U.S. patent application number 11/859804 was filed with the patent office on 2009-03-26 for functionalized carbosilane polymers and photoresist compositions containing the same.
This patent application is currently assigned to INTERNATIONAL BUSINESS MACHINES CORPORATION. Invention is credited to Robert D. Allen, Matthew E. Colburn, Daniel P. Sanders, Ratnam Sooriyakumaran, Hoa D. Truong.
Application Number | 20090081598 11/859804 |
Document ID | / |
Family ID | 40472029 |
Filed Date | 2009-03-26 |
United States Patent
Application |
20090081598 |
Kind Code |
A1 |
Allen; Robert D. ; et
al. |
March 26, 2009 |
FUNCTIONALIZED CARBOSILANE POLYMERS AND PHOTORESIST COMPOSITIONS
CONTAINING THE SAME
Abstract
Linear or branched functionalized polycarbosilanes having an
absorbance less than 3.0 .mu.m.sup.-1 at 193 nm and a relatively
high refractive index are provided. The functionalized
polycarbosilanes contain at least one pendant group that is acid
labile or aqueous base soluble. Also disclosed are photoresists
formulations containing the functionalized polycarbosilanes that
are suitable for use in lithography, e.g., immersion
lithography.
Inventors: |
Allen; Robert D.; (San Jose,
CA) ; Colburn; Matthew E.; (Schenectady, NY) ;
Sanders; Daniel P.; (San Jose, CA) ; Sooriyakumaran;
Ratnam; (San Jose, CA) ; Truong; Hoa D.; (San
Jose, CA) |
Correspondence
Address: |
CANTOR COLBURN, LLP - IBM ARC DIVISION
20 Church Street, 22nd Floor
Hartford
CT
06103
US
|
Assignee: |
INTERNATIONAL BUSINESS MACHINES
CORPORATION
Armonk
NY
|
Family ID: |
40472029 |
Appl. No.: |
11/859804 |
Filed: |
September 24, 2007 |
Current U.S.
Class: |
430/327 |
Current CPC
Class: |
Y10S 430/108 20130101;
Y10S 430/143 20130101; G03F 7/0757 20130101; Y10S 430/168 20130101;
Y10S 430/106 20130101; G03F 7/0397 20130101 |
Class at
Publication: |
430/327 |
International
Class: |
G03C 1/73 20060101
G03C001/73; G03C 5/00 20060101 G03C005/00 |
Claims
1. A process for generating a resist image on a substrate,
comprising: coating a substrate with a film comprising a
photoresist composition comprising a linear or branched
functionalized carbosilane polymer having at least one acid labile
functionality and/or an aqueous base soluble functionality, wherein
the functionalized polycarbosilane has a refractive index greater
than 1.7 and an absorbance less than 3.0 .mu.m.sup.-1 at 193
nanometers and has a formula selected from the group consisting of:
##STR00013## ##STR00014## wherein a, b, and c are integers that
represent a number of repeat units; providing a liquid medium
between the film and a lens of an exposure tool; exposing the film
selectively to a predetermined pattern of radiation so as to form a
latent patterned image in the film; and developing the latent image
with a developer to form the resist image.
2-19. (canceled)
Description
TRADEMARKS
[0001] IBM.RTM. is a registered trademark of International Business
Machines Corporation, Armonk, N.Y., U.S.A. Other names used herein
may be registered trademarks, trademarks or product names of
International Business Machines Corporation or other companies.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates generally to functionalized
carbosilane polymers and photoresist compositions containing the
same.
[0004] 2. Description of Background
[0005] Dry 193 nm resist materials are generally limited to indices
of refraction near or below 1.7. It has been predicted that using a
high refractive index resist in immersion lithography can
significantly enhance the depth of focus, exposure latitude and
mask error enhancement factor (MEEF) at numerical apertures
(Nas)>1.0. The higher the refractive index, the greater the
enhancements. It is expected that immersion lithography at 193-nm
complemented by techniques such as double exposure would be the
main lithography solution for 32-nm node manufacturing. This will
place stringent requirements on 193-nm photoresists, among
others.
[0006] Several polymers having a refractive index n as high as 1.9
have been identified as potential candidates. These materials
include thioacrylates and thiazolines, but share the property of
having a high sulfur content. Unfortunately, however, the 193-nm
absorption of these polymers has also progressively increased with
the increase in sulfur content and has made them unsuitable for
photoresist applications. Some of the polymers that have been
prepared for resist applications have absorbance values
[A=(.alpha..sub.10/.mu.m)] greater than 5.
[0007] A few functional polycarbosilanes have been reported
previously. For, example, Interrante et. al., (I. L. Rushkin and L.
V. Interrante, Macromolecules, 1996, 29, 5784) have reported the
synthesis of several functional polycarbosilanes including a phenol
containing polycarbosilane. The US patents and patent publications
listed below have also reported the use of functional
polycarbosilanes for various applications: U.S. Patent Publication
No. 2005/0042538 to Babich et al.; U.S. Pat. No. 7,172,849 to
Babich et al.; U.S. Pat. No. 6,660,230 to McGill et al.; U.S. Pat.
No. 7,157,052 to McGill et al.; U.S. Patent Publication No
2007/0003440 to McGill et al.; U.S. Patent Publication No
2006/0063905 to Nakagawa et al.; and U.S. Patent Publication No.
2007/0020467 to Nakagawa et al.
[0008] Babich et al. describe polycarbosilanes with cross-linkable
pendant groups for hard-mask applications. McGill et al. describe
the use of fluoroalcohol containing polycarbosilanes for analytical
and purification applications. Nakagawa et al. have reported the
synthesis and utilization of polycarbosilanes for insulating films.
None of the publications or patents mentioned above describes the
use of polycarbosilanes for photoresist applications, or
polycarbosilanes with acid functionalities. Furthermore, no report
has attributed higher refractive index to polycarbosilanes.
[0009] Accordingly, there remains a need for high refractive index
polymers suitable for use in photoresist compositions employed in
immersion lithography.
SUMMARY OF THE INVENTION
[0010] Exemplary embodiments include a linear or branched
functionalized polycarbosilane having an acid labile functionality.
The functionalized polycarbosilane can have a refractive index
greater than 1.7 and an absorbance less than 3 per micrometer at
193 nanometers. In one embodiment, the functionalized
polycarbosilane comprises carbosilane units of formula (I):
##STR00001##
wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are independently
selected from the group consisting of hydrogen, hydrocarbyl moiety,
fluorocarbyl moiety, ethers, esters, lactones, groups containing
sulfur, groups containing phosphorous, groups containing boron,
groups containing silicon, groups containing germanium, groups
containing polar functionalities, groups containing acid-labile
functionalities, groups containing aqueous base soluble
functionalities, groups containing cross linkable functionalities,
and at least one polymer chain including a different
polycarbosilane chain; and x, y, and n are integers independently
.gtoreq.1 with the proviso that at least one of R.sub.1, R.sub.2,
R.sub.3, and R.sub.4 contain the acid-labile functionality.
[0011] Further exemplary embodiments include a photoresist
composition comprising a photoacid generator; a linear or branched
functionalized polycarbosilane having an acid-labile functionality
and/or an aqueous soluble functionality; and a casting solvent.
[0012] Additional exemplary embodiments include a process of
generating a resist image on a substrate, comprising coating a
substrate with a film comprising a photoresist composition
comprising a linear or branched functionalized carbosilane polymer
having at least one acid labile functionality and/or an aqueous
base soluble functionality; exposing the film selectively to a
predetermined pattern of radiation so as to form a latent patterned
image in the film; and developing the latent image with a developer
to form the resist image.
[0013] Another exemplary embodiment includes a process for forming
a multilayer structure, comprising forming a first layer of a
planarizing material on a substrate; forming a second layer of a
resist material on the first layer, wherein the resist layer
comprises a linear or branched functionalized carbosilane polymer
having at least one acid labile functionality and/or an aqueous
base soluble functionality; pattern-wise exposing the second layer
to radiation using a patterning tool; and developing a pattern in
the second layer to remove unexposed portions of the second layer
and to form a patterned resist that reveals portions of the first
layer.
[0014] Additional features and advantages are realized through the
techniques of the present invention. Other embodiments and aspects
of the invention are described in detail herein and are considered
a part of the claimed invention. For a better understanding of the
invention with advantages and features, refer to the description
and to the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The subject matter that is regarded as the invention is
particularly pointed out and distinctly claimed in the claims at
the conclusion of the specification. The foregoing and other
objects, features, and advantages of the invention are apparent
from the following detailed description taken in conjunction with
the accompanying drawings in which:
[0016] FIG. 1 graphically illustrates contrast curves as a function
of temperature for a photoresist composition that included a
functionalized polycarbosilane; and
[0017] FIG. 2 pictorially illustrates a micrograph of a patterned
photoresist composition that included a functionalized
polycarbosilane.
[0018] The detailed description explains the preferred embodiments
of the invention, together with advantages and features, by way of
example with reference to the drawings.
DETAILED DESCRIPTION OF THE INVENTION
[0019] As used herein, the term "alkylene" as used herein refers to
a difunctional linear or branched saturated hydrocarbon linkage,
typically although not necessarily containing 1 to about 24 carbon
atoms, such as methylene, ethylene, n-propylene, n-butylene,
n-hexylene, decylene, tetradecylene, hexadecylene, and the like.
Preferred alkylene linkages contain 1 to about 12 carbon atoms, and
the term "lower alkylene" refers to an alkylene linkage of 1 to 6
carbon atoms, preferably 1 to 4 carbon atoms. The term "substituted
alkylene" refers to an alkylene linkage substituted with one or
more substituent groups, i.e., wherein a hydrogen atom is replaced
with a non-hydrogen substituent group. If not otherwise indicated,
the terms "alkylene" and "lower alkylene" include linear, branched,
cyclic, unsubstituted, substituted, and/or heteroatom-containing
alkylene and lower alkylene, respectively.
[0020] Unless otherwise indicated, the term "hydrocarbyl" is to be
interpreted as including substituted and/or heteroatom-containing
hydrocarbyl moieties. "Hydrocarbyl" refers to univalent hydrocarbyl
radicals containing 1 to about 30 carbon atoms, preferably 1 to
about 18 carbon atoms, most preferably 1 to about 12 carbon atoms,
including linear, branched, cyclic, alicyclic, and aromatic
species.
[0021] The present invention provides functionalized carbosilane
polymers and photoresist compositions containing the same. Also
disclosed are processes for generating a relief image using the
photoresist compositions. The functionalized carbosilane polymers,
also referred to herein as functionalized polycarbosilane polymers,
are configured to have a high refractive index (n>1.7) and
absorbance at 193 nm that is relatively low (A<3.00
.mu.m.sup.-1) rendering them suitable for use in photoresist
compositions. Especially advantageous is the use of the
functionalized carbosilane polymers in photoresist compositions for
immersion lithography.
[0022] The functionalized carbosilane polymers (also referred to
herein as functionalized polycarbosilane) comprise carbosilane
units of the general formula (I).
##STR00002##
wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are independently
selected from hydrogen, hydrocarbon moiety, fluorocarbon moiety,
ethers, esters, groups containing sulfur, groups containing
phosphorous, groups containing boron, groups containing polar
functionalities, groups containing acid-labile functionalities,
groups containing aqueous base soluble functionalities, groups
containing cross linkable functionalities, or one or more polymer
chains including a different polycarbosilane chain; and x, y, and n
are independently > or =1 with the proviso that at least one of
R.sub.1, R.sub.2, R.sub.3, and R.sub.4 contain an acid-labile
functionality or an aqueous base soluble functionality.
[0023] The carbosilane polymer is not intended to be limited to any
particular type and can be random, block, alternating or the like.
Random polymers have a random sequence of monomer residue types;
block polymers have two or more homopolymer subunits linked by
covalent bonds; and alternating polymers possess regularly
alternating monomer residues. Likewise, the carbosilane can be a
homopolymer or a heteropolymer having two or more monomeric species
such as copolymer, a terpolymer, a tetrapolymer, and any higher
order polymer. Still further, the carbosilane polymer may be
linear, or branched.
[0024] As will be discussed in greater detail below, the
carbosilane polymer may initially be base soluble or become base
soluble after irradiation by virtue of acid-catalyzed deprotection
of acid-labile protecting groups.
[0025] Suitable acid-labile functionalities (i.e., acid-labile
pendant groups) include, but are not limited to, esters, acetals,
ketals, carbonates, and the like. The functionalized
polycarbosilanes can include one or more of the acid labile
functionalities, which can be the same or different. Suitable
acid-labile functionalities are of the general formulae (II),
(III), and (IV).
##STR00003##
wherein L is a linking group selected from the group consisting of
linear, branched, or substituted alkylene having 1 to 7 carbon
atoms, cycloalkylene having 3 to 17 carbon atoms,
alkylcycloalkylene having 4 to 20 carbon atoms, a
cycloalkylalkylene having 4 to 20 carbon atoms, and combinations
thereof; n=0 or 1; R.sub.5 is selected from the group consisting of
hydrocarbyl substituents with a tertiary carbon attachment point,
acetal, or ketal; and m=1 or >1.
L .sub.n CR.sub.6R.sub.7--OR.sub.8).sub.p (III),
whereas, L is a linking group selected from the group consisting of
linear, branched, or substituted alkylene having 1 to 7 carbon
atoms, cycloalkylene having 3 to 17 carbon atoms,
alkylcycloalkylene having 4 to 20 carbon atoms, a
cycloalkylalkylene having 4 to 20 carbon atoms, and combinations
thereof; n=0 or 1; R.sub.6, R.sub.7 are independently selected from
hydrogen, C.sub.1 to C.sub.6 alkyl (e.g., methyl, ethyl, isopropyl,
etc.), fluorinated C.sub.1 to C.sub.6 alkyl groups; R.sub.8 is
selected from the group consisting of hydrocarbyl substituents with
a tertiary carbon attachment point, acetal, or ketal; and p=1 or
>1.
##STR00004##
[0026] wherein L is a linking group selected from the group
consisting of linear, branched, or substituted alkylene having 1 to
7 carbon atoms, cycloalkylene having 3 to 17 carbon atoms,
alkylcycloalkylene having 4 to 20 carbon atoms, a
cycloalkylalkylene having 4 to 20 carbon atoms, and combinations
thereof; n=0 or 1; R.sub.9, R.sub.10 are independently selected
from hydrogen, C.sub.1 to C.sub.6 alkyl (e.g., methyl, ethyl,
isopropyl, etc.), fluorinated C.sub.1 to C.sub.6 alkyl groups;
R.sub.11 is selected from the groups consisting of hydrocarbyl
substituents with a tertiary carbon attachment point; and q=1 or
>1.
[0027] Preferred hydrocarbyl substituents with tertiary attachment
point include, but are not limited to, t-butyl group,
1-methyl-cyclopentyl group, 2-methyl-2-adamantyl group,
1-ethyl-1-cyclopentyl group, or 1-ethyl-1-cyclooctyl group.
[0028] Preferred acetal groups include, but are not limited to,
1-ethoxyethyl group, tetrahydrofuranyl group, or tetrahydropyranyl
group.
[0029] Preferred ketal groups include, but are not limited to,
1-methoxy-1-cyclohexyl group, 4-methyl-4-hydroxybutyric acid
lactone (.alpha.-angelicalactone derivative).
[0030] Other suitable acid-labile protecting groups may be found in
U.S. Pat. No. 5,679,495 to Yamachika et al. or in the pertinent
literature and texts (e.g., Greene et al., Protective Groups in
Organic Synthesis, 2.sup.nd Ed. (New York: John Wiley & Sons,
1991)).
[0031] Preferred acid-labile functionalities have the structural
formula (II), which undergo a cleavage reaction in the presence of
photogenerated acid to generate a carboxylic acid group. Typically,
the reaction of acid-labile functional groups with photogenerated
acid occurs only, or is promoted greatly by, the application of
heat to the film. Those skilled in the art will recognize the
various factors that influence the rate and ultimate degree of
cleavage of acid-labile functional groups as well as the issues
surrounding integration of the cleavage step into a viable
manufacturing process. The product of the cleavage reaction is a
polymer-bound carboxylic acid group, which, when present in
sufficient quantities along the polymer backbone, imparts
solubility to the polymer in basic aqueous solutions.
[0032] Suitable aqueous base soluble functionalities include,
without limitation, acidic functionalities such as a fluorinated
alkyl sulfonamide, a carboxylic acid, a phenol, and a
fluoroalcohol.
[0033] Suitable non-acidic polar functionalities include, but are
not limited to, lactones, anhydrides, alkylsulfonamides, nitrites,
and alcohols.
[0034] Suitable cross linking functionalities include, but are not
limited to, any aliphatic or aromatic group that has a pendant
hydrogen bonding functionality or a pendant cross-linkable
functionality. Hydrogen bonding functionality includes hydroxyl,
amido, keto, carboxylate, carboxylic acid, alkoxy, sulfonic acid,
silanol, thiol, amino, and the like. Cross-linkable functionality
also is intended to include epoxy group, oxetane, styrene,
siloxane, furfuryl group, tetrahydrofurfuryl group and the
like.
[0035] The functionalized polycarbosilanes can be prepared via a
well known hydrosilation reaction scheme as is generally
illustrated in reaction scheme (I) using poly(carbomethylsilane)
precursors as shown below:
##STR00005##
[0036] Using this method, numerous functionalized polycarbosilanes
with higher refractive indices (n>1.7) and relatively low
absorbance (A<3.00 .mu.m.sup.-1) at 193 nm have been prepared
that are suitable for use in photoresist compositions. (See the
examples below.) A detailed description of the above reaction
scheme may be found, for example, in R. D. Archer, Inorganic and
Organometallic Polymers, 54 76 (2001); M. A. Brook, Silicon in
Organic and Organometallic, and Polymer Chemistry, 256-367, 400,
(2000); M. Birot et al., Comprehensive Chemistry of
Polycarbosilanes, Polsilazene, and Polycarbosilazene as Precursors
for Ceramics, 95 J. Chem. Rev. 1443 (1995); and L. V. Interrante et
al., Linear and Hyperbranched Polycarbosilanes with
Si--CH.sub.2--Si Bridging Groups. A Synthetic Platform for the
Construction of Novel Polymeric Materials, 12 Appl. Organometal.
Chem. 695 (1998).
[0037] The photoresist compositions including the functionalized
carbosilanes generally comprise an acid generator and a casting
solvent. The acid generator can be a photoacid generator. Upon
exposure to activating radiation, the acid generator generates a
strong acid.
[0038] The photosensitive acid generators (PAGs) used in the resist
compositions of the invention may be any suitable photosensitive
acid generator known in the resist art, which is otherwise
compatible with the other selected components of the resist
composition, and in particular, for positive resist compositions.
Examples of preferred photosensitive acid generators (PAG) include:
(trifluoromethylsulfonyloxy)-bicyclo[2.2.1]hept-5-ene-2,3-dicarboximide
("MDT"), (perfluorobutanesulfonyloxy)
bicyclo[2.2.1]hept-5-ene-2,3-dicarboximide, onium salts, aromatic
diazonium salts, sulfonium salts, diaryliodonium salts and sulfonic
acid esters of N-hydroxyamides or -imides, as disclosed in U.S.
Pat. No. 4,731,605. Also, a PAG that produces a weaker acid such as
dodecane sulfonate of N-hydroxy-naphthalimide ("DDSN") may be used.
Fluorinated PAG is also preferred for higher acidity (lower
pK.sub.a). Combinations of PAGs may be used.
[0039] The casting solvent generally serves to dissolve the other
components so that the overall composition may be applied evenly on
the substrate surface to provide a defect-free coating. Where the
resist composition is used in a multilayer imaging process, the
solvent used in the imaging layer resist is preferably not a
solvent to the underlayer materials, otherwise the unwanted
intermixing may occur. When the underlayer composition uses a
crosslinker approach, a cross-linked underlayer will prevent
intermixing. In this case, the same or a different solvent can be
used for both the imaging layer and the underlayer. Examples of
suitable casting solvents include, without limitation,
cyclopentanone, cyclohexanone, lactate esters such as ethyl
lactate, alkylene glycol alkyl ether esters such as propylene
glycol methyl ether acetate, alkylene glycol monoalkyl esters such
as methyl cellosolve, butyl acetate, 2-ethoxyethanol, and ethyl
3-ethoxypropionate, ethoxyethylpropionate ("EEP"), a combination of
EEP and .gamma.-butyrolactone ("GBL"),
propylene-glycolmonoethylether acetate (PGMEA), and the like. The
above list of solvents is for illustrative purposes only and should
not be viewed as being comprehensive nor should the choice of
solvent be viewed as limiting the invention in any way. Those
skilled in the art will recognize that any number of solvents or
solvent mixtures may be used.
[0040] The resist compositions may further include organic base
additives, surfactants, sensitizers, dissolution modifying
additives, additives intended to modify the contact angle of the
resist surface for immersion lithography applications and to
prevent PAG extraction by the immersion fluid (Sanders et al. Proc.
SPIE 2006, 6519, 651904), or other expedients known in the art. The
compositions of the present invention are not limited to any
specific selection of these expedients.
[0041] Examples of base additives include dimethylamino pyridine,
7-diethylamino-4-methyl coumarin ("Coumarin 1"), tertiary amines,
imidazoles, imides, amides, proton sponge, berberine, and the
polymeric amines as in the PLURONIC.RTM. or TETRONIC.RTM. series
from BASF. Tetraalkyl ammonium hydroxides or cetyltrimethyl
ammonium hydroxide may be used as a base additive when the PAG is
an onium salt.
[0042] Examples of possible surfactants include fluorine-containing
surfactants such as the FLUORAD.RTM. series, preferably FC-430, and
more preferably, FC-4430, both available from 3M Company in St.
Paul, Minn., and siloxane-containing surfactants such as the
SILWET.RTM. series available from Union Carbide Corporation in
Danbury, Conn.
[0043] The resist compositions of the invention are not limited to
any specific proportions of the various components. The resist
composition of the present invention preferably includes about
0.1-25 wt. % PAG, more preferably about 0.5-15 wt. %, based on the
total weight of imaging polymer in the composition. The inventive
resist composition preferably contains about 0.02-8 wt. % of the
base additive, more preferably about 0.1-2 wt. %, based on the
total weight of the polymer. Where the resist compositions of the
invention contain a solvent, the overall composition preferably
contains about 50-98 wt. % solvent.
[0044] The resist compositions of the invention are useful in
single layer photolithographic processes, and are especially useful
as imaging layers in multilayer photolithographic processes, such
as bi-layer or tri-layer processes. Preferably, the resist
compositions of the invention may be patterned using various
radiation types such as 365 nm wavelength, deep-UV (specifically
248 nm, 193 nm, and 157 nm wavelengths), extreme-UV (approximately
13 nm wavelength), x-ray, electron beam, and ion beam. This resist
compositions may be patterned under immersion conditions under
water or a high refractive index fluid (e.g., French et al. Proc.
SPIE 2006, 6154, 6155) with or without an overcoat. The appropriate
radiation type(s) may depend on the components of the overall
resist composition (e.g., the selection of the polymer component,
photosensitive acid generator (PAG), base (or quencher), additives,
surfactant, solvent, etc.). The resist compositions of the
invention generally provide high-resolution capability
(approximately 100 nm resolution or less, more particularly below
70 nm) in combination with desired dissolution behavior.
[0045] The present invention encompasses a method of patterning a
desired substrate, such as, for example, a silicon wafer, a
chrome-on-glass mask blank, or a printed circuit board. The method
includes applying to the substrate a coating of the photoresist
composition containing the functionalized polycarbosilane polymer,
as described above, to form a film. The photoresist material can be
applied by known means, such as spin casting, immersion, and the
like.
[0046] The method also includes patternwise exposing the
photoresist composition to an imaging radiation source, such as
ultraviolet radiation of 193 or 157 nm. In a preferred embodiment,
the imaging radiation source is by immersion lithography at 193 nm.
The areas of the photoresist exposed to the radiation source are
then developed by, for example, immersion, puddle development, or
other processes known to those skilled in the art. Developer
solution can include, for example, dilute aqueous alkali solution,
which may or may not contain a surfactant.
[0047] In the case of positive tone photoresists, the exposed areas
of the film will be rendered soluble in the developer and can be
washed away, leaving a pattern of the unexposed areas. In negative
tone photoresists, the exposed areas of the film will be rendered
insoluble and will remain after development of the unexposed areas.
The developed image can then be rinsed with water to remove excess
developer and dried. The patterned photoresist image can then be
used as an etch mask for subsequent image transfer into the
underlying substrate.
[0048] When the photoresist composition is to be used as a negative
photoresist, a crosslinking agent may be added to the photoresist
composition for example, during resist formulation, and/or the
polycarbosilane can be functionalized with a crosslinking
functionality. Examples of such crosslinking agents that can be
added include, but are not limited to, glycouril, melamine,
epoxide, furyl, tetrahydrofuryl, vinyl ether, oxetane and
combinations thereof. One particular example of a suitable
glycouril is POWDERLINK.RTM. 1174 available from Cytec (West
Paterson, N.J.). Suitable cross-linking functionalities were
described above.
[0049] Pre-application, post-application, post-exposure, and
post-development processes such as, for example, application of an
anti-reflective coating, substrate priming, baking, flood exposure,
or vapor treatment, may also be incorporated into the methodologies
of the invention at least in part to enhance the performance and/or
advantages of the present invention, as is known in the art. In
particular, the incorporation of a post-application bake (PAB) to
remove residual casting solvent of the photoresist film can be
desirable in some applications. A PAB process may include baking
the desired substrate (e.g., wafer), at a temperature of about room
temperature (about 21.degree. C.) to about 120.degree. C. for a
period of about 10 seconds to about 120 seconds.
[0050] Additionally, it may be desirable to include a post-exposure
bake (PEB) in a manner consistent with the PAB methodology
described above. Although it is not necessary for performance of
many low activation energy chemically amplified photoresists (e.g.,
ketal or acetal functionalized polycarbosilanes), a PEB may be
included to enhance lithographic imaging quality. A PEB process may
include baking the wafer or substrate at a temperature of about
room temperature (about 21.degree. C.) to about 120.degree. C. for
a period of about 10 seconds to about 120 seconds. It is to be
appreciated that both PAB and PEB processes may be accomplished
using conventional methods understood by those skilled in the art,
such as, for example, contact hot plate baking, oven baking,
proximity baking, and the like. It may also be desirable to
incorporate prior treatment of the substrate with a surface priming
agent including, but not limited to, conventional silylating agents
such as, for example, hexamethyldisilazane and/or related species
by techniques known to those skilled in the art. Illustrative
techniques suitable for use with the present invention include,
without limitation, vapor priming and liquid puddle
application.
[0051] The method can further include etching the patterned
substrate using a conventional etching process that may include,
but is not limited to, a reactive ion etch. In addition any
remaining photoresist composition can be removed from the
substrate, for example, using a stripping agent.
[0052] The present invention encompasses a single layer method of
forming a structure on a substrate, including providing a
substrate; applying the resist composition to the substrate to form
a resist layer on the substrate, wherein the resist composition
includes a functionalized polycarbosilane polymer as described
above, and a photoacid generator; patternwise exposing the
substrate to radiation, whereby acid is generated by the
radiation-sensitive acid generator in exposed regions of the resist
layer; removing patternwise soluble portions of the resist layer to
form a pattern of spaces in the resist layer; and transferring the
pattern of spaces to the substrate. As noted above, the resist
formulation can be configured to be a negative tone resist or a
positive tone resist.
[0053] The exposed resist layer may be baked to promote an
acid-catalyzed reaction in exposed portions of the resist layer.
The substrate may include a material layer to be patterned, and the
method may further include a step of transferring the pattern of
spaces in the resist layer to the underlying substrate by removing
portions of the material layer through the pattern of spaces in the
resist layer. Alternatively, the method may include a step of
transferring the pattern of spaces in the resist layer to the
underlying substrate material (which may include one or more layers
of material) by depositing a material (such as an organic
dielectric, a metal, a ceramic or a semiconductor) onto the
substrate at the spaces in the resist layer, or by implanting
dopants into the substrate material. The substrate may include any
suitable material useful in the formation of microelectronic
structures, and is preferably selected from any of an organic
dielectric, a metal, a ceramic or a semiconductor.
[0054] The invention also encompasses a multilayer (e.g., bi-layer
or tri-layer) lithography method including forming a first layer of
a planarizing material on a substrate; forming a second (imaging)
layer of a resist material on the first layer, wherein the second
layer includes a resist composition of the invention; pattern-wise
exposing the second layer to radiation using a patterning tool,
optionally followed by post-exposure baking (PEB); and developing a
pattern in the second layer to remove unexposed portions of the
second layer and to form a patterned resist that reveals portions
of the first layer. As in a single layer method, the multilayer
method may further include transferring the pattern of spaces in
the resist by any conventional method such as depositing,
implanting or etching.
[0055] Preferably, the first layer is a planarizing underlayer that
is highly energy absorbing, and/or reduces reflection to the
imaging resist layer. The planarizing underlayer is preferably
applied directly over the material layer to be patterned.
Subsequently, a layer of the inventive resist composition is
applied over the first planarizing underlayer, using spin coating
or other techniques. The resist coating is preferably as thin as
possible (generally less than 100 nm) provided that the thickness
is preferably substantially uniform and that the resist layer is
sufficient to withstand subsequent processing (typically reactive
ion etching (RIE)) to transfer the lithographic pattern to the
planarizing underlayer. Optionally, the substrate with the resist
coating may be heated (pre-exposure bake or post-apply bake (PAB))
to remove the solvent and improve the coherence of the resist
layer. The PAB step is preferably conducted for about 10 seconds to
about 15 minutes, more preferably about 15 seconds to about two
minutes. The PAB temperature may vary depending on the T.sub.g of
the resist. Optionally, the functionalized carbosilane photoresist
composition, once coated, may further include an overcoat to
provide, for example, protection of the lens from photoacid or
photoacid generators that may diffuse into the liquid medium during
immersion lithography, for example. Optionally, a suitably designed
additive added to the resist may segregate to the surface and act
as an in-situ overcoat.
[0056] The resist pattern is then patternwise exposed to the
desired radiation (e.g., 193 nm, 157 nm radiation). Where scanning
particle beams, such as electron beam, are used, patternwise
exposure may be achieved by scanning the beam across the substrate
and selectively applying the beam in the desired pattern. More
typically, wavelike radiation, such as 193 nm or 157 nm UV
radiation, is projected through a mask to provide patternwise
radiation exposure to the resist. Preferably, the resist image
formed in the second layer is a high resolution resist image.
Resolution enhancement techniques (RET), such as attenuated phase
shift (attPSM), or alternating phase-shift (altPSM) masks or other
RET methodologies, may be used as the radiation wavelengths
decrease.
[0057] Optionally, the patternwise exposed resist layer may be
baked (post-exposure bake or PEB) between the exposure and
developing steps to further complete the acid-catalyzed reaction,
to facilitate the deprotection of acid labile groups in the
radiation-exposed portions of the resist layer and to enhance the
contrast of the exposed pattern. The PEB is preferably conducted at
about 20-120.degree. C. The PEB is preferably conducted for about
10 seconds to 5 minutes.
[0058] The resist structure with the desired pattern is obtained by
contacting the resist layer with an alkaline solution that
selectively dissolves the areas of the resist, which were exposed
to radiation. Preferred alkaline solutions (developers) are aqueous
solutions of tetramethyl ammonium hydroxide (TMAH). Preferably, the
step of developing the second layer uses an aqueous solution of
TMAH of about 0.14 N or greater, about 0.20 N or greater in some
embodiments, and about 0.26 N or greater in still other
embodiments. The resulting lithographic structure on the substrate
is then typically dried to remove any remaining developer
solvent.
[0059] The portions of the first planarizing underlayer are
preferably removed by etching using remaining portions of the
patterned second layer as a mask. Preferably, the etching is
performed by O.sub.2 plasma reactive ion etching (RIE) or other
anisotropic etching techniques. Once the desired portions of the
underlayer have been removed, the pattern may be transferred to
portions of the substrate, for example, by etching (e.g., by
reactive ion etching) the substrate at positions corresponding to
the removed portions of the underlayer. Once the desired pattern
transfer has taken place, any remaining underlayer and resist may
be removed by using conventional stripping techniques.
[0060] The planarizing underlayer should be sufficiently etchable,
selective to the overlying resist (to yield a good profile in the
etched underlayer) while being resistant to the etch process needed
to pattern the underlying material layer (substrate). Additionally,
the planarizing underlayer composition should have the desired
optical characteristics (e.g., refractive index, optical density,
etc.) such that the need for any additional antireflective coating
(ARC) layer is avoided. The planarizing underlayer composition
should also have physical/chemical compatibility with the imaging
resist layer to avoid unwanted interactions which may cause footing
and/or scumming.
[0061] The following non-limiting examples are presented to better
illustrate the present disclosure. In the following examples, the
polycarbosilane starting materials, e.g., poly(carbomethylsilane),
were obtained from Aldrich Chemical Company and Starfire Systems
Inc. Aldrich polymers are solids and our analysis by NMR
spectroscopy indicated that these polymers are highly branched and
may contain Si--Si units. The polymer obtained from Starfire
systems was a viscous liquid and had a broad polydispersity as
determined by Gel Permeation Chromatography (GPC).
[0062] Where appropriate, the following techniques and equipment
were utilized in the Examples: .sup.1H and .sup.13C NMR spectra
were obtained at room temperature on an Avance 400 spectrometer.
Quantitative .sup.13C NMR was run at room temperature in an
inverse-gated .sup.1H-decoupled mode using Cr(acac).sub.3 as a
relaxation agent on an Avance 400 spectrometer. For polymer
composition analysis .sup.19F NMR (379 MHz) spectra were also
obtained using a Bruker Avance 400 spectrometer. Thermo-gravimetric
analysis (TGA) was performed at a heating rate of 5.degree. C./min
in N.sub.2 on a TA Instrument Hi-Res TGA 2950 Thermo-gravimetric
Analyzer. Differential scanning calorimetry (DSC) was performed at
a heating rate of 10.degree. C./min on a TA Instruments DSC 2920
modulated differential scanning calorimeter. Molecular weights were
measured in tetrahydrofuran (THF) on a Waters Model 150
chromatograph relative to polystyrene standards. IR spectra were
recorded on a Nicolet 510 FT-IR spectrometer on a film cast on a
KBr plate. Film thickness was measured on a Tencor alpha-step 2000.
A quartz crystal microbalance (QCM) was used to study the
dissolution kinetics of the resist films in an aqueous
tetramethylammonium hydroxide (TMAH) solution (CD-26).
[0063] The 193 nm dry exposures were carried out on an ISI
mini-stepper with 0.60 NA. Immersion exposures were carried out on
a 193 nm interferometric tool assembled in-house. E-beam exposures
were carried out on a Leica 100 kV exposure tool.
[0064] The following examples are intended to provide those of
ordinary skill in the art with a complete disclosure and
description of how to prepare and use the compositions disclosed
and claimed herein. Efforts have been made to ensure accuracy with
respect to numbers (e.g., amounts, temperature, etc.), but
allowance should be made for the possibility of errors and
deviations. Unless indicated otherwise, parts are parts by weight,
temperature is in .degree. C. and pressure is at or near
atmospheric. Additionally, all starting materials were obtained
commercially or were synthesized using known procedures.
EXAMPLES
Example 1
[0065] Allylmalonic acid di-tetrahydropyranyl ester was prepared.
Allylmalonic acid (7.21 grams, 0.05 mole), 3,4-dihydro-2H-pyran
(16.82 g, 0.20 mole), and dichloromethane (50 ml) were placed in a
round bottom flask equipped with a magnetic stirrer, nitrogen
inlet, and a water condenser. Pyridine p-toluenesulfonate (300 mg)
was added to this mixture and stirred at room temperature for 3
hours. According to the IR spectrum of the reaction product, the
reaction was complete. The reaction mixture was washed with
2.times.100 ml saturated sodium bicarbonate solution followed by
100 ml brine and was dried over anhydrous magnesium sulfate. The
volatiles were removed in a rotary evaporator and the residue was
dried under vacuum at room temperature. The NMR spectrum of the
residue indicated that it contained only the desired product.
Example 2
[0066] In this example, poly(carbomethylsilane) partially
substituted with propylmalonic acid di-tetrahydropyranyl ester of
formula (V) was prepared from the allylmalonic acid
di-tetrahydropyranyl ester produced in accordance with Example
1.
##STR00006##
[0067] Polycarbomethylsilane (Aldrich, M.sub.w.about.800) (1.16 g),
allylmalonic acid di-tetrahydropyranyl ester (4.68 g, 0.015 mole),
and tetrahydrofuran (THF) (5 ml) were placed in a round bottom
flask equipped with a magnetic stirrer, nitrogen inlet, and a water
condenser. Platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane
complex in xylene (0.25 ml) was added to this mixture and heated at
80-90.degree. C. for 2 hours. Afterwards, another portion of the
catalyst, platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane
complex in xylene (0.25 ml), was added and heated at 80-90.degree.
for 2 more hours. The solution was allowed to cool to room
temperature and added drop wise into 200 ml HFE-7100 (Ultra Pure
Solutions, Inc.). The precipitated polymer was filtered through a
frit funnel and dried under vacuum at room temperature for 72
hours. Yield: 0.60 grams. M.sub.w=4848, PDI=1.65 and (a:b is
approximately 1:1). NMR data indicated that about 50% of the
hydrogen had been substituted. Refractive Index=1.82,
Absorbance=1.99/micrometer.
Example 3
[0068] In this example, allylmalonic acid
di-.alpha.-methyl-.gamma.-butyrolactone ester was prepared.
Allylmalonic acid (7.21 grams, 0.05 mole), .alpha.-angelicalactone
(16.82 g, 0.20 mole), and dichloromethane (50 ml) were placed in a
round bottom flask equipped with a magnetic stirrer, nitrogen
inlet, and a water condenser. Pyridine p-toluenesulfonate (300 mg)
was added to this mixture and heated to reflux for 19 hours.
According to the IR spectrum of the reaction product, the reaction
was complete. The reaction mixture was washed with 2.times.100 ml
saturated sodium bicarbonate solution followed by 100 ml brine and
was dried over anhydrous magnesium sulfate. The volatiles were
removed at 40.degree. C. under high vacuum. The NMR spectrum of the
residue indicated that it contained only the desired product.
Example 4
[0069] In this example, polycarbomethylsilane partially substituted
with propylmalonic acid di-.alpha.-methyl-.gamma.-butyrolactone
ester of formula (VI) was prepared from the allylmalonic acid
di-.alpha.-methyl-.gamma.-butyrolactone ester produced in
accordance with Example 3.
##STR00007##
[0070] Polycarbomethylsilane (Aldrich, M.sub.w.about.800) (1.16 g),
Allylmalonic acid di-.alpha.-methyl-.gamma.-butyrolactone ester
(5.10 g, 0.015 mole), and tetrahydrofuran (THF) (10 ml) were placed
in a round bottom flask equipped with a magnetic stirrer, nitrogen
inlet, and a water condenser.
Platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex in
xylene (0.50 ml) was added to this mixture and heated at
80-90.degree. for 3 hours. Afterwards, another portion of the
catalyst, platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane
complex in xylene (0.25 ml), was added and heated at 80-90.degree.
C. for 2 more hours. The solution was allowed to cool to room
temperature and added drop wise into 200 ml HFE-7100. The
precipitated polymer was separated by decantation and dried under
vacuum at 50.degree. C. for 15 hours. The sticky polymer was
dissolved in 20 ml acetone and added drop wise into 400 ml hexanes
and the precipitated polymer was separated by decantation. This
polymer was dried under vacuum at 50.degree. C. for 15 hours.
Yield: 1.30 grams. M.sub.w=6476, PDI=1.8, Refractive Index=1.80,
Absorbance=1.35/micrometer. NMR data indicated that about 50% of
the hydrogen had been substituted (a:b.about.1:1).
Example 5
[0071] In this example, polycarbomethylsilane partially substituted
with 1-methylcyclopentyl-2-norbornanecarboxylate of formula (VII)
was prepared.
##STR00008##
[0072] Polycarbomethylsilane (Aldrich, M.sub.w.about.800) (2.32 g)
and 1-methylcyclopentyl-5-norbornene-2-carboxylate (17.65 g, 0.08
mole) were placed in a round bottom flask equipped with a magnetic
stirrer, nitrogen inlet, and a water condenser.
Platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex in
xylene (0.50 ml) was added to this mixture and heated at
80-90.degree. C. for 22 hours. The solution was allowed to cool to
room temperature and added drop wise into 300 ml methanol. The
precipitated polymer was filtered through a frit funnel. According
to NMR spectra of the polymer, some monomer remained. This polymer
was dissolved in 12.5 ml of tetrahydrofuran and precipitated again
into 250 ml methanol. It was filtered through a frit funnel and
dried under vacuum at 60.degree. C. for 15 hours. Yield: 1.73
grams. M.sub.w=3546, PDI=1.6, Refractive Index=1.83,
Absorbance=2.37/micrometer. NMR data indicated that about 50% of
the hydrogen had been substituted (a:b.about.1:1).
Example 6
[0073] In this example, polycarbomethylsilane partially substituted
with 1,1,1-trifluoro-2-trifluoromethyl-2-hydroxypentane of formula
(VIII) was prepared.
##STR00009##
[0074] Polycarbomethylsilane (Aldrich, M.sub.w.about.800) (2.32 g)
and 1,1,1-trifluoro-2-trifluoromethyl-4-penten-2-ol (16.64 g, 0.08
mole) were placed in a round bottom flask equipped with a magnetic
stirrer, nitrogen inlet, and a water condenser.
Platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex in
xylene (0.50 ml) was added to this mixture and heated at
80-90.degree. C. for 23 hours. The unreacted monomer was removed in
a rotary evaporator and then dried under vacuum at 60.degree. C.
for 15 hours. Yield: 3.54 grams. M.sub.w=4074, PDI=2.06, Refractive
Index=1.75, Absorbance=1.67/micrometer. NMR data indicated that
about 50% of the hydrogen had been substituted (a:b.about.1:1).
Example 7
[0075] In this example, polycarbomethylsilane partially substituted
with 1-methylcyclopentyl-2-norbornanecarboxylate and norbornane
spirolactone of formula (IX) was prepared.
##STR00010##
[0076] Polycarbomethylsilane, (Aldrich, M.sub.w.about.800) (2.32
g), 1-methylcyclopentyl-5-norbornene-2-carboxylate (8.82 g, 0.04
mole), and norbornene spirolactone (6.56 g, 0.04 mole) were placed
in a round bottom flask equipped with a magnetic stirrer, nitrogen
inlet, and a water condenser.
Platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex in
xylene (0.50 ml) was added to this mixture and heated at
80-90.degree. C. for 21 hours. The viscous solution was allowed to
cool to room temperature and diluted with 10 ml tetrahydrofuran.
This solution was added drop wise into 500 ml methanol. The
precipitated polymer was filtered through a frit funnel. According
to proton NMR spectrum of the polymer, some monomer remained. This
polymer was dissolved in 10 ml of tetrahydrofuran and precipitated
again into 100 ml methanol. It was filtered through a frit funnel
and dried under vacuum at 60.degree. C. for 15 hours. Yield: 1.00
gram. M.sub.w=4340, PDI=1.54, Refractive index=1.85,
Absorbance=2.63/micrometer. NMR data indicated that about 50% of
the hydrogen had been substituted (a:b:c.about.1.0:0.5:0.5).
Example 8
[0077] In this example, polycarbomethylsilane partially substituted
with 2-Trifluoromethanesulfonylaminomethyl norbornane of formula
(X) was prepared.
##STR00011##
[0078] Polycarbomethylsilane (Aldrich, M.sub.w.about.800) (1.16 g)
and 2-trifluoromethane-sulfonylaminomethyl norbornene (5.42 g, 0.02
mole) were placed in a round bottom flask equipped with a magnetic
stirrer, nitrogen inlet, and a water condenser.
Platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex in
xylene (0.30 ml) was added to this mixture and heated at
80-90.degree. C. for 18 hours. The solution was allowed to cool to
room temperature and added drop wise into a mixture of 300 ml
methanol and 100 ml deionized water. The precipitated polymer was
filtered through a frit funnel and washed with 2.times.50 ml
methanol/water mixture (4:1) and dried under vacuum at 60.degree.
C. for 15 hours. Yield: 1.40 grams. M.sub.w=4421, PDI=2.0,
Refractive Index=1.77, Absorbance=2.17/micrometer. NMR data
indicated that about 50% of the hydrogen had been substituted
(a:b.about.1:1).
Example 9
[0079] In this example, polycarbomethylsilane partially substituted
with norbornanedicarboxylic anhydride and
1-methylcyclopentyl-2-norbornanecarboxylate of formula (XI) was
prepared.
##STR00012##
[0080] Polycarbomethylsilane (commercially obtained from Starfire)
(1.45 g), 1-methylcyclopentyl-5-norbornene-2-carboxylate (3.40 g,
0.015 mole), and cis-5-norbornene-endo-2,3-dicarboxylic anhydride
(2.46 g, 0.015 mole), and 15 ml anhydrous tetrahydrofuran (THF)
were placed in a round bottom flask equipped with a magnetic
stirrer, nitrogen inlet, and a water condenser.
Platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex in
xylene (0.50 ml) was added to this mixture and heated at
80-90.degree. C. for 2 hours. This solution was added drop wise
into 300 ml methanol. The precipitated polymer was filtered through
a frit funnel, washed with 2.times.100 ml methanol and dried under
vacuum at 50.degree. C. for 15 hours. Yield: 2.32 gram.
M.sub.w=120,557, PDI=22.81, Refractive Index=1.78,
Absorbance=0.75/micrometer film. NMR data indicated that about 50%
of the hydrogen had been substituted (a:b:c.about.1.0:0.5:0.5).
Example 10
[0081] In this example, a photoresist composition based on
carbosilane polymer (VII) prepared in accordance with Example 2 was
prepared. 0.5 g of the polymer, 20 mg of triphenylsulfonium
perfluoro-1-butanesulfonate (photoacid generator), and 3.3 mg of an
organic base were dissolved in 5 g of propylene glycol monomethyl
ether acetate (PGMEA). This solution was filtered through a 0.2
micron syringe filter. Refractive Index=1.82,
Absorbance=2.60/micrometer. FIG. 1 provides contrast curves as a
function of temperature. FIG. 2 provides a micrograph of a
patterned photoresist illustrating 170 nanometer dense and isolated
lines. The photoresist was exposed using water at 193 nm with an
exposure energy of 23.2 mJ/cm.sup.2 and included a PEB at
60.degree. C. for 60 seconds. Film thickness was 159
nanometers.
[0082] Advantageously, the functionalized carbosilane polymers
provide refractive index greater than 1.7 and an absorbance less
than 3.0. The photoresist compositions of the present invention are
particularly useful as radiation-sensitive photoresists employed in
the manufacture of electronic parts, especially semiconductor
devices, or in the manufacture of photolithography masks using
optical, electron beam, ion beam or x-ray radiation. Moreover, the
compositions of the present invention may be employed for
patterning printed circuit boards or photolithographic masks (i.e.,
photomasks), micromachining, the fabrication of microfluidic cells,
or other related practices that require the definition of
high-resolution patterns.
[0083] While the preferred embodiment to the invention has been
described, it will be understood that those skilled in the art,
both now and in the future, may make various improvements and
enhancements which fall within the scope of the claims which
follow. These claims should be construed to maintain the proper
protection for the invention first described.
* * * * *