Novel anionic photoacid generators (PAGs) and corresponding PAG bound polymers for sub-50 nm EUV lithography

Article abstract of DOI:10.1039/b617133h

A new series of anionic photoacid generators (PAGs) and corresponding polymers were prepared. The thermostability of PAG bound polymers was superior to that of PAG blend polymers. PAG incorporated into the polymer main chain showed improved resolution when compared with the PAG blend polymers. This was demonstrated by extreme ultraviolet lithography (EUVL) results: the fluorine PAG bound polymer resist gave 45 nm (1: 1), 35 nm (1: 2), 30 nm (1: 3) and 20 nm (1: 4) Line/Space as well as the 50 nm (1: 1) elbow pattern. The Royal Society of Chemistry.

Full text of DOI:10.1039/b617133h

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www.rsc.org/materials | Journal of Materials Chemistry
Novel anionic photoacid generators (PAGs) and corresponding PAG bound
polymers for sub-50 nm EUV lithography
Mingxing Wang,a Kenneth E. Gonsalves,*a Monica Rabinovich,a Wang Yuehb and Jeanette M. Robertsb
Received 23rd November 2006, Accepted 15th January 2007
First published as an Advance Article on the web 5th February 2007
DOI: 10.1039/b617133h
A new series of anionic photoacid generators (PAGs) and corresponding polymers were prepared.
The thermostability of PAG bound polymers was superior to that of PAG blend polymers. PAG
incorporated into the polymer main chain showed improved resolution when compared with the
PAG blend polymers. This was demonstrated by extreme ultraviolet lithography (EUVL) results:
the fluorine PAG bound polymer resist gave 45 nm (1 : 1), 35 nm (1 : 2), 30 nm (1 : 3) and 20 nm
(1 : 4) Line/Space as well as the 50 nm (1 : 1) elbow pattern.
PAG. The inherent incompatibility can lead to PAG phase
1. Introduction
separation, non-uniform initial PAG and photoacid distribu-
tion, as well as acid migration during the PEB processes.9
Extreme ultraviolet lithography (EUVL) at 13.5 nm wave-
length has emerged as a leading candidate to meet the
To alleviate these problems, the potential use of a polymer
resolution requirements of the microelectronic industry road-
bound PAG blended with a CA resist, for controlling acid
map.1 Although critical dimensions below 50 nm have been
achieved, extensive research still needs to be conducted in the
development of EUV technology to meet the 32 nm and the
lower 22 nm technology nodes.2 In addition to developing
the exposure tools themselves, significant challenges remain in
developing photoresist materials with all of the required
imaging properties. An EUV resist system requires high
sensitivity, low outgassing, sub-50 nm resolution and low
line-edge roughness (LER). In addition to meeting these
imaging requirements, the resist should also provide adequate
etch resistance for process implementation. Currently, the
major challenge for resist development is to cope with all
requirements simultaneously. Indeed, a fundamental interplay
exists among the above mentioned issues, there is no clear
path to meet resolution, LER and sensitivity requirements
simultaneously.3 Chemical amplification (CA) serves as a key
technology to enhance the sensitivity of the photoresists. The
acid formed by the photoacid generator (PAG) on exposure
catalyzes reaction during post-exposure baking (PEB), leading
to a polarity change in the pendant protecting group of the
resist polymer.4–6 Acid diffusion control in the PEB process
during which deprotection progress occurs is important.
Through diffusion, acid can be uniformly distributed in the
resin matrix. In this case, LER would be improved, but acid
also diffuses into the non-exposed areas, and this contributes
to LER.7 The outgassing of resists has also been identified as a
problem in EUV lithographic processes, because of organic
films that can be deposited on an exposure lens which can
cause transmission loss and severe image distortion.8
Conventional CA photoresist formulations are complex
mixtures of a protected polymer matrix and a small molecule
diffusion and outgassing, has been reported.10 Several systems
with ionic or non-ionic PAG incorporated in the main chain
have been studied.11–16 The incorporation of ionic PAG
units into the main chain of the hydroxystyrene and
adamantyl methacrylate based polymers showed improved
EUV lithographic performance, such as faster photospeed
and higher stability, lower outgassing, and lower LER than
corresponding blend resists.14–16 In this paper, we report a
series of novel anionic bound (vinyl functionalized PAG)
and blend anionic PAGs as well as corresponding photo-
resists incorporating PAG in the main chain of the hydroxy-
styrene and adamantyl methacrylate based polymers (Fig. 1
and 2). An investigation of their thermostability, acid
generating efficiency, outgassing and EUVL properties is also
outlined.
2. Experimental
Materials
2,3,5,6-Tetrafluorophenol, 2,29-azobisisobutyronitrile (AIBN),
sodium 4-styrenesulfonate and triflic acid were purchased from
Aldrich. Trifluoroacetic acid (TFA), trifluoroacetic anhydride
(TFAA), and acetic acid 4-vinylphenyl ester were purchased
from Tokyo Kasei Kogyo Co., Ltd. Japan. Methacrylic acid,
isobutyric acid, sodium 4-phenylsulfonate and tetrabromophe-
nol blue (TBPB) were purchased from ACROS ORGANICS.
Triphenylsulfonium chloride 50% aqueous solution was
purchased from City Chemical LLC. 2-Ethyl-2-adamantyl-
methacrylate (EAMA) and tetramethylammonium hydroxide
(TMAH) were supplied by AZ Electronic Materials Ltd. All
chemicals and solvents were used as received unless otherwise
noted. AIBN was recrystallized from methanol before use,
and tetrahydrofuran (THF) and acetonitrile were dried
(over sodium, calcium hydride) before use. Hydroxystyrene
(HOST) was prepared by the hydrolysis of acetic acid
4-vinylphenyl ester.
aPolymer Nanotechnology Laboratory at Center for Optoelectronic and
Optical Communications & Department of Chemistry, University of
North Carolina, Charlotte, North Carolina, 28223, USA.
E-mail: kegonsal@email.uncc.edu
bIntel Corp., Hillsboro, OR, 97124, USA
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Fig. 1 Photoacid generator (PAG) structures.
Fig. 2 Design of microstructures for EUV lithography.
Characterization
was reported previously.11,12 This scheme outlines a typical
synthetic process for bound vinyl monomeric PAG (3),
triphenylsulfonium salt 4-(methacryloxy)-2,3,5,6-tetrafluoro-
benzenesulfonate (F4-MBS-TPS).
The NMR spectra were obtained on a JEOL500 spectrometer
with DMSO-d6 and TMS as the solvent and internal standard,
respectively. Elemental analyses were performed at Atlantic
Microlab Inc. UV-VIS absorption spectra were obtained on a
Varian CARY 300 Bio UV-Visible spectrophotometer. Gel
permeation chromatography (GPC, Waters Breeze software)
was performed with THF or DMF as the eluent. The mole-
cular weights of polymers were calculated with respect to poly-
styrene as narrow Mw standards. Thermogravimetric analyses
(TGA) were performed on a TA instrument, Hi-Res TGA
Synthesis of polymers
Terpolymers (6a, 6b, 6c) were prepared by free radical
polymerization in sealed pressure vessels (Scheme 2).
Hydroxystyrene (HOST), 2-ethyl-2-adamantylmethacrylate
(EAMA), anionic PAG (1, 2, 3), and 2,29-azobisisobuty-
ronitrile (AIBN) as a free radical initiator (5 mol% to the
monomers) were dissolved in freshly distilled anhydrous
tetrahydrofuran (THF) and acetonitrile. Polymerization was
performed at 65 uC for 24 h. The polymer solutions were
precipitated into a large amount of diethyl ether or petroleum
ether and dried under vacuum.
2950 Thermogravimetric Analyzer 7, at a rate of 10 uC min21
,
.
heating to 800 uC with N2 gas flow of 25 cm3 min21
Differential scanning calorimetry (DSC) measurements were
performed on a TA instrument (DSC 2920) at a heating rate of
10 uC min21. For acid generating measurements, a 254 nm UV
lamp (model R 52 G UVP lnc) was used. The outgassing
experiments were performed at the Center of Nanotechnology,
University of Wisconsin in Madison, and the data were
analyzed by Intel Corporation. The EUV exposure was con-
ducted at Lawrence Berkeley National Laboratory. The LER
were measured at Georgia Institute of Technology. The thick-
ness of the films was measured with a Woollam Variable Angle
Spectroscope Ellipsometer. All scanning electron micrography
(SEM) analyses were performed on a RAITH 150/SEM.
Copolymer HE (10) was prepared by
a
similar
procedure (Scheme 3). Hydroxystyrene (HOST), 2-ethyl-2-
adamantylmethacrylate (EAMA), and 2,29-azobutyronitrile
(AIBN) as
a free radical initiator were dissolved in
freshly distilled anhydrous tetrahydrofuran (THF) and
maintained at 65 uC in sealed ampoules for 24 h,
followed by precipitating into petroleum ether and dried under
vacuum.
The PAG blend resists (10+4, 10+5) were prepared by
blending PAG (4, 5) into copolymer (10) at 6.5 wt%, 7.1 wt%,
8.2 wt%, respectively.
Synthesis of photoacid generators (PAGs)
The polymerization composition was calculated by 1H
These novel polymerizable PAGs and blend PAGs were
synthesized as shown in Scheme 1. The detailed procedure
NMR. The results are given in Table 1.
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Scheme 1 Synthesis of photoacid generators (PAGs).
Scheme 2 Synthetic scheme of terpolymers (6a, 6b, 6c).
Scheme 3 Synthetic scheme of copolymer (10), and PAG blend resists (10+4, 10+5).
Acid generation efficiency
tetrabromophenol blue (TBPB) in DMF. The total volume
was then raised to 10 mL by addition of DMF. The resulting
solution was characterized on a UV spectrometer. The amount
of acid generated in the film by UV radiation was determined
by monitoring the absorbance change of the TBPB indicator at
602 nm,17 against the calibration curves predetermined by
using known amounts of triflic acid. Calibration curves
showed a linear relationship between the amount of acid
added to the indicator solution and the resulting absorbance
intensity change at 602 nm. For comparison, the acid
generating efficiency of each resist is expressed as mole of
acid per mole of PAG units in the resist. The number of moles
In order to investigate the acid generating rate for the bound
PAGs and blend PAGs in photoresists, the following protocol
was followed: resist films were spin-cast onto 4 inch Si
wafers, whose weights were predetermined on an analytical
balance, from 7.0 wt% resist solutions in cyclohexanone. After
casting, the films were baked at 130 uC for 5 min to remove the
solvent and were weighed again. The amount of resists on the
film was calculated. The resist films were exposed to a 254 nm
UV lamp equipped with a radiometer. Dose was calculated
by exposure times multiplied by lamp intensity. Each film
to be analyzed was stripped from the silicon wafer with
DMF and added to 1 mL of a stock solution of 0.3 mM
1
of PAG units in each resist was determined by H NMR and
resist weight.
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Table 1 Polymerization results
Mole feed ratio
Polymer composition
Polymer
HOST
EAMA
PAG
HOST
EAMA
PAG
Yield (%)
Mwa/PDI
Tdec./uC
Tg/uC
HE (10)
HE-VBS-TPS (6a)
HE-MBS-TPS (6b)
40
30
25
25
25
60
65
73.5
72.5
72.5
45.8
41.7
37.7
35.0
40.2
54.2
48.6
55.8
57.9
51.6
58.5
44.3
35.4
37.3
36.8
4500/2.5
3700/1.7
3800/1.8
3600/1.6
3100/1.9
157
156
153
145
154
138
131
130
113
c
5
9.7
6.5
7.1
c
c
c
1.5
2.5
2.5
@HE-F4-MBS-TPS (6c@)d
@@HE-F4-MBS-TPS (6c@@)e
HE + IBBS-TPS (10+4)
@HE + F4-IBBS-TPS (10+5@)d
@@HE + F4-IBBS-TPS (10+5@@)e
a
8.2
6.5b
7.1b
8.2b
b
The molecular weight was determined by GPC with THF or DMF as mobile phase and polystyrene as narrow standards. wt%, in order to
c
compare the thermostability and acid generating efficiency of PAG bound polymer with PAG blend polymer. Could not be determined by
DSC, probably due to rigidity of these polymers , resulting from the bulky adamantyl and triphenylsulfonium moiety of the PAG in the
d
e
polymer. The two samples marked @ were used for acid generation efficiency measurement. The two samples marked @@ were used for
outgassing and EUV exposure.
Outgassing and resist processing
co-workers.1,19 At least six 1 mm long lines with 100 points
(10 nm in pitch, high-spatial frequency) of each line were
scanned. The threshold method was applied for determining
the position of the line edge. The final LER was obtained by
averaging the average value of each line.
The outgassing test was performed at the Center for
Nanotechnology at the University of Wisconsin, at Madison.
The outgassing chamber is built on the synchrotron beam line.
A Si3N4 plate is located in the chamber and is analyzed by
electron spectroscopy for chemical analysis (ESCA) for
evidence of contamination build-up. Before the experiments
start, the outgassing chamber is baked and pumped down
overnight to ensure the chamber is clean. Each run first
involves introducing a known amount of a toluene standard,
typically 10 ng, in dry, clean nitrogen through the system and
collecting the toluene and any contaminants in thermal
desorption (TD) tubes. These data indicate the cleanliness of
the chamber as well as providing an internal standard. The TD
tubes are sent to Intel Corp. for gas chromatography/mass
spectroscopy (GC/MS) analysis.
3. Results and discussion
The anionic bound and blend PAGs were prepared in good
1
yield, and characterized by H, 19F and 13C NMR, as well as
elemental analyses.
The terpolymers (6a, 6b, 6c@, 6c@@) and copolymer (10)
were prepared by free radical polymerization and obtained in
moderate yield from 35.4–58.5%, and the PAG contents were
9.7, 6.5, and 7.1, 8.2% (mole ratio) for HE-VBS-TPS (6a), HE-
MBS-TPS (6b), and HE-F4-MBS-TPS (6c@, 6c@@), respec-
tively. The molar compositions of each unit in the terpolymers
1
EUV exposures were conducted at Lawrence Berkeley
National Laboratory, USA.18 The 0.3 NA MET based
micro-exposure station is designed to deliver a diffraction
limited resolution of approximately 30 nm under conventional
illumination and smaller than 15 nm using dipole illumination.
The synchrotron-based exposure station includes a custom
coherence illuminator allowing arbitrary pupil fills with a
maximum of approximately 0.83 in y and 1 in x to be
generated. The coherence control being based on scanning
rather than apertures in the condenser pupil plane, affords a
low loss method of modifying the pupil fill.
were determined by H NMR. The characteristic peaks were:
9.1 ppm from the hydroxyl group of HOST, 7.6–7.8 ppm from
PAG’s cation TPS, 6.6–6.9 ppm from HOST and PAG’s
anionic part, 0.7–2.6 ppm from the EAMA and main chain of
the polymer. The molar composition was calculated based on
the integral and proton numbers for the above corresponding
peaks. The molecular weight was determined by GPC with
THF or DMF as mobile phase. The results showed the
copolymer (10) had a Mw of 4500 with PDI 2.5, and the other
three terpolymers had similar Mw ranging from 3100–3800,
and PDI from 1.6–1.9. As for the thermostability, the PAG
bound polymers (Tdec. of 6a, 6b, 6c@, 6c@@ are 156, 153, 145
and 154 uC, respectively) are superior to the PAG blend
polymers (Tdec. of 10+4, 10+5@, 10+5@@ are 138, 131,
130 uC, respectively). The fluorine-free PAG polymers (Tdec. of
6b, 10+4 are 153, 138 uC, respectively) showed better stability
than fluorine-substituted PAG polymers (Tdec. of 6c, 10+5@,
10+5@@ are 145, 131, 130 uC, respectively). The glass transi-
tion temperature of copolymer (10) was 113 uC. The other
PAG bound polymers showed no obvious Tg, suggesting that
these polymers are probably quite rigid, resulting from the
restrictive motion of the bulky adamantly protecting group
and the bulky triphenylsulfonium moiety of the PAG in the
polymer chain. As reported previously for analogous rigid
polymers,20 no transitions were observed below the decom-
position temperature for the polymers in this study also.
For resist formulation, 3.3 g of polymer bound PAG resist
was dissolved in 50 g of cyclohexanone. The same formulation
condition was used for the polymer blend PAG resist. The
resist solutions were filtered through 0.2 mm filter, and spin-
coated (3000 rpm, 60 s) onto silicon wafers primed with a 20%
1,1,1,3,3,3-hexamethyldisilazane (HMDS)–80% propylene
glycol-1-monomethyl ether 2-acetate (PGMEA) solution. The
post apply bake was carried out at 100 uC for 90 seconds. The
thickness of the resists was determined to be in the range
of 110–130 nm. The exposed wafers were baked at 100 uC
for 90 s. The development was conducted in conventional
2.38 wt% TMAH for approximately 15 s and rinsed with
de-ionized water.
The line-edge roughness (3s LER) were measured according
to ITRS report and the guideline proposed by Yamaguchi and
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Fig. 4 Acid generation efficiency vs. exposure doses.
polymer bound PAG resist is more thermally stable than the
blend PAG resist.
In order to investigate the effect of the PAG bound or
blended to the polymers on the photoresist performance, the
acid generating efficiencies for the bound PAG and blend PAG
in photoresists were measured (see Fig. 4). It indicates that the
acid generation efficiencies for PAG blend polymers (24.5%,
25.0% for resists 10+4, 10+5, respectively) are higher than
those of the PAG bound polymers (6.8%, 15.2%, 17.0% for 6a,
6b, 6c, respectively) at an exposure dose of 150 mJ cm22 at
254 nm. On the other hand, the PAG (MBS-TPS, F4-MBS-TPS)
bound polymers (6b, 6c) showed higher efficiency than the VBS-
TPS bound polymer (6a). It also shows no obvious difference
between the fluorine substituted and non-fluorine PAGs.
In view of our previous research results on 193 nm
photoresists,11 which indicated the fluorine substituted PAG
bound polymers or blend resists have a higher photospeed and
better lithographic performance than fluorine-free PAG bound
polymers or blend polymers, we therefore investigated the
PAG F4-MBS-TPS bound polymer (6c@@) and F4-IBBS-
TPS blend polymer (10+5@@) for outgassing and EUV
lithography study.
Fig. 3 Thermogravimetric analysis curves of a) 6c@@ (HE-F4-MBS-
TPS) and b) 10+5@@ (HE + F4-IBBS-TPS). The weight loss (%) was
measured under identical experimental conditions over a temperature
range of 40 uC to 200 uC under N2.
In order to test their thermal stability, thermogravimetric
analysis was performed on the polymer bound PAG resist
and the corresponding blend PAG resist. TGA curves of
polymer bound PAG and polymer blend PAG resist are shown
in Fig. 3. The weight loss (%) was measured under identical
experimental conditions (i.e. temperature range between
40–200 uC). It was found that the polymer bound PAG resist
showed less weight loss (2.9%) than the polymer blend PAG
resist (6.5%) at 160 uC. These data demonstrate that the
The outgassing study is essential in order to perform expo-
sures in vacuum, without the use of a purge gas to eliminate
contaminants in the exposure chamber. Important design
criteria for EUV systems and EUV resists are the chemical
Table 2 Outgassing results for the photoresists HE-F4-MBS-TPS(6c@@) and HE + F4-IBBS-TPS (10+5@@)
Resist HE-F4-MBS-TPS(6c@@): Total = 1.67 6 1013
Toluene/RF
cts/molecule
Assume F = 1, outgassing conc.
for single wafer/molecules cm22
R.T./min
Peak area
Detected compd.
Ion (m/z)
2.875
9.197
10.205
15.660
15.866
469854
2626
4648
367322
9833
Benzene
Chlorobenzene
Unknown ketone
Unknown C11 ketone
Unknown adamantyl compd.
78
112, 77
55, 98, 42
162, 91, 105
135, 164
7.87 6 10210
7.87 6 10210
7.87 6 10210
7.87 6 10210
6.44 6 10210
9.17 6 1012
5.13 6 1010
9.07 6 1010
7.17 6 1012
2.35 6 1011
Resist HE + F4-IBBS-TPS (10+5@@): Total = 4.36 6 1012
Toluene/RF
cts/molecule
Assume F = 1, outgassing conc.
for single wafer/molecules cm22
R.T./min
Peak area
Detected compd.
Ion (m/z)
2.905
15.665
15.866
132890
88772
1307
Benzene
Unknown C11 ketone
Unknown adamantyl compd.
78
162, 91, 105
135, 164
7.87 6 10210
7.87 6 10210
6.44 6 10210
2.59 6 1012
1.73 6 1012
3.12 6 1010
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composition and quantity of outgassed material during and
after exposure.21,22 The outgassing results of these resists are
shown in Table 2. Ester type bulky protective groups such as
the adamantyl group have high activation energy, so their
deprotection reaction will take place mainly during the PEB
step. The outgassing concentrations for F4-MBS-TPS bound
resist and F4-IBBS-TPS blend resist are 1.67 6 1013, 4.36 6
1012, respectively, both are below 5 6 1013, which is within the
limits of the ITRS2005 specification for EUV lithography.1
To explore and delineate the imaging properties such as
photospeed and LER, the resists were exposed on the beam
line at Lawrence Berkeley National Laboratory. The resist
formulated with polymer bound F4-PAG sample showed
better lithographic performance than the blend PAG sample.
The top-down scanning electron micrographs of the polymer
bound PAG resist are depicted in Fig. 5a and b: resolved 45 nm
(1 : 1), 35 nm (1 : 2), 30 nm (1 : 3), 20 nm (1 : 4) patterns at a
dose of 43.5 mJ cm22. The corresponding elbow patterns are
depicted in Fig. 5c: resolved 50 nm (1 : 1) and 30 nm (1 : 2).
The resist formulated with polymer blend F4-PAG resist
(see Fig. 6a) showed resolved 50 nm (1 : 1), 45 nm (1 : 2), 35 nm
(1 : 3), 30 nm (1 : 4) at a dose of 24.7 mJ cm22, the
Fig. 5 (a) Top-down SEM images of 20–120 nm (L/S) patterns (dose: 43.5 mJ cm22) for polymer bound F4-PAG: HE-F4-MBS-TPS (6c@@). (b)
Top-down SEM images (L/S) patterns (dose: 43.5 mJ cm22) for polymer bound F4-PAG: HE-F4-MBS-TPS (6c@@). (c) Top-down SEM images of
elbow patterns (dose: 43.5 mJ cm22) for polymer bound F4-PAG: HE-F4-MBS-TPS (6c@@). L/S is the ratio of the line width to the spacing
between the lines.
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Fig. 6 (a) Top-down SEM images (L/S) patterns (dose: 24.7 mJ cm22) for polymer blend F4-PAG: HE + F4-IBBS-TPS (10+5@@). (b) Top-down
SEM images of elbow patterns (dose: 24.7 mJ cm22) for polymer blend F4-PAG: HE + F4-IBBS-TPS (10+5@@).
corresponding elbow patterns showed resolved 60 nm (1 : 1)
and 40 nm (1 : 2) patterns and unresolved 50 nm (1 : 1), 35 nm
(1 : 2) patterns (Fig. 6b).
bound polymers was superior to PAG blend polymers.
Although the acid generating efficiency of PAG blend
polymers was higher than that of the PAG bound polymers,
higher resolution was observed in the PAG bound polymer.
This was indicated by the fluorine PAG bound polymer resist
HE-F4-MBS-TPS (6c) giving 45 nm (1 : 1), 35 nm (1 : 2),
30 nm (1 : 3), 20 nm (1 : 4) L/S, and 50 nm (1 : 1), 35 nm (1 : 2)
elbow patterns as well as the LER which is comparable
with conventional EUV resist LERs of 6–14 nm3,24–26
Additional studies to optimize photospeed, to investigate
the correlation of reactivity ratios and composition hetero-
geneity of the polymer resist are under way. The synthesis
of anionic PAGs with faster photospeed is being conducted,
which will be reported subsequently, along with acid diffusion
studies.
Among the issues of post-optical lithography, line edge
roughness (LER) or line width roughness (LWR) in the CA
resists is the most critical problem. The cause of LER is a
complex combination of the exposure beam image, process
factors, and resist material.4 The LERs (3s) measured on the
45 nm EUV pattern features for polymer bound F4-PAG
and polymer blend F4-PAG were 11.0 nm and 12.1 nm,
respectively.23 These LER should show significant improve-
ment on the addition of base in the resist formulations. The
PAG blend polymer HE + F4-IBBS-TPS showed faster
photospeed than the corresponding PAG bound polymer
(HE-F4-MBS-TPS). Although the bound PAG (F4-MBS-
TPS) and blend PAG (F4-IBBS-TPS) have very similar
structures, the lower efficiency for the PAG bound polymer
appears to be due to a decrease in acid generating efficiency of
the PAG. These results indicate that the PAG bound resist
improved the resolution.
Acknowledgements
KEG acknowledges support from INTEL Corp. The authors
would also like to thank Dr B. Hoef and Dr G. Jones at
Lawrence Berkeley Lab., USA, for EUV exposure; Dr Q.
Leonard at the Center for NanoTechnology at the University
of Wisconsin–Madison, USA for outgassing testing; Dr H.
Cao at INTEL Corp. for outgassing and EUV testing; and
Dr Cliff L. Henderson, and C-T, Lee at Georgia Institute of
4. Conclusions
A new series of anionic PAGs bound or blend polymers were
prepared and characterized. The thermostability of PAG
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13 N. N. Matsuzawa, H. Oizumi, S. Mori, S. Irie, E. Yano, S. Okazaki
and A. Ishitani, Microelectron. Eng., 2000, 53, 671.
14 H. Wu and K. E. Gonsalves, Adv. Funct. Mater., 2001, 11, 271.
15 H. Wu and K. E. Gonsalves, Adv. Mater., 2001, 13, 195.
16 M. Thiyagarajan, K. Dean and K. E. Gonsalves, J. Photopolym.
Sci. Technol., 2005, 18, 737.
Technology, USA for LER measurements, as well as AZ
Electronic Materials Ltd for supplying monomers.
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