Radiation sensitive polymers and use thereof

Organometal-containing polymers having side chains of the formula I ##STR1## in which, for example, M is Si, X is O, R.sup.1 and R.sup.2 are hydrogen and R.sup.4 to R.sup.6 are each methyl and which have an average molecular weight between 1,000 and 1,000,000, are suitable for the preparation of dry-developable photoresists, such as are required for the generation of structured images, in particular in microelectronics.

The invention relates to novel organometal-containing polymers, 
radiation-sensitive, dry-developable, oxygen plasma-resistant compositions 
containing these compounds and also use thereof for the production of 
structured positive images. 
Self- or dry-developable compositions (resists) are understood to mean a 
class of compounds which on irradiation disintegrate into volatile 
particles or can be structured in a plasma without wet development being 
necessary for the generation of the image. Various materials have been 
proposed for this purpose, for example polymethyl methacrylate, 
polyethylene terephthalate, nitrocellulose or polyisoprene [see, for 
example, H. Franke, Appl. Phys. Lett. 45(1), 110 ff (1984)]. In using 
these materials, various disadvantages frequently arise, such as low 
sensitivity, insufficient stability, formation of nonvolatile residues, 
insufficient resistance to oxygen plasma or insufficient resolution. 
U.S. Pat. No. 4,491,628 describes resist compositions of matter containing 
a polymer having acid-labile side groups, for example tert-butyl ester or 
tert-butyl carbonate groups and a photoinitiator which upon irradiation 
generates an acid. The polymers used are preferably vinyl polymers such as 
polystyrene or polyacrylate, while the photoinitiators used are in 
particular onium salts, for example diaryliodonium or triarylsulfonium 
salts. In the exposed areas, an acid is generated and the acid-labile 
groups are cleaved off, thereby changing the polarity of the polymer. By 
choosing a suitable polar or non-polar solvent for the development of the 
image, both positive and negative images can be generated by means of this 
photoresist. 
For many applications, in particular in microelectronics, the use of 
wet-developable resists results in some disadvantages; additional process 
steps, risk of contamination by the solvents, problems in waste disposal, 
etc. For this reason, dry-developable compositions are preferred. 
EP-A 178,208 and Microcircuit Engineering, 471-481 (1985) describe 
polystyrenes having silicon-containing side groups which are suitable in 
combination with certain photiniators for use as dry-developable positive 
resists. In this process, in the irradiated areas of the resist film, 
trialkylsilyl groups which are bound to the polystyrene chain via ether 
oxygen atoms or amine nitrogen atoms are cleaved off. In this manner, the 
irradiated areas of the film can be removed by development in a plasma, 
while the nonirradiated, silicon-containing areas of the film are 
plasma-resistant. The disadvantage of this system is the relatively high 
light intensity of 80-120 mJ/cm.sup.2 required for generation of the image 
and also the insufficient solubility of the polymer in suitable solvents. 
The volatility of the silicon-containing compounds cleaved off on 
irradiation is also not always satisfactory. 
U.S. Pat. No. 4,433,044 describes silicon-containing oxime esters of 
methacrylic acid, the polymers of which can also be used as 
dry-developable positive resists which are sensitive in the short-wave UV 
region. In these compounds, trimethylsilyl groups are bound directly to 
the benzene ring of the acetophenoneoxime radical of the polymer side 
chains via methylene bridges. However, this system requires a very high 
light intensity of 1,000-4,500 mJ/cm.sup.2 to effect the removal of enough 
silicon-containing radicals. In addition, the system needs to be heated in 
a high vacuum at elevated temperature before the plasma etching process to 
obtain a good image structure. 
A class of organometal-containing polymers has now been found which in a 
mixture with catalytic amounts of certain photoinitiators have a very high 
sensitivity to radiation. In addition, these polymers are distinguished by 
a high resistance to oxygen plasma. If desired, the irradiated polymers 
can also be developed wet, making it possible to generate not only 
positive but also negative images, depending on the polarity of the 
developer used. In addition, the compounds which are liberated and removed 
from the polymer side chains on irradiation are very volatile, making it 
unnecessary to use very high temperatures or even high vacuum for the dry 
development. 
The invention relates to organometal-containing polymers having groupings 
of the formula I 
##STR2## 
in which R.sup.1 to R.sup.6 independently of one another are C.sub.1 
-C.sub.4 alkyl, C.sub.1 -C.sub.4 -alkoxy, phenyl, benzyl, phenoxy, a group 
-M(R.sup.8).sub.3 or 
##STR3## 
or R.sup.3 and R.sup.4 together are 
##STR4## 
and in addition R.sup.1 to R.sup.3 can also be hydrogen atoms, R.sup.8 is 
C.sub.1 -C.sub.4 alkyl, C.sub.1 -C .sub.4 alkoxy, phenyl, benzyl or 
phenoxy, M is Si, Ge, Sn, CH.sub.2 Si or OSi and X is O, S or NR', where 
R' is hydrogen or a single bond, b is a whole number from 1 to 6 and c is 
a whole number from 3 to 6, and an average molecular weight between 1,000 
and 1,100,000. 
Preferably, the groupings of the formula I are bound to a polystyrene 
polymer and thus the polymers according to the invention contain repeating 
units of the formula II 
##STR5## 
in which R.sup.1 to R.sup.6 and M are as defined above, X'is O, S or NH, 
R.sup.7 is hydrogen or C.sub.1 -C.sub.4 alkyl and a is zero or 1. 
The C.sub.1 -C.sub.4 alkyl groups or the alkyl radicals of the C.sub.1 
-C.sub.4 alkoxy groups of the radicals R.sup.1 to R.sup.8 of the compounds 
according to the invention can be branched or preferably straight-chain 
and are, for example, n-, iso-, sec- or tert-butyl, n- or iso-propyl, 
ethyl and in particular methyl. 
Particularly preferably, compounds according to the invention are silicon 
compounds, in which M is CH.sub.2 Si, OSi or in particular Si. Likewise, 
compounds according to the invention are preferably those in which X is S 
or in particular O. 
The organometal-containing groupings of the formula I of the polymers 
according to the invention contain by definition at least one silicon, 
germanium or tin atom M, although they can also have two or more of these 
atoms. Where the substituents R.sup.3 and R.sup.4 together are a divalent 
##STR6## 
radical, the groupings form a ring which contains, for example, a carbon 
atom and several metal atoms. These compounds preferably contain five- and 
six-membered rings. Preferably, the compounds according to the invention 
are also those in which the radicals R.sup.4, R.sup.5 and R.sup.6 are 
identical. 
In general, preference is given to those polymers according to the 
invention which, upon irradiation in the presence of an acid-liberating 
photoinitiator, eliminate a very volatile compound 
##STR7## 
in addition to CO. 
It will be readily understood that this goal can be achieved by suitable 
combinations of the substituents R.sup.1 to R.sup.6 and of the metal atom 
M. 
Where one of the radicals R.sup.1 to R.sup.6 of the compounds according to 
the invention is 
##STR8## 
b is preferably a whole number from 1 to 3, in particular 1. 
Preference is also given to polymers according to the invention in which 
R.sup.1 and R.sup.2 are each hydrogen, R.sup.3 is methyl or 
Si(CH.sub.3).sub.3 and R.sup.4 to R.sup.6 are each methyl or in which 
R.sup.3 and R.sup.4 together are 
##STR9## 
Particular preference is given to polymers in which R.sup.1 and R.sup.2 are 
each hydrogen, R.sup.3 is methyl or Si(CH.sub.3).sub.3, R.sup.4 to R.sup.6 
are each methyl, M is Si and X is O. Preference is also given to compounds 
having repeating units of the formula II in which a is zero and R.sup.7 is 
hydrogen or methyl. 
The polymers according to the invention preferably have an average 
molecular weight from 10,000 to 500,000 and in particular from 25,000 to 
100,000. 
The polymers according to the invention having repeating units of the 
formula II are preferably homopolymers. However, the radiation-sensitive, 
dry-developable composition may also comprise for example copolymers which 
are synthesized from two or more building blocks of the formula II having 
different structures or copolymers which, in addition to structural units 
of the formula II, contain other building blocks which are derived from 
copolymerizable monomers. Accordingly, the present invention also relates 
to organometal-containing copolymers containing the repeating structural 
element of the formula II and up to 50 mo 1%, based on the entire 
copolymer, of structural units which are derived from other 
copolymerizable monomers. 
Preference is given to copolymers which, in addition to structural elements 
of the formula II, contain at least one of the structural elements of the 
formulae III or IV 
##STR10## 
in which R.sup.7 is as defined above, R.sup.9 is hydrogen, C.sub.1 
-C.sub.4 alkyl or C.sub.1 -C.sub.4 -alkoxy and R.sup.10 is hydrogen, 
C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 alkoxy, C.sub.1 -C.sub.4 
alkoxycarbonyl or C.sub.1 -C.sub.4 alkylcarbonyloxy. 
The C.sub.1 -C.sub.4 alkyl groups of the radicals R.sup.9 and R.sup.10 can 
be branched or preferably straight-chain and are, for example, butyl, 
propyl, ethyl and in particular methyl. 
Typical examples of monomers from which the structural elements of the 
formulae III and IV are derived are styrene, .alpha.-methylstyrene, methyl 
acrylate or methyl methacrylate and vinyl acetate. 
Particular preferably, monomers from which the structural elements of the 
formula II are derived are 
4-(2'-trimethylsilyl-2'-propoxycarbonyloxy)styrene, 
4-(2'-trimethylsilyl-2'-propoxycarbonyloxy)-.alpha.-methyl styrene and 
4-(1', 1'-bistrimethylsilylethoxycarbonyloxy)-.alpha.-methyl styrene. 
The organometal-containing polymers according to the invention having 
groupings of the formula I can be obtained either by polymerization of 
corresponding monomers of the formula II* already containing these 
groupings 
##STR11## 
or by modification of a polymer by reaction with an organometal-containing 
compound of the formula I* 
##STR12## 
R.sup.1 -R.sup.7, M and a in the formulae I* and II* being as defined 
above, X' being O, S or NH and Y being a leaving group suitable for a 
nucleophilic substitution. 
Polymers particularly suitable for the reaction with compounds of the 
formula I* are those containing nucleophilic functional groups, for 
example hydroxyl, mercapto, amino or imido groups. This gives polymers 
according to the invention, in which the groupings of the formula I are 
bound directly or, for example, via a group of the formula V 
##STR13## 
in which Z is O, S or NR' where R' is hydrogen or a single bond, to a 
polyalcohol, a polyphenol, a polythiol, a polyamine or a polyimide. In 
these polymers, the radicals X or Z of the organometal-containing grouping 
are O, S or NR' atoms or groups, which were present in the original 
unmodified polymer and were linked to the organometal-containing grouping 
by nucleophilic substitution of the leaving group Y of the compounds of 
the formula 1*. Polymers suitable for the reaction are, for example, 
polyvinyl alcohol, phenol novolaks or cresol novolaks, poly-4-hydroxy 
styrene, polymaleimide, etc. The reaction is preferably carried out in an 
aprotic solvent such as toluene, tetrahydrofuran or methylene chloride, if 
desired, in the presence of a base, for example of a tertiary amine such 
as pyridine or dimethylaniline. 
The polymerization or copolymerization of the organometal-containing 
monomers of the formula II* and possibly also of the monomers from which 
the structural elements of the formulae III and IV are derived is carried 
out in a manner known per se by radical or cationic polymerization, for 
example in the presence of catalytic amounts of 
2,2'-azobisisobutyronitrile or of boron trifluoride etherate. The monomers 
from which the structural elements III and IV are derived are known and 
can be prepared in a known manner. 
The organometal-containing monomers of the formula II* can be prepared 
either 
(a) directly by reaction of an organometal-containing alcohol of the 
formula VI 
##STR14## 
with a chloroformic acid derivative of the formula VIIa 
##STR15## 
or by reaction of an organometal-containing chloroformate of the formula 
IX 
##STR16## 
with a compound of the formula Xa 
##STR17## 
or 
(b) via the corresponding carbonyl compounds by reaction of the 
organometal-containing alcohol of the formula VI with a chloroformic acid 
derivative of the formula VIIb 
##STR18## 
to give the carbonyl compound of the formula VIII 
##STR19## 
by reaction of the organometal-containing chloroformate of the formula IX 
with a compound of the formula Xb 
##STR20## 
to give the compound of the formula VIII followed by a Wittig reaction of 
the carbonyl compound of the formula VIII with a phosphorus ylide, the 
symbols R.sup.1 to R.sup.7, M, X' and a in the formulae VI to X having the 
meanings given above for the formulae I and II. 
Organometal-containing alcohols of the formula VI are known or can be 
prepared in a known manner. Thus, in J. Organomet. Chem. 49 (1973) C9-C12, 
the preparation of a silicon-containing alcohol by reaction of 
trimethylchlorosilane with acetone is described. Organometal-containing 
alcohols of the formula VII can also be prepared as described in J. Org. 
Chem. 45 (1980) 3571-3578, in Zh. Obshch. Khim. 36 (1966) 1709 in 
Tetrahedron Lett. 1976, 1591-1594 or in J. Organomet. Chem. 1981, 33-47 or 
by an analogous procedure. 
Chloroformic acid derivatives of the formula VII are also known and can be 
prepared, for example, by reaction of phosgene with a substituted phenol, 
thiophenol or aniline of the formula X, preferably in the presence of a 
base, for example of a tertiary amine such as pyridine or dimethylaniline. 
In an analogous manner, it is also possible to synthesize 
organometal-containing chloroformates of the formula IX by reacting an 
alcohol of the formula VI with phosgene. A preparative method of 
chloroformic acid derivatives of the formula VIIa is described, for 
example, in Angew. Makromol. Chem. 60/61 (1977) 125-137 or in German 
Offenlegungsschrift 2,508,512. Chloroformic acid derivatives of the 
formula IIIa can also be prepared by reaction of the corresponding 
compounds of the formula VIa with phosgene, as described, for example, in 
German Pat. No. 1,193,031. A plurality of suitable syntheses of 
chloroformic acid derivatives, for example of chloroformates, and also 
reaction products thereof with alcohols, thiols and amines are described, 
for example, in Chem. Rev. 64 (1964) 645-687. 
Compounds of the formula X are known and are in general commercially 
available. 
The organometal-containing carbonyl compounds of the formula VIII were 
developed for the preparation of the polymers according to the invention 
having structural units of the formula II. They can be converted to 
styrene derivatives of the formula II*, for example, by means of a Wittig 
reaction in a known manner by reaction with a phosphorus ylide. Suitable 
phosphorus ylides can be prepared, for example, by reaction of a 
methyltriarylphosphonium salt such as methyltriphenylphosphonium bromide 
with a strong base such as sodium hydride or potassium tert-butylate. 
Wittig reactions have been described in many reviews, for example in House 
"Modern Synthetic Reactions", 2nd Ed., pages 682-709, W. A. Benjamin Inc. 
Menlo Park CA, U.S.A., 1972. 
Leaving groups Y of the compounds of the formula I* suitable for a 
nucleophilic substitution are known. The most important requirement in 
selecting a leaving group is that this leaving group is less nucleophilic 
than the functional groups of the polymers with which it will be reacted. 
Particularly suitable leaving groups Y of the compounds of the formula I* 
are phenoxy radicals substituted by electron acceptor groups of five-or 
six-membered heterocycles containing at least one, preferably two, 
heteroatoms, for example O, S and in particular N atoms in the ring, which 
are bound to the carbonyl group in the molecule via one of these 
heteroatoms. Examples of suitable radicals Y are, for example, 
1-imidazolyl or a group of the formula XI 
##STR21## 
in which R.sup.11 is halogen, in particular fluorine, chlorine or bromine, 
NO.sub.2, CN or CF.sub.3 and d is a whole number from 1 to 5, preferably 
from 1 to 3. A particularly suitable radical of the formula XI is 
4-nitrophenoxy. 
Compounds of the formula I* can be prepared in a manner known per se, for 
example by reaction of the organometal-containing chloroformates of the 
formula IX with a compound of the formula XII 
EQU YH (XII) 
Another suitable synthetic route is the reaction of the 
organometal-containing alcohols of the formula VI with a chloroformic acid 
derivative of the formula XIII 
##STR22## 
or with a carbonyl compound of the formula XIV 
##STR23## 
the compounds of the formulae VI and IX and also Y in the formulae XII, 
XIII and XIV being as defined above. 
The compounds of the formulae XIII or XIV can be prepared, for example, by 
reaction of phosgene with a compound of the formula XII. 
The compounds of the formula XII are known and in general commercially 
available. 
The synthetic route via compounds of the formula XIV in the preparation of 
compounds of the formula I* is particularly suitable, if Y is one of the 
abovementioned heterocyclic radicals. A suitable compound of the formula 
XIV is, for example, 1,1'-carbonyldiimidazole. 
The polymers according to the invention are highly suitable for use as 
radiation-sensitive, dry-developable recording material. As already 
mentioned, the polymers having groupings of the formula I can be used for 
the preparation of negative- or preferably positive-working photoresist 
systems. 
Accordingly, the invention also relates to radiation-sensitive, 
dry-developable compositions containing an organometal-containing polymer 
according to the invention having side chains of the formula I and a 
compound liberating an acid under the influence of radiation. 
A large number of compounds are known as radiation-sensitive components 
which form or eliminate acid under the influence of light. Among them are, 
for example, diazonium salts, such as are used in diazotype, o-quinone 
diazides, such as are used in known positive-working copying materials, or 
even halogen compounds which form hydrohalic acid upon irradiation. 
Compounds of this type are described, for example, in U.S. Pat. Nos. 
3,515,552, 3,536,489 or 3,779,778 and also in German Offenlegungsschriften 
2,718,259, 2,243,621 or 2,610,842. 
However, cationic photoinitiators from the group consisting of iodonium or 
sulfonium salts are also suitable for use as radiation-sensitive 
components of the compositions according to the invention. These compounds 
are described, for example, in "UV-Curing, Science and Technology" 
(Editor: S. P. Pappas, Technology Marketing Corp., 642 Westover Road, 
Stamford, Conn., USA). 
In particular, diaryliodosyl salts can also be used. These compounds are 
described, for example, in EP-A 106,797. 
Furthermore, sulfoxonium salts can be used as radiation-sensitive 
compounds. These salts are described, for example, in EP-A 35,969, 44,274 
and 54,509. These salts are in particular aliphatic sulfoxonium salts 
which absorb in the far UV. 
In particular, it is also possible to use compounds which liberate sulfonic 
acids upon irradiation with actinic light. These compounds are known per 
se and described, for example, in GB-A 2,120,263, EP-A 84,515, 37,512 or 
58,638 and in U.S. Pat. No. 4,258,121 or 4,371,605. 
In the case where salts are used as radiation-sensitive, acid-eliminating 
components, these salts are preferably soluble in organic solvents. 
Particularly preferably, these salts are precipitation products containing 
complex acids, for example fluoroboric acid, hexafluorophosphoric acid or 
hexafluoroarsenic acid, or perfluoroalkanesulfonic acids such as 
trifluoromethanesulfonic acid. Suitable salts are, for example, 
diphenyliodonium, triphenylsulfonium or 
4-phenylthiophenyldiphenylsulfonium hexafluoroarsenate or diphenyliodonium 
trifluoromethanesulfonate. 
The amount of radiation-sensitive component of the compositions according 
to the invention can be varied in wide limits, depending on the nature and 
composition of the radiation-sensitive mixture. Favourable results are 
obtained by using about 1 to 20% by weight, preferably 3 to 15% by weight, 
in particular 5 to 10% by weight, of the acid-eliminating component, 
relative to the polymer. Since the radiation-sensitive component 
(initiator) remains in the system after the dry development, preferably as 
little as possible of these substances is used to avoid adverse influences 
in further process steps. Preferably, radiation-sensitive initiators are 
used which are completely removed during the dry development. 
The compositions according to the invention can contain further 
conventional additives, for example stabilizers, sensitizers, for example 
polycyclic aromatics such as pyrene, anthracene or perylene, or dyestuffs 
suitable as sensitizers, for example acridines, customary polymers such as 
polystyrene or polymethyl methacrylate, pigments, dyes, fillers, adhesion 
promoters, flow-improving agents, wetting agents and plasticizers. 
Furthermore, for application the compositions can be dissolved in suitable 
solvents. 
The compositions according to the invention are highly suitable for use as 
coating agents for substrates of any type, for example wood, textiles, 
paper, ceramics, glass, plastics such as polyester, polyethylene 
terephthalate, polyolefins or cellulose acetate, in particular in the form 
of films, and also of metals such as Al, Cu, Ni, Fe, Zn, Mg or Co, and of 
semiconductor materials such as Si, Si.sub.3 N.sub.4, SiO.sub.2, GaAs, Ge, 
etc. to which an image is to be applied by imagewise exposure. The present 
invention further relates to the use of the compositions according to the 
invention for the preparation of structured positive images and also to 
the substrates coated by the compositions. 
The preparation of the coated substrates can be carried out, for example, 
by preparing a solution or suspension of the composition. Suitable 
solvents are all too polar and not too low boiling solvents, for example 
ethers, ketones or aromatics such as tetrahydrofuran, dioxane, 
cyclohexanone, benzene or toluene. Preference is given to 1-20%, in 
particular 5-15%, polymer solutions. The solution is applied to a 
substrate uniformly by means of known coating processes, for example by 
spin coating, dip coating, knife coating, curtain coating, brush coating, 
spray coating and reverse roll coating. It is also possible to apply the 
light-sensitive layer to a temporary flexible base and then to coat the 
final substrate, for example a silicon wafer, by layer transfer via 
lamination. 
The amount applied (coating thickness) and the type of substrate (coating 
base) depend on the desired field of application. It is particularly 
advantageous that the compositions according to the invention can be 
employed in very thin layers and are notable for excellent resolution. By 
selecting an appropriate radiation source and radiation-sensitive 
component, they can be used for a wide range of applications in which the 
production of structured images is desirable. However, it is particularly 
advantageous to use them in submicron lithography and also in multi-layer 
lithography in which today the microelectronic requirements of a resist 
system are particularly high. For this reason, film coating thicknesses 
are preferably 0.3-2.0 .mu.m. 
After coating, the solvent is usually removed by drying, which produces an 
amorphous coating of the resist on the base. 
If desired, another layer can be applied between base and resist. This 
so-called planarizing resin makes it possible to apply extremely thin 
homogeneous resist layers on a base having topographical features. In 
practice, any organic polymer or oligomer which can be applied as a 
polymer solution to a base is suitable. Examples of these are polyimides, 
polyamide acids, polymethyl methacrylate, novolaks or else other resist 
systems. 
The radiation-sensitive layer is subjected in a conventional manner 
imagewise to a suitable type of radiation. The exposed areas of this layer 
decompose upon heat treatment into CO.sub.2, the very volatile compound 
##STR24## 
and the radical 
##STR25## 
After evaporation of the very volatile compound, the exposed areas are 
thus free from metal-containing groupings. By means of an oxygen plasma, 
these metal-free areas can be developed, while the unexposed areas which 
still contain metal-containing groupings are resistant to the oxygen 
plasma. An advantage of the system according to the invention is that no 
solvent has to be used in this clean and residue-free dry development and 
that positive images of very high resolution are obtained. 
For the heating for removing the volatile decomposition products after the 
exposure step, temperatures are preferably between 70.degree. C. and 
120.degree. C. over a period of 1-60, in particular 5-30, minutes. 
Irradiations using actinic radiation are carried out through a quartz mask 
containing a predetermined pattern or by means of a laser beam moving for 
example under computer control across the surface of the coated substrate. 
Preferably, UV radiation (200-450 nm), electron beams, X-rays or ion beams 
are used for irradiation. 
An additional distinction of the system according to the invention compared 
with the prior art is its unexpectedly high sensitivity for the same 
coating thickness. Thus, the desired result is obtained using no more 
than, for example, 1-10 mJ/cm.sup.2. 
The examples which follow illustrate the invention in more detail.

EXAMPLE 1 
2-Trimethysilyl-2-propanol. 
83 g (12 mol) of lithium powder are initially introduced under nitrogen 
into a 10 1 vessel equipped with ground joints and a mechanical stirrer. 
61 of dry THF are added, and the mixture is cooled to 0.degree. C. 1,500 g 
of trimethylchlorosilane (13.8 mol) and 313 g of acetone (5.4 mol) are 
mixed and are added dropwise using a dropping funnel to the lithium 
suspension. During the addition, the reaction temperature should be 
0.degree. C. After the addition, the cooling is removed and the mixture is 
stirred at 50.degree. C. for 1 -2 hours. The salt and excess lithium are 
removed from the solution. The residue is washed with n-pentane, and the 
filtrate is concentrated by first removing the solvent at atmospheric 
pressure through a mirror-coated packed column. The trimethylsilyl ether 
of 2-trimethylsilyl-2-propanol is then recovered at 20 mbar. This gives 
300 g (28%) of a colourless liquid of boiling point 47-48.degree. C. 
.sup.1 H-NMR (CCl.sub.4): 0 ppm (s, 9H) (H.sub.3 C).sub.3 Si-C, 
0.1 ppm (s, 9H) (H.sub.3 C).sub.3 Si-O, 
1.3 ppm (s, 6H) (H.sub.3 C).sub.2 C. 
______________________________________ 
Elemental analysis: 
Calculated 
Found 
______________________________________ 
% C 52.8 51.6 
% H 11.8 11.7 
______________________________________ 
232 g of the trimethylsilyl ether are dissolved in 900 ml of diethyl ether, 
and 700 ml of 15% HCL are added to this solution. The 2-phase mixture is 
refluxed for about one hour with vigorous stirring. The organic phase is 
separated off, washed once with water and then thoroughly with sodium 
bicarbonate solution, dried, and the ether is evaporated at atmospheric 
pressure. The residue is distilled through a packed column at 100 mbar. 
This gives 63 g (65%) of a clear liquid which distils at 65.degree. C. and 
has a purity of more than 97% by GC. 
.sup.1 H-NMR (CCl.sub.4): 0 ppm (s, 9H) (H.sub.3 C).sub.3 Si, 
1.1 ppm (s, 6H) (H.sub.3 C).sub.2 C, 
1.7 ppm (s, 1H) HO--, 
______________________________________ 
Elemental analysis: 
Calculated 
Found 
______________________________________ 
% C 54.48 54.19 
% H 12.19 11.98 
______________________________________ 
EXAMPLE 2 
4-(2'-Trimethylsilyl-2'-propoxycarbonyloxy)styrene 
244 g (2 mol) of 4-hydroxybenzaldehyde and 2 1 of 2M phosgene solution in 
toluene (4 mol of phosgene) are initially introduced under nitrogen into a 
5 1 vessel equipped with ground joints and a mechanical stirrer and 
thermometer. At -5.degree. C, 242 g (2 mol) of dimethylaniline are added 
dropwise. After the dropwise addition is completed, stirring is continued 
at 0.degree. C. for 2 hours. The mixture is allowed to warm to room 
temperature, excess phosgene is driven off using nitrogen, and the mixture 
is poured into icewater. The organic phase is thoroughly washed with 
diluted hydrochloric acid and dried with sodium sulfate. The solvent is 
distilled off on a rotatory evaporator. The residue is distilled in a high 
vacuum. This gives 250 g (68%) of 4-(chlorocarbonyloxy)benzaldehyde, a 
clear liquid which boils at 84.degree. C/0.2 mbar. Upon cooling, the 
liquid solidifies; the melting point is slightly above room temperature. 
______________________________________ 
Elemental analysis: 
Calculated 
Found 
______________________________________ 
% C 52.06 51.07 
% H 2.73 2.74 
% Cl 19.21 21.26 
______________________________________ 
43 g (233 mmol) of this chloroformate are dissolved in 30 ml of methylene 
chloride and added dropwise under nitrogen to a solution of 30.8 g (233 
mmol) of 2-trimethylsilyl-2-propanol and 18.4 g of pyridine (233 mmol) in 
120 ml of methylene chloride. During the addition, the temperature of the 
solution is kept at .ltoreq.5.degree. C. After the dropwise addition is 
completed, the mixture is allowed to warm to room temperature. The mixture 
is left to stand under nitrogen for 12 hours, the salt is separated off, 
and the organic phase is washed with diluted hydrochloric acid, water and 
sodium bicarbonate solution. The organic phase is dried and freed from the 
solvent. The residue is chromatographed over silica gel using chloroform 
as the eluant. This gives 30.6 g (46%) of 
4-(2'-trimethylsily-2'-propyloxycarbonyloxy)benzaldehyde as a colourless 
liquid. 
.sup.1 H-NMR (acetone-d.sub.6): 0.1 ppm (s, 9H) (H.sub.3 C).sub.3 Si, 
1.5 ppm (s, 6H) (H.sub.3 C).sub.2 C, 
7.3-7.9 ppm (m, 4H) H-Ar, 
10 ppm (s, 1H) CHO. 
______________________________________ 
Elemental analysis: 
Calculated 
Found 
______________________________________ 
% C 59.97 59.62 
% H 7.19 7.18 
% Si 10.01 9.95 
______________________________________ 
The benzaldehyde derivative is converted to the corresponding styrene 
derivative by means of a Wittig reaction: 38.6 g (1 08 mmol) of 
methyltriphenylphosphonium bromide in 400 ml of dry THF are initially 
introduced into a 1 1 3-neck round-bottomed flask equipped with dropping 
funnel and thermometer. 12.2 g (108 mmol) of potassium tert-butylate are 
added, and the mixture is stirred under nitrogen at room temperature for 1 
hour. 20 g (72 mmol) of benzaldehyde derivative dissolved in 180 ml of THF 
are then added dropwise at room temperature. After 15 hours, the TLC 
(toluene/hexane=1:1) shows only the product. The mixture is poured onto 
ice and extracted twice with n-hexane. The organic phase is washed twice 
with water, dried and evaporated. The residue is chromatographed over a 
silica gel column using toluene/hexane=1:1. This gives 13 g (65%) of a 
colourless liquid which can be distilled in a high vacuum (boiling point 
110.degree. C./0.05 mbar). 
.sup.1 H-NMR (acetone-d.sub.6): 0.05 ppm (s, 9H) (H.sub.3 C).sub.3 Si, 
1.45 ppm (s, 6H) (H.sub.3 C).sub.2 C, 
5.1-5.8 ppm (m, 2H) H.sub.2 C.dbd. 
6.5-6.8 ppm (m, 1H).dbd.CH-- 
7.0-7.5 ppm (m, 4H) H-Ar. 
______________________________________ 
Elemental analysis: 
Calculated 
Found 
______________________________________ 
% C 64.71 63.95 
% H 7.97 7.91 
% Si 10.09 10.24 
______________________________________ 
EXAMPLE 3 
4-(2'-Trimethylsilyl-2'-propoxycarbonyloxy)-.alpha.-methyl styrene 
This monomer is prepared starting from 4-hydroxyacetophenone exactly in the 
same manner as the styrene derivative described in Example 2. The yields 
and physical data of the compounds prepared are as follows: 
4-(Chlorocarbonyloxy)acetophenone 
Yield 82%, melting point 33.degree. C. 
.sup.1 H-NMR (CDCl.sub.3): 2.6 ppm (s, 3H) 
##STR26## 
7.25-8.10 ppm (m, 4H) H-Ar. 
______________________________________ 
Elemental analysis: 
Calculated 
Found 
______________________________________ 
% C 54.43 54.41 
% H 3.55 3.59 
% Cl 17.85 17.78 
______________________________________ 
4-(2'-Trimethylsilyl-2'-propoxycarbonyloxy)acetophenone 
Yield 68%, melting point 41.degree. C. 
.sup.1 H-NMR (acetone-d.sub.6): 0.1 p pm (s, 9H) (H.sub.3 C).sub.3 Si, 1.5 
p pm (s, 6H) (H.sub.3 C).sub.2 C, 2.6 p pm (s,3H) 
##STR27## 
7.25-8.1 p pm (m, 4H) H-Ar. 
______________________________________ 
Elemental analysis: 
Calculated 
Found 
______________________________________ 
% C 61.19 60.90 
% H 7.53 7.48 
______________________________________ 
4-(2'-Trimethylsilyl-2'-propoxycarbonylooxy).alpha.-methyl styrene 
Yield 53%, boiling point 118.degree. C./0.04 mbar. 
.sup.1 H-NMR (acetone-d.sub.6): 0.1 p pm (s, 9H) (H.sub.3 C).sub.3 Si, 1.5 
p pm (s, 6H) (H.sub.3 C).sub.2 C, 2.1 p pm (m, 3H) 
##STR28## 
5.1-5.4 p pm (m, 2H) H.sub.2 C.dbd.C&lt;, 7.1-7.6 p pm (m, 4H) H-Ar. 
______________________________________ 
Elemental analysis: 
Calculated 
Found 
______________________________________ 
% C 65.71 65.77 
% H 8.27 8.30 
______________________________________ 
EXAMPLE 4: 
Poly[4-(2'-trimethylsilyl-2'-propoxycarbonyloxy)styrene] 
10 g (36 mmol) of 4-(2'-trimethylsilyl-2'-propoxycarbonyloxy)styrene 
(prepared according to Example 2) are dissolved in 20 ml of toluene, and 1 
mol % of 2,2'-azobisisobutyronitrile is added to this solution. The 
solution is freed from oxygen and polymerized at 70.degree. C. under 
nitrogen. After several hours, the viscous solution is diluted with 50 ml 
of methylene chloride and poured into 500 ml of methanol. The precipitated 
polymer is again dissolved in methylene chloride and reprecipitated in 
methanol. The polymer is dried at 50.degree. C. in the high vacuum. Yield 
6 g (60%). 
.sup.1 H-NMR (CDCl.sub.3): 0.1 p pm (s, 9H) (H.sub.3 C).sub.3 Si, 0.75-2.25 
(m/s, 9H) 
##STR29## 
and (H.sub.3 C).sub.2 C, 6.2-7.1 ppm (m, 4H) H-Ar. 
______________________________________ 
Elemental analysis: 
Calculated 
Found 
______________________________________ 
% C 64.71 64.75 
% H 7.96 7.92 
______________________________________ 
Using gel permeation chromatography (GPC) in tetrahydrofuran with 
polystyrene as a standard, a molecular weight of M.sub.n= 42,000 and 
M.sub.w= 87,000 is found. Thermogravimetric analysis: at a heating rate of 
4.degree. C./min. in air, the weight loss is about 10% at 160.degree. C. 
At 175.degree. C., the compound is completely decarboxylated. The weight 
loss is 55%, which exactly corresponds to the elimination of CO.sub.2 and 
of isopropenyltrimethylsilane. 
EXAMPLE 5: 
Poly[4-(2'-trimethylsilyl-2'-propoxycarbonyloxy)-.alpha.-methyl styrene] 
In a 100 ml round-bottomed flask equipped with a glass attachment, 20 g (68 
mmol) of the monomer are dissolved in 60 ml of methylene chloride. The 
oxygen is removed from the solution, and 1.1 ml of a 1M solution of 
BF.sub.3.Et.sub.2 O in methylene chloride are added under nitrogen at 
-78.degree. C. The polymerization is then allowed to proceed at -20 to -40 
.degree. C. After 18 hours, the viscous solution is poured into 1 litre of 
methanol. The precipitated polymer is separated off, dried and again 
dissolved in methylene chloride and precipitated in methanol. It is then 
dried at 50.degree. C. in the high vacuum. This gives 13 g (65%) of the 
polymer. 
.sup.1 H-NMR (CDCl.sub.3): 0.1 p pm (s, 9H) (H.sub.3 C).sub.3 Si, 
1.0-2.1 p pm (m/s, 11H) H.sub.3 C--C, --CH.sub.2 --, H.sub.3 
C--C--CH.sub.3, 
6.4-1.2 p pm (m, 4H) H-Ar. 
______________________________________ 
Elemental analysis: 
Calculated 
Found 
______________________________________ 
% C 65.71 65.73 
% H 8.27 8.20 
% Si 9.60 9.68 
______________________________________ 
GPC measurements in THF show a M.sub.n of 33,000 and a M.sub.w of 84,000. 
TGA analysis: at a heating rate of 4.degree. C./minute in air, the weight 
loss is about 10% at 155.degree. C. and about 53% at 171 .degree. C. The 
weight loss of 53% corresponds to the complete elimination of CO.sub.2 and 
isopropenyltrimethylsilane. 
EXAMPLE 6: 
4-(2'-Trimethylsilyl-2'-propoxycarbonyloxy)nitrobenzene 
10 g (76 mmol) of 2-trimethylsilyl-2-propanol, 6 g (76 mmol) of pyridine 
and 30 ml of methylene chloride are initially introduced under nitrogen 
into a 100 ml glass flask equipped with a thermometer, dropping funnel and 
magnetic stirrer, and the solution is cooled to 0.degree. C. 15.2 g (76 
mmol) of 4-nitrophenyl chloroformate are dissolved in 20 ml of methylene 
chloride and are added dropwise to the solution initially introduced at 
such a rate that the temperature remains between 0.degree. C. and 
5.degree. C. After the dropwise addition is completed, the mixture is 
allowed to warm to room temperature and stirring is continued for about 
another hour. The mixture is poured into ice water, the organic phase is 
washed with lN HCl and then with NaHCO.sub.3. The dried organic phase is 
concentrated, and the residue is recrystallized from n-hexane. This gives 
10 g (44%) of a crystalline substance of melting point 61.degree. C. 
.sup.1 H-NMR (acetone-d.sub.6): 0.1 p pm (s, 9H) (H.sub.3 C).sub.3 Si, 
1.55 p pm (s, 6H) (H.sub.3 C).sub.2 C, 
7.4-8.1 p pm (m, 4H) H-Ar. 
______________________________________ 
Elemental analysis: 
Calculated 
Found 
______________________________________ 
% C 52.51 52.31 
% H 6.44 6.41 
% N 4.71 4.60 
______________________________________ 
EXAMPLE 7: 
1-(2'-Trimethylsilyl-2'-propoxycarbonyl)imidazole 
10 g (76 mmol) of 2-trimethylsilyl-2-propanol, 14.7 g (91 mmol) of 
1,1'-carbonyldiimidazole and 50 ml of methylene chloride are initially 
introduced under nitrogen into a sulfonating flask equipped with cooler, 
thermometer and magnetic stirrer. The mixture is then stirred under reflux 
for 21 hours. The mixture is poured into ice water, the phases are 
separated, and the organic phase is washed twice with water. The organic 
phase is dried, concentrated on a rotary evaporator, and the residue is 
distilled in a high vacuum. This gives 11.3 g (66%) of a colourless liquid 
of boiling point 90.degree. C./0.1 mbar. 
.sup.1 H-NMR (acetone-d.sub.6): 0.2 p pm (s, 9H) (H.sub.3 C).sub.3 Si, 
1.6 p pm (s8 6H) (H3C).sub.2 C, 
7.74 and 8.1 p pm (s, 3H) H-imidazole 
______________________________________ 
Elemental analysis: 
Calculated 
Found 
______________________________________ 
% C 53.06 52.31 
% H 8.02 8.02 
% N 12.38 12.40 
______________________________________ 
EXAMPLE 8: 
4-(1',1'-Bistrimethylsilylethoxycarbonyloxy)-.alpha.-methyl styrene 
The condensation reaction between 4-(chlorocarbonyloxy)acetophenone and 
1,1-bistrimethylsilylethanol (prepared according to Tetrahedron Lett., 
1976, 1591-1594) in methylene chloride proceeds analogously to the 
condensation described in Example 2. Purification by column chromatography 
gives a solid which can be recrystallized from hexane. 
4-(1',1'-Bistrimethylsilylethoxycarbonyloxy)acetophenone 
Yield 60%, melting point 79.5.degree. C. 
.sup.1 H-NMR (CDCl.sub.3): (CH.sub.3).sub.3 Si (1 8H, s):0.12 p pm, 
CH.sub.3 --C (3H, s):1.6 p pm, CH.sub.3 --C.dbd.O (3H, s):2.6 p pm, 
H-Ar (4H, m):7.2-8.05 p pm 
______________________________________ 
Elemental analysis: 
Calculated 
Found 
______________________________________ 
% C 57.91 58.01 
% H 8.01 8.13 
% Si 15.93 15.92 
______________________________________ 
4-(1',1'-Bistrimethylsilylethoxycarbonyloxy)-.alpha.-methylstyrene 
The Wittig reaction is carried out analogously to Example 2. Purification 
by column chromatography gives a colourless liquid in a yield of 41%. 
.sup.1 H-NMR (CDCl.sub.3): (CH.sub.3).sub.3 Si (1 8H, s):0.15 p pm, 
CH.sub.3 --C (3H, s):1.6 p pm, 
CH.sub.3 --C.dbd. (3H, m):2.15 p pm, 
H-Ar (4H, m):7.00-7.53 p pm 
______________________________________ 
Elemental analysis: 
Calculated 
Found 
______________________________________ 
% C 61.66 61.57 
% H 8.63 8.77 
% Si 16.02 16.08 
______________________________________ 
EXAMPLE 9: 
Poly[4-(1',1'-bistrimethylsilylethoxycarbonyloxy)-.alpha.-methyl-styrene] 
In a 250 ml round-bottomed flask equipped with magnetic stirrer, 20 g (57 
mmol) of 
4-(1',1'-bistrimethylsilylethoxycarbonyloxy)-.alpha.-methylstyrene (prepar 
ed according to Example 8) are dissolved in 60 ml of anhydrous methylene 
chloride and are freed from oxygen on a vacuum/nitrogen line using the 
freezing/thawing technique. The solution is cooled to minus 60.degree. C., 
and 1.2 mmol of freshly distilled BF.sub.3.ET.sub.2 O are added. The 
solution is allowed to polymerize between minus 60.degree. C. and minus 
40.degree. C. for 18 hours. The polymer is precipitated by pouring the 
viscous solution into 1 of methanol. The white polymer powder is dried and 
dissolved in 100 ml of THF, the solution is filtered and the polymer is 
again precipitated by pouring the filtrate into 1 of methanol. The polymer 
is separated off, sucked dry in air and dried at 50.degree. C. in a high 
vacuum. Yield: 6.1 g of a white polymer powder (31%). 
______________________________________ 
Elemental analysis 
Calculated 
Found 
______________________________________ 
% C 61.66 61.60 
% H 8.63 8.62 
% Si 16.02 16.03 
______________________________________ 
GPC (THF):M.sub.n =52,000, 
M.sub.w =102,000 
Thermogravimetric analysis: The polymer decomposes at 170 .degree. C. into 
CO.sub.2 and 1,1-bistrimethylsilylethylene. 
EXAMPLE 10 
Preparation of 
4-(2'-trimethylsilyl-2'-propoxycarbonyloxy)-.alpha.-methylstyrene by 
reaction of 2-trimethylsilyl-2-propanol with 
4-chloroformyloxy-.alpha.-methylstyrene 
In a 250 ml three-necked flask equipped with dropping funnel and 
thermometer, 10 g (75.6 mmol) of 2-trimethylsilyl-2-propanol and 7.2 g (91 
mmol) of pyridine are dissolved in 100 ml of anhydrous methylene chloride. 
After the solution has been cooled to 0.degree. C., 17.8 g (90.5 mmol) of 
4-chloroformyloxy-.alpha.-methylstyrene (prepared according to Example 6.2 
of German Offenlegungsschrift 2,508,512) are added dropwise. After the 
dropwise addition is completed, the suspension is allowed to warm to room 
temperature and stirred for another hour. The resulting pyridine 
hydrochloride is separated off, and the organic phase is thoroughly washed 
two times each with 1N HCl, water and saturated sodium bicarbonate 
solution. It is then dried with sodium sulphate and concentrated on a 
rotary evaporator. The liquid product is purified over a silica gel column 
using toluene as the eluant. This gives 14 g (40 mmol, a yield of 63%) of 
4-(2'-trimethylsilyl-2'-propoxycarbonyloxy)-.alpha.-methylstyrene whose 
properties are identical to those of the substance described in Example 3. 
APPLICATION EXAMPLES 
Example A1 
10% by weight of 4-phenylthiophenyldiphenylsulfonium hexafluoroarsenate 
[prepared according to J. Polymer Sci., Polymer Chem. Ed., 18, 2677-2695 
(1980)], relative to the polymer of Example 4, are added to a 10% by 
weight solution of this polymer in cyclohexanone. This solution is added 
dropwise through a 0.5 micron filter onto a silicon wafer and a 
homogeneous film is produced by spin coating. The polymer film is dried at 
90.degree. C. over a period of 20 minutes. The coating thickness of the 
amorphous, homogeneous film is 0.5 .mu.m. Through a chromium/quartz mask, 
the film is exposed at 254 nm to an intensity of 1-2 mJ/cm.sup.2. The 
exposed material is then developed at 90.degree. C. for 10 minutes. The 
highly resolved masked pattern can be easily recognized. The exposed zones 
are completely removed by etching under anisotropic conditions in an 
oxygen plasma (O.sub.2 flow: 20 sccm/min, pressure: 4.times.10.sup.-2 
mbar, 35 watt) using an RIE instrument (reactive ion etching), while the 
unexposed zones are not attacked. Measurements showed that exposed zones 
are etched off about 30 times faster than unexposed zones. Using this 
technique, it is possible to dry-develop even submicron structures in the 
resist. 
Example A2 
5% by weight of diphenyliodonium trifluoromethanesulfonate (prepared 
according to German Offenlegungsschrift 2,731,396, Example 4), relative to 
the polymer of Example 5, are added to a 10% by weight solution of this 
polymer in cyclohexanone. The solution is applied to a silicon wafer as 
described in Example A1 to give a resist film, 0.7 .mu.m thick. The film 
is exposed through a chromium/quartz mask at 254 nm to an intensity of 4 
mJ/cm.sup.2 and then developed at 90.degree. C. over a period of 10 
minutes. The poly[(4-hydroxy)-.alpha.-methylstyrene] formed in the exposed 
zones is dissolved off using an aqueous/alkaline developer containing 1 
part of Microposit MF 315.RTM. (from Shipley Co. Inc., Newton, Mass., 
U.S.A.), 1 part of deionized water and 1 part of isopropanol, while the 
unexposed zones are not attacked by the basic developer. In this manner, 
it is possible to produce unswollen patterns of high resolution in the 
resist film. 
Example A3 
5% by weight of 4-phenylthiophenyldiphenylsulfonium hexafluoroarsenate, 
based on the polymer of Example 5, are added to a 10% by weight solution 
of this polymer in cyclohexanone. The solution is applied to a crosslinked 
polyimide layer (Probimid.RTM. 284 from Ciba-Geigy AG), 2.3 .mu.m in 
thickness, as described in Example A1, to produce a resist film, 0.7 .mu.m 
in thickness. The film is exposed through a chromium/quartz mask at 254 nm 
to an intensity of 10 mJ/cm.sup.2 and then developed at 100.degree. C. 
over a period of 30 minutes. The exposed zones freed from silicon are 
etched off under anisotropic conditions (plasma flow: 20 sccm/min; gases: 
CF.sub.4 for one minute, then O.sub.2 ; pressure 4.times.10.sup.-2 mbar, 
35 watt) using an RIE instrument together with the underlying polyimide 
layer, while the unexposed zones are plasma-resistant.