U.S. patent application number 13/620754 was filed with the patent office on 2013-03-21 for methods of forming electronic devices.
This patent application is currently assigned to Rohm and Haas Electronic Materials LLC. The applicant listed for this patent is Young Cheol BAE, Thomas Cardolaccia, Yi Liu. Invention is credited to Young Cheol BAE, Thomas Cardolaccia, Yi Liu.
Application Number | 20130069246 13/620754 |
Document ID | / |
Family ID | 42711855 |
Filed Date | 2013-03-21 |
United States Patent
Application |
20130069246 |
Kind Code |
A1 |
BAE; Young Cheol ; et
al. |
March 21, 2013 |
METHODS OF FORMING ELECTRONIC DEVICES
Abstract
Methods of forming electronic devices are provided. The methods
involve alkaline treatment of photoresist patterns and allow for
the formation of high density resist patterns. The methods find
particular applicability in semiconductor device manufacture.
Inventors: |
BAE; Young Cheol; (Weston,
MA) ; Cardolaccia; Thomas; (Newton, MA) ; Liu;
Yi; (Shrewsbury, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BAE; Young Cheol
Cardolaccia; Thomas
Liu; Yi |
Weston
Newton
Shrewsbury |
MA
MA
MA |
US
US
US |
|
|
Assignee: |
Rohm and Haas Electronic Materials
LLC
Marlborough
MA
|
Family ID: |
42711855 |
Appl. No.: |
13/620754 |
Filed: |
September 15, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12825157 |
Jun 28, 2010 |
8338083 |
|
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13620754 |
|
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|
61269600 |
Jun 26, 2009 |
|
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61281681 |
Nov 19, 2009 |
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Current U.S.
Class: |
257/774 |
Current CPC
Class: |
H01L 23/481 20130101;
H01L 2924/0002 20130101; G03F 7/0035 20130101; G03F 7/40 20130101;
H01L 21/0273 20130101; H01L 2924/0002 20130101; H01L 2924/00
20130101 |
Class at
Publication: |
257/774 |
International
Class: |
H01L 23/48 20060101
H01L023/48 |
Claims
1-8. (canceled)
9. A coated substrate, comprising: (a) a semiconductor substrate
comprising one or more layers to be patterned; (b) a resist pattern
over the one or more layers to be patterned, the resist pattern
comprising a first plurality of openings and having an alkaline
surface; and (c) a layer of a composition in the first plurality of
openings of the resist pattern, the composition comprising a resin
component and an acid generator.
10. The coated substrate of claim 9, wherein the layer is
photosensitive and the acid generator is a photoacid generator.
Description
[0001] This application is a Continuation of U.S. non-provisional
application Ser. No. 12/825,157, which application claims the
benefit of priority under 35 U.S.C. .sctn.119(e) to U.S.
Provisional Application Nos. 61/269,600, filed Jun. 26, 2009 and
61/281,681, filed Nov. 19, 2009, the entire contents of which
applications are incorporated herein by reference.
[0002] This invention relates generally to the manufacture of
electronic devices. More specifically, this invention relates to
methods of forming photolithographic patterns in which a resist
pattern is treated with a material effective to make alkaline a
surface of the resist pattern. The invention finds particular use
in the manufacture of semiconductor devices for forming
high-density lithographic patterns and features.
[0003] In the semiconductor manufacturing industry, photoresist
materials are used for transferring an image to one or more
underlying layers, such as metal, semiconductor or dielectric
layers, disposed on a semiconductor substrate, as well as to the
substrate itself. To increase the integration density of
semiconductor devices and allow for the formation of structures
having dimensions in the nanometer range, photoresists and
photolithography processing tools having high-resolution
capabilities have been and continue to be developed.
[0004] One approach to achieving nm-scale feature sizes in
semiconductor devices is the use of short wavelengths of light, for
example, 193 nm or less, during exposure of chemically amplified
photoresists. Immersion lithography effectively increases the
numerical aperture of the lens of the imaging device, for example,
a scanner having a KrF or ArF light source. This is accomplished by
use of a relatively high refractive index fluid (i.e., an immersion
fluid) between the last surface of the imaging device and the upper
surface of the semiconductor wafer. The immersion fluid allows a
greater amount of light to be focused into the resist layer than
would occur with an air or inert gas medium.
[0005] The theoretical resolution limit as defined by the Rayleigh
equation is shown below:
R = k 1 .lamda. NA ##EQU00001##
where k.sub.1 is the process factor, .lamda. is the wavelength of
the imaging tool and NA is the numerical aperture of the imaging
lens. When using water as the immersion fluid, the maximum
numerical aperture can be increased, for example, from 1.2 to 1.35.
For a k.sub.1 of 0.25 in the case of printing line and space
patterns, 193 nm immersion scanners would only be capable of
resolving 36 nm half-pitch line and space patterns. The resolution
for printing contact holes or arbitrary 2D patterns is further
limited due to the low aerial image contrast with a dark field mask
wherein the theoretical limit for k.sub.1 is 0.35. The smallest
half-pitch of contact holes is thus limited to about 50 nm The
standard immersion lithography process is generally not suitable
for manufacture of devices requiring greater resolution.
[0006] In an effort to achieve greater resolution and to extend
capabilities of existing manufacturing tools beyond theoretical
resolution limits, various double patterning processes have been
proposed, for example, self-aligned double patterning (SADP),
litho-etch-litho-etch (LELE) and litho-litho-etch (LLE) techniques.
Such techniques as typically implemented, however, suffer from one
or more disadvantages. SADP processes typically involve a
relatively large number of process steps, thereby adversely
affecting production throughput. Product contamination and
defectivity can result from LELE techniques from transport of
wafers back and forth between photolithography and etching
processing modules, and from etching and resist removal processes
themselves. LLE procedures involve formation and stabilization of a
first lithographic (L1) resist pattern followed by formation of a
second lithographic (L2) pattern. Various resist stabilization
techniques have been proposed such as ion implantation, UV curing,
thermal hardening, thermal curing and chemical curing. U.S. Patent
Application Publication No. US 2008/0199814 A1, to Brzozowy et al,
discloses an overcoat chemical curing technique in which the resist
pattern is coated with a fixer solution comprising a solvent, a
fixer compound containing at least two functional groups reactive
with an anchor group in a resist polymer, and optional additives
such as catalysts, surfactants and polymers. While LLE processes
involve fewer process steps than SADP and LELE, it can be difficult
to avoid: pattern deformation during resist stabilization;
intermixing between L1 and L2 resist layers during the L2 resist
coating/soft bake process; and development of L1 patterns during
the L2 exposure/develop process.
[0007] There is a continuing need in the art for lithographic
methods which address one or more of the foregoing problems
associated with the state of the art.
[0008] In accordance with a first aspect of the invention, methods
of forming an electronic device are provided. The methods comprise:
(a) providing a semiconductor substrate comprising one or more
layers to be patterned; (b) forming a resist pattern over the one
or more layers, the resist pattern comprising a first plurality of
openings; (c) treating the resist pattern with a material effective
to make alkaline a surface of the resist pattern; (d) heat-treating
the resist pattern in a hardbake process; (e) applying a layer of a
composition in the first plurality of openings of the resist
pattern, the composition comprising a resin component and an acid
generator; (e) exposing the layer to conditions causing the acid
generator to generate an acid; and (f) contacting the resist
pattern and the layer with a developer solution.
[0009] In accordance with a further aspect of the invention, coated
substrates are provided. The coated substrates comprise: (a) a
semiconductor substrate comprising one or more layers to be
patterned; (b) a resist pattern over the one or more layers to be
patterned, the resist pattern comprising a first plurality of
openings and having an alkaline surface; and (c) a layer of a
composition in the first plurality of openings of the resist
pattern, the composition comprising a resin component and an acid
generator.
[0010] The present invention will be discussed with reference to
the following drawings, in which like reference numerals denote
like features, and in which:
[0011] FIG. 1A-H illustrates a process flow for a contact hole
shrink process in accordance with the invention;
[0012] FIG. 2A-E illustrates a process flow for a contact hole
formation process in accordance with the invention;
[0013] FIG. 3A-E illustrates a process flow for a further contact
hole formation process in accordance with the invention;
[0014] FIG. 4A-E illustrates a process flow for forming a
donut-shaped pattern in accordance with the invention; and
[0015] FIG. 5A-E illustrates a process flow for forming a
pillar-shaped pattern in accordance with the invention.
[0016] The invention allows for improved photolithographic
patterning techniques, for example, shrink processes useful in
contact hole and trench formation, and for patterning of resist
patterns having various shapes such a donut- or
pillar-geometries.
[0017] Exemplary aspects of the invention will be described with
reference to FIG. 1A-H, which illustrates an exemplary process flow
for a photolithographic shrink process in accordance with the
invention. While the exemplified process is for a contact hole
shrink process, it should be clear that the process can be applied
to other shrink applications in electronic device fabrication. As
used herein, the term "contact hole" is inclusive of via holes.
Typically, the contact hole is formed in one or more layers of a
dielectric material, such as one or more oxide layers, for example,
doped or undoped silicon oxide layers, with the underlying feature
forming the bottom of the contact hole being conductive or
semiconductive, such as a metal or semiconductor layer or region.
The contact hole may, for example, join together two metal layers
or a metal layer with an active region of a semiconductor
substrate.
[0018] FIG. 1A depicts a substrate 100 which may include various
layers and features formed on a surface thereof. The substrate can
be of a material such as a semiconductor, such as silicon or a
compound semiconductor (e.g., III-V or II-VI), glass, quartz,
ceramic, copper and the like. Typically, the substrate is a
semiconductor wafer, such as single crystal silicon or compound
semiconductor wafer, and may have one or more layers and patterned
features formed on a surface thereof. One or more layers to be
patterned 102 may be provided over the substrate 100. Optionally,
the underlying base substrate material itself may be patterned, for
example, when it is desired to form trenches in the substrate
material. In the case of patterning the base substrate material
itself, the pattern shall be considered to be formed in a layer of
the substrate.
[0019] The layers may include, for example, one or more conductive
layers such as layers of aluminum, copper, molybdenum, tantalum,
titanium, tungsten, alloys, nitrides or silicides of such metals,
doped amorphous silicon or doped polysilicon, one or more
dielectric layers such as layers of silicon oxide, silicon nitride,
silicon oxynitride, or metal oxides, semiconductor layers, such as
single-crystal silicon, and combinations thereof. The layers to be
etched can be formed by various techniques, for example: chemical
vapor deposition (CVD) such as plasma-enhanced CVD, low-pressure
CVD or epitaxial growth; physical vapor deposition (PVD) such as
sputtering or evaporation; or electroplating. The particular
thickness of the one or more layers to be etched 102 will vary
depending on the materials and particular devices being formed.
[0020] Depending on the particular layers to be etched, film
thicknesses and photolithographic materials and process to be used,
it may be desired to dispose over the layers 102 a hard mask layer
103 and/or a bottom antireflective coating (BARC) 104 over which a
photoresist layer is to be coated. Use of a hard mask layer may be
desired, for example, with very thin resist layers, where the
layers to be etched require a significant etching depth, and/or
where the particular etchant has poor resist selectivity. Where a
hard mask layer is used, the resist patterns to be formed can be
transferred to the hard mask layer which, in turn, can be used as a
mask for etching the underlying layers 102. Suitable hard mask
materials and formation methods are known in the art. Typical
materials include, for example, tungsten, titanium, titanium
nitride, titanium oxide, zirconium oxide, aluminum oxide, aluminum
oxynitride, hafnium oxide, amorphous carbon, silicon oxynitride and
silicon nitride. The hard mask layer 103 can include a single layer
or a plurality of layers of different materials. The hard mask
layer can be formed, for example, by chemical or physical vapor
deposition techniques.
[0021] A bottom antireflective coating 104 may be desirable where
the substrate and/or underlying layers would otherwise reflect a
significant amount of incident radiation during photoresist
exposure such that the quality of the formed pattern would be
adversely affected. Such coatings can improve depth-of-focus,
exposure latitude, linewidth uniformity and CD control.
Antireflective coatings are typically used where the resist is
exposed to deep ultraviolet light (300 nm or less), for example,
KrF excimer laser light (248 nm), ArF excimer laser light (193 nm),
electron beams and soft x-rays. The antireflective coating 104 can
comprise a single layer or a plurality of different layers.
Suitable antireflective materials and methods of formation are
known in the art. Antireflective materials are commercially
available, for example, those sold under the AR trademark by Rohm
and Haas Electronic Materials LLC (Marlborough, Mass. USA), such as
AR.TM. 40A and AR.TM. 124 antireflectants.
[0022] A first photosensitive composition is applied on the
substrate over the antireflective layer 104 (if present) to form a
first photosensitive layer 106. As used herein, the terms
"photosensitive material(s)", "photosensitive composition(s)" and
"photoresist(s)" are used interchangeably. Suitable photoresist
materials are known in the art and include, for example, those
based on acrylate, novolak and silicon chemistries. Suitable
resists are described, for example, in U.S. Application Publication
Nos. US20090117489 A1, US20080193872 A1, US20060246373 A1,
US20090117489 A1, US20090123869 A1 and U.S. Pat. No. 7,332,616. The
photoresist materials useful in the methods of the invention
include both positive- and negative-acting materials. Suitable
positive-acting materials include positive-acting chemically
amplified photoresists which undergo a photoacid-promoted
deprotection reaction of acid labile groups of one or more
components of the composition to render exposed regions of a
coating layer of the resist more soluble in an aqueous developer
than unexposed regions. Typical photoacid-labile groups of the
photoresist resins include ester groups that contain a tertiary
non-cyclic alkyl carbon (e.g., t-butyl) or a tertiary alicyclic
carbon (e.g., methyladamantyl) covalently linked to the carboxyl
oxygen of the ester. Acetal photoacid-labile groups also are
typical.
[0023] The photosensitive composition comprises a resin component
and a photoactive component. The resin preferably has functional
groups that impart alkaline aqueous developability to the resist
composition. For example, typical are resin binders that comprise
polar functional groups such as hydroxyl or carboxylate. The resin
component is used in the composition in an amount sufficient to
render an exposed layer of the composition developable in a
developer solution, such as an aqueous alkaline solution. The resin
component will typically comprise about 70 to about 97 wt % of
total solids of the resist.
[0024] The photosensitive composition further comprises a
photoactive component employed in an amount sufficient to generate
a latent image in a coating layer of the composition upon exposure
to activating radiation. For example, the photoactive component
will suitably be present in an amount of from about 1 to 20 wt % of
total solids of the resist. Typical photoactive components in the
resist compositions are photoacid generators. Suitable PAGs are
known in the art of chemically amplified photoresists and include,
for example: onium salts, for example, triphenyl sulfonium salts,
nitrobenzyl derivatives, sulfonic acid esters, diazomethane
derivatives, glyoxime derivatives, sulfonic acid ester derivatives
of an N-hydroxyimide compound and halogen-containing triazine
compounds. One or more of such PAGs can be used.
[0025] A typical optional additive of the resists is an added base,
particularly tetrabutylammonium hydroxide (TBAH), or
tetrabutylammonium lactate, which can enhance resolution of a
developed resist relief image. For resists imaged at 193 nm, a
typical added base is a hindered amine such as diazabicyclo
undecene or diazabicyclononene. The added base is suitably used in
relatively small amounts, for example, about 0.03 to 5 wt %
relative to the total solids.
[0026] Photoresists used in accordance with the invention also may
contain other optional materials. For example, other optional
additives include anti-striation agents, plasticizers and speed
enhancers. Such optional additives typically will be present in
minor concentrations in a photoresist composition except for
fillers and dyes which may be present in relatively large
concentrations, for example, in amounts of from about 0.1 to 10 wt
% based on the total weight of a resist's dry components.
[0027] Suitable negative-acting resists typically will contain a
crosslinking component. The crosslinking component is typically
present as a separate resist component Amine-based crosslinkers
such as a melamine, for example, the Cymel melamine resins, are
typical. Negative-acting photoresist compositions useful in the
invention comprise a mixture of materials that will cure, crosslink
or harden upon exposure to acid, and a photoactive component of the
invention. Particularly useful negative acting compositions
comprise a resin binder such as a phenolic resin, a crosslinker
component and a photoactive component. Such compositions and the
use thereof are disclosed in European Patent Nos. EP0164248B1 and
EP0232972B1, and in U.S. Pat. No. 5,128,232. Typical phenolic
resins for use as the resin binder component include novolaks and
poly(vinylphenol)s such as those discussed above. Typical
crosslinkers include amine-based materials, including melamine,
glycolurils, benzoguanamine-based materials and urea-based
materials. Melamine-formaldehyde resins are generally most typical.
Such crosslinkers are commercially available, for example: the
melamine resins sold by Cytec Industries under the trade names
Cymel 300, 301 and 303; glycoluril resins sold by Cytec Industries
under the trade names Cymel 1170, 1171, 1172; urea-based resins
sold by Teknor Apex Company under the trade names Beetle 60, 65 and
80; and benzoguanamine resins sold by Cytec Industries under the
trade names Cymel 1123 and 1125. For imaging at sub-200 nm
wavelengths such as 193 nm, typical negative-acting photoresists
are disclosed in International Application Pub. No. WO
03077029.
[0028] The photoresists useful in the invention are generally
prepared following known procedures. For example, a resist can be
prepared as a coating composition by dissolving the components of
the photoresist in a suitable solvent, for example, a glycol ether
such as 2-methoxyethyl ether (diglyme), ethylene glycol monomethyl
ether, propylene glycol monomethyl ether; propylene glycol
monomethyl ether acetate; lactates such as ethyl lactate or methyl
lactate; propionates, particularly methyl propionate, ethyl
propionate and ethyl ethoxy propionate; a Cellosolve ester such as
methyl Cellosolve acetate; an aromatic hydrocarbon such toluene or
xylene; or a ketone such as methylethyl ketone, cyclohexanone and
2-heptanone. Typically the solids content of the photoresist varies
between about 2 and 25 wt % based on the total weight of the
photoresist composition. Blends of such solvents also are
suitable.
[0029] The methods of the invention can be used with a variety of
imaging wavelengths, for example, radiation having a wavelength of
sub-400 nm, sub-300 or sub-200 nm exposure wavelength, with I-line
(365 nm), 248 nm and 193 nm being typical exposure wavelengths, as
well as EUV and 157 nm. In an exemplary aspect, the photoresists
are suitable for use with and imaged at a sub-200 nm wavelength
such as 193 nm. At such wavelengths, the use of immersion
lithography is typical although dry processing can be used. In
immersion lithography, a fluid (i.e., an immersion fluid) having a
refractive index of between about 1 and about 2 is maintained
between an exposure tool and the photoresist layer during exposure.
A topcoat layer is typically disposed over the photoresist layer to
prevent direct contact between the immersion fluid and photoresist
layer to avoid leaching of components of the photoresist into the
immersion fluid.
[0030] The photosensitive composition can be applied to the
substrate by spin-coating, dipping, roller-coating or other
conventional coating technique. Of these, spin-coating is typical.
For spin-coating, the solids content of the coating solution can be
adjusted to provide a desired film thickness based upon the
specific coating equipment utilized, the viscosity of the solution,
the speed of the coating tool and the amount of time allowed for
spinning. A typical thickness for the first photosensitive layer
106 is from about 500 to 1500 .ANG.. The first photosensitive layer
can next be softbaked to minimize the solvent content in the layer,
thereby forming a tack-free coating and improving adhesion of the
layer to the substrate. The softbake can be conducted on a hotplate
or in an oven, with a hotplate being typical. The softbake
temperature and time will depend, for example, on the particular
material of the photosensitive layer and thickness. Typical
softbakes are conducted at a temperature of from about 90 to
150.degree. C., and a time of from about 30 to 90 seconds.
[0031] If the first photosensitive layer 106 is to be exposed with
an immersion lithography tool, for example a 193 nm immersion
scanner, a topcoat layer (not shown) can be disposed over the
photosensitive layer 106. Use of such a topcoat layer can act as a
barrier between the immersion fluid and underlying photosensitive
layer. In this way, leaching of components of the photosensitive
composition into the immersion fluid, possibly resulting in
contamination of the optical lens and change in the effective
refractive index and transmission properties of the immersion
fluid, can be minimized or avoided. Suitable topcoat compositions
are commercially available, for example, OPTICOAT.TM. topcoat
materials such as OC.TM. 2000 (Rohm and Haas Electronic Materials)
and otherwise known in the art, for example, those described in
U.S. Patent Application Pub. No. 2006/0246373A1 and in U.S.
Provisional Application Nos. 61/204,007, filed Dec. 31, 2008. Such
compositions can be applied over the photosensitive layer by any
suitable method such as described above with reference to the
photosensitive compositions, with spin coating being typical. The
topcoat layer thickness is typically .lamda./4n (or an odd multiple
thereof), wherein .lamda. is the wavelength of the exposure
radiation and n is the refractive index of the topcoat layer. If a
topcoat layer is present, the first photosensitive layer 106 can be
softbaked after the topcoat layer composition has been applied
rather than prior to topcoat application. In this way, the solvent
from both layers can be removed in a single thermal treatment
step.
[0032] The first photosensitive layer 106 is next exposed to
activating radiation 108 through a first photomask 110 to create a
difference in solubility between exposed and unexposed regions. The
mask 110 used in the exposure process illustrated in FIG. 6A
includes contact hole patterns taking the form of circular patterns
(as illustrated) or cross-line patterns. For a positive-acting
material, as illustrated, the photomask has optically transparent
and optically opaque regions, the optically transparent regions
corresponding to regions of the photosensitive layer to be removed
in a subsequent development step. For negative-acting materials,
the optically opaque regions would correspond with portions of the
resist layer to be developed away. The exposure energy is typically
from about 1 to 100 mJ/cm.sup.2, dependent upon the exposure tool
and the components of the photosensitive composition. References
herein to exposing a photosensitive composition to radiation that
is activating for the composition indicates that the radiation is
capable of forming a latent image in the photosensitive composition
such as by causing a reaction of the photoactive component, for
example, by producing photoacid from a photoacid generator
compound. The photosensitive compositions are typically
photoactivated by a short exposure wavelength, particularly a
sub-400 nm, sub-300 or sub-200 nm exposure wavelength, with I-line
(365 nm), 248 nm and 193 nm being typical exposure wavelengths, as
well as EUV and 157 nm.
[0033] Following exposure of the first photosensitive layer 106, a
post-exposure bake (PEB) of the photosensitive layer is performed
at a temperature above the softening point of the layer. The PEB
can be conducted, for example, on a hotplate or in an oven.
Conditions for the PEB will depend, for example, on the particular
material of the photosensitive layer and thickness. The PEB is
typically conducted at a temperature of from about 80 to
150.degree. C., and a time of from about 30 to 90 seconds.
[0034] The exposed photosensitive layer 106 is next developed to
form a first resist pattern 106' as shown in FIG. 1B. While the
developer material will depend on the particular material of the
photosensitive layer 106, suitable developers and development
techniques are known in the art. Typical developers include, for
example, aqueous base developers such as quaternary ammonium
hydroxide solutions, for example, tetra-alkyl ammonium hydroxide
solutions such as 0.26 N tetramethylammonium hydroxide.
[0035] Following development, the first resist pattern 106' is
heat-treated in a first hardbake process to further remove solvent
from the resist and to form a hardened resist pattern 106'', as
shown in FIG. 1C. The hardbake is typically conducted with a hot
plate or oven, and is typically conducted at a temperature of about
150.degree. C. or higher, for example, from about 170 to
180.degree. C., and a time of from about 30 to 120 seconds.
[0036] With reference to FIG. 1D, the hardbaked first resist
pattern 106'' is treated with a material effective to make alkaline
a surface of the first resist pattern. The alkaline surface
interferes with reaction during exposure of a subsequently applied
photosensitive layer over the resist pattern. For example, in the
case of a positive-acting photosensitive layer, acid-catalyzed
deprotection reaction is prevented in regions in the immediate
vicinity of the underlying alkaline-treated resist pattern. As a
consequence, portions of the photosensitive layer would remain in
those regions after development.
[0037] While not limited thereto, particularly suitable materials
comprise an alkaline material and a surfactant which is different
from the alkaline material. It is believed that the surfactant
promotes formation of a substantially uniform coating layer of the
second resist over the alkaline material treated resist
pattern.
[0038] The alkaline material can take various forms, and may be in
the form of a solution formed by dissolving a solid compound in a
suitable solvent. Suitable alkaline materials for the resist
pattern treatment include, for example, aqueous base developers
such as quaternary ammonium hydroxide solutions, for example,
tetra-alkyl ammonium hydroxide solutions such as 0.26 Normality (N)
(2.38 wt %) tetramethylammonium hydroxide (TMAH). Solvent materials
used for the alkaline material and otherwise in the compositions
should not dissolve or minimize dissolution of the underlying
photoresist The alkaline material (absent any solvent, e.g., water,
alcohol or the like) is typically present in the compositions in an
amount of from about 1 to 10 wt %, based on the total
composition.
[0039] Suitable surfactants for the resist pattern treatment
compositions include those which exhibit an amphiphilic nature,
meaning that they can be both hydrophilic and hydrophobic at the
same time. Amphiphilic surfactants possess a hydrophilic head group
or groups, which have a strong affinity for water and a long
hydrophobic tail, which is organophilic and repels water. Suitable
surfactants can be ionic (i.e., anionic, cationic) or nonionic.
Further examples of surfactants include silicone surfactants,
poly(alkylene oxide) surfactants, and fluorochemical surfactants.
Suitable non-ionic surfactants for use in the aqueous solution
include, but are not limited to, octyl and nonyl phenol ethoxylates
such as TRITON.RTM. X-114, X-100, X-45, X-15 and branched secondary
alcohol ethoxylates such as TERGITOL.TM. TMN-6 (The Dow Chemical
Company, Midland, Mich. USA). Still further exemplary surfactants
include alcohol (primary and secondary) ethoxylates, amine
ethoxylates, glucosides, glucamine, polyethylene glycols,
poly(ethylene glycol-co-propylene glycol), or other surfactants
disclosed in McCutcheon's Emulsifiers and Detergents, North
American Edition for the Year 2000 published by Manufacturers
Confectioners Publishing Co. of Glen Rock, N.J.
[0040] Nonionic surfactants that are acetylenic diol derivatives
also can be suitable, including such surfactants of the following
formulae:
##STR00001##
[0041] wherein R.sub.1 and R.sub.4 are a straight or a branched
alkyl chain having from 3 to 10 carbon atoms; R.sub.2 and R.sub.3
are either H or an alkyl chain suitably having from 1 to 5 carbon
atoms; and m, n, p, and q are numbers that range from 0 to 20. Such
surfactants are commercially available from Air Products and
Chemicals, Inc. of Allentown, Pa. trade names of SURFYNOL.RTM. and
DYNOL.RTM..
[0042] Additional suitable surfactants for use in coating
compositions of the invention include other polymeric compounds
such as the tri-block EO--PO-EO co-polymers PLURONIC.RTM. 25R2,
L121, L123, L31, L81, L101 and P123 (BASF, Inc.).
[0043] Particularly suitable surfactants include amines, typically
primary and secondary amines, i.e., an amine including one or more
primary amine groups and one or more secondary amine groups,
respectively, and combinations thereof. Tertiary amine groups can
be present in addition to the primary and/or secondary amine
groups. Typically, the amine is a multifunctional amine The amine
can be a polyamine, such as a diamine, triamine or tetra-amine.
Suitable primary amines include compounds of the following formula
(I):
N--(--R--NH.sub.2).sub.3 (I)
wherein R is chosen from optionally substituted alkyl such as
optionally substituted C1 to C6 alkyl, such as methyl, ethyl or
propyl, with ethyl being typical. Other suitable primary amines
include poly(allyl amines) represented by the following formula
(II):
##STR00002##
wherein: R.sub.1 is chosen from hydrogen and optionally substituted
alkyl such as C1 to C3 alkyl; R.sub.2 is chosen from optionally
substituted alkylene such as C1 to C6 alkylene, typically methylene
or ethylene; and n is an integer greater than or equal to 3. In an
exemplary primary amine of the formula (N-II), R.sub.1 is hydrogen
and R.sub.2 is methylene. Other suitable amines include those
represented by the following general formulae (III), (IV) and
(V):
##STR00003##
wherein R.sub.1 and R.sub.2 are each independently a hydrogen atom
or an alkyl group with 1 to 10 carbon atoms, and n is an integer
from 1 to 10. Other suitable amines include the following:
##STR00004## ##STR00005##
Of these, tris(2-aminoethyl)amine (TAEA) is particularly
preferred.
[0044] The surfactant is typically present in the compositions in a
relatively small amount, for example, from 0.01 to 5 wt %, for
example, from 0.01 to 1 wt %, based on the weight of total solids
in the composition (total solids being all compositions components
except solvent carrier).
[0045] The resist pattern treatment compositions can comprise one
or more optional components in addition to the alkaline material
and surfactant components. For example, the compositions can
include one or more solvent in addition to any solvent used for the
alkaline material and surfactant. As described above, solvent
materials used for the alkaline material and otherwise in the
compositions should not dissolve or minimize dissolution of the
underlying photoresist. Suitable solvents will therefore depend on
the particular underlying resist material and may include, for
example, water and alcohols such as n-butanol. The optional
components also include one or more base generator compound, such
as a thermal base generator compound and/or a photobase generator
compound.
[0046] The photoresist pattern treatment compositions can be
prepared by admixture in any order of the alkaline material and
surfactant components, and any additional components such as
solvent and base generator compounds. One or more of the components
can be added as a solid or as a pre-mixed solution using a suitable
solvent.
[0047] Preferably, the alkaline treatment includes treatment with a
quaternary ammonium hydroxide and an amine. The quaternary ammonium
hydroxide material and amine can be simultaneously applied to the
substrate, for example, either from a premixed composition or by
applying the materials simultaneously but separate from one another
in which case the composition is formed in situ. Preferably, the
quaternary ammonium hydroxide material and amine are sequentially
applied in that order. The quaternary ammonium hydroxide and amine
materials can be applied as a liquid, gas or vapor, and can be
applied, for example, by spin-coating, dipping, vapor-coating,
chemical vapor deposition (CVD) or other conventional coating
technique. Of these, spin-coating of liquid materials is typical.
Typically, the quaternary ammonium hydroxide and amine materials
can be applied as aqueous solution(s). Where the quaternary
ammonium hydroxide and amine are applied simultaneously, the
surface treated substrate can be rinsed, for example, with
deionized water. Where the quaternary ammonium hydroxide and amine
materials are sequentially applied, the amine can be applied as an
aqueous solution, functioning also as a water rinse. The surface
treated substrate can optionally be rinsed, for example, with
deionized water to remove excess composition.
[0048] A critical dimension (CD) of the first resist pattern 106''
becomes slightly reduced as a result of the surface treatment as
compared with the original CD of resist pattern 106'. This CD loss
is believed to be attributed to further development of the first
resist pattern during the surface treatment. The surface treatment
forms a modified first resist pattern surface 112 which is alkaline
and which has a line width roughness less than that of the
pre-treated surface.
[0049] Following the surface treatment, the substrate can
optionally be heat-treated in a second hardbake process. Dimensions
of the first resist pattern resulting from the process can be
accurately adjusted and controlled by selection of appropriate
conditions of the second hardbake. This heat-treatment process is
typically conducted on a hotplate or in an oven, and conditions
will depend, for example, on the particular material and thickness
of the resist pattern, and the desired change in CD of the pattern.
Typical conditions for the optional heat treatment include a
temperature of from about 120 to 200.degree. C. and a time of from
about 60 to 120 seconds.
[0050] A second photosensitive composition as described above is
coated over the first resist pattern 106'' and BARC layer 104 to
form a second photosensitive layer 114, as shown in FIG. 1E. The
second photosensitive composition can be the same or different from
the first photosensitive composition and, except as otherwise
stated, can be applied and processed in the same manner including
the materials and conditions described above with respect to the
first photosensitive layer. While the first photosensitive
composition can be a positive-acting or negative-acting material,
the tone of the second photosensitive composition is
positive-acting. Selection of this composition will depend on the
particular application and geometries involved. In the illustrated
method, both the first and second photosensitive compositions are
positive acting. The second photosensitive layer 114 can next be
softbaked. If the second photosensitive layer 114 is to be exposed
with an immersion lithography tool, a topcoat layer (not shown) as
described above can be disposed over the second photosensitive
layer 114. If a topcoat layer is used, the second photosensitive
layer 114 can be softbaked after the topcoat layer composition has
been applied rather than prior to its application.
[0051] The second photosensitive layer 114 is exposed to activating
radiation 108 in a flood exposure step. The exposed second
photosensitive layer is heat-treated in a post-exposure bake and
developed. The alkaline-modified surface region 112 of the first
resist pattern 106'' prevents photoreaction in the second resist
layer 114 in the vicinity of the surface region. As a result, a
layer 114' of the unreacted second photosensitive composition
remains over the first resist pattern 106''. The resulting
developed image has an improved (i.e., reduced) surface roughness
as compared with that of the resist pattern following development
of the first photoresist layer. Following development of the second
photosensitive layer as shown in FIG. 1F, if desired to adjust the
pattern width, for example to increase the patterned thickness of
the second photosensitive layer 114' over the first resist pattern
106'', corresponding to a decreased contact hole diameter, a series
of steps in the process can be repeated one or more times beginning
with the first hardbake through development of an additional
photosensitive layer of the second photosensitive composition, as
indicated by the dashed arrow.
[0052] Following development of the second photosensitive layer,
the BARC layer 104 is selectively etched using the modified first
resist pattern 106'' as an etch mask to expose the underlying
hardmask layer 103. The hardmask layer is next selectively etched,
again using the modified first resist pattern 106'' as an etch
mask, resulting in patterned BARC and hardmask layers 104', 103',
as shown in FIG. 1G. Suitable etching techniques and chemistries
for etching the BARC layer and hardmask layer are known in the art
and will depend, for example, on the particular materials of these
layers. Dry-etching processes such as reactive ion etching are
typical. The modified first resist pattern 106'' and patterned BARC
layer 104' are next removed from the substrate using known
techniques, for example, an oxygen plasma ashing.
[0053] Using the hardmask pattern 103' as an etch mask, the one or
more layers 102 are selectively etched. Suitable etching techniques
and chemistries for etching the underlying layers 102 are known in
the art, with dry-etching processes such as reactive ion etching
being typical. The patterned hardmask layer 103' can next be
removed from the substrate surface using known techniques, for
example, a dry-etching process such as reactive ion etching. The
resulting structure is a pattern of etched contact hole features
116, shown in cross-sectional and top-down views in FIG. 1H.
[0054] In an alternative exemplary method, it may be desirable to
pattern the layer 102 directly using the modified first photoresist
pattern 106'' without the use of a hardmask layer 103. Whether
direct patterning with the resist patterns can be employed will
depend on factors such as the materials involved, resist
selectivity, resist pattern thickness and pattern dimensions.
[0055] In an alternative exemplary method, a non-photoimageable
thermally-sensitive composition can be used in place of the
photosensitive composition for the second layer 114 in certain
instances. A thermally-sensitive material can be substituted for
the photoimageable material, for example, in processes using a
flood exposure for the second photosensitive layer 114.
Thermally-sensitive compositions are as described above with
respect to the first photosensitive compositions except a
thermally-sensitive component such as a thermal acid generator
(TAG) is used in place of the photoactive component. Suitable TAGs
are known in the art. For example, in the case of a material based
on a deprotection reaction, suitable TAGs include any that on
heating generate an acid which can cleave the bond of the acid
labile group of the thermally-sensitive layer 114, particularly a
strong acid such as a sulfonic acid. Typically, the thermal acid
generator is activated at above 90.degree., for example, above
120.degree. C. or above 150.degree. C. The thermally-sensitive
layer is heated for a sufficient length of time for the thermal
acid generator to react with the resin component of the
composition. Examples of thermal acid generators include
nitrobenzyl tosylates, such as 2-nitrobenzyl tosylate,
2,4-dinitrobenzyl tosylate, 2,6-dinitrobenzyl tosylate,
4-nitrobenzyl tosylate; benzenesulfonates such as
2-trifluoromethyl-6-nitrobenzyl 4-chlorobenzenesulfonate,
2-trifluoromethyl-6-nitrobenzyl 4-nitro benzenesulfonate; phenolic
sulfonate esters such as phenyl, 4-methoxybenzenesulfonate; alkyl
ammonium salts of organic acids, such as triethylammonium salt of
10-camphorsulfonic acid. A variety of aromatic (anthracene,
naphthalene or benzene derivatives) sulfonic acid amine salts can
be employed as the TAG, including those disclosed in U.S. Pat. Nos.
3,474,054, 4,200,729, 4,251,665 and 5,187,019. Typically, the TAG
will have a very low volatility at temperatures between 170 and
220.degree. C. Examples of TAGs include those sold by King
Industries, Norwalk, Conn. USA under NACURE.TM., CDX.TM. and
K-PURE.TM. names, for example, NACURE 5225, CDX-2168E, K-PURE.TM.
2678 and K-PURE.TM. 2700. The thermally-sensitive component is
typically present in the composition in an amount of from about 1
to 20 wt % based on the total solids of the composition.
[0056] The invention can be applied to a variety of situations in
the manufacture of electronic devices. For example, the invention
finds particular use as the basis for shrink processes such as
those useful in forming contact holes and trenches and also can
provide improved resist pattern line width roughness.
[0057] FIG. 2 is a process flow for contact hole formation which is
generally as discussed above with reference to FIG. 1. FIG. 2A is a
top-down view of the substrate following patterning and hardbake of
the first photosensitive layer and post-exposure bake to form
resist pattern 106' having contact hole patterns. FIG. 2B shows the
substrate following alkaline surface treatment to form alkaline
surface 112. FIG. 2C shows the substrate after formation of the
second photosensitive layer 114. The substrate after second
photosensitive soft-bake, flood-exposure and development is shown
in FIG. 2D. FIG. 2E is a cross-sectional view taken along dashed
line F-F in FIG. 2E. The softbake causes diffusion of the alkaline
material to form alkaline region 112'. The contact hole opening
becomes smaller as compared with the original contact pattern due
to poisoning of the second resist layer in region 112'. In this
exemplary process, the first photosensitive composition used to
form resist pattern 106' has a higher characteristic post-exposure
bake temperature than that of the second photosensitive composition
used for second photosensitive layer 114. By using the lower second
composition post-exposure bake temperature following the flood
exposure, the critical dimension of the contact holes becomes
reduced as a result of the poisoned regions 112' in the contact.
The resist pattern 106' is not removed due to its higher
characteristic post-exposure bake temperature than that used
following exposure of the second photosensitive layer.
[0058] FIG. 3 illustrates a process flow for a contact hole
pitch-splitting process in accordance with the invention in which
interstitial contact holes 117 are formed. The process for FIG.
3A-C is the same as that described above with respect to FIG. 2A-C,
including first photosensitive patterning, second photosensitive
layer coating, flood-exposure, post-exposure bake and development.
In this case, the higher post-exposure bake temperature
characteristic of the first resist pattern is used after the
flood-exposure. As a result, the original contact holes 116 shrink
and interstitial contact holes 117 can be formed, as shown in FIG.
3D-E. Interstitial holes typically result for higher density
patterns of resist pattern contact holes, for example, 76 nm
diameter/140 nm pitch holes.
[0059] FIG. 4 illustrates a process flow for a process which can be
used to form donut shaped patterns 118. The process for FIG. 4A-C
is the same as that described above with respect to FIG. 2A-C,
including first photosensitive patterning, second photosensitive
layer coating, flood-exposure, post-exposure bake and development.
In this case, a post-exposure bake temperature higher than that
characteristic of the first resist pattern is used after the
flood-exposure. As a result, the original contact holes 116 shrink
and the first resist pattern 106' can be removed as shown in FIG.
4D-E, resulting in donut-shaped patterns 118. Donut-shaped patterns
are typically formed with semi-dense or isolated contact holes, for
example, 88 nm diameter/250 nm pitch and 84 nm diameter/700 nm
pitch holes.
[0060] As shown in FIG. 5, the methods of the invention can also be
used to form pillar-shaped patterns. This process is generally the
same as that described above with respect to FIG. 4, except process
conditions are selected such that the second photosensitive layer
114 becomes completely poisoned by the alkaline material. This can
be accomplished, for example, by applying an increased amount of
the alkaline material in the alkaline treatment process and/or by
using a higher second photosensitive layer softbake temperature. In
this way, the second photosensitive layer would not be removed
following flood-exposure and development.
[0061] The following non-limiting examples are illustrative of the
invention.
EXAMPLES
Example 1
Contact Shrink Process Assisted by Double Exposure (SPADE)
L1 Resist Polymer (Poly(IAM/.alpha.-GBLMA/ODOTMA/HAMA))
Synthesis
[0062] 10.51 grams (g) of 2-methyl-acrylic acid
1-isopropyl-adamantanyl ester (IAM), 6.82 g of 2-methyl-acrylic
acid 2-oxo-tetrahydro-furan-3yl ester (.alpha.-GBLMA), 6.36 g of
2-methyl-acrylic acid
3-oxo-4,10-dioxa-tricyclo[5.2.1.0.sup.2.6]dec-8-yl ester (ODOTMA)
and 6.31 g of 2-methyl-acrylic acid 3-hydroxy-adamantanyl ester
(HAMA) were dissolved in 27 g of tetrahydrofuran (THF). The mixture
was degassed by bubbling with nitrogen for 20 minutes. A 500 ml
flask equipped with a condenser, nitrogen inlet and mechanical
stirrer was charged with 11 g of THF, and the solution was brought
to a temperature of 67.degree. C. 5.23 g of
dimethyl-2,2-azodiisobutyrate (17 mol % based on total monomers)
was dissolved in 5 g of THF and charged into the flask. The monomer
solution was fed into a reactor at a rate of 16.0 milliliters per
hour (mL/h) for 3 hours 30 minutes. The polymerization mixture was
then stirred for an additional 30 minutes at 67.degree. C. 5 g of
THF was next added to the reactor and the polymerization mixture
was cooled to room temperature. Precipitation was carried out in
1.0 L of isopropyl alcohol. After filtration, the polymer was
dried, re-dissolved in 50 g of THF, re-precipitated into 1.1 L of
isopropyl alcohol, filtered and dried in a vacuum oven at
45.degree. C. for 48 hours, resulting in 25.4 g of the
poly(IAM/.alpha.-GBLMA/ODOTMA/HAMA) polymer (Mw=7,934 and
Mw/Mn=.about.1.46) shown below:
##STR00006##
L1 Resist Formulation
[0063] 3.169 g of the polymer formed as described above was
dissolved in 96.38 g of a solvent mixture of 70 wt % propylene
glycol monomethyl ether acetate (PGMEA) and 30 wt % cyclohexanone.
To this mixture was added 0.405 g of triphenylsulfonium
(adamantan-1yl methoxycarbonyl)-difluoro-methanesulfonate, 0.041 g
of 1-(tert-butoxycarbonyl)-4-hydroxypiperidine and 0.005 g of
POLYFOX.RTM. PF-656 surfactant (Omnova Solutions Inc.). The
resulting mixture was rolled on a roller for six hours and then
filtered through a Teflon filter having a 0.2 micron pore size,
thereby forming a positive-acting photoresist composition.
Surface Treatment Solution Formulation
[0064] A surface treatment solution was prepared by adding 0.01 g
of (TAEA) (Sigma-Aldrich) to 99.99 g of a surfactant solution
(OptiPattern.TM. Clear-I, Air Products and Chemicals, Inc.,
Allentown, Pa., USA). The resulting solution was filtered through a
nylon filter having a 0.1 micron pore size.
First Lithography (L1) Patterning of Contact Holes
[0065] A 300 mm silicon wafer was spin-coated with AR.TM. 40A
antireflectant (Rohm and Haas Electronic Materials) to form a first
bottom antireflective coating (BARC) on a TEL CLEAN TRACK.TM.
LITHIUS.TM. i+coater/developer. The wafer was baked for 60 seconds
at 215.degree. C., yielding a first BARC film thickness of 75 nm. A
second BARC layer was next coated over the first BARC using AR.TM.
124 antireflectant (Rohm and Haas Electronic Materials), and was
baked at 205.degree. C. for 60 seconds to generate a 23 nm top BARC
layer.
[0066] The L1 resist formulation was coated on top of the dual
BARCs and soft-baked at 110.degree. C. for 60 seconds with the
coater/developer, resulting in a resist film thickness of 1000
.ANG.. The first resist layer was coated with a topcoat layer
(OC.TM. 2000 topcoat material, Rohm and Haas Electronic Materials)
and exposed at various doses from 12.5 to 87.5 mJ/cm.sup.2 through
a binary reticle having contact hole patterns with various CDs and
pitches using an ASML TWINSCAN.TM. XT:1900i immersion scanner with
a numerical aperture of 1.35 and annular illumination (0.8 outer
sigma/0.6 inner sigma) with XY-polarization. The wafer was then
post-exposure baked (PEB) at 100.degree. C. for 60 seconds and
developed for 12 seconds using Microposit.TM. MF CD-26 developer
(Rohm and Haas Electronic Materials) to render contact hole (C/H)
patterns with various CDs at different pitches. A full focus
exposure matrix (FEM) of the C/H images was obtained by changing
focus offset through X-direction and exposure dose through
Y-direction. The C/H diameter was measured with a Hitachi CG 4000
SEM, with the results being shown in Table 1.
Curing and Surface Treatment
[0067] The wafer was hardbaked at 180.degree. C. for 60 seconds.
The wafer was next exposed to surface treatment chemistry in a
sequential process by which the wafer was first rinsed with 2.38 wt
% TMAH in water solution for 12 seconds using a TEL GP nozzle, and
then rinsed with the surface treatment solution formulation.
L2 Resist Processing
[0068] EPIC.TM. 2098 photoresist (Rohm and Haas Electronic
Materials) was coated on the wafer containing the surface-treated
contact hole patterns at a spin speed that would provide a film
thickness of 650 .ANG. on a bare silicon wafer. The wafer was
soft-baked at 120.degree. C. for 60 seconds on a the
coater/developer. The wafer was then coated with OC.TM. 2000
topcoat material (Rohm and Haas Electronic Materials), and exposed
using the same scanner settings as in the first lithographic
process but using flood exposure and no mask at exposure doses of
28.7 mJ/cm.sup.2, 20.5 mJ/cm.sup.2 and 12.3 mJ/cm.sup.2 at a fixed
focus. The wafers were then post-exposure baked (PEB) at 90.degree.
C. for 60 seconds and developed for 12 seconds using Microposit.TM.
MF CD-26 developer (Rohm and Haas Electronic Materials). The
contact hole diameter was again measured, with the results being
shown below in Table 1. It was found that contact hole patterns
having reduced CD as compared with the original patterns resulted
from CD growth on the L1 resist patterns. Additionally, greater
shrinkage of contact holes was obtained with a decrease in second
(L2) resist exposure dose.
TABLE-US-00001 TABLE 1 L1 Exposure L2 Exposure Mask CD before CD
after CD Dose Dose CD/pitch Shrinkage Shrinkage Change (mJ/cm2)
(mJ/cm2) (nm/nm) (nm) (nm) (nm) 47.5 28.7 70/120 79.3 72.5 -6.8
50.0 76/140 87.6 78.9 -8.7 75.0 80/250 105 93.9 -11.1 60.0 84/250
102.3 90.6 -11.7 62.5 84/700 102.7 94.3 -8.4 52.5 90/700 102.3 96
-6.3 47.5 20.5 70/120 79.3 67.1 -12.2 50.0 76/140 87.6 75.2 -12.4
75.0 80/250 105 87 -18 60.0 84/250 102.3 85.2 -17.1 62.5 84/700
102.7 86.2 -16.5 52.5 90/700 102.3 90.1 -12.2 47.5 12.3 70/120 79.3
59.8 -19.5 50.0 76/140 87.6 64.3 -23.3 75.0 80/250 105 66.9 -38.1
60.0 84/250 102.3 59.2 -43.1 62.5 84/700 102.7 69.2 -33.5 52.5
90/700 102.3 75.8 -26.5
Example 2
Contact Hole Pitch Splitting
Surface Treatment Solution Formulation
[0069] A surface treatment solution was prepared by adding 2.5 g of
a 1 wt % solution of TAEA in deionized water and 0.5 g of a 10%
solution of Tergitol.TM. TMN-6 in deionized water to 97 g of
deionized water. The solution was filtered through a nylon filter
having a 0.1 micron pore size.
First Lithography (L1) Patterning of Lines and Spaces
[0070] A 300 mm silicon wafer was spin-coated with AR.TM. 40A
antireflectant (Rohm and Haas Electronic Materials) to form a first
bottom antireflective coating (BARC) on a TEL CLEAN TRACK.TM.
LITHIUS.TM. i+coater/developer. The wafer was baked for 60 seconds
at 215.degree. C., yielding a first BARC film thickness of 75 nm A
second BARC layer was next coated over the first BARC using AR.TM.
124 antireflectant (Rohm and Haas Electronic Materials), and was
baked at 205.degree. C. for 60 seconds to generate a 23 nm top BARC
layer.
[0071] An L1 photoresist composition as described in Example 1 was
coated on top of the dual BARCs and soft-baked at 110.degree. C.
for 60 seconds, resulting in a resist film thickness of 1000 .ANG..
The first resist layer was coated with a topcoat layer (OC.TM. 2000
topcoat material, Rohm and Haas Electronic Materials) and exposed
at various doses from 16 to 46 mJ/cm.sup.2 through a binary reticle
having various critical dimensions using an ASML TWINSCAN.TM.
XT:1900i immersion scanner with a numerical aperture of 1.35 and
annular illumination (0.8 outer sigma/0.6 inner sigma) with
XY-polarization. The wafer was then post-exposure baked (PEB) at
100.degree. C. for 60 seconds and developed for 12 seconds using
Microposit.TM. MF CD-26 developer (Rohm and Haas Electronic
Materials) to render first lithography (L1) patterns. The CD was
measured with a Hitachi CG 4000 SEM and the mask CD used in this
measurement was 76 nm holes at 140 nm pitch to give 78.8 nm hole CD
at 37 mJ/cm.sup.2.
Curing and Surface Treatment
[0072] The wafer was hardbaked at 180.degree. C. for 60 seconds.
The wafer was next surface treated in a sequential process by which
the wafer was first rinsed with 2.38 wt % TMAH in water solution
for 12 seconds using a TEL GP nozzle with rotation, and then rinsed
with the surface treatment solution formulation described
above.
Second Lithography (L2)
[0073] EPIC.TM. 2098 positive photoresist (Rohm and Haas Electronic
Materials) was coated over the surface-treated L1 patterns on the
coater/developer at a spin speed that would provide a film
thickness of 650 .uparw.1 on a bare silicon wafer. The wafer was
soft-baked at 120.degree. C. for 60 seconds, and then coated with
OC.TM. 2000 topcoat material (Rohm and Haas Electronic Materials).
The second lithography (L2) was carried out using the same scanner
settings as in the first lithographic process but using flood
exposure with no mask at 21 mJ/cm.sup.2. The wafer was then
post-exposure baked at three temperatures (90, 100, and 110.degree.
C.) for 60 seconds and developed for 12 seconds using
Microposit.TM. MF CD-26 developer (Rohm and Haas Electronic
Materials). The changes in the original contact hole CD of 90 nm
were measured with a Hitachi CG 4000 SEM. It was found that when
higher a PEB temperature (110.degree. C.) was used in the L2
process, interstitial holes were formed between the original L1
contact holes such as shown in FIG. 3. The original contact holes
were also shrunk in this process when a lower L2 PEB temperature
(90 and 100.degree. C.) was used.
* * * * *