Metal-catalyzed addition polymers for 157 nm resist applications. Synthesis and polymerization of partially fluorinated, ester-functionalized tricyclo [4.2.1.02,5]non-7-enes

Article abstract of DOI:10.1021/ma021131i

Fluorinated tricyclo[4.2.1.0^2,5]non-7-ene-3-carboxylic acid esters are shown to undergo metal-catalyzed addition polymerization. The resulting homopolymers are transparent at 157 nm and demonstrate the utility of these monomers in development of photoresists for 157 nm lithography. Fluorinated tricyclononene (TCN) structures with ester substituents exhibit up to 3 orders of magnitude more transparency at 157 nm than conventional ester-functionalized norbornene structures as determined by gas-phase vacuum-ultraviolet spectroscopy and variable angle spectroscopic ellipsometry. Unlike their fluorinated norbornene counterparts, the fluorinated, ester-functionalized TCN monomers successfully undergo transition-metal-catalyzed addition polymerization to produce polymers with high glass transition temperatures and the etch resistance required for photolithographic resist materials applications. The potential use of fluorinated TCN structures for 157 nm photoresists is demonstrated through the synthesis and characterization of TCN monomers and polymers.

Full text of DOI:10.1021/ma021131i

1
534
Macromolecules 2003, 36, 1534-1542
Metal-Catalyzed Addition Polymers for 157 nm Resist Applications.
Synthesis and Polymerization of Partially Fluorinated,
2
,5
Ester-Functionalized Tricyclo[4.2.1.0 ]non-7-enes
Da n iel P . Sa n d er s, Er ic F . Con n or , a n d Rober t H. Gr u bbs*
Arnold and Mabel Beckman Laboratories of Chemical Synthesis, Division of Chemistry and Chemical
Engineering, California Institute of Technology, Pasadena, California 91125
Ra ym on d J . Hu n g, Br ia n P . Osbor n , Ta k a sh i Ch iba , Scott A. Ma cDon a ld , a n d
C. Gr a n t Willson
Departments of Chemistry and Chemical Engineering, University of Texas, Austin, Texas 78712
Will Con ley
International SEMATECH, 2706 Montopolis Drive, Austin, Texas 78741-6499
Received J uly 16, 2002; Revised Manuscript Received November 4, 2002
ABSTRACT: Fluorinated tricyclo[4.2.1.02,5]non-7-ene-3-carboxylic acid esters are shown to undergo metal-
catalyzed addition polymerization. The resulting homopolymers are transparent at 157 nm and
demonstrate the utility of these monomers in development of photoresists for 157 nm lithography.
Fluorinated tricyclononene (TCN) structures with ester substituents exhibit up to 3 orders of magnitude
more transparency at 157 nm than conventional ester-functionalized norbornene structures as determined
by gas-phase vacuum-ultraviolet spectroscopy and variable angle spectroscopic ellipsometry. Unlike their
fluorinated norbornene counterparts, the fluorinated, ester-functionalized TCN monomers successfully
undergo transition-metal-catalyzed addition polymerization to produce polymers with high glass transition
temperatures and the etch resistance required for photolithographic resist materials applications. The
potential use of fluorinated TCN structures for 157 nm photoresists is demonstrated through the synthesis
and characterization of TCN monomers and polymers.
In tr od u ction
Specialized, alicyclic fluoropolymers are the focus of
intense research as the semiconductor industry at-
tempts to develop the functional photoresists required
to enable the timely introduction of 157 nm optical
lithography, as outlined in the International Technical
1
,2
F igu r e 1. Norbornene-type monomers for lithography ap-
plications.
Roadmap for Semiconductors (ITRS) timeline.
A
prominent concern for 157 nm lithography is the feasi-
bility of employing a practical resist thickness (>200
nm), which requires a photoresist with a low absorption
5
Fortunately, through computational and experi-
6
3
mental efforts, it was discovered that the incorporation
coefficient. To fulfill this requirement while retaining
of fluorinated substituents dramatically reduces the
absorption of various structures at 157 nm. For ex-
ample, the hexafluoroisopropyl alcohol functionalized
norbornene (NBHFA, 2) was found to be highly trans-
optimal imaging properties, a critical balance of several,
often competing, material properties, such as transpar-
ency, etch resistance, glass transition temperature,
thermal stability, and dissolution behavior, must be
achieved. Carbon-rich and heteroatom-deficient nor-
bornene structures, such as the norbornene tert-butyl
ester (NTBE, 1, Figure 1), were developed for use at 193
nm, proving to be suitable replacements for the heavily
absorbing, etch-resistant aromatics used in previous
generations of photoresists. Unfortunately, while the
majority of the polar functionalities (esters, carbonates,
alcohols, and anhydrides) used in resist chemistry are
transparent at 193 nm, the absorption coefficients of
carbon-carbon double bonds, carbon-oxygen single
bonds, carbon-oxygen double bonds, and even some
carbon-hydrogen bonds are all too high at 157 nm for
these functionalities to be useful.4
6
parent. In addition, because of the inductive effects of
the two trifluoromethyl groups, the acidity of the this
type of fluorinated alcohol is similar to that of phenol,7
allowing this polar monomer to replace the highly
absorbing phenolic structures used in previous genera-
tions of resists. This discovery has renewed interest in
resists based on metal-catalyzed addition polymers of
functionalized norbornenes, originally developed for 193
8
nm, as promising candidates for 157 nm photoresists.
Protection of the hexafluoroisopropyl alcohol functional-
ity of 2 with t-BOC groups has produced monomers
6
suitable for resist development. Efforts to expand the
scope of 157 nm resists to include those based on the
more thermally stable tert-butyl and tetrahydropyranyl
esters have achieved only partial success due to the
high absorbance of ester-functionalized monomers such
as 1 at 157 nm. Fortunately, the incorporation of an
*
To whom correspondence should be addressed: e-mail
rhg@caltech.edu.
1
0.1021/ma021131i CCC: $25.00 © 2003 American Chemical Society
Published on Web 02/11/2003

Macromolecules, Vol. 36, No. 5, 2003
Fluorinated Tricyclo[4.2.1.02,5]non-7-enes 1535
most reports of TCN chemistry to date have investigated
1
1
the regio- and stereospecificity and concertedness of
1
7
the cyclization reaction, the value of photoresist
materials prompted us to consider these compounds for
materials development. In this paper, we report the
development of partially fluorinated tricyclo[4.2.1.02 ]-
non-7-ene-3-carboxylic acid esters, such as monomer 4,
as transparent, ester-functionalized norbornene-like
monomers useful for incorporation into addition-type
photoresist polymers.
,5
F igu r e 2. Cyclizations of quadricyclane with electron-
deficient olefins (EWG ) electron-withdrawing group).
R-trifluoromethyl group was found to significantly re-
duce the absorption of these esters.6 Similarly, the
absorbance of norbornane structures could be reduced
by the incorporation of judiciously positioned fluorine
Exp er im en ta l Section
Ma ter ia ls. All manipulations and polymerizations were
carried out in a N -filled drybox or using standard Schlenk
2
6
substituents. The fluorinated monomer 3 was subse-
techniques. Argon was purified by passage through columns
of BASF RS-11 (Chemalog) and Linde 4-Å18 molecular sieves.
Dichloromethane was rigorously degassed in 18 L reservoirs
and passed through two sequential purification columns
consisting of activated alumina. All starting materials were
procured from Aldrich except methyl 2-(trifluoromethyl)-3,3,3-
trifluoropropenoate (Synquest) and (2-trifluoromethyl)acrylic
acid (Honeywell) and were used as received unless noted
otherwise. 2,2-Difluoronorbornane was synthesized according
quently designed as an ideal replacement for the highly
absorbing norbornene 1. Unfortunately, norbornene
monomers of this type with geminal electron-withdraw-
ing ester and trifluoromethyl substituents were found
to be unsuitable for polymerization with common nickel
9
and palladium catalysts. The addition of an R-trifluo-
romethyl group in 3, while addressing the transparency
problem, hinders the polymerization. Thus, alternative
approaches toward a polymerizeable monomer incorpo-
rating these transparent esters were investigated.
6a
to the literature procedures. All liquid reagents used for
vacuum-UV measurements were distilled from appropriate
drying agents, thoroughly degassed by freeze, pump, thaw
cycles and sealed in glass ampules under vacuum.
Recently, Grubbs et al. reported that, in the copolym-
erization of ethylene and functionalized norbornene-type
monomers to produce functionalized polyethylene, high
incorporation (up to 31 mol %) of polar functionalities
could be achieved through the use of functionalized
Meth od s. Nuclear magnetic resonance (NMR) spectra were
obtained using either a Bruker AMX300, Varian Unity Plus
1
13
3
7
00, or a Varian Gemini 300 spectrometer ( H, 300 MHz; C,
5 MHz; 19F, 282 MHz). Select NMR spectra for compound 10
were obtained using a Varian 500 MHz spectrometer ( C, 125
MHz; F, 470 MHz). Shifts for NMR spectra are reported in
3
ppm relative to TMS (for F, CFCl ) or to the chemical shift
13
tricyclo[4.2.1.0 ]non-7-ene (TCN) monomers.10 The com-
bination of reduced steric interference due to the 100%
exo configuration of the cyclobutane ring (moving the
geminal electron-withdrawing functionalities an ad-
ditional carbon away from the double bond) and in-
creased ring strain improved the reactivity of the
tricyclononene monomers toward metal-catalyzed ad-
dition polymerization. The use of TCN chemistry in
photoresists is a potential solution to the polymerization
difficulties of the partially fluorinated norbornenes
mentioned previously.
2,5
19
19
of the residual proteo solvent. Infrared spectra were recorded
on either a Nicolet Avatar 360 or a Perkin-Elmer Paragon 1000
IR spectrometer. Mass spectra were measured on a Finnigan
n
MAT TSQ-700 spectrometer. Molecular weights (M ) and
polydispersity indices (PDI) were measured from THF solu-
tions by size exclusion chromatography (SEC) using a Viscotek
gel permeation chromatograph (GPC) equipped with a set of
two 5 mm cross-linked polystyrene columns (linear mix and
1
00 Å) from American Polymer Standards and are reported
relative to polystyrene standards. Polymers containing acidic
functional groups were pretreated with either diazomethane
or iodomethane/DBU before GPC measurement, unless noted
otherwise. Select samples were analyzed by SEC using a GPC
apparatus equipped with two PLgel 5 µm mixed-C columns
Tricyclo[4.2.1.02,5]non-7-enes (TCNs) are formed from
the [2σ + 2 σ + 2π] cycloaddition of quadricyclane
2
,7 4,6
(
tetracyclo[3.2.0.0 .0 ]heptane) with electron-deficient
dieneophiles, such as alkenes, alkynes, and azo com-
(Polymer Labs) connected in series with a DAWN EOS
pounds (Figure 2).1
1,12
The cycloadditions proceed readily
multiangle laser light scattering (MALLS) detector and an
Optilab DSP digital refractometer (both from Wyatt Technol-
ogy). No calibration standards were used and dn/dc values
were obtained for each injection by assuming 100% mass
elution from the columns. Differential scanning calorimetry
(DSC) measurements and thermal gravimetric analysis (TGA)
were performed on a Perkin-Elmer Series 7 thermal analysis
system. Gas chromatographs were recorded on a Hewlett-
Packard 5890 Series II with an HP-5 (cross-linked 5% PH ME
siloxane) capillary column and flame ionization detector (FID).
Va cu u m -UV Sp ectr oscop y. Gas-phase VUV measure-
ments were made on an Acton CAMS-507 spectrophotometer
fitted with a custom-made gas cell attachment. The details of
at moderate temperature with electron-deficient olefins
to produce norbornene-like structures with a fused
cyclobutane ring in the exo configuration. While the
allowed thermal homo-Diels-Alder [2π + 2π + 2π]
reaction between norbornadiene and electron-deficient
olefins can be catalyzed by nickel and cobalt species14
to produce deltacyclanes, in certain cases metal-
catalyzed [2π + 2π] cycloadditions can also occur to
produce a mixture of tricyclononenes in which the
13
cyclobutane ring appears be in either the exo or the endo
configuration.1
4b,15
Unfortunately, the tri- and tetrasub-
1
6
stituted double bonds of the resulting tricyclononenes,
the cell design and implementation have been described
coupled with the complex mixture of exo and endo
isomers, renders this route unattractive for the produc-
tion of valuable monomers. At present, the quadricy-
clane pathway is the only viable synthetic route toward
TCN monomers suitable for metal-catalyzed addition
polymerization.
previously.19 VUV spectra of polymer films were calculated
from measurements made with a J .A. Woollam VU301 variable
angle spectroscopic ellipsometer (VASE) and/or measured with
the Acton CAMS-507 spectrophotometer. The films were cast
on either silicon wafers (VASE) or calcium fluoride disks
(Acton) from solutions in propylene glycol methyl ether acetate
(
PGMEA) or cyclohexanone and baked at 100-130 °C for at
The wide variety of electron-withdrawing groups
nitriles, anhydrides, esters, etc.) able to undergo cy-
least 5 min prior to analysis. All absorbance data reported are
in base 10.
(
clizations with quadricyclane allows TCNs to retain the
versatility of established norbornene chemistry. While
Gen er al Syn th esis P r ocedu r e for Tr icyclon on en e Com -
p ou n d s. One equivalent of tetracyclo[3.2.0.02 .0 ]heptane
,7
4,6

1
536 Sanders et al.
Macromolecules, Vol. 36, No. 5, 2003
(
quadricyclane) and 1-3 equiv of acrylate were placed in a
1.45 (s, 9H, C(CH
3
)
3
, anti), 1.40 (d, 3H, -CH
, anti). 13C NMR (CDCl
,
3
3
, syn), 1.36-1.18
thick-walled Schlenk tube. The components were degassed,
and the flask was sealed under an atmosphere of argon. For
reactions in which radical polymerization of the olefin occurs
readily, small amounts (0.001 equiv) of suitable radical inhibi-
tors, such as hydroquinone, were added. The reaction mixture
was heated to 96 °C for 24-72 h. The tricyclononene product
was separated from the residual quadricyclane starting mate-
rial and norbornadiene and polymeric byproducts by Kugelrohr
vacuum distillation to yield colorless liquids (or solids).
(4H, syn + anti), 1.16 (d, 3H, -CH
3
75 MHz, ppm): δ 178.25 (COOtBu, anti), 176.43 (COOtBu,
syn), 136.37 (olefin C, anti), 136.23 (olefin C, syn), 135.71
(olefin C, anti), 135.48 (olefin C, syn), 79.94 (C(CH
79.79 (C(CH , anti), 48.91 (CH, C-2, syn), 44.63 (CH, C-6,
syn), 44.30 (CH, C-2, anti), 43.53 (CH, C-6, anti), 42.99 (CH,
C-1, syn), 41.88 (CH , C-9, anti), 41.52 (CH, C-1, anti), 41.35
(quat. C, C-3, syn), 41.07 (quat. C, C-3, anti), 40.65 (CH , C-9,
syn), 33.09 (CH, C-5, anti), 31.36 (CH , C-4, anti), 31.08 (CH
C-4, syn), 30.48 (CH, C-5, syn), 28.37 (CH , syn), 28.32
(C(CH , syn), 28.17 (C(CH , anti), 16.91 (CH , anti). IR
3 3
) , syn),
3 3
)
2
2
2
2
,
2
,5
Tr icyclo[4.2.1.0 ]n on -7-en e-3-car boxylic Acid (5). 3-Cy-
3
2
,5
ano-tricyclo[4.2.1.0 ]non-7-ene (prepared by the cycloaddition
3
)
3
3
)
3
3
2
0
-1
of quadricyclane with acrylonitrile ) (23.6 g, 0.162 mol) was
dissolved into 40 mL of ethylene glycol and added to a 250
mL round-bottom flask charged with 1.5 equiv of potassium
(KBr, cm ): 3057 (alkene), 2972, 1720 (CdO), 1470, 1456,
1391, 1367, 1313, 1281, 1256, 1227, 1131, 849, 757, 703.
+
HRMS-EI (m/z): [M + H] calcd for C15
found: 235.1698.
23 2
H O : 235.1698;
hydroxide (13.7 g, 0.244 mol) in 25 mL of H
biphasic system was stirred vigorously while refluxing at 140
C for 24 h. The resulting mixture was acidified with 20 mL
of HCl (37% solution in H O). The product was extracted into
ethyl ether and dried over MgSO . Removal of the solvent in
2
O. The resulting
Met h yl 3-(Tr iflu or om et h yl)t r icyclo[4.2.1.02,5]n on -7-
en e-3-ca r boxyla te (8). Quadricyclane (1.5 equiv, 4.25 g, 0.046
mol) and methyl (2-trifluoromethyl)acrylate6a (1 equiv, 4.55
g, 0.30 mol) were reacted according to the general procedure
mentioned above to produce, after Kugelrohr vacuum distil-
°
2
4
vacuo produced a viscous, colorless oil, which crystallized
overnight into a white crystalline material. Removal of re-
sidual ethylene glycol was achieved via Kugelrohr distillation
lation, 6.78 g (0.028 mol) of colorless liquid. Yield: 94%. Isomer
composition: 32% syn, 68% anti. H NMR (CDCl
1
3
, 300 MHz,
(
80 °C, 60 mTorr) to produce 16.4 g (0.098 mol) of a viscous,
ppm): 6.1-5.9 (m, 4H, H-7 + H-8, syn + anti), 3.80 (s, 3H,
colorless oil, which crystallized overnight into a white crystal-
COOCH , syn), 3.78 (s, 3H, COOCH , anti), 3.06 (s, 1H, H-1,
3
3
line material. Yield: 61%. Isomer composition: >98% anti.
syn), 2.99 (s, 1H, H-1, anti), 2.82 (s, 1H, H-6, syn), 2.74 (s, 1H,
1
Anti isomer: H NMR (CDCl
3
, 300 MHz, ppm): δ 11.27 (br s,
H-6, anti), 2.68 (ddd, J ) 3.0, 7.5, 13.2 Hz, 1H, anti), 2.5-1.9
COOH), 6.01 (dd, J ) 2.7, 6.0 Hz, 1H, H-7), 5.96 (dd, J ) 2.7,
(7 H), 1.48-1.24 (4 H). 13C NMR (CDCl
, 75 MHz, ppm): δ
3
6
1
.0 Hz, 1H, H-8), 2.78 (s, 1H, H-1), 2.70 (s, 1H, H-6), 2.50 (m,
H, H-3), 2.40 (m, 1H, H-4), 2.23 (m, 1H, H-2), 2.05 (m, 1H,
171.16 (d, J ) 2.9 Hz, COOMe, syn), 168.85 (d, J ) 2.4 Hz,
COOMe, anti), 136.74 (olefin C, anti), 136.62 (olefin C, syn),
135.24 (olefin C, syn), 135.06 (olefin C, anti), 126.32 (q, J )
H-5), 1.67 (d, J ) 8.7 Hz, 1H, H-9 anti), 1.62 (m, 1H, H-4),
1
3
1
.37 (dt, J ) 1.7, 9.6 Hz, 1H, H-9 syn). C NMR (CDCl
3
, 75
280 Hz, CF
(COOCH3, syn), 52.81 (COOCH
3
, anti), 125.16 (q, J ) 281 Hz, CF
3
, syn), 53.30
, anti), 49.56 (q, J ) 28.6 Hz,
MHz, ppm): δ 182.91 (COOH), 136.07 (CH, C-7), 134.68 (CH,
C-8), 44.31 (CH, C-6), 44.13 (CH, C-1), 40.72 (CH, C-2), 40.48
3
quat. C, C-3, syn), 49.40 (q, J ) 26.5 Hz, quat. C, C-3, anti),
44.50 (CH, C-6, anti) 44.18 (CH, C-6, syn), 44.15(CH, C-2, syn),
42.86 (CH, C-1, syn), 42.50 (CH, C-1, anti), 41.95 (m, J ) 2.0
(
CH
2 2
, C-9), 37.55 (CH, C-3), 34.47 (CH, C-5), 24.02 (CH , C-4).
-
1
IR (KBr, Nujol, cm ): 3050, 1700, 1464, 1417, 1267, 1240,
1
1
+
211, 927, 692. HRMS-EI (m/z): [M + H] calcd for C10
H
13
O
2
:
Hz, CH, C-2 anti), 41.14 (m, CH
syn), 32.98 (CH, C-5, syn), 32.83 (CH, C-5, anti), 26.07 (d, J )
2.4 Hz, CH , C-4, anti), 25.93 (d, J ) 1.9 Hz, CH , C-4, syn).
F NMR (CDCl , 282 MHz, ppm) (referenced to external C
standard at -166.717 ppm): δ -66.25 (s, 3F, -CF , syn), δ
2 2
, C-9, anti), 40.71 (CH , C-9,
65.0916; found: 165.0903.
ter t-Bu t yl Tr icyclo[4.2.1.02,5]n on -7-en e-3-ca r b oxyla t e
2
2
1
9
(
6). Quadricyclane (15 mL, 14.7 g, 0.16 mol) and 4 equiv of
3
6 6
F
tert-butyl acrylate (92 mL, 80.7 g, 0.63 mol) were reacted
according to the general procedure mentioned above to pro-
duce, after Kugelrohr vacuum distillation, 28.0 g (0.13 mol) of
3
-1
-75.13 (s, 3F, -CF3, anti). IR (KBr, cm ): 3060 (alkene), 2970,
2892, 1742 (CdO), 1473, 1436, 1333, 1322, 1275, 1225, 1163,
1132, 1087, 712, 671. HRMS-EI (m/z): [M] calcd for
+
colorless liquid. Yield: 80%. Isomer composition: 57% syn, 43%
1
anti. H NMR (CDCl
3
, 300 MHz, ppm): δ 5.94 (m, 4H, H-7 +
12 14 3 2
C H F O : 246.0868; found: 246.0868.
(Tr ieth yla m in o)bor on Tr iflu or id e. To a cooled (dry ice/
2
1
H-8, syn + anti), 3.12 (ddd, J ) 7.8, 9.6, 11.1 Hz, 1H, H-3,
syn), 2.90 (s, 1H, H-1, syn), 2.70 (s, 1H, H-1, anti), 2.63 (s, 2H,
H-6, syn + anti), 2.34-2.05 (5H, syn + anti), 2.02-1.87 (2H,
H-5 syn + anti), 1.68 (dd, J ) 4.8, 7.8 Hz, 1H, H-4, syn), 1.65-
acetone) 250 mL round-bottom flask equipped with a stir bar
and addition funnel was added boron trifluoride diethyl
etherate (30 g, 211 mmol). Triethylamine (60 mL) was added
dropwise to the flask via an addition funnel. The formation of
white precipitate was immediately observed. After the addition
of triethylamine, the reaction was allowed to warm to room
temperature, and excess triethylamine was removed in vacuo.
The white residue was purified by vacuum fractional distil-
lation (85 °C/3 mmHg) to give a white solid (32.0 g, 91%), which
melted at approximately 25 °C. The compound was kept in
the refrigerator and used in the next step without further
purification.
1
(
)
.58 (2H, H-9 anti, syn + anti), 1.57-1.48 (1H, H-4, anti), 1.44
s, 9H, C(CH , syn), 1.43 (s, 9H, C(CH , anti), δ 1.29 (dt, J
1.5, 8.1 Hz, 1H, H-9 syn, anti), 1.17 (dt, J ) 1.5, 9.6 Hz, 1H,
3
)
3
3 3
)
1
3
H-9 syn, syn). C NMR (CDCl
3
, 75 MHz, ppm): δ 175.22
(
COOtBu, anti), δ 173.40 (COOtBu, syn), 136.07 (olefin C, syn),
1
35.81 (olefin C, anti), 135.13 (olefin C, syn), 134.61 (olefin C,
, syn), 79.77 (C(CH , anti), 44.92 (CH,
C-6, syn), 44.17 (CH, C-6, anti), 43.96 (CH, C-1, anti), 42.46
CH, C-1, syn), 40.57 (CH, C-2, anti), 40.41 (CH , C-9, anti),
0.36 (CH , C-9, syn), 40.14 (CH, C-2, syn), 38.48 (CH, C-3,
anti), 35.56 (CH, C-3, syn), 34.26 (CH, C-5, anti), 33.50 (CH,
C-5, syn), 28.30 (COOC(CH , syn), 28.18 (COOC(CH , anti),
, C-4, anti), 23.07 (CH , C-4, syn). IR (KBr, cm ):
anti), 80.03 (C(CH
3
)
3
3 3
)
(
4
2
2
Meth yl 3,3-Diflu or o-2-(tr iflu or om eth yl)acr ylate. A slight
2
2
modification of the literature procedure was used. To a 100
mL round-bottom flask equipped with a magnetic stir bar and
reflux condenser were added triethylaminoboron trifluoride
(32.0 g, 189 mmol) and methyl 2-(trifluoromethyl)-3,3,3-
trifluoropropionate (30.5 g, 145 mmol). The reaction mixture
was refluxed for 3 h and then cooled to room temperature. The
3
)
3
3 3
)
-
1
2
3
1
3.79 (CH
2
2
057 (alkene), 2972, 1723 (CdO), 1456, 1391, 1367, 1349, 1322,
256, 1228, 1215, 1154, 848, 754, 698. HRMS-EI (m/z): [M +
+
H] calcd for C14
21 2
H O : 221.1542; found: 221.1546.
2
,5
ter t-Bu tyl 3-(Meth yl)tr icyclo[4.2.1.0 ]n on -7-en e-3-ca r -
boxyla te (7). Quadricyclane (15 mL, 14.7 g, 0.16 mol) and 3
equiv of tert-butyl methacrylate (78 mL, 68.2 g, 0.48 mol) were
reacted according to the general procedure mentioned above
to produce, after Kugelrohr vacuum distillation, 3.0 g (0.013
residue was purified by vacuum transfer (bulb-to-bulb distil-
1
lation) to give a clear oil (19.8 g, 71%). H NMR (CDCl
3
, 300
OD, 282
), -59.1 (m, 3F, CF ),
). IR (NaCl, cm ): 2960, 1767 (CdO),
1710, 1439, 1372, 1152, 1081, 1040, 1024. HRMS-CI (m/z):
MHz, ppm): δ 3.84 (s, 3H, methyl). 19F NMR (CD
MHz, ppm): δ -58.5 (m, 1F, RCdCF
3
2
3
-
1
-59.5 (m, 1F, RCdCF
2
mol) of colorless liquid. Yield: 8%. Isomer composition: 55%
1
+
syn, 45% anti. H NMR (CDCl
4
3
, 300 MHz, ppm): δ 5.98 (m,
5 3 5 2
[M + H] calcd for C H F O : 191.0131; found: 191.014.
H, H-7 + 8, syn + anti), 2.95 (s, 1H, H-1, syn), 2.74 (s, 1H,
H-1, anti), 2.65 (s, 2H, H-6, syn + anti), 2.44 (m, 1H), 2.1-1.6
6H, syn + anti), 1.56-1.48 (m, 1H), 1.46 (s, 9H, C(CH , syn),
Methyl4,4-Difluoro-3-(trifluoromethyl)tricyclo-[4.2.1.02,5]-
n on -7-en e-3-ca r boxyla te (9). To a 300 mL Parr pressure
reactor equipped with a magnetic stir bar were added quad-
(
3 3
)

Macromolecules, Vol. 36, No. 5, 2003
Fluorinated Tricyclo[4.2.1.02,5]non-7-enes 1537
ricyclane (1.5 g, 16.3 mmol) and methyl 3,3-difluoro-2-(trif-
luoromethyl)acrylate (3.9 g, 20.4 mmol). The pressure vessel
was sealed, and the reaction mixture was stirred at 100 °C
for 72 h. After cooling to room temperature, the residue was
purified by fractional vacuum distillation (39-40 °C/0.30
mmHg) to yield a clear oil (1.0 g, 22%). In a subsequent
synthesis, it was found that if the reaction was allowed to sit
at room temperature for 14 days after the initial heating, the
bound 2,6-di-tert-butylpyridine (1 mg/mg catalyst). The reac-
tion mixture was stirred at room temperature for 96 h, then
filtered through a 0.45 µm PTFE syringe filter to remove the
polymer-bound base, concentrated in vacuo, and precipitated
into hexanes (100 mL). The crude polymer was dissolved in
ethyl acetate (50 mL) and stirred vigorously under a hydrogen
atmosphere overnight. The solution was allowed to sit, un-
stirred, for another hour, at which time a black solid (Pd)
aggregated and precipitated. The black solid was removed by
filtration through Celite. The filtrate was treated with acti-
vated carbon and stirred for 3 h. The activated carbon was
removed by filtration through Celite, and the resulting filtrate
isolated yield increased to 73%. Isomer composition: 49% syn,
1
5
2
1% anti. H NMR (CDCl
3
, 300 MHz, ppm): δ 6.27 (dd, J )
.7, 5.7 Hz, olefin H, 1H, anti), 6.05-6.15 (m, olefin H, 3H, 2
, 3H, anti), 3.86 (s, COOCH
H, syn), 3.53 (s, 1H, H-1, syn), 3.22 (2H, H-1, H-6, anti), 3.13
s, 1H, H-6, syn), 2.84-2.75 (m, 1H, H-5, anti), 2.75-2.6 (m,
H, H-5, syn), 2.39-2.31 (m, 1H, H-2, syn), 2.10 (d, J ) 10.2
Hz, 1H, H-2, anti), 1.50-1.30 (m, 4H, H-9 syn, H-9 anti,
syn + 1 anti), 3.87 (s, COOCH
3
3
,
3
(
1
was washed with saturated NaHCO
3
, water, and brine, dried
with MgSO , filtered, concentrated in vacuo at 50 °C, and
4
precipitated into hexanes. Filtration provided the product as
a white powder.
P oly(t er t -b u t ylb icyclo[2.2.1]h e p t -5-e n e -2-ca r b oxyl-
a te) (P oly-1). tert-Butyl bicyclo[2.2.1]hept-5-ene-2-carboxylate
(NBTBE, 1) was polymerized by the general procedure men-
1
3
syn+anti). C NMR (C
syn), 162.91 (COOMe, anti), 139.62 (olefin C, anti), 137.82
olefin C, syn), 136.93 (olefin C, syn), 136.77 (olefin C, anti),
23.97, (q, J ) 283 Hz, CF , syn), 123.68 (q, J ) 280 Hz, CF
anti), 116.72 (t, J ) 292 Hz, C-5), 114.09, (t, J ) 296 Hz, C-5),
6
D
6
, 75 MHz, ppm): 165.11 (COOMe,
(
1
3
3
,
tioned previously ([M]/[C] ) 10:1) to produce a 60% yield of
1
white polymeric powder. H NMR (acetone-d
6
, 300 MHz,
). IR
(KBr, cm ): 2971, 2879, 2571, 1724 (CdO), 1455, 1392, 1367,
1290, 1151, 1049, 886, 846, 660. GPC: M ) 5380; PDI ) 1.79.
5
1
4
8
4
3.32 (COOCH
3
, anti), 52.64 (COOCH
3
, syn), 50.70 (dd, J )
3 3
ppm): δ 3.0-1.0 (m, aliphatic), 1.40 (br s, COOC(CH )
-1
9.2, 26 Hz, CH, C-5, anti), 50.36 (t, J ) 23 Hz, CH, C-5, syn),
3.71 (CH, C-1, anti), 43.26 (CH, C-1, syn), 43.11 (dd, J ) 4.4,
n
-
1
.2 Hz, CH
2
, C-9, anti), 42.82 (d, J ) 6.6 Hz, CH
2
, C-9, syn),
A157 ) 6.02 µm
.
2.08 (CH, C-6, anti), 41.29 (t, J ) 2.3 Hz, CH, C-6, syn), 37.21
P oly(3-(b icyclo[2.2.1]h ep t -5-en -2-yl)-1,1,1-t r iflu or o-2-
(
dd, J ) 4.9, 12 Hz, CH, C-2, anti), 36.90 (m, CH, C-2, syn).
(tr iflu or om eth yl)p r op a n -2-ol) (P oly-2). 3-(Bicyclo[2.2.1]-
hept-5-en-2-yl)-1,1,1-trifluoro-2-(trifluoromethyl)propan-2-ol (NB-
HFA, 2)6a was polymerized by the general procedure mentioned
previously ([M]/[C] ) 10:1) to produce a 55% yield of white
1
9
F NMR (acetone, 282 MHz, ppm): δ -61.67 (d, J ) 6.7 Hz,
3
(
1
-
3
8
F, CF
3
, anti), -68.36 (d, J ) 2.0 Hz, 3F, CF , syn), -85.70
3
dm, J ) 211 Hz, 1F, F-4 syn, anti), -97.15 (dm, J ) 217 Hz,
F, F-4 anti, syn), -106.87 (d, J ) 217 Hz, 1F, F-4 syn, syn),
113.94 (d, J ) 211 Hz, 1F, F-4 anti, anti). IR (NaCl, cm-1):
058 (alkene), 2991, 2909, 1752 (CdO), 1429, 1317, 1219, 1045,
1
powdery polymer. H NMR (DMSO-d , 300 MHz, ppm): δ 7.6
6
19
(br s, OH), 2.80-0.50 (br m, aliphatic). F NMR (CD OD, 282
3
-
1
MHz, ppm): δ -75.0 to -77.0. IR (KBr, cm ): 3600, 3471,
+
97, 794, 697. HRMS-CI (m/z): [M
: 283.0757; found: 283.0755.
,4-Diflu or o-3-(tr iflu or om eth yl)tr icyclo-[4.2.1.02,5]n on -
-en e-3-ca r boxylic Acid (10). Hydrolysis of 9 with KOH and
+
H] calcd for
2954, 2881, 1453, 1214, 1145, 1025, 714. GPC: M ) 3860;
n
-
1
C
12
H
12
F
5
O
2
PDI ) 2.11. A157 ) 1.15 µm .
2,5
4
P oly(ter t-bu tyltr icyclo[4.2.1.0 ]n on -7-en e-3-ca r boxy-
la te) (P oly-6). tert-Butyl tricyclo[4.2.1.02 ]non-7-ene-3-car-
boxylate was polymerized by the general procedure mentioned
previously ([M]/[C] ) 50:1) to produce a white polymeric
,5
7
water under standard conditions produced the carboxylic acid.
One of the isomers selectively crystallized from solution and
1
was determined to be the syn isomer by X-ray crystallography.
powder. H NMR (CD Cl , 300 MHz, ppm): δ 3.3-2,9 (br m,
aliphatic), 2.8-1.9 (br m, aliphatic), 1.9-1.0 (br m, aliphatic),
1.4-1.2 (br s, COOC(CH) ). SEC (GPC-MALLS): M ) 18 800,
2
2
1
Syn isomer: H NMR (CDCl
3
, 300 MHz, ppm): δ 9.6-8.4 (br
s, 1H, COOH), 6.16 (m, 2H, H-7 + H-8), 3.50 (s, 1H, H-1), 3.16
3
n
(
1
s, 1H, H-6), 2.69 (m, J ) 4.2 Hz, 1H, H-5), 2.35 (m, 1H, H-2),
PDI ) 2.01.
1
3
P oly(m eth yl 3-(tr iflu or om eth yl)tr icyclo[4.2.1.02,5]n on -
7-en e-3-ca r boxyla te) (P oly-8). Methyl 3-(trifluoromethyl)-
tricyclo[4.2.1.02 ]non-7-ene-3-carboxylate was polymerized by
the general procedure mentioned previously ([M]/[C] ) 50:1)
3
.45 (s, 2H, H-9 syn, H-9 anti). C NMR (CDCl , 125 MHz,
ppm): δ 167.63 (COOH), 137.94 (C-8), 137.082 (C-7), 122.93
,5
(
q, J ) 282 Hz, CF ), 116.08 (t, J ) 290 Hz, C-4), 59.5 (quat
3
C, C-3), 50.25 (t, J ) 23 Hz, CH, C-5), 43.04 (CH, C-1), 42.80
1
(
(
d, J ) 6.4 Hz, CH
2
, C-9), 41.25 (t, J ) 1.8 Hz, CH, C-6), 36.77
m, CH, C-2). F NMR (CDCl , 470 MHz, ppm): δ -68.94 (dd,
), -97.81 (dm, J ) 217 Hz, 1F, F-4
anti), -107.95 (d, J ) 217 Hz, 1F, F-4 syn). HRMS-CI (m/z):
to produce a 79% yield of white polymeric powder. H NMR
1
9
3
(CD Cl , 300 MHz, ppm): δ 4.20-3.30 (br s, COOCH ), 0.50-
2
2
3
-
1
J ) 2.4, 17.0 Hz, 3F, CF
3
3.20 (br m, aliphatic). A1 ) 3.79 µm . SEC (GPC): M )
57
n
66 300, PDI ) 2.11
+
[
M + H] calcd for C11
H
10
F
5
O
2
: 269.0601; found: 269.0589.
P oly(m eth yl 4,4-d iflu or o-3-(tr iflu or om eth yl)tr icyclo-
Gen er a l Hyd r ogen a tion P r oced u r e. Norbornene or tri-
[4.2.1.02,5]n on -7-en e-3-ca r boxyla te (P oly-9). Methyl 4,4-
cyclononene monomer (5.86 mmol) was dissolved in 16 mL of
ethyl acetate in a 250 mL Parr bomb (Parr Instrument Co.,
MAWP 3000 psi at 350 °C). Palladium (10% on carbon, 0.015
g) was added to the bomb, which was pressurized to 50 psi
difluoro-3-(trifluoromethyl)tricyclo-[4.2.1.02,5]non-7-ene-3-car-
boxylate was polymerized by the general procedure mentioned
previously ([M]/[C] ) 10:1) to produce a 50% yield of white
polymeric powder. A1 ) 2.86 µm-1. SEC (GPC): M ) 7200,
57
n
with H
2
. The reaction mixture was stirred overnight at room
PDI ) 2.58.
temperature, the catalyst was removed with a 0.45 µm PTFE
syringe filter, and the solvent was removed by rotary evapora-
tion to yield a clear oil.
Resu lts a n d Discu ssion
Syn th esis of TCN Mon om er s A series of tricy-
clononene compounds (5-9, Table 1) were synthesized
from quadricyclane and the appropriate olefin as shown
in Scheme 1. The numbering system and nomenclature
used are shown in Figure 2 and Table 1, respectively.
The methylene bridge (C9) hydrogens will be referred
to as either syn or anti to the C(7)-C(8) olefin. The most
important substituent (nitrile or ester) at C(3) on the
cyclobutane ring will be referred to as being syn or anti
to the C(1)-C(2) bond, to avoid confusion with the exo
notation used to describe the cyclobutane ring fusion.
Since the majority of TCN compounds reported in the
Gen er a l P olym er iza tion P r oced u r e. To a 20 mL vial
equipped with a stir bar were added allyl palladium chloride
dimer (13.0 mg, 0.032 mmol) and silver hexafluoroantimonate
(28 mg, 0.064 mmol) in a drybox. Dichloromethane (5 mL) was
added, and the mixture was stirred at room temperature for
2
0 min. The mixture was filtered through a 0.45 µm PTFE
syringe filter into a 25 mL round-bottom flask containing a
solution of tricyclononene monomer (3.25 mmol, [M]/[C] ) 50:
1
) in dichloromethane (10 mL). For resist evaluation, higher
catalyst loadings ([M]/[C] ) 10) were used to ensure only low
molecular weight polymer (<10 000 g/mol) was formed. For
monomers with tert-butyl ester functionalities, the resulting
solution was stirred for 10 min at room temperature and then
transferred to a 25 mL round-bottom flask containing polymer-
1
1
literature were made from symmetrical 1,1- or 1,2-

1
538 Sanders et al.
Macromolecules, Vol. 36, No. 5, 2003
Ta ble 1. Selectivity in TCN Mon om er Syn th esis
Ta ble 2. Com p a r ison of Cyclop en ta d ien e a n d
Qu a d r icycla n e Cycloa d d ition s
tecting groups are required for use in imageable pho-
toresists, the more synthetically and commercially
accessible methyl esters of the fluorinated acrylates
were employed in this initial study.
The nitrile-functionalized TCN monomer was synthe-
sized by the cycloaddition of quadricyclane and acry-
2
0
lonitrile, using the procedure of Noyori, to produce
2
,5
3
-cyano-tricyclo[4.2.1.0 ]non-7-ene with a 2:1 syn:anti
ratio and 100% exo cyclobutane ring fusion. Subsequent
base-catalyzed hydrolysis of the nitrile afforded the
carboxylic acid (5) with a syn:anti ratio of approximately
2
:98. During the hydrolysis, epimerization around the
C(3) position converts the syn isomer into the more
stable anti isomer, consistent with the results of Tabushi
et al.
Sch em e 1. Syn th esis of TCN Mon om er s, Mod el
Com p ou n d s, a n d P olym er s
1
1e
regarding the base-catalyzed isomerization of
cis and trans diester and dinitrile-substituted tricy-
clononenes.
Cyclization of quadricyclane with acrylonitrile or tert-
butyl acrylate produced high yields (80%+ with respect
to quadricyclane) of TCN products with a preference for
the syn product. While this syn structure is formed via
a transition state with the maximal orbital overlap on
C(2) and C(4) of quadricyclane as is the case in Diels-
Alder reactions, the role of electrostatic effects or
intermolecular attractive forces remains unknown. The
predominant byproducts of the reaction are norborna-
diene formed by slow isomerization of quadricyclane
under the reaction conditions and acrylate or acryloni-
2
3
trile homopolymer.
tert-Butyl methacrylate and methacrylonitrile also
undergo cyclizations with quadricyclane, albeit in dra-
matically reduced yields (∼8% for tert-butyl methacry-
2
4
late). Interestingly, no appreciable difference in the
syn/anti ratio is observed despite the introduction of the
R-methyl group. This is in direct contrast to the cy-
cloaddition behavior of cyclopentadiene, as shown in
Table 2. In cycloadditions with cyclopentadiene, the
presence of an R-methyl group on an acrylate induces a
preference for the exo isomer (∼70% exo vs ∼30% exo
for acrylate), while a trans â-methyl group has only a
disubstituted olefins, less is known about the resultant
TCN isomer distribution produced using nonsymmetri-
cal 1,1-disubstituted olefins. Particular attention will
be paid to the syn/anti isomer distribution as it may
significantly affect the rate of polymerization and/or
incorporation ratio in copolymerizations. The syn/anti
isomer distributions produced by the quadricyclane
cyclizations will be compared with the more familiar
exo/endo isomer distributions achieved by Diels-Alder
reactions with cyclopentadiene. Finally, while esters
with readily removable tert-butyl or cyclic acetal pro-
2
5
small effect. This deviation from endo selectivity has
been attributed to either steric interference between the
R-methyl group and the methylene hydrogens of cyclo-
pentadiene or secondary attractive forces between the
2
5
methyl and the unsaturated carbons. Since the transi-
tion state in the quadricyclane cycloaddition is centered

Macromolecules, Vol. 36, No. 5, 2003
Fluorinated Tricyclo[4.2.1.02,5]non-7-enes 1539
on C(6) and C(7) (Figure 2), steric interference by the
C-3 methylene hydrogens appears to be minimal as
exhibited in the small effect on the syn/anti ratio upon
incorporation of the R-methyl group (6 and 7, Table 1).
Cyclization of quadricyclane with methyl 2-(trifluo-
1
romethyl)acrylate proceeded nearly quantitatively by H
NMR to produce 8 in 94% isolated yield after 72 h. The
inability of the fluorinated methacrylate to undergo
radical homopolymerization prevents it from being
consumed in the production of polymeric byproducts,
leading to a high yield. The facile cycloaddition is
consistent with the observed behavior of olefins with
F igu r e 3. X-ray crystal structure of the carboxylic acid 10.
Displacement ellipsoids are scaled to the 30% probability level.
Hydrogen atoms are drawn to an arbitrary size.
2
6
trifluoromethyl substituents in 1,3-dipolar and Diels-
Alder cycloaddition reactions.27 Unlike the previous
acrylate and methacrylate cyclizations, this reaction
produced predominantly the anti product (syn/anti )
field of H(6), H(1) of the syn isomer is shifted 0.27 ppm
downfield due to closer proximity of the ester group, in
agreement with the reported NMR assignments for the
3
2:68), similar to the cycloaddition of cyclopentadiene
and either trans-crotonic acid or trans-4,4,4-trifluoro-
crotonic acid (Table 2).28 In contrast, the cycloaddition
of 2-(trifluoromethyl)acrylic acid with cyclopentadiene
exhibits little change in exo/endo preference relative to
10
isolated anti isomer of 6. Since the bridgehead hydro-
gens in TCNs 5-9 appear between 2.5 and 3.6 ppm (well
resolved from each other and the other protons in these
compounds) and agree with the integration of the
protons belonging to any ester substituents for the
corresponding isomer, the isomer ratio for each com-
pound was determined by integration of the H(1) and
H(6) bridgehead protons.
2
9
acrylic acid. Since the trifluoromethyl group is more
sterically bulky than a methyl group (being more similar
to an isopropyl group),30 the high yield in the cyclization
with the methyl 2-(trifluoromethyl)acrylate (unlike the
cyclizations with tert-butyl methacrylate or methacry-
lonitrile) demonstrates the importance of the electronics
of the dienophile in cyclizations with quadricyclane.
The hydrolysis of the fluorinated TCN methyl ester
9) produced a mixture of carboxylic acid isomers, one
(
Unfortunately, the cyclization with the methyl 3,3-
difluoro-2-(trifluoromethyl)acrylate produced only a mod-
erate yield (∼25%) of TCN 9 after 72 h. This was in
distinct contrast to the excellent yields obtained in the
Diels-Alder reaction of this perfluorinated olefin with
cyclopentadiene. The yield was increased to 73% upon
allowing the reaction mixture to continue at room
temperature for several days. This is similar to some
cycloadditions with furan in which high yields are
observed after long reaction times at room tempera-
of which was isolated by crystallization. X-ray crystal-
lographic analysis revealed that this isomer is the syn
compound (10, Figure 3). The crystal structure of 10 is
similar to that of an imide-functionalized TCN structure
reported in the literature. From the crystal structure,
the proximity of the carboxylic acid in the syn position
to the bridgehead H(1) proton, responsible for significant
deshielding of the proton, is apparent. The crystal
structure and NMR data from the syn isomer of the
fluorinated TCN carboxylic acid (10) complement the
NMR data from the anti isomer of the nonfluorinated
TCN carboxylic acid (5), confirming the assignments of
the isomers and the validity of using the ∆δ for H(1)-
H(6) as a diagnostic.
3
3
3
1
ture. Further work is required to explain the reluc-
tance of this fluorinated methacrylate to undergo cy-
clization with quadricyclane.
Assign m en t of TCN Isom er s As mentioned previ-
ously, little has been published on TCN compounds
obtained from nonsymmetric 1,1-disubstituted olefins.
Therefore, we endeavored to find a simple diagnostic
to determine the isomeric product distribution in these
compounds. Fortunately, because of epimerization dur-
ing the hydrolysis reaction, the TCN carboxylic acid (5)
Syn th esis of Sa tu r a ted TCN Com p ou n d s The first
concern with these TCN monomers was preservation of
the transparency demonstrated in the analogous nor-
bornane structures. It was unknown whether the ad-
dition of the fused cyclobutane ring would pose any
absorbance problems at 157 nm, similar to those of
cyclopropane rings in nortricyclane-based polymers at
1
13
13
is almost exclusively the anti isomer. H, C, C DEPT,
1
1
1
13
34
H- H COSY, H- C HMQC, and HETCOR NMR
experiments were used to assign the carbon and proton
resonances in this compound. The spectra were com-
193 nm. To investigate this, several tricyclononane
compounds were produced by hydrogenating the double
bonds of various TCN monomers. Gas-phase vacuum-
ultraviolet (VUV) spectra of the fluorinated tricy-
clononane compounds, shown in Figure 4, reveal prom-
ising transparency. In fact, the saturated version of 9
exhibits even higher transparency than norbornane.
While still more heavily absorbing than 2,2-difluoronor-
bornane (one of the most transparent norbornanes at
157 nm discovered to date), these results were encour-
aging enough to pursue additional experimental veri-
fication of transparency. Variable angle spectroscopic
ellipsometry (VASE), currently the most accurate and
representative technique to measure lithographic mate-
1
0e,16,31
pared with the available published spectral data
for other tricyclo[4.2.1.02,5]non-7-ene compounds. The
exo configuration of the cyclobutane ring fusion was
established by the W-coupling between H(9syn) and H(2)
4
and H(5) ( J ) 1.7 Hz), that is similar to the reported
values for exo-3-thiatricyclo[4.2.1.0 ]non-7-ene-3,3-
2
,5
dioxide.32
The bridgehead protons H(1) and H(6) each appear
as distinct unresolved multiplets with the H(1) proton
appearing about 0.08 ppm downfield from H(6). The ∆δ
for H(1)-H(6) is diagnostic of syn and anti due to
deshielding by the nearby substituents on C(3). For
example, in the tert-butyl ester TCN compound (6), H(6)
of both the syn and anti isomer are identical; however,
while H(1) of the anti isomer appears 0.07 ppm down-
3
5
rial transparency at 157 nm, necessitated the synthe-
sis of TCN homopolymers for the analysis of thin films.
Syn th esis of TCN Hom op olym er s The most com-
mon late-transition-metal catalyst systems used to

1
540 Sanders et al.
Macromolecules, Vol. 36, No. 5, 2003
F igu r e 4. Vacuum-UV spectra of model tricyclononane
structures.
F igu r e 5. VASE spectra of TCN homopolymers.
polymerize norbornene systems by an addition mecha-
nism are based on palladium36 and nickel. To produce
model polymers, TCN compounds 6-9 were polymerized
using cationic palladium allyl hexafluoroantimonate
catalyst reported by Risse,3 selected for its ready
availability, ease of preparation, and tolerance to polar
functionalities. Polymerization proceeded at room tem-
perature with quantitative disappearance of the mono-
37
with hydrogen followed by filtration and multiple pre-
cipitations produced polymer sufficiently clean for VASE
analysis (Figure 5). The homopolymer of NTBE (Poly-
6e
-1
1
) has an absorbance coefficient at 157 nm of 6.02 µm
compared to the homopolymer of NBHFA (Poly-2),
which is around 1.14 µm . In any copolymer of these
-1
two monomers, even small amounts of the highly
absorbing ester-containing monomer 1 will raise the
overall absorbance of the polymer considerably. In
comparison, the homopolymer of TCN 8 (Poly-8) pos-
1
mer after 24-36 h by H NMR. While the reaction is
considerably slower than the polymerization of nor-
bornene, it is comparable to the polymerization of
3
6e,38
norbornenes possessing polar substituents.
Indeed,
-1
sesses an absorbance coefficient of 3.79 µm at 157 nm.
because of the nearly identical olefin structure, the
behavior of TCN monomers is similar to that of nor-
bornene monomers. For example, we have observed that
TCN monomers undergo facile radical copolymerization
with maleic anhydride to produce alternating copoly-
mers,39 analogous to the functionalized norbornene-
The addition of the trifluoromethyl group R to the ester
increases the transparency of the material by ap-
proximately 2 orders of magnitude. The further incor-
poration of fluorine in TCN 9 serves to increase the
transparency of the homopolymer (Poly-9) by another
-1
order of magnitude (A157 ) 2.86 µm at 157 nm).
4
0
maleic anhydride copolymers developed for 193 nm
lithography.
With these fluorinated TCN monomers, polymers
with identical ester content and higher transparency or
identical transparency and higher ester content, relative
to copolymers of NTBE (1), can be synthesized. The
extremely high transparency of these materials offers
the possibility of ester-containing norbornene-type ad-
dition polymers as single layer resists. Toward this end,
the synthesis and copolymerization of a number of
fluorinated TCN monomers with tert-butyl ester func-
tionalities to produce imageable resist materials have
been investigated and are reported elsewhere.41 Explo-
ration of other potential pathways to producing photo-
resist polymers with a wide range of TCN monomers
via free radical, ring-opening metathesis (ROMP), and
addition polymerization is currently underway.
During polymerization of the TCN monomers con-
taining tert-butyl esters (such as 6 and 7), catalytic
deprotection of the tert-butyl esters was observed (with
the generation of isobutylene and carboxylic acid ob-
1
served by H NMR), resulting in aggregation and
precipitation of the deprotected polymers. Use of steri-
cally hindered bases to inhibit this catalytic deprotection
was successfully employed and will be discussed in more
detail in a separate publication.4
1
Polymerization of fluorinated TCN compounds 8 and
proceeded similarly to the nonfluorinated TCN com-
9
9
pounds, in stark contrast to the very low yields
achieved with norbornene monomers like 3 under
identical conditions. The facts that polymerization
proceeds in the presence of basic pyridine moieties and
the observed unreactivity of TCN monomers toward
radical initiators at moderate temperatures39 rule out
any cationic or radical polymerization mechanism. The
Con clu sion s
Partially fluorinated tricyclo[4.2.1.02,5]non-7-ene mono-
mers containing ester functionalities undergo metal-
catalyzed addition polymerization to produce polymers
with transparency suitable for 157 nm resist applica-
tions. A number of nonfluorinated and partially fluori-
nated acrylic and methacrylic acid esters undergo
cyclizations with quadricyclane to produce tricyclonon-
ene structures in moderate to high yield. The exo
configuration of the cyclobutane ring relieves steric
crowding of the olefin and reduces inductive effects by
locating the highly electron-withdrawing fluorine, tri-
fluoromethyl, and carboxylic acid ester functionalities
further from the double bond. In this way, the electronic
1
lack of double bonds (as observed by H NMR) and the
high glass transition temperatures of TCN polymers
confirm the 2,3-addition polymer structure. Further-
more, the moderate molecular weights and polydisper-
sity indices (1.7 < PDI < 2.7) of the polymers are typical
of polymerizations with palladium catalysts.36 It should
be noted that the fluorinated TCN compound 8 was also
readily polymerized by nickel systems such as Ni(tolyl)-
(
perfluorophenyl)2.
VASE An a lysis of TCN Hom op olym er s Removal
of the palladium from the polymer chains by treatment

Macromolecules, Vol. 36, No. 5, 2003
Fluorinated Tricyclo[4.2.1.02,5]non-7-enes 1541
and steric issues of the transparent ester motif are
balanced with the polymerizability of the monomer. The
tricyclononene monomers are readily polymerized in the
presence of palladium and nickel catalysts, in marked
contrast to the norbornene monomers with geminal
trifluoromethyl and carboxylic acid ester groups. Vacuum-
UV measurements on saturated model TCN systems
and VASE measurements on TCN homopolymers show
the high transparency imparted by the selective incor-
poration of trifluoromethyl and fluorine substituents.
These TCN polymers demonstrate improvements in
transparency of up to 3 orders of magnitude over
conventional polymers of tert-butyl ester-functionalized
norbornene and constitute a new viable route toward
advanced photoresist materials. Copolymerization of
these TCN monomers with transparent, polar nor-
bornene monomers will lead to transparent, ester-
functionalized 157 nm photoresists.
3333, 463-471. (d) Goodall, B. L.; J ayaraman, S.; Shick, R.
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(
9) No homopolymer of methyl 2-(trifluoromethyl)norborn-5-
ene-2 carboxylate was isolated after attempted polymeriza-
tion with palladium or nickel catalysts. In copolymerizations
with the hexafluoroisopropyl alcohol norbornene 2, the gemi-
nally disubstituted norbornene was incorporated in signifi-
cantly lower than stoichiometric amounts and low (<10%)
overall yields were observed. (a) Hung, R. J .; Tran, H. V.;
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ECH and its member companies. D.P.S. especially
acknowledges Dr. Todd R. Younkin, Dr. J ohn P. Morgan,
and Dr. Hoang V. Tran for helpful discussions. SEMAT-
ECH employee Danny Miller is acknowledged for help
with the VASE measurements.
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MA021131I