherein the pressurizing the process
chamber results in a pressure of less than or equal to atmospheric
pressure.
51. The method of claim 1 further comprising evacuating the
processing chamber prior to pressurizing the processing chamber to
a level greater than an evacuation pressure.
52. An apparatus for processing a substrate, the apparatus
comprising: a chamber in fluid communication with a processing
chemistry source; a pressurization source in fluid communication
with the chamber, the pressurization source operable to increase a
pressure within the chamber during processing; and a radiation
source in communication with the chamber to heat at least one of a
layer of a substrate, a substrate contacting member, and a
processing chemistry positioned within the chamber.
53. The apparatus of claim 52 wherein the radiation source
comprises a source of at least one of microwave, UV, IR, RF, and
electromagnetic induction radiation.
54. The apparatus of claim 52 further comprising a substrate
support positioned within the chamber and configured to support a
substrate such that an orientation of the substrate changes
relative to the radiation source during processing.
55. The apparatus of claim 52 further comprising a substrate
support positioned within the chamber, the substrate support
comprising at least one layer of radiation absorbing material.
56. The apparatus of claim 52 further comprising a vacuum pump in
fluid communication with a processing chamber to allow evacuation
at least one of prior to and after the pressurization.
57. The apparatus of claim 52 further comprising a mode stirrer
positioned in the chamber and configured to deflect radiation from
the radiation source during processing.
58. The apparatus of claim 52 wherein the radiation source is
configured to emit radiation varying in at least one of frequency
and power.
59. The apparatus of claim 52 wherein the radiation source is in
communication with the chamber through a radiation permeable
window.
60. The apparatus of claim 52 wherein the radiation source is in
communication with the chamber through a network comprising at
least one of lenses and mirrors.
61. The apparatus of claim 52 further comprising a second radiation
source.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This nonprovisional application claims priority from
provisional application No. 60/387,155, filed Jun. 6, 2002 and
hereby incorporated by reference for all purposes. This
nonprovisional application also claims priority as a
continuation-in-part of U.S. parent application Ser. No.
10/150,748, filed May 17, 2002, also hereby incorporated by
reference for all purposes.
BACKGROUND OF THE INVENTION
[0002] During fabrication of semiconductor devices, it is
frequently useful to develop an organic photoresist material in a
pattern that serves as a mask for processes such as etching or
ion-implantation. Following ion-implantation of metals into a
masked substrate, however, the developed organic photoresist mask
is difficult to remove without damaging the underlying
material.
[0003] Conventionally, such ion-implanted organometallic
photoresist materials are removed in two stages. First, the
substrate bearing the organo-metallic material is exposed to an
oxygen asher using a microwave-induced plasma. This initial ashing
step typically results in substantial amounts of
particles/implanted metals remaining on the surface of the
substrate.
[0004] Therefore, a second step of exposing the ashed substrate
surface to wet processing in the piranha process with Caro's acid
(a combination of sulfuric acid and hydrogen peroxide) at
temperatures over 100.degree. C. is conventionally employed.
Neither of the ozone ashing nor the wet processing stages are
effective alone. Moreover, the intense microwave radiation applied
to generate the plasma creates long-lived reactive chemical
species, typically radicals, which may damage fragile structures
present on the substrate surface.
[0005] Accordingly, there is a need in the art for improved methods
and apparatuses for treating a semiconductor wafer.
BRIEF SUMMARY OF THE INVENTION
[0006] Embodiments in accordance with the present invention provide
methods and apparatuses for heating a substrate with radiation
during chemical processing. Specifically, radiation in the radio or
microwave portion of the electromagnetic spectrum is applied to a
substrate housed within a processing chamber in order to promote
desirable chemical reactions involving the substrate. Processing in
accordance with embodiments of the present invention may utilize
the application of microwaves, RF, IR, or UV radiation, or
electromagnetic induction, to heat the substrate. Alternative
embodiments of the present invention may use combinations of these
energy types for more effective processing. For example, UV
radiation may be introduced into the chamber in conjunction with
microwave heating in order to generate reactive species from the
processing chemistry.
[0007] Processing in accordance with embodiments of the present
invention may take place at elevated pressures to enhance
concentrations of reactant material, or may take place at
sub-ambient pressures in order to prolong the lifetime and hence
processing effectiveness of radicals or other reactive species
present within the chamber. One particular promising embodiment of
the present invention is the stripping of photoresists that have
been subjected to ion implantation, utilizing exposure of the
implanted wafers to ozone gas.
[0008] Processing chemistry introduced into the chamber to react
with the heated substrate may be in the form of a gas, a liquid, or
some combination of a gas and a liquid such as a mist.
Alternatively, the processing chemistry could also be utilized in
the form of a solid such as a dust. In these cases, the processing
chemistry may be transported to or through the processing chamber
under the influence of a pressure differential.
[0009] An embodiment of a method in accordance with the present
invention for performing processing of a substrate, comprises,
providing a processing chamber, inserting a substrate into the
processing chamber, and introducing a processing chemistry into the
processing chamber. The processing chamber is pressurized by at
least one of introducing a component of the processing chemistry
into the processing chamber and introducing a gas into the
processing chamber. Radiation is applied to heat at least one of a
layer of the substrate and a component of the processing chemistry,
thereby promoting reaction between the substrate and the processing
chemistry, wherein the pressurizing step occurs at least one of
before, after, and simultaneously with radiation application
step.
[0010] An embodiment of an apparatus in accordance with the present
invention for processing a substrate, comprises, a chamber in fluid
communication with a processing chemistry source, and a
pressurization source in fluid communication with the chamber, the
pressurization source operable to increase a pressure within the
chamber during processing. A radiation source is in communication
with the chamber to heat at least one of a layer of a substrate, a
substrate contacting member, and a processing chemistry positioned
within the chamber.
[0011] A further understanding of the nature and advantages of the
inventions disclosed herein may be realized by reference to the
remaining portions of the specification and the attached
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 shows a simplified cross-sectional view of one
embodiment of an apparatus for processing a substrate in accordance
with the present invention.
[0013] FIG. 2 shows a simplified cross-sectional view of an
alternative embodiment of an apparatus for performing processing in
accordance with the present invention.
[0014] FIG. 3 shows a simplified plan view of another alternative
embodiment of a processing apparatus in accordance with the present
invention.
[0015] FIG. 4 shows a simplified cross-sectional view of another
alternative embodiment in accordance with the present
invention.
[0016] FIG. 5 shows a simplified plan view of yet another
alternative embodiment of a processing apparatus in accordance with
the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] FIG. 1 shows a simplified cross-sectional view of one
embodiment of an apparatus 10 for processing a substrate in
accordance with the present invention. Substrate or wafer 2 is
supported upon turntable 4 positioned within chamber 6. Substrate 2
may comprise a number of different materials, including but not
limited to silicon, GaAs, and other semiconductor materials,
quartz, borosilicate glass, flat panel displays,
microelectro-mechanical (MEMS) devices, hard disk substrates,
biomedical slides, and other media. The surface of substrate 2 may
further comprise patterned layers of different materials such as
dielectric, metallic, organic, or organo-metallic materials. For
the purposes of this application, the term "organo-metallic" refers
to any carbon-containing material which also includes one or more
metals. One example of an organometallic material is organic
photoresist material that has been ion-implanted with metals such
as phosphorous or boron. Another example of an organometallic
material are the chemical by-products of plasma etching, which may
deposit on the sidewalls of device features.
[0018] Chamber 6 includes inlet 8 and outlet 9 for receiving and
exhausting respectively, chemistries intended to react with
substrate 2. Chamber 6 may be completely or partially closed, such
that the processing chemistries may be maintained under elevated or
reduced pressures during processing. Chemistries introduced into
chamber 6 for processing may comprise any gas, liquid, or
gas/liquid combination intended to react with substrate 2 or
material present thereon.
[0019] Chamber 6 is composed of material permeable to radiation
utilized in heating the substrate or a layer of material on top of
the substrate, such that radiation 12 emitted by generator 14
enters chamber 6, contacts wafer 2, and results in heating of wafer
2 or a layer on wafer 2. Alternatively, chamber 6 may comprise
material that is not permeable to the radiation, but may further
include a window comprising a radiation-permeable material which
permits entry of the radiation into the chamber.
[0020] Radiation generator 14 may comprise a magnetron 11 in
communication with the chamber through a waveguide 13. Radiation
generator 14 may comprise a generator of microwave radiation of
frequency 915 or 2450 MHz. Such microwave sources typically exhibit
a power of between about 300 and 1200 W. However, a microwave
generator utilized by embodiments in accordance with the present
invention is not limited to any particular frequency or power
range, and alternatively could be of a specialized industrial
design utilizing a specific fixed or changeable power, frequency,
or pulse duration. For example, generators utilizing variable
frequency, variable power, and/or precisely controlled power levels
could also be advantageously utilized in accordance with
embodiments of the present invention.
[0021] Waveguide 13 is configured to receive radiation from
generator 14, and to convey this radiation in a single mode to
chamber 6. Chamber 6 is designed to ensure that the applied
radiation uniformly heats the substrate(s) located therein. In one
embodiment, chamber 6 may exhibit dimensions sufficiently similar
to waveguide 13 to preserve the unipolar character of the applied
radiation. While not wishing to be limited to any particular
approach, in one possible embodiment of the present invention
utilizing unipolar radiation, interior surfaces of the chamber
could be lined with radiation-absorbing materials to suppress
internal reflectance of the radiation giving rise to unwanted
multi-mode radiation.
[0022] It may also be desired that radiation applied to the chamber
to heat the wafer will be multi-mode radiation. This is because
many materials, including single crystal silicon substrates
utilized in the fabrication of semiconductor devices, are
relatively transparent to microwave radiation, with a majority of
the energy of the radiation encountering the substrate will pass
through without being absorbed. Accordingly, the methods and
apparatuses in accordance with embodiments of the present invention
may require the passage of reflected radiation in order to effect
the desired rapid heating.
[0023] Application of multi-mode radiation to the processing
chamber to accomplish uniform heating of substrates positioned
therein can be accomplished in several ways. In the specific
embodiment illustrated in FIG. 1, uniform heating of the wafer(s)
is ensured by rotating the wafers utilizing a turntable, relative
to the direction of the applied radiation. Alternatively, a mode
stirrer structure such as a rotating metal fan could be positioned
in the chamber such that unipolar radiation incident from the
generator is reflected at random within the cavity to heat
substrate(s) present therein. Further alternatively, the microwave
generator could emit radiation of oscillating frequencies or
differing pulse durations in order to accomplish uniform heating
with multi-mode radiation in accordance with embodiments of the
present invention. Still further alternatively, multiple microwave
generators could be employed to simultaneously apply radiation
having a plurality of modes.
[0024] The embodiment of FIG. 1 shows wafer 2 supported
horizontally on turntable 4 in a plane parallel with the direction
of radiation 12 from generator 14. However, the present invention
is not limited to this particular configuration, and in an
alternative embodiment the substrate could be supported
perpendicular relative to the incident radiation, or in any other
orientation relative to the direction of radiation emitted by the
generator.
[0025] In operation, substrate 2 is positioned upon turntable 4
within chamber 6. A processing chemistry is flowed into chamber 6
through inlet 8. Radiation 12 from generator 14 is transmitted into
chamber 6 and into contact with wafer 6, resulting in heating of
wafer 2. Radiation 12 may also indirectly contact wafer 2 by
reflecting off of the interior surfaces 6a of the chamber 6.
[0026] As a result of interaction between the radiation 12 and
wafer 2 or a layer of material present thereon, the wafer or the
material overlying the wafer is heated. Chemistry present in
chamber 6 then reacts with heated substrate 2 or materials present
on the surface thereof. The elevated temperature of the substrate,
combined with the reactive properties of the processing chemistry,
effectuate a desired chemical reaction.
[0027] At the conclusion of processing, or during processing where
a continuous flow of processing chemistry is passed through the
chamber, the spent processing chemistry may be evacuated from
chamber 6 through outlet 9. Radiation generator 14 ceases applying
radiation to chamber 6, allowing the processed wafer 2 to cool at a
much faster rate than is experienced with conventional contact
heaters. The rapid cooling afforded by embodiments in accordance
with the present invention allows for faster throughput and hence
reduced operating costs
[0028] Embodiments in accordance with the present invention are not
limited to performing any particular type of chemical processing on
a substrate. One particularly promising application for the present
invention is in the stripping (removal) of patterns of
organometallic photoresist material from the surface of a
semiconductor wafer utilizing ozone. In such an embodiment, the
elevated temperature of the microwave-heated substrate promotes
rapid reaction with the ozone to consume the organometallic
material.
[0029] In accordance with an embodiment of the present invention,
the application of microwave radiation may be decoupled from
application of a reactive ozone-containing oxygen gas, or other
processing chemistry. In an implanted-photoresist stripping
process, the implanted wafer is heated and an independent generator
creates ozone from oxygen. The ozone gas does not interact with the
microwave energy and hence is not affected by the microwave energy
and does not decompose until reaching the heated surface of the
organo-metallic coating. The ozone produced does not include large
quantities of high energy reactive ions or radicals which can
damage sensitive structures present on the wafer surface.
[0030] Due to the high concentration of relatively low energy
reactive species at the substrate surface resulting from the
decomposition of ozone, substrates cleaned utilizing this process
in accordance with the present invention may be substantially free
of residues. In one experiment, a positive novolac photoresist
resin having a thickness of 12,500 .ANG. was formed on each of two
200 mm wafers. The photoresist on the first wafer was implanted
with arsenic, and the photoresist on the second wafer was implanted
with phosphorous. Both the As and P implants were performed at a
dose of about 3.times.10.sup.15 atoms/cm.sup.2 with an implant
energy of 50 KeV at 10,000 .mu.A.
[0031] The wafers bearing the implanted resist were then heated at
atmospheric pressure in a 1100 W microwave oven operated at a power
setting of 40%, while ozone gas generated at a concentration of
greater than about 150,000 ppm was forced through the oven chamber
at a flow rate of 1.5 slm. As a result of this processing, the
wafers were stripped clean of the implanted photoresist in less
than eight minutes. For purposes of comparison with conventional
photoresist removal processes, the same implanted resist material
was not stripped at all utilizing conventional high or low
temperature ozone processes.
[0032] While the above experiment describes removal of photoresist
material through exposure to gas generated with an ozone
concentration of about 150,000 ppm, this is not required by the
present invention and other ozone concentrations could be utilized,
ranging from 1000 to 400,000 ppm and greater, as there is no known
upper limit in the concentration of ozone useful in accordance with
the present invention. In addition, while the above experiment
involves the application of ozone as an oxidant, this is not
required by the present invention and other oxidizing species or
combinations of oxidizing species, such as oxygen, hydrogen
peroxide, and other peroxides, could alternatively be utilized.
[0033] In the photoresist stripping or other applications utilizing
embodiments in accordance with the present invention, the
processing chemistry may be maintained under positive pressure
within either a sealed or substantially sealed processing chamber
to enhance the effectiveness and/or rate of the process. Discussion
of processing at elevated pressures is described in detail in
copending parent U.S. patent application Ser. No. 10/150748, filed
May 17, 2002 and incorporated by reference herein for all
purposes.
[0034] As described in detail in the above-incorporated
application, processing under positive pressures may be
accomplished by flowing processing fluids into a sealed processing
vessel, or by flowing processing fluids into a processing vessel
having a outlets of limited capacity such that pressure within the
processing vessel increases above the pressure at the exit or
exhaust from the outlet from the vessel. For gaseous or
compressible processing chemistries and components, this increased
pressure within the processing vessel may result in an increase in
volumetric concentration. Elevated pressures within the chamber
during processing would most typically lie between about 1 and 100
ATM. In accordance with certain embodiments of the present
invention the processing vessel can be pre-pressurized.
[0035] Increased pressure and/or elevated concentration of active
processing components in the gas phase may promote direct
interaction between the gas phase component and the wafer surface.
Alternatively or in conjunction with direct interaction between the
gas phase component and the wafer surface, increased gas phase
pressure may enhance the resulting concentration of these
components in a liquid phase that may be present in the chamber,
thereby increasing desirable processing effects such as chemical
reactivity. Such pressurized processing, performed at elevated
temperatures resulting from the application of radiation in
accordance with embodiments of the present invention, may even
further enhance the rate and effectiveness of such processing.
[0036] While processing in accordance with embodiments of the
present invention may be characterized as being performed in a
"chamber", a discrete processing vessel is not required where as
processing fluid is flowed to or through a processing region by
virtue of a pressure drop. And while embodiments in accordance with
the present invention just discussed may operate at greater than
atmospheric pressure, other embodiments may operate at less than
atmospheric pressure, for example where the processing chamber has
been evacuated prior to the introduction of processing
chemistry.
[0037] Combinations of chemistries may be introduced into the
chamber in accordance with embodiments of the present invention.
For example, acids may be employed in conjunction with the oxidant
to enhance the process of photoresist removal. Examples of acids
which may be utilized as components of processing chemistries in
accordance with embodiments of the present invention include, but
are not limited to, inorganic acids and organic acids such as
acetic acid, formic acid, butyric acid, propionic acid, citric
acid, oxalic acid, and sulfonic acid. Such acids could be
introduced into the chamber in the gaseous phase, in the liquid
phase in the form of droplets, or in the solid phase in the form of
dust. Other examples of active components of process chemistries
include but are not limited to surfactants and chelating
agents.
[0038] While the present invention has been described above in
conjunction with heating a semiconductor wafer to promote removal
of an organometallic photoresist utilizing an ozone-based
chemistry, the present invention is not limited to this particular
application. Methods and apparatuses in accordance with the present
invention could be employed in conjunction with other types of
processing chemistries to perform other types of wafer processing.
Examples of other types of wafer processing suited for the present
invention include, but are not limited to etching inorganic layers
such as silicon oxide or silicon nitride overlying a substrate, and
performing a post-processing cleaning such as those analogous to
the RCA cleaning series as is well-known in the art.
[0039] In addition, while the above description focuses upon
application of microwave radiation to heat the contents of the
chamber, this is not required by the present invention. Forms of
radiation other than microwave could be applied to heat substrates
present within the chamber, and the methods and apparatuses would
fall within the scope of the present invention. For example,
alternative embodiments in accordance with the present invention
could employ electromagnetic induction heating (EMIH) of substrates
utilizing radiation ranging in frequencies of a few MHz to tens of
GHz.
[0040] Moreover, FIG. 1 illustrates only one embodiment of an
apparatus for performing processing in accordance with the present
invention, and other apparatuses and methods would also fall within
the scope of the present invention. For example, FIG. 2 shows a
simplified cross-sectional view of an alternative embodiment of an
apparatus for performing processing in accordance with the present
invention. Apparatus 20 of FIG. 2 is similar to that shown in FIG.
1, but further includes a water-filled coil 22 within chamber 24.
Water-within coil 22 absorbs radiation within the chamber and heats
up, thereby dampening the effect of radiation reflected off of the
walls of the chamber.
[0041] While the embodiment of FIG. 2 includes a coil filled with a
circulating water stream to absorb radiation within the chamber,
the present invention is not limited to this configuration. Other
approaches include coating the chamber walls with a
radiation-absorbing material, spraying a mist of water or other
radiation-absorbing material in the chamber or onto the surface of
the wafer, or simply placing a tank of water or other
radiation-absorbing material within the chamber.
[0042] FIG. 3 shows a simplified plan view of another alternative
embodiment of a processing apparatus in accordance with the present
invention. Apparatus 30 of FIG. 3 is similar to that shown in FIG.
1, but turntable 32 is configured to support and rotate a plurality
of wafers 34 relative to the direction of radiation 36 emitted from
microwave generator 38. In addition, inlet 40 and outlet 42 of
chamber 44 are configured such that a continuous supply of
processing chemistry is flowed across surfaces 34a of wafers 34.
Again, while the embodiment of FIG. 3 shows substrates 34 oriented
perpendicular to the direction of microwave radiation 36, this is
not required by the present invention. Substrates 34 could be
supported by turntable 32 in other orientations relative to the
microwave generator 38. In addition, while FIG. 3 shows rotation of
a turntable structure supporting the wafer, this is also not
required by the present invention. In alternative embodiments, the
substrates could be rotated relative to radiation within the
chamber through contact between a rotating or spinning roller or
other structure, and an edge of the substrate.
[0043] FIG. 4 shows a simplified cross-sectional view of another
alternative embodiment of a processing apparatus in accordance with
the present invention. Apparatus 40 of FIG. 4 is similar to that
shown in FIG. 1, but additionally includes source 42 of ultraviolet
(UV) radiation in communication with chamber 44 through the chamber
walls or through a UV-permeable window in the chamber walls. While
UV radiation source 42 is located outside chamber 44 in FIG. 3,
this is not required by the present invention and in alternative
embodiments the UV radiation source could be present directly
within the chamber.
[0044] UV source 42 provides to chamber 44 radiation 46 having a
substantially shorter wavelength range
(10.sup.-6.ltoreq..lambda..ltoreq.- 10.sup.-8 m) than the microwave
radiation (10.sup.-4.ltoreq..lambda..ltore- q.10.sup.-1 m) provided
by microwave source 48. Accordingly, UV radiation 46 transmitted to
the chamber 44 may allow advantageous interaction with chemistries
present within the chamber.
[0045] For example, applied UV radiation having a wavelength of 254
nm may generate highly reactive species such as molecular oxygen or
oxygen radicals from ozone within the chamber. Alternatively or in
conjunction with this process, applied UV radiation having a
wavelength of 222 nm could generate hydroxyl radicals from hydrogen
peroxide present within the chamber. In accordance with still
another alternative embodiment of the present invention, UV
radiation at 172 nm may be applied from a source such as an excimer
lamp to oxygen present within a processing chamber. This 172 nm UV
radiation can result in formation of reactive oxygen radicals
directly from molecular oxygen, without the need for ozone at all.
Other potentially reactive species generated from the application
of UV radiation includes but is not limited to N.sub.2O, which upon
irradiation may form the highly reactive oxygen radical.
[0046] In any of these approaches, the proximity of the radiation
source to the surface of the substrate results in close proximity
of the generated radical species to the surface with which reaction
is desired. Rapid reaction with the substrate surface can thus
occur before the short-lived radical species generated by
interaction with the UV radiation decay into non-energized species
and reduce the effectiveness of the processing.
[0047] Moreover, introduction of the gaseous species into an
evacuated chamber may prolong the lifetime of radicals and other
reactive species generated by interaction with the UV radiation.
Accordingly, the embodiment of an apparatus shown in FIG. 4
includes a vacuum pump 50 in fluid communication with the chamber,
allowing for evacuation of the chamber during processing.
Utilization of low-pressures is not limited to UV-assisted
processing in accordance with the present invention, however, and
low pressures could be employed without UV radiation.
[0048] FIG. 5 shows a simplified plan view of yet another
alternative embodiment of a processing apparatus in accordance with
the present invention. Apparatus 50 of FIG. 5 is similar to that
shown in FIG. 4, but microwave source 52 and UV source 54 are
positioned on opposite sides of wafer 56, with microwave source 52
proximate to wafer backside 56a and UV source 54 proximate to wafer
front side 56b. The embodiment shown in FIG. 5 allows a flow of
inlet gas to be provided across both the wafer front side and back
side, with exhaust port 58 utilized both to maintain a continuous
flow of processing chemistry across the surface of the substrate,
and to remove spent processing chemistry.
[0049] In certain applications, the embodiment shown of FIG. 5
could exploit the presence of wafer 56 or materials in intimate
contact therewith or present thereon, to absorb the incident
microwave or rf radiation and become hot, while at the same time
the wafer package may block and/or reflect the microwave or radio
frequency radiation and prevent it from reaching and interacting
with processing chemistries overlying the front side of the wafer.
The configuration shown in FIG. 5 allows UV radiation to be applied
simultaneous with microwave wafer heating to achieve the processing
desired. While the embodiment of FIG. 5 shows the UV source in
direct communication with the chamber, this is not required by the
present invention and the UV radiation could be directed to the
chamber and wafer through a reflecting/focusing network comprising
lenses or mirrors.
[0050] Embodiments of methods and apparatuses in accordance with
the present invention offer a number of advantages over
conventional processing techniques. One advantage is enhanced
precision of heating and a corresponding increase in processing
effectiveness. For example, it may be desirable to employ ozone in
the chamber to accomplish processing such as stripping of
photoresist material. However, the stability of ozone declines with
increased temperature. Conventional processing approaches utilizing
contact heating of wafers or heating of wafers through exposure to
hot gases may result in heating of the entire chamber rather than
just the wafer itself. In such conventional contact heating
approaches, ozone or other reactive processing chemistry may
decompose prior to reaching the surface of the wafer. This
decomposition reduces the effectiveness and rate of processing.
[0051] By contrast, embodiments in accordance with the present
invention apply microwaves to the chamber to accomplish specific,
precise heating of the wafer without resulting in generalized
heating of the entire chamber. Ozone or other reactive processing
chemistries introduced into the chamber will thus remain intact
until they reach the hot surface of the wafer, whereupon the
desired processing reaction can efficiently take place.
[0052] Another advantage offered by embodiments in accordance with
the present invention is increased throughput. Specifically, the
transfer of thermal energy to and from the wafer during heating and
cooling consumes time, and can reduce the effective throughput of
an apparatus. Conventional approaches for heating a wafer may
employ contact heating, requiring both the contacting member and
the wafer to be heated to an elevated temperature. Moreover, such
conventional approaches may typically employ cooling of both the
heated wafer and the heating member, through mechanisms such as
convection utilizing a flow of a cooling gas or a cooled structure
within the chamber. However, this approach wastes much of the
energy utilized in heating, which must be removed from the
processing chamber during each run.
[0053] By contrast, many embodiments in accordance with the present
invention avoid the use of a separate contacting member, such that
there is no need to heat and then cool the contacting member in
addition to the wafer. The application of microwave radiation to
heat the wafer, and the cessation of application of microwave
radiation to allow cooling of the wafer, occur without any delay
time associated with heating or cooling of a proximate contact
member. The increased speed and efficiency of heating and cooling
increases throughput of the processing chamber.
[0054] Still another advantage offered by embodiments in accordance
with the present invention is enhanced exposure of surfaces of the
substrate to processing chemistries. For example, conventional
contact heating techniques typically employ a heated member in
direct physical contact with, or in close physical proximity to, at
least one surface of the substrate, typically the wafer backside.
The presence of this contacting member can physically interfere
with the flow of processing chemistries to the wafer backside
surface, thereby reducing processing effectiveness and flexibility,
particularly as wafer backside cleanliness emerges as an important
issue in semiconductor fabrication.
[0055] Heating of the wafer in accordance with embodiments of the
present invention, however, avoids this drawback. The substrate can
be supported in the chamber by its sides or edges, with application
of microwave or other radiation serving to heat both the wafer
front side and the wafer backside. Processing chemistries can then
be applied simultaneously and flow unimpeded to the heated front
side and backside of the wafer to accomplish the desired chemical
reaction.
[0056] A further advantage of embodiments in accordance with the
present invention is the ability to conduct rapid thermal
processing. In conventional apparatuses and methods utilizing
contact heating of the wafer, the application of thermal energy to
the wafer is prolonged by the time required to heat up and cool
down the contacting member. This extended time of exposure to high
temperatures must be accounted for in the thermal budget allowed
for a particular process in order to avoid unwanted effects such as
migration of implanted dopants within a substrate.
[0057] In accordance with embodiments of the present invention
however, heating and cooling of the wafer is extremely rapid due to
the absence of an intervening contacting member. The ability to
rapidly and precisely apply thermal energy to the substrate
increases the precision of the processing in a manner analogous to
rapid thermal processing (RTP) techniques known in the art, and may
prevent unwanted phenomena such as thermally-induced dopant
migration. Embodiments in accordance with the present invention
would be expected to heat an exposed substrate or process chemistry
at a rate of between about 10.degree. C. and 10,000.degree. C./min.
Similarly, by the selected application of cooling techniques to the
processed wafer, a heated substrate or process chemistry could be
cooled at a rate of between about 10.degree. C. and 10,000.degree.
C./min.
[0058] Yet another advantage offered by embodiments in accordance
with the present invention is the ability to selectively heat
different components of a processing chemistry present within the
chamber. For example, microwave or other radiation may tend to heat
one component of a processing chemistry while leaving other
components relatively unaffected. For example, certain polar
compounds (such as water or hydrogen peroxide) may be relatively
lossy or easily absorb the applied radiation and heat up quickly,
while other compounds (such as tetraethoxysilicate-TEOS) are
relatively transparent or inert in response to exposure to the
applied radiation.
[0059] Therefore, in accordance with embodiments of the present
invention, it may be possible to tailor the processing to
accomplish a particular goal. One component of the processing
chemistry could advantageously be heated through exposure to the
radiation, while the temperature of another component of the
processing chemistry remains relatively constant. This difference
in temperature between the components of the processing chemistry
can advantageously impart enhanced activity and/or selectivity to a
particular cleaning or stripping process. An example of this effect
could be present in a application utilizing ozone with a water
mist, where the water is heated by the radiation but the ozone is
relatively unaffected.
[0060] A still further advantage of embodiments in accordance with
the present invention is increased flexibility. In conventional
contact heating systems, the substrate is cooled by convection as a
cooling airflow containing processing chemistry is flowed past the
substrate. In such conventional approaches, the mass transfer of
processing chemistry to the wafer surface is limited by the need to
maintain the wafer above a certain temperature. Embodiments in
accordance with the present invention, however, decouple the mass
transfer of processing chemistry to the wafer surface from the
cooling effects, such that the power of the radiation can be
increased to compensate for cooling effects associated with an
elevated flow of processing chemistry.
[0061] Embodiments in accordance with the present invention are
generally applicable to any processing step wherein it is desired
to apply thermal energy to a substrate. Thus while the invention
has been described above in connection with stripping developed
organic photoresist material through exposure to ozone, the
invention is not limited to this particular application. An example
of another processing step which may be performed in accordance
with the present invention is etching inorganic material through
exposure to an acid, for example removal of silicon dioxide through
exposure to HF in a gas or dissolved in a liquid solution. A
nonexclusive list of acids which may be employed to etch inorganic
layers in accordance with embodiments of the present invention
include F.sub.2, Cl.sub.2, HF, HCl, H.sub.2SO.sub.4,
H.sub.2CO.sub.3, HNO.sub.3, H.sub.3PO.sub.4, Aqua Regia, chromic
and sulfuric acid mixtures, sulfuric and ammonium persulfate
mixtures, and various combinations thereof.
[0062] In still other applications for embodiments of the present
invention, the processing chemistry introduced into the chamber may
comprise a base. A non-exclusive list of bases which could be
utilized by embodiments in accordance with the present invention
includes but is not limited to NH.sub.3, NH.sub.4OH, NaOH, TMAH,
and KOH. These materials can be in the form of a gas, liquid, or
solid.
[0063] In still further applications for embodiments of the present
invention, the processing chemistry introduced into the chamber may
comprise a surfactant. In accordance with still other applications
for embodiments of the present invention, the processing chemistry
introduced into the chamber may comprise a chelating agent such as
ethylenediaminetetracetic acid (EDTA).
[0064] Wafer cleaning is yet another type of processing which may
be performed in accordance with the present invention. In wafer
cleaning applications, unwanted residue from prior processing
remaining on a wafer surface is removed in preparation for further
processing. Such wafer cleaning may involve exposing the wafer to a
single cleaning chemistry, or may involve exposing the wafer to a
series of complementary cleaning chemistries.
[0065] General classes of chemistries useful for wafer cleaning
include acidic solutions, basic solutions, aqueous solutions
containing oxidizing components, and combinations thereof. One
class of reactant that may be useful for substrate cleaning or
other processing applications in accordance with the present
invention are organic acids. A list of such organic acids includes,
but is not limited to, acetic acid, formic acid, butyric acid,
propionic acid, citric acid, oxalic acid, and sulfonic acid.
[0066] One example of a particular wafer cleaning process is the
RCA washing series generally known in the art. This multi-step wet
processing employs a series of five complementary chemical baths to
remove the residual organic materials, particles and metals. In a
first step, the substrate is subjected to a heated aqueous bath of
H.sub.2SO.sub.4 and H.sub.2O.sub.2 to form Caro's acid
(H.sub.2SO.sub.5) to remove residual organic materials, for example
developed photoresist material remaining on a substrate surface. In
a second step, the substrate is subjected to a dilute aqueous HF
bath at room temperature to remove the oxide layer and impurities
contained therein. In a third step, the substrate is subjected to a
heated aqueous bath of ammonium hydroxide (NH.sub.4OH) and
H.sub.2O.sub.2, to remove particles and other contaminants. In a
fourth step, the substrate is subjected to a heated aqueous bath of
hydrochloric acid (HCl) and H.sub.2O.sub.2, to remove metals.
Finally, in the fifth step, the substrate is again subjected to a
bath of dilute hydrofluoric acid (HF) to remove the oxide layer
formed by oxidation in the prior step, freeing metallic
contaminants embedded in the oxide layer and permitting their
removal, and rendering the surface of the wafer hydrophobic. In
accordance with embodiments of the present invention, radiation may
be applied during one or more of the above-referenced RCA cleaning
steps to enhance their effectiveness.
[0067] Wafer surface modification is still another type of
processing which may be advantageously performed in accordance with
embodiments of the present invention. For example, a processing
chemistry comprising elevated concentrations of a reducing agent
such as hydrogen gas may be present in a chamber to passivate or
alter surface properties of a substrate, or to conduct a process
wherein reaction with the processing chemistry present within the
chamber leads to a reduced surface structure. Thus during
processing of a silicon wafer, hydrogen gas or another reducing
agent may be present to minimize formation of an oxide layer, or to
replace hydrophilic surface SiO bonds with hydrophobic SiH
bonds.
[0068] While the present invention has described heating of a wafer
utilizing microwave radiation, it is not required that the
temperature remain constant during processing. Embodiments in
accordance with the present invention could utilize heating
according to predetermined temperature gradients in order to
achieve maximum effectiveness. In addition to temperature, other
processing parameters could also be varied over time. For example,
the timing of introduction of various components of the processing
chemistry could be specifically tailored to accomplish certain
results. Moreover, where the processing chemistry is present under
pressure, this pressure could vary over time to effectuate
processing in accordance with embodiments of the present
invention.
[0069] While embodiments in accordance with the present invention
may relate to chemical processing of substrates utilized during the
manufacture of semiconductor devices, for example substrates
comprising silicon, SiGe, GaAs, Si, GaAs, GaInP, and GaN to name a
few. However, the present invention is not limited to processing of
semiconductor substrates, and other materials may be subjected to
microwave heating during processing. Examples of other candidates
for chemical processing utilizing the present invention include,
but are not limited to, hard disks and hard disk substrates,
optical devices such as mirrors, lenses, or waveguides, and
substrates utilized in the fabrication of micro-electrical
mechanical systems (MEMS), liquid crystal display devices,
biomedical slides, optical devices, mirrors, lenses, waveguides,
substrates for DNA or genetic markers, liquid crystal displays, and
other media. In particular embodiments, these substrates could be
intentionally coated with a radiation-absorbing material in order
to enhance their temperature-responsiveness under exposure to
applied radiation. The use of multiple layers of different types of
radiation-absorbing materials to tailor temperature responsiveness
is also contemplated in accordance with embodiments of the present
invention.
[0070] Although the invention has been described in terms of
preferred methods and structures, it will be understood to those
skilled in the art that many modifications and alterations may be
made to the disclosed embodiments without departing from the
invention. Hence, these modifications and alterations are intended
to be considered as within the spirit and scope of the invention as
defined by the appended claims. For example, while some examples of
specific embodiments previously described may suggest a particular
sequence of steps, these particular sequences are not required by
the present invention.
* * * * *