U.S. patent application number 17/455185 was filed with the patent office on 2022-03-10 for vacuum-integrated hardmask processes and apparatus.
This patent application is currently assigned to Lam Research Corporation. The applicant listed for this patent is Lam Research Corporation. Invention is credited to George Andrew Antonelli, Richard A. Gottscho, Dennis M. Hausmann, Thomas Joseph Knisley, Artur Kolics, Adrien LaVoie, Jeffrey Marks, Sirish K. Reddy, Bhadri N. Varadarajan.
Application Number | 20220075260 17/455185 |
Document ID | / |
Family ID | 53755444 |
Filed Date | 2022-03-10 |
United States Patent
Application |
20220075260 |
Kind Code |
A1 |
Marks; Jeffrey ; et
al. |
March 10, 2022 |
VACUUM-INTEGRATED HARDMASK PROCESSES AND APPARATUS
Abstract
Vacuum-integrated photoresist-less methods and apparatuses for
forming metal hardmasks can provide sub-30 nm patterning
resolution. A metal-containing (e.g., metal salt or organometallic
compound) film that is sensitive to a patterning agent is deposited
on a semiconductor substrate. The metal-containing film is then
patterned directly (i.e., without the use of a photoresist) by
exposure to the patterning agent in a vacuum ambient to form the
metal mask. For example, the metal-containing film is
photosensitive and the patterning is conducted using sub-30 nm
wavelength optical lithography, such as EUV lithography.
Inventors: |
Marks; Jeffrey; (Saratoga,
CA) ; Antonelli; George Andrew; (Portland, OR)
; Gottscho; Richard A.; (Pleasanton, CA) ;
Hausmann; Dennis M.; (Lake Oswego, OR) ; LaVoie;
Adrien; (Newberg, OR) ; Knisley; Thomas Joseph;
(Beaverton, OR) ; Reddy; Sirish K.; (Portland,
OR) ; Varadarajan; Bhadri N.; (Beaverton, OR)
; Kolics; Artur; (Lake Oswego, OR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Lam Research Corporation |
Fremont |
CA |
US |
|
|
Assignee: |
Lam Research Corporation
Fremont
CA
|
Family ID: |
53755444 |
Appl. No.: |
17/455185 |
Filed: |
November 16, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16691508 |
Nov 21, 2019 |
11209729 |
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17455185 |
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15691659 |
Aug 30, 2017 |
10514598 |
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16691508 |
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14610038 |
Jan 30, 2015 |
9778561 |
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15691659 |
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61934514 |
Jan 31, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C 14/56 20130101;
G03F 7/36 20130101; H01L 21/67167 20130101; G03F 7/167 20130101;
C23C 16/44 20130101; G03F 7/16 20130101; C23C 18/165 20130101; G03F
1/76 20130101; C23C 18/145 20190501; G03F 7/26 20130101; C23C
18/1612 20130101; G03F 7/70808 20130101; C23C 18/182 20130101; C23C
18/143 20190501; G03F 7/0043 20130101; H01L 21/0332 20130101; H01L
21/67161 20130101; H01L 21/0337 20130101; H01L 21/67213 20130101;
H01L 21/3213 20130101 |
International
Class: |
G03F 1/76 20060101
G03F001/76; C23C 18/16 20060101 C23C018/16; C23C 18/18 20060101
C23C018/18; G03F 7/004 20060101 G03F007/004; G03F 7/16 20060101
G03F007/16; H01L 21/033 20060101 H01L021/033; H01L 21/3213 20060101
H01L021/3213; C23C 14/56 20060101 C23C014/56; G03F 7/20 20060101
G03F007/20; G03F 7/26 20060101 G03F007/26; G03F 7/36 20060101
G03F007/36; H01L 21/67 20060101 H01L021/67; C23C 16/44 20060101
C23C016/44; C23C 18/14 20060101 C23C018/14 |
Claims
1. A semiconductor processing apparatus, comprising: a dry
deposition module comprising a reactor chamber for dry depositing
an EUV-sensitive organometallic film on a semiconductor substrate;
and a dry development module for removing an unexposed portion of a
pattern formed in the organometallic film on the substrate by EUV
exposure of a portion of the organometallic film; a controller
including one or more memory devices, one or more processors and
system control software coded with instructions for conducting
photoresist-less metal mask formation, the instructions comprising
instructions for, in the deposition module, dry depositing the
EUV-sensitive organometallic film on a semiconductor substrate; and
in the dry development module, obtaining the semiconductor
substrate following EUV lithographic patterning of the
organometallic film by exposure of a portion of the organometallic
film to EUV radiation, resulting in a pattern of exposed and
unexposed portions in the organometallic film, and dry developing
the pattern in the organometallic film to remove the unexposed
portion of the organometallic film to form a metal-containing
hardmask.
2. The apparatus of claim 1, further comprising vacuum transfer
module interfaces connecting the deposition and development modules
of the processing apparatus.
3. The apparatus of claim 1, further comprising an organometallic
film patterning module comprising an Extreme Ultraviolet (EUV)
photolithography tool with a source of sub-30 nm wavelength
radiation.
4. The apparatus of claim 3, further comprising vacuum transfer
module interfaces connecting the deposition, patterning and
development modules of the processing apparatus.
5. The apparatus of claim 4, wherein the controller further
comprises system control software coded with instructions for,
following the dry deposition, transferring the substrate under
vacuum to the patterning module comprising the Extreme Ultraviolet
(EUV) photolithography tool and exposing the portion of the
organometallic film on the substrate to EUV radiation to form the
pattern.
6. The apparatus of claim 3, wherein the EUV photolithography tool
source emits radiation having a wavelength in the range of 10 to 20
nm.
7. The apparatus of claim 6, wherein the EUV photolithography tool
source emits radiation having a wavelength of 13.5 nm.
8. The apparatus of claim 1, wherein the organometallic film is an
organotin film.
9. The apparatus of claim 1, wherein the dry development module
further comprises a heater to heat the substrate to volatilize
unexposed regions of the organometallic film.
10. A method of processing a semiconductor substrate, comprising:
dry depositing an EUV-sensitive an organometallic film on a
semiconductor substrate; obtaining EUV lithographic patterning of
the organometallic film by exposure of a portion of the
organometallic film to EUV radiation, resulting in a pattern of
exposed and unexposed portions in the organometallic film; and dry
developing the pattern in the organometallic film to remove the
unexposed portion of the organometallic film to form a
metal-containing hardmask.
11. The method of claim 10, wherein the semiconductor substrate is
a silicon wafer including partially-formed integrated circuits, and
the method further comprising: prior to the deposition, providing
the semiconductor substrate in a first reactor chamber for the
organometallic film deposition; and following the deposition,
transferring the substrate under vacuum to a EUV lithography
processing chamber for the patterning.
12. The method of claim 11, further comprising, prior to entering
the EUV lithography processing chamber, outgassing the
substrate.
13. The method of claim 10, wherein the EUV lithography processing
chamber has a EUV photolithography source that emits radiation
having a wavelength in the range of 10 to 20 nm.
14. The method of claim 13, wherein the EUV photolithography tool
source emits radiation having a wavelength of 13.5 nm.
15. The method of claim 10, wherein the organometallic film is an
organotin film.
16. The method of claim 10, wherein the dry development of the
pattern comprises heating the substrate to volatilize unexposed
regions of the organometallic film.
Description
INCORPORATION BY REFERENCE
[0001] An Application Data Sheet is filed concurrently with this
specification as part of the present application. Each application
that the present application claims benefit of or priority to as
identified in the concurrently filed Application Data Sheet is
incorporated by reference herein in its entirety and for all
purposes.
BACKGROUND
[0002] This disclosure relates generally to the field of
semiconductor processing. In particular, the disclosure is directed
to vacuum-integrated processes for forming metal hardmasks without
the use of photoresist.
[0003] Patterning of thin films in semiconductor processing is
often a critical step in the manufacture and fabrication of
semiconductors. Patterning involves lithography. In conventional
photolithography, such as 193 nm photolithography, patterns are
printed by emitting photons from a photon source onto a mask and
printing the pattern onto a photosensitive photoresist, thereby
causing a chemical reaction in the photoresist that, after
development, removes certain portions of the photoresist to form
the pattern.
[0004] Advanced technology nodes (as defined by the International
Technology Roadmap for Semiconductors) include nodes 22 nm, 16 nm,
and beyond. In the 16 nm node, for example, the width of a typical
via or line in a Damascene structure is typically no greater than
about 30 nm. Scaling of features on advanced semiconductor
integrated circuits (ICs) and other devices is driving lithography
to improve resolution.
SUMMARY
[0005] Aspects of the present invention are directed to
vacuum-integrated photoresist-less methods and apparatuses for
forming metal hardmasks. Such methods and apparatuses can provide
sub-30 nm patterning resolution. Generally, a metal-containing
(e.g., metal salt or organometallic compound) film that is
sensitive to patterning agent such as photons, electrons, protons,
ions or neutral species such that the film can be patterned by
exposure to one of these species is deposited on a semiconductor
substrate. The metal-containing film is then patterned directly
(i.e., without the use of a photoresist) by exposure to the
patterning agent in a vacuum ambient to form the metal mask. For
example, the metal-containing film is photosensitive and the
patterning is conducted using optical lithography, such as EUV
lithography.
[0006] In one implementation, a EUV-sensitive metal-containing film
is deposited on a semiconductor substrate. The metal-containing
film is then patterned directly by EUV exposure in a vacuum ambient
to form the metal hardmask. In this way, a vacuum-integrated metal
hardmask process and related vacuum-integrated hardware that
combine steps of film formation (condensation/deposition) and
optical lithography with the result of greatly improved EUV
lithography (EUVL) performance--e.g. reduced line edge
roughness--is provided. By using a metal-containing hardmask and by
directly patterning the metal-containing film using the EUV photon
flux, the process entirely avoids the need for photoresist.
[0007] In another implementation, an apparatus for conducting
photoresist-less metal hardmask formation can provide the vacuum
integration to conduct the described processes. The apparatus
includes a metal-containing film deposition module, a
metal-containing film patterning module, and a vacuum transfer
module connecting the deposition module and the patterning
module.
[0008] These and other features and advantages of the invention
will be described in more detail below with reference to the
associated drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIGS. 1A-E illustrate a representative process flow for a
vacuum-integrated photoresist-less hardmask formation process.
[0010] FIG. 2 provides the emission spectrum of a EUV source which
uses excited Sn droplets.
[0011] FIG. 3 depicts a semiconductor process cluster architecture
with metal deposition and patterning modules that interface with a
vacuum transfer module, suitable for implementation of the
vacuum-integrated processes described herein.
DETAILED DESCRIPTION
[0012] Reference will now be made in detail to specific embodiments
of the invention. Examples of the specific embodiments are
illustrated in the accompanying drawings. While the invention will
be described in conjunction with these specific embodiments, it
will be understood that it is not intended to limit the invention
to such specific embodiments. On the contrary, it is intended to
cover alternatives, modifications, and equivalents as may be
included within the spirit and scope of the invention. In the
following description, numerous specific details are set forth in
order to provide a thorough understanding of the present invention.
The present invention may be practiced without some or all of these
specific details. In other instances, well known process operations
have not been described in detail so as to not unnecessarily
obscure the present invention.
Introduction
[0013] Extreme ultraviolet (EUV) lithography can extend
lithographic technology beyond its optical limits by moving to
smaller imaging source wavelengths achievable with current
photolithography methods to pattern small critical dimension
features. EUV light sources at approximately 13.5 nm wavelength can
be used for leading-edge lithography tools, also referred to as
scanners. The EUV radiation is strongly absorbed in a wide range of
solid and fluid materials including quartz and water vapor, and so
operates in a vacuum.
[0014] EUV lithography typically makes use of an organic hardmask
(e.g., an ashable hardmark of PECVD amorphous hydrogenated carbon)
that is patterned using a conventional photoresist process. During
photoresist exposure, EUV radiation is absorbed in the resist and
in the substrate below, producing highly energetic photoelectrons
(about 100 eV) and in turn a cascade of low-energy secondary
electrons (about 10 eV) that diffuse laterally by several
nanometers. These electrons increase the extent of chemical
reactions in the resist which increases its EUV dose sensitivity.
However, a secondary electron pattern that is random in nature is
superimposed on the optical image. This unwanted secondary electron
exposure results in loss of resolution, observable line edge
roughness (LER) and linewidth variation in the patterned resist.
These defects are replicated in the material to be patterned during
subsequent pattern transfer etching.
[0015] Unlike an insulator such as photoresist, a metal is less
susceptible to secondary electron exposure effects since the
secondary electrons can quickly lose energy and thermalize by
scattering with conduction electrons. Suitable metal elements for
this process may include but are not limited to: aluminum, silver,
palladium, platinum, rhodium, ruthenium, iridium, cobalt,
ruthenium, manganese, nickel, copper, hafnium, tantalum, tungsten,
gallium, germanium, tin, antimony, or any combination thereof.
[0016] However, electron scattering in the photoresist used to
pattern a blanket metal film into a mask would still lead to
unacceptable effects such as LER.
[0017] A vacuum-integrated metal hardmask process and related
vacuum-integrated hardware that combines film formation
(deposition/condensation) and optical lithography with the result
of greatly improved EUV lithography (EUVL) performance--e.g.
reduced line edge roughness--is disclosed. By using a
metal-containing hardmask film and by directly patterning the
metal-containing film using the EUV photon flux, the process
entirely avoids the need for photoresist.
[0018] In various embodiments, a deposition (e.g., condensation)
process (e.g., ALD or MOCVD carried out in a PECVD tool, such as
the Lam Vector.RTM.) can be used to form a thin film of a
metal-containing film, such a photosensitive metal salt or
metal-containing organic compound (organometallic compound), with a
strong absorption in the EUV (e.g., at wavelengths on the order of
10-20 nm), for example at the wavelength of the EUVL light source
(e.g., 13.5 nm=91.8 eV). This film photo-decomposes upon EUV
exposure and forms a metal mask that is the pattern transfer layer
during subsequent etching (e.g., in a conductor etch tool, such as
the Lam 2300.RTM. Kiyo.RTM.).
[0019] The metal-containing film can be deposited in a chamber
integrated with a lithography platform (e.g., a wafer stepper such
as the TWINSCAN NXE: 3300B.RTM. platform supplied by ASML of
Veldhoven, NL) and transferred under vacuum so as not to react
before exposure. Integration with the lithography tool is
facilitated by the fact that EUVL also requires a greatly reduced
pressure given the strong optical absorption of the incident
photons by ambient gases such as H.sub.2O, O.sub.2, etc.
[0020] In some embodiments, a selective film deposition can be
carried out after the EUV exposure/decomposition step to increase
the thickness of the mask material if needed for optical or
mechanical reasons; a process referred to as pattern amplification.
Viewed in this context, the initial hardmask then serves as a seed
layer upon which the final mask is formed, similar to the use of a
metal seed layer for electroless (ELD) or electrochemical (ECD)
deposition.
Vacuum-Integrated Photoresist-Less Metal Hardmask Formation
Processes
[0021] FIGS. 1A-E illustrate a representative process flow for a
vacuum-integrated photoresist-less hardmask formation process.
Generally, a metal-containing film that is sensitive to a
patterning agent such as photons, electrons, protons, ions or
neutral species such that the film can be patterned by exposure to
one of these species is deposited on a semiconductor substrate. The
metal-containing film is then patterned directly (i.e., without the
use of a photoresist) by exposure to the patterning agent in a
vacuum ambient to form the metal mask. This description references
primarily metal-containing films, particularly where the metal is
Sn, that are patterned by extreme ultraviolet lithography (EUV
lithography (EUVL)), particularly EUVL having an EUV source which
uses excited Sn droplets. Such films are referred to herein as
EUV-sensitve films. However, it should be understood that other
implementations are possible, including different metal-containing
films and patterning agents/techniques.
[0022] A desirable hardmask metal will be a strong absorber and
will have a relatively broad absorption profile, high melting
point, low malleability/high physical stability and be readily
deposited. For the purposes of this disclosure, it is important to
note that a material that emits a photon of a given energy will
also absorb a photon of that energy. Strongly absorbed light will
result in the desired decomposition or will otherwise sensitize the
film so that the exposed areas can be removed with heat, wet
chemistry, etc. FIG. 2 provides the emission spectrum of a EUV
source which uses excited Sn droplets. See, R. W. Coons, et al.,
"Comparison of EUV spectral and ion emission features from laser
produced Sn and Li plasmas", Proc. Of SPIE Vol. 7636 73636-1
(2010); R. C. Spitzer, et al., "Conversion efficiencies from
laser-produced plasmas in the extreme ultraviolet region", 79 J.
Appl. Phys., 2251 (1996); and H. C. Gerritsen, et al.,
"Laser-generated plasma as soft x-ray source", J. Appl. Phys. 59
2337 (1986), incorporated herein by reference for their disclosure
relating to the emission/absorption properties of various metals.
The emitted photons are on the order of 13.5 nm or 91.8 eV.
Therefore, Sn is a desirable hardmask metal for this
application.
[0023] Referring to FIG. 1A, a semiconductor substrate to be
patterned 100 is shown. In a typical example, the semiconductor
substrate 100 is a silicon wafer including partially-formed
integrated circuits.
[0024] FIG. 1B illustrates a metal-containing film 102 that is
sensitive to a patterning agent deposited on the semiconductor
substrate 100. The metal-containing film may be a metal salt, for
example a metal halide, or an organometallic compound sensitive to
exposure to a patterning agent such that the metal-containing film
gets decomposed to the base metal or is rendered sensitive to a
subsequent development process. Suitable patterning agents may be
photons, electrons, protons, ions or neutral species, such that the
metal-containing film 102 can be patterned by exposure to one of
these species by decomposition to the base metal or is rendered
sensitive to a subsequent development process. As further explained
below, a particular example of an effective metal and patterning
agent combination is Sn, deposited as a metal halide (e.g.,
SnBr.sub.4) or organometallic (e.g., Sn(CH.sub.3).sub.4), patterned
by EUV lithography. In general, prior to the deposition, the
semiconductor substrate 100 is placed in a reactor chamber for
metal-containing film deposition under vacuum.
[0025] A blanket of the metal-containing film 102 can be formed by
condensation from a suitable precursor (e.g., in a non-plasma CVD
reactor, such as an Altus.RTM. CVD tool, available from Lam
Research Corporation, Fremont, Calif.). For example, tin bromide,
SnBr.sub.4, has a normal boiling point of 205.degree. C. and a
melting point of 31.degree. C. at 760 Torr, and a vapor pressure of
10 Torr at 10.degree. C. It can be condensed onto the substrate to
form a solid SnBr.sub.4 film with a thickness that depends on
exposure time and substrate temperature, for example on the order
of 5 to 200 nm, e.g., 10 nm. Suitable process conditions for this
deposition via condensation include a deposition temperature
between about 0 and 30.degree. C., for example about 20.degree. C.,
and a reactor pressure of less than 20 Torr, for example maintained
between 14 and 15 Torr at 20.degree. C. Maintaining the precursor
flow rate between about 100 and 1000 sccm allows for control of the
deposition rate.
[0026] An alternative source of Sn metal may be organometallic. For
example, tetramethyl tin (Sn(CH.sub.3).sub.4) has a normal boiling
point of 75.degree. C. and a melting point of -54.degree. C. at 760
Torr. It can be also be condensed onto the substrate to form a
solid Sn(CH.sub.3).sub.4 film with a thickness that depends on
exposure time and substrate temperature, for example on the order
of 5 to 200 .ANG., e.g., 100 .ANG.. Suitable process conditions for
this deposition via condensation include a deposition temperature
between about -54.degree. C. and 30.degree. C., for example about
20.degree. C., and a reactor pressure of less than 20 Torr, for
example maintained at about 1 Torr at 20.degree. C. Maintaining the
precursor flow rate between about 100 and 1000 sccm allows for
control of the deposition rate.
[0027] Another suitable metal for formation of the metal mask is
hafnium (Hf). Hafnium chloride, HfCl.sub.4 (1 Torr vapor pressure
at 190.degree. C. with a melting point of 432.degree. C.) can be
condensed onto the substrate to form a solid HfCl.sub.4 crystalline
film with a thickness that depends on exposure time and substrate
temperature, for example on the order of 50 to 2000 nm, e.g., 1000
nm. Suitable process conditions for this deposition via
condensation include a deposition temperature between about 0 and
300.degree. C., for example about 100.degree. C., and a reactor
pressure of less than 10 Torr, for example maintained between 0.1
and 1 Torr at 100.degree. C. Maintaining the precursor flow rate
between about 10 and 100 sccm allows for control of the deposition
rate.
[0028] To prevent degradation due to water vapor, formation and
transfer of the Sn- and Hf-containing films is conducted in a
vacuum-ambient. The formed film is then transferred to a EUV
patterning tool and patterned via direct exposure, without the use
of a photoresist, as illustrated in FIGS. 1C-D.
[0029] It should be noted that a EUVL tool typically operates at a
higher vacuum than a deposition tool. If this is the case, it is
desirable to increase the vacuum environment of the substrate
during the transfer from the deposition to the patterning tool to
allow the substrate and deposited metal-containing film to degas
prior to entry into the patterning tool. This is so that the optics
of the patterning tool are not contaminated by off-gassing from the
substrate.
[0030] Referring to FIG. 1C, for metal halide Sn-based
metal-containing films patterned by EUVL, the decomposition
chemistry can proceed by:
SnBr.sub.4.fwdarw.Sn+2Br.sub.2.
Photons directly decompose the SnBr.sub.4 to Sn (tin metal) and
bromine gas (Br.sub.2). Alternatively, a reactant X.sub.2 (e.g.,
wherein X is Cl, I or H) could be used to promote a reaction
pathway SnBr.sub.4+X.sub.2.fwdarw.SnX.sub.4+2Br.sub.2, and
ultimately to Sn by photodecomposition, in particular where
SnX.sub.4 is easier to photo-activate than the easily condensed
SnBr.sub.4. In either case, the byproducts (Br.sub.2) and reactants
(X.sub.2) require containment, such as vacuum.
[0031] For organometallic Sn-based metal-containing films patterned
by EUVL, photons directly decompose the Sn(CH.sub.3).sub.4 to Sn
(tin metal) and ethane gas, the decomposition chemistry proceeding
by:
Sn(CH.sub.3).sub.4.fwdarw.Sn+2C.sub.2H.sub.6.
[0032] For metal halide Hf-based metal-containing films patterned
by EUVL, the decomposition chemistry can proceed by:
HfCl.sub.4.fwdarw.Hf+2Cl.sub.2.
Photons directly decompose the HfCl.sub.4 to Hf metal and chlorine
gas (Cl.sub.2). Alternatively, a reactant X.sub.2 (e.g., wherein X
is Br, I or H) could be used to promote a reaction pathway
HfCl.sub.4+X.sub.2.fwdarw.HfX.sub.4+2Cl.sub.2, and ultimately to Hf
by photodecomposition, in particular where HfX.sub.4 is easier to
photo-activate than the easily condensed HfCl.sub.4. In either
case, the byproducts (Cl.sub.2) and reactants (X.sub.2) require
containment, such as vacuum.
[0033] As shown in FIG. 1C, the patterning results in exposed
metal-containing film regions of formed metal mask 102a and
unexposed regions 102b of material to be removed by pattern
development.
[0034] Referring to FIG. 1D, the pattern can then be developed.
Development of the pattern can occur simply by heating the
substrate to volatilize the unexposed regions 102b of the
metal-containing film, so that only the exposed regions 102a remain
as a fully-formed metal mask. It should be noted that this pattern
development operation may not require vacuum integration since a
thermally and environmentally stable patterned metal mask would
have been formed. It may also be desirable to conduct the pattern
development outside the patterning tool to avoid contaminating the
tool optics with any incompatible byproducts of the
metal-containing film decomposition.
[0035] Referring to FIG. 1E, as an optional step, a pattern
amplification can be done. For example selective ALD or electroless
deposition (ELD) may be performed on the patterned substrate
following the operations depicted in FIGS. 1C and/or 1D to build up
the thickness of the metal mask with additional selectively
deposited metal 106. This may be helpful to reduce optical
transmission of the mask or make it more mechanically robust. Such
amplification may be accomplished, for example, by adaptation of an
electroless deposition process such as that described in U.S. Pat.
Nos. 6,911,067, 6,794,288, 6,902,605 and 4,935,312, the disclosures
of which in this regard are incorporated by reference herein.
[0036] For example, an initial 1 nm seed could be amplified to 10
nm in this way. Like the pattern development discussed with
reference to FIG. 1D, this operation may not require vacuum
integration since a thermally and environmentally stable patterned
metal mask would have been formed before amplification.
Alternative Process Embodiments
[0037] As an alternative to the metal salt or organometallic
metal-containing film depositions, a metal-containing EUV-sensitive
film could be deposited by a multistep process of metalorganic CVD
using a suitable precursor (e.g., in a non-plasma CVD reactor, such
as an Altus.RTM. CVD tool or PECVD reactor, such a Vector.RTM.
PECVD tool, both available from Lam Research Corporation, Fremont,
Calif.). For example, a plasma deposition of alkyl and amino
precursors, such as a CH.sub.4/H.sub.2plasma deposition followed by
an ammonia (NH.sub.3/H.sub.2) plasma, can produce an
amino-functionalized self-assembled monolayer (SAM) of
aminopropyltriethoxysilane (APTES) on a semiconductor substrate.
Such amine terminated surfaces enable conformal electroless
deposition (ELD). The SAM can then be transferred to a EUV
patterning tool and patterned. Selective growth of the patterned
SAM by ELD, such as by PdCl.sub.2/H.sub.2O solution exposure to
provide a Pd catalyst, followed by ELD of Ni or Co and then copper
(Cu) according to processes known in the art given these
parameters, results in a metal-based mask formed without the use of
photoresist. Such a SAM-based approach can also be used for pattern
amplification as an alternative to the ELD technique described with
ref to FIG. 1E for that purpose.
[0038] It should also be noted that while this disclosure primarily
references EUVL as a patterning technique, alternative embodiments
could use a focused beam of electrons, ions or neutral species to
directly write the pattern onto the blanket mask, these steps also
performed in vacuum. In-situ chamber cleaning may be used if
byproducts condense on the reflective optics of the EUVL
system.
Apparatus
[0039] FIG. 3 depicts a semiconductor process cluster tool
architecture with vacuum-integrated metal deposition and patterning
modules that interface with a vacuum transfer module, suitable for
implementation of the vacuum-integrated processes described herein.
The arrangement of transfer modules to "transfer" wafers among
multiple storage facilities and processing modules may be referred
to as a "cluster tool architecture" system. Metal deposition and
patterning modules are vacuum-integrated, in accordance with the
requirements of a particular process. A vacuum transport module
(VTM) 338 interfaces with four processing modules 320a-320d, which
may be individually optimized to perform various fabrication
processes. By way of example, processing modules 320a-320d may be
implemented to perform condensation, deposition, evaporation, ELD,
etch, and/or other semiconductor processes. For example, module
320a may be a non-plasma CVD reactor, such as an Altus.RTM. CVD
tool, available from Lam Research Corporation, Fremont, Calif.
suitable for conducting deposition of metal-containing films, as
described herein. And module 320b may be a PECVD tool, such as the
Lam Vector.RTM.. It should be understood that the figure is not
necessarily drawn to scale.
[0040] Airlocks 342 and 346, also known as a loadlocks or transfer
modules, interface with the VTM 338 and a patterning module 340.
For example, a suitable patterning module may be the TWINSCAN NXE:
3300B.RTM. platform supplied by ASML of Veldhoven, NL). This tool
architecture allows for work pieces, such as substrates with
deposited metal-containing films, to be transferred under vacuum so
as not to react before exposure. Integration of the deposition
modules with the lithography tool is facilitated by the fact that
EUVL also requires a greatly reduced pressure given the strong
optical absorption of the incident photons by ambient gases such as
H.sub.2O, O.sub.2, etc.
[0041] Airlock 342 may be an "outgoing" loadlock, referring to the
transfer of a substrate out from the VTM 338 serving a deposition
module 320a to the patterning module 340, and airlock 346 may be an
"ingoing" loadlock, referring to the transfer of a substrate from
the patterning module 340 back in to the VTM 338. The ingoing
loadlock 346 may also provide an interface to the exterior of the
tool for access and egress of substrates. Each process module has a
facet that interfaces the module to VTM 338. For example,
deposition process module 320a has facet 336. Inside each facet,
sensors, for example, sensors 1-18 as shown, are used to detect the
passing of wafer 326 when moved between respective stations.
Patterning module 340 and airlocks 342 and 346 may be similarly
equipped with additional facets and sensors, not shown.
[0042] Main VTM robot 322 transfers wafer 326 between modules,
including airlocks 342 and 346. In one embodiment, robot 322 has
one arm, and in another embodiment, robot 322 has two arms, where
each arm has an end effector 324 to pick wafers such as wafer 326
for transport. Front-end robot 344, it is used to transfer wafers
326 from outgoing airlock 342 into the patterning module 340, from
the patterning module 340 into ingoing airlock 346. Front-end robot
344 may also transport wafers 326 between the ingoing loadlock and
the exterior of the tool for access and egress of substrates.
Because ingoing airlock module 346 has the ability to match the
environment between atmospheric and vacuum, the wafer 326 is able
to move between the two pressure environments without being
damaged.
[0043] It should be noted that a EUVL tool typically operates at a
higher vacuum than a deposition tool. If this is the case, it is
desirable to increase the vacuum environment of the substrate
during the transfer from the deposition to the patterning tool to
allow the substrate and deposited metal-containing film to degas
prior to entry into the patterning tool. Outgoing airlock 342 may
provide this function by holding the transferred wafers at a lower
pressure, no higher than the pressure in the patterning module 340,
for a period of time and exhausting any off-gassing, so that the
optics of the patterning tool 340 are not contaminated by
off-gassing from the substrate. A suitable pressure for the
outgoing, off-gassing airlock is no more than 1E-8 Torr.
[0044] In some embodiments, a system controller 350 (which may
include one or more physical or logical controllers) controls some
or all of the operations of the cluster tool and/or its separate
modules. It should be noted that the controller can be local to the
cluster architecture, or can be located external to the cluster
architecture in the manufacturing floor, or in a remote location
and connected to the cluster architecture via a network. The system
controller 350 may include one or more memory devices and one or
more processors. The processor may include a central processing
unit (CPU) or computer, analog and/or digital input/output
connections, stepper motor controller boards, and other like
components. Instructions for implementing appropriate control
operations are executed on the processor. These instructions may be
stored on the memory devices associated with the controller or they
may be provided over a network. In certain embodiments, the system
controller executes system control software.
[0045] The system control software may include instructions for
controlling the timing of application and/or magnitude of any
aspect of tool or module operation. System control software may be
configured in any suitable way. For example, various process tool
component subroutines or control objects may be written to control
operations of the process tool components necessary to carry out
various process tool processes. System control software may be
coded in any suitable compute readable programming language. In
some embodiments, system control software includes input/output
control (IOC) sequencing instructions for controlling the various
parameters described above. For example, each phase of a
semiconductor fabrication process may include one or more
instructions for execution by the system controller. The
instructions for setting process conditions for condensation,
deposition, evaporation, patterning and/or etching phase may be
included in a corresponding recipe phase, for example.
CONCLUSION
[0046] The vacuum-integration of film deposition and lithography
processes and apparatus described herein provides EUV-sensitive
metal film deposition and subsequently patterning directly by
direct EUV exposure in a vacuum ambient to prevent their
decomposition or degradation. EUVL is done in a vacuum to avoid
degradation of the incident 13.5 nm light flux by optical
absorption of ambient gases. Among the advantages of described
vacuum-integrated hardmask processes are: Vacuum operation of the
EUV system opens up the possibility of using compounds that are
oxygen and moisture sensitive; vacuum integration of the deposition
system with the EUV system in an apparatus enables use of these
materials. Photo decomposition of a metal precursor creates a
non-linear reaction where the photo decomposition is enhanced by
the increased adsorption of the metal film. Metals are better at
thermalization of high energy secondary electrons than photoresist,
thereby improving contrast or LER. Using metal film directly as
masks or with pattern amplification allows much thinner films and
reduce required exposure times. Metal films make better hardmasks
for etch and decrease the thickness required from a mask
perspective. Moreover, further development and optimization of
materials compatible with the EUV vacuum and optics, organometalic
precursors with appropriate dose thresholds for metal deposition,
and nucleation films with multiple photo decomposition events to
eliminate a nucleation site in a given space may proceed in
accordance with the processes described herein.
[0047] It is understood that the examples and embodiments described
herein are for illustrative purposes only and that various
modifications or changes in light thereof will be suggested to
persons skilled in the art. Although various details have been
omitted for clarity's sake, various design alternatives may be
implemented. Therefore, the present examples are to be considered
as illustrative and not restrictive, and the invention is not to be
limited to the details given herein, but may be modified within the
scope of the appended claims.
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