Note: Descriptions are shown in the official language in which they were submitted.
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EM/K-18880/A
Radiation-sensitive pol~ners
The present invention relates to radiation-sensitive polymers which are based ~n phenyl-
acetic acid esters comprising a substituent having olefinic unsaturatation, to compositions
containing said polymers, to the production of images using these compositions and tO the
use of said polymers as positive resists
Positive-working, radiation-sensitive compositions and the use thereof as photoresists are
known in the art. In addition to high sensitivity in the UV range, such photoresists must be
easy to develop and have good resistance to etching
Positive-working photoresist compositions comprising a water-soluble organic compound
having specific acid~degradable linkages and a compound which generates acid upon
exposwre to actinic radiation are disclosed, for example, in US patent specification
3,779,778, These photorcsist compositions can only be devcloped in quite strongly aL~a-
line solutions and thoy have poor heat stability,
The positive-working photorcsist composidons disclosed in EP-A-0 254 853 give, after
exposure and dcvelopment, images of high heat stability, but their light-sensitivity is rela-
tively poor and they can only be developed in strongly alkaline aqueous solutions
It has now been found that polymers prepared from phenylacetic acid esters comprising a
substituent having olcfinic unsaturation can be used with advantage for radiation-sensitive,
positive-working compositions, The photoresists obtained therefrom have enhanced sensi-
tivity to actinic radiation, Fspecially in the DUV range ~eep ultraviolet; the range from
200 to 300 nm) these photoresists have superior transparency and sensitivity In addition,
they can be developed after exposure under very mild development conditions, forcxample in a very weakly alkaline medium, such as 1 % by weight aqueous NaHCO3 solu-
tion Layers with submicron resolution can be prepared, so that the photoresists can also
be used for making semiconductors. Furthermore, the structures obtained from the photo-
resists of this invention have excellent heat stability.
;~$~5
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Specif1cally, the invendon provides novel polymers having a molecular weight (M"3 of
103 to 106, detennined by gel pe~meation chromato~aphy, said polymers comprising,
based on the total number of structural units present in the polymer, 100 to 10 % molar of
the structural repeating unit of formula I
Rl
2 1-3--
~0 ' (1)
o--A -
wherein A is a radical of formula Ia
~R3 (Ia)
R2
and 90 to 0 % molar of the structural repeadng unit of formula II
~ 6 R7
R8 R9~-- ' (II)
wherein
Rl is hydrogen, methyl or halogen,
R2 is hydrogen or methyl,
R3 is hydrogen, Cl-C6alkyl or C6-C12aryl, and
R4 i8 Cl-C6aL~yl, un8ubstituted C6-CI2aryl or C6-CI2aryl which is 8ubstituted byCI~C4aLlcyl, Cl-C4alkoxy, C6-CI2aryl, halogen ~r nitro, or i8 a -ORS radical, whcrein
Rs is Cl-C6alkyl or C6-CI2aryl, or wherein
R3 and Rs, when taken together, are a propylene, butylene or pentylene radical which is
unsubstituted or substituted by Cl-C4aLkyl, Cl-C4alkoxy-, C6-C12aryl or
C6-CI2aryloxy,
R6 and R7 are each independently of the other hydrogen, unsubstituted C1-C4alkyl or
- 3- ;~
Cl-C4aLkyl which is substituted by halogen, cyano or nitro, or are unsubstitutedphenyl or naphthyl or phenyl or naphthyl which are each substituted by halogen,
Cl-C4aLtcoxy, hydroxy, cyano or nitro,
R8 and R9 are each independendy of dhe odher hydrogen or halogen, unsubstituted
Cl-Cl2a11cyl or Cl-C12aL~cyl which is substituted by halogen, cyano or nitro; phenyl,
naphthyl or benzyl, each unsubstituted or substituted by halogen, hydroxy, cyano,
nitro, Cl-C4aL~cyl or C~-C4alkoxy, or are a radical selected from dhe group consisting
of -ORlo, -COORll and -CORl2, wherein Rlo and Rll are each independendy of the
odler hydrogen, unsubstituted Cl-Cl2alkyl or Cl-Cl2aL~cyl which is substituted by
ha10gen, cyano or nitro; unsubstituted phenyl or naphthyl or phenyl or naphdhyl which
are each subgtituted by ha10gen, cyano, nitro, Cl-4aLlcyl or Cl-C4allcoxy, and Rl2 has
the same meaning as Rlo and is also the radical--N~Rl4, wherein Rl3 and Rl4, each
independently of the other, have the same meaning as Rlo.
Thc novcl polymcrs prefcrably have a molecular weight (Mw) of S 000 to 500 000, most
preferably of lS 000 to lSO 000.
The polymers prefcrably contain 100 to 25 % molar of the structural repeating unit of
fonnula I ant 75 to O % molar of thc structural repeating unit of formula II.
Preferred polymers are those whcrcin Rl in formula I is hydrogen or methyl and the group
s -CH2-COOA is in para-poddon at the ring, and in formula Ia R2 is hy~rogen or methyl, R3
i~ hydrogen or Cl-C4alkyl and R4 is hydrogen, Cl-C4alkyl or -OR5, wherein Rs is
s Ct-C4allcyl, unsubstituted phcnyl or naphthyl or phenyl or naphthyl which are substituted
s by halogen, cyano, nitro, Cl-C4allcyl or Cl-C4alkoxy, or R3 and R5, when taken together,
; are an unsubstituted or a Cl-C4allcyl-, Cl-C4alkoxy- or phenoxy-substituted propylene,
s butylcne or pentylcne radical
Particularly prcferrcd polymers are thosc wherein Rl in formùla I is hydrogen or methyl,
and the group -CHrCOOA is in para-position at the ring, and where1n R2 and R3 in, fonnula Ia arc each indcpendcntly of thc other hydrogen or methyl and R4 i8 Cl-C4alkyl or
-OR5, wherein R~ is Cl-C4alkyl or unsubsdtuted or halogen- or nitro-substituiertcd phenyl,
or R3 and Rs, when taken together, are an unsubsdtuted or a methyl-substituted propy1ene
or butylene radical.
.,
;~$~
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Very particularly preferred polymers are those wherein Rl in formula I is hydrogen or
methyl and the group -CH2-COOA is in para-position at the ring, and A is a radical of
formula
~CH3, --~ or ~
Cl-C4alkyl, Cl-C6alkyl or Cl-CI2alkyl subsdtucnts may bc straigbt-cbain or branched.
Cl-C4Alkyl is typically mcthyl, etbyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or
tert-buql; Cl-C6alkyl rnay typically furtbcr bc penql or hexyl; and Cl-CI2alkyl may
further be heptyL octyl, nonyl, decyl, undecyl or dodccyl. Substituted alkyl may suitably
bo ~cbloroethyl, 2-nitrocthy1, ~nitrohcxyl or 9-bromononyl.
Halogcn i~ typically fluoro, chloro, bromo or iodo, prefcrably chloro and bromo.
C6-Cl2Aryl i8 phenyl, biphcnyl or naphthyl which may carry one or more substituents.
Pw8ible wb8dtuents aro halogon atom8, profe ab1y chlorine or bromine atoms, and
mothyl, othyl, mothoxy, othoxy or nitro ~oups. Suitablo substituted aryl radicals are
typically o-, m and p-tolyl, xylyl, o-, m- and p-chlorophenyl, o-nitrophonyl, 2,4-dichloro-
phonyl and 2-chloronaphthyl.
C1-4Alkoxy sub~dtuents are typically methoxy, ethoxy, n-propoxy or n-butoxy.
C6-CI2Aryloxy wbsdtuents arv typically phenoxy and naphthoxy.
The polymers of this invention can be prepared by subjecting at least one compound of
formula m
H2C= C--Rl
~ (m)
CHz~
0 A
or a mixture comprising at least one compound of formula III and up to ~0 % molar, pre-
ferably up to 75 % molar, of at least one compound of formula IV
- s -
R6 R7
/c = c\ (IV)
R8 R9
wherein Rl, R6, R7, R8, R9 and A are as defined above, in a manner known per se, to
radical polymerisation.
Thc radical polymerisation can be carried out using different techniques. These techniques
are described, inter alia, by S Sandler and W Karo in "Polymer Synthesis" Vol 1-3,
1968, Academic Press, New York. Standard polymerisation methods are typically mass
polyrnerisadon or solvent, emulsion, suspension or precipitation polymerisation.
The compounds of formula III may be prepared in a manner known per se, conveniently
by reacting a compound of formula Va
H2C= C--Rl
'~ ~CHffO (Va)
OH
wherdn Rl is as defined above, with a compound of formula VIa
2~ C ~ ~ R5
eH~ , (~Ia)
R15
wherein R2 and Rs have the meanings assigned to them above, RlS is hydrogen or a radi-
cal R3 as defined above from which one carbon atom has been removed, or wheTein Rs
and RlS, when taken together, are an ethylene, propylene or butylene radical which is
unsubstituted or substituted by Cl-C4alkyl Cl-C4alkoxy~ C6-CI2aryl or C6-Ct2aryloxy, or
with a compound of forrnula VIb
HO A, (VIb)
,
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wherein A is as defined above,
in an acid medium to give a compound of formula L
or by reacting a compound of formula Vb
HzC=c_Rl
~ , ~Vb)
ff
. H~l
wherein R~ is as defined above and Hd is a hdogen atom, preferably chlorine and
bromine, with a compound of formula VIb as indicated abovc, in a basic medium, to give
a compound of formula m
The compounds of fonnula Va are disclosed, intcr dia, in US-A 4,499,300. The com-
pound~ of formula Vb are tho acid ha1ides of fo~mula Va Typical examplos of compounds
of formula Va and Vb are 4- or 2-vinylphenylacetic acid, 4-(1'-chloro)-vinylphenylacctic
acid, 4~i~opropenylphenylacetic acid and 4-isobutenylphenylacetic acid, as well as the
corresponding acid chloddes.
The compounds of formula VIa are likowise known compounds, some of which are
commercially available. Typical examples thereof are methyl butenyl ether, phenyl
butenyl ether, methyl styryl ether, methyl vinyl ether, ethyl vinyl ether, 2,3-dihydropyran,
2,3-dihydrofuran or 2,3,4,5-totrahydrooxepinh
The compounds of formula VIb are also known compounds, some of which are commer-cia11y available. Typical examples thereof are tertiary alcohols such as tert-butanol, as
we11 as benzyl alcohol or nitrobenzyl alcohol.
The acid medium of the reaction solution may be prepared by adding a few drops of con-
centrated hydrochloric or su1furic acid to the reaction solution.
The basic medium of the reacdon solution may be prepared by adding equimolar amounts
of triethylamine or pyridine to the reaction solution.
,~
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The reaction of the compounds of formula Va or Vb with dle compounds of formula VIa
or VIb is preferably carried out under an inert gas, more particularly under ni~ogen, and at
slightly elevated temperature, conveniendy in dhe range from c. 25 to 80C.
The compounds of formula IV are known and some are commercially available. Besides
olefins such as edhylene or propylene, examples of compounds of formula rv are
especiaUy the vinyl compounds. Exemplary of such monomers are the styrene ~ypes such
as styrene, a~methylstyrene, p-medhylstyrene, p-hydroxystyrene, p-acetylstyrene or
p-hydroxyphenylstyrene, esters or amides of a,~unsaturated acids, including methyl
acrylate, acrylamide, the corresponding methacrylic compounds, methyl maleate,
maleimide, p-hydroxyphenylmaleimides or tert-butyl ~vinylbenzoate, halogen-containing
vinyl compounds, including vinyl chloride, vinyl fluoride, vinylidene chloride and
vinylidene fluoride, vinyl esters such as vinyl acetate, or vinyl ethNs such as medhyl vinyl
ether or butyl vinyl ether
~7urther suitable eornpounds inelude the allyl compounds, such as allyl chloride, allyl
bromidc or a11yl cyanide,
Thc polymerisatioA is normally inidated by ono of the eustoma y initiators of radieal
polymerisatdon, Sueh inidators inelude thermal inidtiators such as azo compounds,
typieally azoisobutyronitrile (AIBN), or peroxidcs, conveniently benzoyl peroxide, or
rcdox inidator systems, for example a mixture of iron(III)acetylacetonato, benzoin and
benzoyl peroxidc, or photoehemical radical formers such as benzoin or benzil methyl
ketal
The polymerisation i5 pref~rably earried out in solution, The reaction temperature is
nonnally in the range from 10 to 200C, preferably from 40 to lS0C and, most
preferably, from 40 to 100C
Any solvents present must be inert under the reaetion conditions Suitable solvents include
aromadc hydroearbons, chlorinated hydrocarbons, ketones and ethers Typical examples
of such solvents are benzene, toluene, xylene, ethyl benæne, isopropyl benzene, ethylene
ehloride, propylene chloride, methylene chloride, chlorofo~n, methyl e~yl ketone, ace-
tone, cyclohexanone, diethyl ether or tetrahydrofuran
s~
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As mentioned at the outset, the polymers of this invention are useful materials for positive
photoresists which have a very good high sensitivity to acids and, together with acid-gene-
rating photoinitiators, form a radiation-sensitive composition. The sensitivity of the novel
polymers to acids persists even in high layer thicknesses, for example of about 30 llm. In
addition, the compounds obtained by acid cleavage from the novel polymers are very rea-
dily soluble in wealdy basic developer solutions. In contrast, the novel polymers are very
stable to these bases, so that very good differentiation between exposed and unexposed
areas is obtained in the photoresist.
Accordingly, the invendon a1so provides positive worlcing radiation-sensitive composi-
dons comprising, based on the total amount of components a) and b),
a) 80 to 99.5 % by weight of a polymer of formula I, and
b) 0.5 to 20 % by weight of a substance which generates an acid upon exposure toactinic radiation.
Prcferred compositions are those comprising, based on the total amount of components a)
and b),
a) 90 to 99.5 % by weight of a polymer of formula I, and
b) O.S to 10 % by wdght of a substance which generates an acid upon exposure to
actinic radiation.
;
f A large number of compounds are known as radiation-sensitive component~ b) which,
upon exposurc to light, form or eliminate an acid. These compounds include, for example,
the diazonium salts used in the diazo process, the o-quinone-diazides used in known posi-
s tive-worlcing copying compositions, or also halogen compounds which form a hydrohalic
acid upon irradiation. Compounds of this type are disclosed, for cxample, in US patents
3,515,552, 3,536,489 or 3,779,778, and in DE~A 27 18 259, 22 43 621 or 26 10 842.
Particularly suitable radiation-sensitive components b) of the compositions of this inven-
s tion are photoinitiators selected from the group consisdng of iodonium or sulfonium salts.
Such compounds are described, for example, in "UV-Curing, Science and Technology"
(l~dito~: S.P. Pappas, Technology Markedng Corp., 642 Westover Road, Stanford,
Connecticut, USA).
Sulfoxonium salts can also be used as radiadon-sensitive compounds. Such salts are
disclosed, for example, in EP patent 35 969 or in EP-A 44 274 and 54 509. Particular
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mention is made of aliphatic sulfoxonium salts which absorb in the low UV range.
It is also possible to use those compounds which generate sulfonic acids when irradiated
with actinic light. Such compounds are known per se and are described, for example, in
GB-A 2 120 263,1~P-A 84 515, 37 512 or 58 638 and in US^A 4,258,121 or 4,3?1,605.
If salts are used as the radiation-sensitive, acid-releasing components b), then said salts are
prefcrably soluble in organic solvents. Most preferably, these salts are products with com-
plex acids, for example with hydrofluoroboric acid, hexafluorophosphonic acid, hexa-
fluoroarsenic acid or hexafluoroantimonic acid.
The compositions of this invention may contain further conventiona1 modifiers such as
stabilisers, pigments, dyes, f~llers, adhesion promoters, flow control agents, wetting agents
and plasdcisers. For application, the compositions may also be dissolved in suitable
solvents.
The compodtions of this invention have excellent suitabi1ity as coating agents for sub-
st ates of all kinds, for example wood, textiles, paper, ceramics, glass, plastics materials
such a8 polyc~ters, polyethylene terephthalate, polyolcfins or cellulose acetate, preferably
in the forrn of films, and also of mctals such as Al, Cu, Ni, Pc, Zn, Mg or Co, and of
~aA~, Si or SiO2, on which it is dcsired to produce an imagc by image-wise exposure.
Thc invention thcrefore also provides a process for producing positive images byI.) coating a substrate with a novel radiation-sensitive composition,
II.) exposing the coated substrate to irradiation with acdnic light in a predetermined
pattern, and
m.) developing the irradiated substrate.
The 8ub8trates can be conveniently be coated by applying a solution or suspension of the
novcl composition to the substrate.
The choice of solvent and the concentration depends mainly on the nature of the composi-
tion and on the coa~ing method. The solution is uniforrnly applied to a substrate by known
coating methods, for example by spin coating, immersion, doctor coating, curtain coating,
brushing, spraying and reverse roller coating. It is also possible to apply the light-sensitive
layer to a temporary flexible support and then to coat the final substrate, for example a
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copper clad circuit board, by coat transfer by means of lamination.
The add-on (layer thickness) and the nature of the substrate are contingent on the desired
utility. A particular advantage of the compositions of the invention is that they can be used
in widely varying layer thicknesses. This thickness range comprises values of ca. 0.5 ~m
to more -than 100 llm. With conventional positive-working systems based on naphthoqui-
nonediazide, layer thicknesses greater than 10 ,um can no longer be used.
Afta the substrate has been coated, the solvent is no~mally removed by drying to give a
layer of photoresist on the substrate.
After image-wise exposure of the material in conventional manna, the exposed areas of
the photoresist are washed out with a developer.
The expression "imagewise" exposure will be understood as meaning exposure through a
photomask which contains a predetermined pattern, for examp1e a photographic transpa-
rency, expo8ure by a laser beam which is moved by computa control over the surface of
the coated 8ubstrate to produce an image, as well as exposure with compula-controlled
electron beams or treatment with X-rays through an absorber mask.
The light-~ensitivity of the compositions of this invention extends generally from the UV
s region (ca. 250 nm) to ca. 600 nm and i8 thu8 very wide ranging. Suitable light .~ources
therefore comprise a large number of very widely varying types. Especia11y in the DUV
range (200-300 nm) the compositions of this invention exhiWt excellent transparency.
Point light sources as well as arrays of reflector lamps are suitable. Examples are: carbon
arcs, xenon arcs, mercury vapour lamps which may be doped with halogen atoms (metal
halide lamps), fluorescent lamps, argon glow lamps, electronic flash lamps, photographic
s flood lamp~, electron beams and X-rays. The distance between lamp and image material
may vary, depending on the udlity and the type and strength of the lamp, for example from
2 cm to lS0 cm. Particularly suitable light sources are laser light sources, for example
argon ion lasers or crypton ion lasers. With this type of exposure, a photomask in contact
with the photopolymer layer is no longer absolutely necessary, as the controlled laser
beam writes direct on to the layer. The high ~ensitivity of the composition~ of the inven-
don is very advantageous here and perrnits high wAting speeds at relatively low intensi-
des. This method can be used to make pAnted circuits for the electronics indus~y, litho-
graphic offset plates or relief pAnting plates as well as photographic image recording
materials.
The choice of developer depends on the type of photoresist or of the photolysis products.
The developer may comprise aqueous solutdons of bases to which organic solvents or
mixtures thereof may be added.
Pardcularly preferred developers are the aqueous-aL~aline soludons used for the develop-
ment of naphthoquinone diazide layers. These solutions include in particular aqueous solu-
tions of alkali metal silicates, phosphates and hydroxides, carbonates and hydrogen carbo
nates. These solutdons may additdonally contain minor amounts of wettdng agents and/or
organic solvents.
Typical organic solvents which may be added to the developer liquids are cyclohexanone,
2-ethoxycthanol, toluene, acetone, as wdl as mixtures of two or more of these solvents.
Possiblc utilitdes of the composidons of this invention are as photoresists in the electronics
flleld (galvanoresist, discharge rcsist, solder resist), the production of printing platcs such
a~ offset plates or scrcen printing formes, mould etching, or as microresist in the produc-
don of integrated circuits. The possible substrates and conditions for processing the coated
~ubstrate~ differ corrcspondingly.
Sheets made from polyestcr, cellulose acetate or plastics-coatcd papers are typically uscd
7 for the photographic rccording of information. Specially treated aluminium is used for off-
ts ~et formes, and coppcr-clad laminatcs are used for producing printed circuits, and silicon
wafers arc used for making integrated circuits. The layer thicknesses for photographic
matcrials and offset printing formes are from ca. 0.5 ~lm to 10 ~,lm, and for printed circuits
1 to ca. 100 ~,lm, and for integrated circuits 0.5 ~,lm to 2 s~lm.
Tho invention thcrcfore further relates to the prindng formes, printed circuits, integrated
circuits or silver-frce photographic films produced by using said composidons.
,,
The following Examples illustrate the invention in more detail.
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I. Preparation of the monomers
Example A: Synthesis of tetrahydrofuran-2-yl 4vinylphenylacetate
To a mixture of 10 g (62 mmol) of 4vinylpheny1acetic acid lm.p. 99C, prepared accor-
ding to US-A 4,499.3001 and 25 g (357 mmol) of dihydt~furan are addcd 4 drops of con-
centrated hydrochiQdc acid. This m1xture is stirred for 2 hours at 40C. The clear solution
is dUuted with 200 mi of n-hexane. The Qrganic phase is then washed three times with a
cold 5 96 solution of NaHCO3. The Qrganic phase is dtied over Na2SO4 and filtered. The
solvent is then removed on a rotary evapo~or. The clear liquid is distilled in a bu1b tube
at lOD C11.3 Pa.
Yield: 12.2 g (85 % of theQry).
Elemental ana1ysis: ca1cd: C 72.39 %; H 6.94 %.
found: C 72.35 %; H 6.94 %.
IH-NMR (CDCi3): 1.842.06 ppm, m (-CHrCH2-); 3.57 ppm, s (-CH2-(~O-);
3.87-4.04 ppm, m (-CH2-O-); 5.20, 5.24 and 5.69, 5.75 ppm, m (CH2--); 6.29 ppm,
m (-O~CH~); 6.64-6.74 ppm, m (zCH-); 7.21-7.37 ppm, m (aryl-H).
Exam~lo B: Synthods of tetrahydropyran-2-yl 4viny1pheny1acetate
To a mixture of 50 g (308 mmo1) of 4-vinylpheny1acetic acid and 125 g (1.49 mo1) di-
hydropyran are addcd 4 drops of concentrated hydrochloric acid. This mixture is then
~timd for 2 hours at 40C. Tho solution is diluted with 200 m1 of n-hoxane and and
poured into a 5 % so1ution of KzCX)3. The organic phaso is dried over Na2SO4 and concen-
trated, giving 74 g ~g7 %) of a liquid which is disso1ved in 200 m1 of hexane. The so1ution
i8 coo1ed to -20C and the precipitated nysta1s are isolated.
Yield: 51 g (67 % of theory).
Melting point: 34C.
E,lemental ana1ysis: calcd: C 73.15 9~o; H 7.37 ~6.
found: C 72.38 %; H 7.45 %.
1H-NMR (CDC13): 1.53-1.77 ppm, m (-CH2-CH2-CH2-); 3.53-3.80 ppm, m (-CH24-);
3.65 ppm, s (-CH2-CO-); 5.21, 5.25 and 5.70, 5.76 ppm, m (CH2=); 5.99 ppm,
s (~-CH-~); 6.65-6.74 ppm, m (=CH-); 7.23-7.38 ppm, m (aryl-H).
Bxarnple C: Synthosis of tert-buty1 4viny1pheny1acetate
a) 4Viny1pheny1acety1 ch1Oride:
100 g (0.62 mo1) 4viny1pheny1acetic acid are disso1ved in 600 ml of ethyl acetate. To this
so1ution are added 1 g of hydroquinone and 10 drops of dimethy1 formamide. Then 70.2 g
- 13-
(Q59 mol) of thionyl chloride are added dropwise to this solution. Afterwards the mixture
is sti~ed for S hours at 70C. The solvent is then removed on a rotary evaporator and the
residual liquid is distilled at 69C under a high vacuum (6.7 Pa).
Yield: 73 g (67 % of theory).
Elemental analysis: calcd: C 66.49 %; H 5.02 % Cl 19.53 %.
found: C 66.38 %; H 5.08 % Cl 19.55 %.
lH-NMR (CDCl3): 4.09 ppm, s (-CHrC~); 5.28,5.29 and 5.70, 5.76 ppm, m (CH2=);
6.64-6.73 ppm, m (=CH-); 7.11-7A1 ppm, m (aryl-H).
b) Tert-butyl 4vinylphenylacetate
15 g (83 mmol) of 4vinylphenylacetyl chloride are added drop vise to 9.3 g of
: 1125 mmoV of tert-butanol. 25 g of Na2CO3 and 2 g of benzyltriethylammonium chloride
in 100 ml of mcthylene chloride. The mixture is then stined for 2.5 hours at 50C. Solid
matter is thereafter removed. The organic phase is washed twice with water and twice
s with a 5 % solution of NaHCO3, dried over Na2SO4, and filtered. The solvent is removed
by evaporation and she residual liquid is distilled in a bulb tube at 100C/6.7 Pa to give a
clcar 1iquid in a purity of ~ 99.5 % (GC ana1ysis).
Yie1d: 9 g (S0 % of tbeory).
E1cmcntal analysis: calcd: C 77.03 %; H 8.31 %.
s found: C 76.94 %; H 8.47 %.
lH NMR (CDC13): 1.42 ppm, 8 (-C(CH3)3); 3.49 ppm, 8 (-CH2-CO-); 5.18, 5.21 and 5.67,
5.73 ppm, m (CH2-); 6.63-6.72 ppm, m (=CH-); 7.19-7.35 ppm, m (aryl-H).
IL Sy~he~is of the Dolvmers
ExamDle l: Synthesig of poly(tetrahydropyran-2-yl 4-vinylphenylacetate)
21.3 g of tctrahydropyran-2-yl 4vinylphenylacetate (E~xample B) and 142 mg (1 mol %)
of azoisobutyronitrilc (AIBN) arc dissolved in 85 ml of toluene. Thc solution is degassed
twicc at -78C and placed undcr nitrogen. This solution i8 stirred at 70C for 20 hours,
whcrcupon thc polymer precipitatcs. The precipitate i,j isolated, dissolved in tetrahydro-
furan and precipitated in n-hexane. This procedure is repeated once more,
Yield: 10.5 g (50 % of theory)
Detcrmination of thc molecular weight by gel perrneation chromatography (GPC) intetrahydrofuran ¢~)~ = 69 000; Ml, = 41 000; M~ = 1.68.
Elemental analysis: calcd: C 73.15 %; H 7.35 %.
found: C 72 66 %; H 7 34 %
L~
- 14-
TGA [thermogravimetric analysis] (air, 10C/min):
At 149C dihydropyran is split off thermally (mass loss 33 %), whereas the deprotected
polymer remains stable at ab~ve 350C.
DSC [differendal scanning ca1Orimetry] (air, 10Clmin):
At 150C a strongly endothermic peak is visible, indicating the elimination of
dihydropyran.
Absorpdon of a polymer film on quartz:
A 1 micron thick polymer film is spin-coated on to a quartz wafer. At a wavelength of
256 nm this film has an absorpdon of 0.15 per micron, i.e. such polymer films have
excellent suitability as DW resists.
Exam~le 2: Synthesis of poly(tetrahydrofuran-2-yl 4-vinylphenylacetate)6 g (26 mmol) of tetrahydrofuran-2-yl 4-vinylphenylacetate (Example A) and 42 mg(1 mol %) of AIBN are dissolved in 24 ml of dry tetrahydrofuran and the solution is put
into a glass ampoule. After degassing at -78C, the ampoule is fused under a high vacuum.
Polymerisàtion is car;ried out at 65C for 18 hours. The contents of the ampoule are then
precipitatod with n-hexane. Afterwards the polymer is isolated, dried, dissolved once more
in tetrahydrofuran and again precipitated with n-hexane. The precipitate is dried to give a
whitc powder.
Yield: 2.5 g (42 % of thcory).
~PC ~ Mw ~ 40 000; M" = 18 000; M,~M" z 2.22.
Elemcntal ana1ysis: calcd: C 72.39 %; H 6.94 %.
found: C 71.35 %; H 6.86 %.
TGA (air, 10C/min):
Thc eliminatdon of dihydrofuran is observed at 142C.
DSC (air, 10C/min):
At 150C a strongly endothermic peak is visible, indicadng the eliminadon of
dihydropyran.
Absorpdon of a polymer film on quartz:
At a wavelength of 254 nm a 1 micron polymer film has an absorpdon of 0.20 per micron.
Example 3: Synthesis of poly(tert-butyl 4-vinylphenylacetate)
21.8 g (100 mmol) of tert-butyl 4-vinylphenylacetate (E~xample C) are polymerised with
164 mg (1 mol %) of AIBN in 80 ml of toluene and worked up in accordance with the
general procedure of E~xample 2.
Yield: 12 g (55 % of theory).
X~
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GPC (THF): Mw = 49 000; M" = 25 500; MW/M,, = 1.92.
Elemental analysis: calcd: C 77.03 %; H 8.31 %.
found: C 76.84 %; H 8.26 %.
TGA (air 10Clmin):
The elimination of isobutylene is observed at 180C (mass loss ~ 25 %).
DSC ~air, 10C/min):
At 180C a strongly endothermic peak is visible, indicating the elimination of isobutylene.
Abso~ption of a polymer film on quartz:
At a wavclength of 254 nm a 1 micron polymer film has an absorption of 0.16 per micron.
III. .Application ExamD1es
Example 4: 5 g of a polymcr of Example 1 together with 250 mg (5 % by weight) of tri-
phenylsulfonium hexafluoroarsenatc are dissolved in 25 ml of cyclopentanone. Thesolution is filtered through a 0,5 llm filter and applied to a silicon wafer having a diameter
of 76,2 mm, A homogenenus f11m is produced on the silicon wafer by spin coadng at
3000 rpm. After drying for 2 minutes at 90C on a hot plate the film has a thickness of
l ,l microns. By vacuum contact a mask is placed on the resist film, The resist is then
cxposed through a narrow band filter with light of 254 nm wavelength. Ihe exposure
energy is 4.S mJ/c,m2. Thc resist film is heated for 60 scconds at 70C on a hot plate and
thereaftcr developcd for 150 seconds in a 1 % soludon of NaHCO3, whereupon the
exposed zoncs dissoh~e in the developer (positive resist).
Analysis by scanning electron microscopy shows submicron structures of good resolution
having an edgc stecpness of 80.
Examplc 5: 1.5 g of a polymer of Example 2 together with 30 mg (2 % by weight) of tri-
phenylsulfonium hexafluoroantimonate are dissolved in 6 ml of cyclopentanone. This
solution is spin coated on to a si1icon wafcr at 2500 rpm and dried to give a 1 micron film.
This film is cxposed ~rough a mask with light of 254 nm wavclength at an exposurc
energy of 5-7 mJ/cm2 and then hcatcd for 1 minute at 90C, Thc latent imagcs so obtained
are devcloped with a 1 % solution of NaHC03.
Submicron structurcs of marked resoludon with high edge steepncss arc obtained.
Examplc 6: 2.5 g of a polymer of Example 1 together with 75 mg (3 % by weight) of tri-
phenylsulfonium trifluoromethanesulfonate are dissolved in 10 ml of cyclopentanone. This
solution is spin coated on to a silicon wafer at 2500 rpm and dried to give a 0.9 micron
36
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film. This film is exposed through a mask with light of 254 nm wavelength at an exposure
energy of ~9 mJ/cm2 and then heated for 90 seconds at 90C. The latent images soobtained are developed at 22C for 120 seconds with a 1 % solution of NaHCO3.
The positive-working resist has resolved structures with a wid~ of 0.5 micron.
