High-resolution negative photoresist with wide process latitude

The invention relates to a chemically amplified negative photoresist which can be developed in aqueous alkaline media, which contains a radiation-sensitive acid generator and a compound which reduces the solubility of the resist in aqueous alkaline solutions in the presence of acid, and a polyhydroxyl compound of the formula I ##STR1## in which n is an integer between 2 and 6, PA1 R is hydrogen, halogen, C.sub.1 -C.sub.4 alkoxy or C.sub.1 -C.sub.4 alkyl, and PA1 Z is an n-valent radical which is unsubstituted or substituted by one or more substituents from the group consisting of hydroxyl, halogen and C.sub.1 -C.sub.4 alkoxy, and is selected from the group consisting of: PA2 a) aliphatic radicals having 1 to 12 carbon atoms, PA2 b) cycloaliphatic radicals having 5 to 20 carbon atoms, PA2 c) aromatic radicals having 6 to 20 carbon atoms and PA2 d) radicals having 7 to 30 carbon atoms which comprise at least two different structural units selected from aliphatic, cycloaliphatic or aromatic groups. The resists described make it possible to reduce the demands made on the focusing accuracy during imagewise exposure.

The invention relates to a chemically amplified negative photoresist which 
can be developed in aqueous alkaline media, and to a process for the 
production of negative images using this resist. 
Chemically amplified photoresists which can be developed in aqueous 
alkaline media are known. Negative photoresists of this type are 
described, for example, in EP-A-0 404 499 and generally exhibit increased 
resolution over conventional resists. They contain at least one 
radiation-sensitive acid generator, ie. chemical groups which form an acid 
on exposure to actinic radiation, and groups which, catalyzed by the acid 
formed, undergo a chemical reaction which reduces the solubility of the 
resist in the developer solution. The chemical reaction resulting in 
reduction in the solubility of the resist can be, for example, an 
acid-catalyzed crosslinking reaction between one or more components of the 
resist composition. 
In addition to these principal components, the photoresists generally also 
contain other components which are intended to improve certain properties. 
For example, EP-A-0 445 058 describes a negative photoresist which 
contains triphenylsulfonium triflate as radiation-sensitive acid generator 
and an epoxy novolak resin as binder. The binder simultaneously forms the 
compound which, catalyzed by the acid formed on irradiation of the resist, 
cures, ie. undergoes a chemical reaction which reduces the solubility of 
the resist in a suitable developer. In addition, this resist also contains 
a polyhydroxyl compound, hydroquinone, in an amount of 2.5 per cent by 
weight in order to increase the radiation sensitivity. 
The production of a resist coating structured in a certain way on a 
substrate is carried out by a widely used method in which a coherent 
coating of the resist composition applied to a substrate is first 
irradiated through a mask which only allows the radiation to penetrate to 
the coating in desired areas, so that the solubility of the resist coating 
drops in these areas, and the soluble parts of the coating are then 
dissolved out using a developer. 
However, certain properties of the known negative resists are not 
satisfactory in all respects. Thus, continuing miniaturization, in 
particular in microelectronics, requires the resolution of ever smaller 
structures. For example, a resolution of structures between 0.5 and 0.6 
.mu.m is sufficient for the production of integrated 16 Mbit memory units, 
but the resolution capacity of the resist must be below 0.4 .mu.m for the 
production of 64 Mbit memories. In addition, the known photoresists make 
excessive demands on the focusing accuracy during imagewise exposure, in 
particular if structures in the submicron or subsemimicron range are to be 
resolved. 
The object is therefore to provide a novel negative photoresist which has 
such a composition that it enables improved resolution at the same time as 
increased focusing latitude. 
The resist according to the invention is a chemically amplified negative 
photoresist which can be developed in aqueous alkaline media and contains 
a radiation-sensitive acid generator and a monomeric or polymeric compound 
which reduces the solubility of the resist in aqueous alkaline solutions 
in the presence of acid, and a polyhydroxyl compound, wherein the 
polyhydroxyl compound has the formula I 
##STR2## 
in which n is an integer between 2 and 6, 
R is hydrogen, halogen, C.sub.1 -C.sub.4 alkoxy or C.sub.1 -C.sub.4 alkyl 
and 
Z is an n-valent radical which is unsubstituted or substituted by one or 
more substituents from the group consisting of hydroxyl, halogen and 
C.sub.1 -C.sub.4 alkoxy, and is selected from the group consisting of: 
a) aliphatic radicals having 1 to 12 carbon atoms, 
b) cycloaliphatic radicals having 5 to 20 carbon atoms, 
c) aromatic radicals having 6 to 20 carbon atoms and 
d) radicals having 7 to 30 carbon atoms which comprise at least two 
different structural units selected from aliphatic, cycloaliphatic or 
aromatic groups. 
If Z in the formula I is an aliphatic radical, it may be a straight-chain 
or branched aliphatic radical having a corresponding number of carbon 
atoms, for example an n-valent group derived from ethane, propane, 
isopropane, butane, tert-butane, pentane, hexane or octane. The aliphatic 
radicals Z are preferably straight-chain radicals having 2 to 4 carbon 
atoms. 
Examples of cycloaliphatic radicals Z are n-valent radicals derived from 
cyclopentane, cyclohexane, cycloheptane or bicyclohexyl. 
If Z in the formula I is an aromatic radical, it may be, for example, a 
radical derived from benzene, naphthalene, biphenyl or terphenyl by 
removal of n hydrogen atoms. 
Examples of radicals having 7 to 30 carbon atoms which comprise at least 
two different structural units selected from aliphatic, cycloaliphatic or 
aromatic groups are n-valent groups derived from compounds such as 
ethylheptane, toluene, xylene, 2,2-diphenylpropane, biscyclohexylmethane, 
2-cyclohexyl-2-phenylpropane or fluorene. 
Polyhydroxyl compounds of the said type are known and are commercially 
available in many forms. They are obtainable, for example, in a manner 
known per se by the acid-catalyzed reaction of polyols, ketones and 
aldehydes or polyketones and polyaldehydes with phenols of a suitable 
structure. Examples of the preparation of these compounds are given, for 
example, in Houben-Weyl, "Methoden der organischen Chemie" [Methods of 
Organic Chemistry], 4th Edition, Volume VI/1c, "Phenole/Teil 2" 
[Phenols/Part 2], Georg Thieme Verlag Stuttgart, 1976, pp. 1022-1032, and 
in Belgian Patent 576 136 and U.S. Pat. No. 3 689 572. 
In general, preference is given to the use of polyhydroxyl compounds of the 
formula I in which R is hydrogen, and to the use of compounds of the 
formula I in which n is either 3 or 4, and to the use of compounds having 
the structure 
##STR3## 
in which n, Z and R are as defined above, but R is preferably hydrogen. A 
combination of the abovementioned structural features is particularly 
preferred, in particular if the radical Z additionally conforms to one of 
the preferred forms mentioned below. 
Preferred radicals Z are aliphatic radicals having 2 to 4 carbon atoms, and 
radicals built up from aromatic and aliphatic structural units, and 
preferably contain 7 to 20 carbon atoms. It is furthermore preferred if 
the radicals Z are unsubstituted, ie. contain no hydroxyl, halogen or 
C.sub.1 -C.sub.4 alkoxy substituents. 
Examples of compounds of the formula I which are very particularly suitable 
according to the invention are 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, 
1,2,2,3-tetrakis(4-hydroxyphenyl)propane, 
1,3,3,5-tetrakis(4-hydroxyphenyl)pentane and in particular the compound of 
the formula II 
##STR4## 
The negative resists according to the invention generally contain the 
polyhydroxyl compounds of the formula I in an amount of at least 5 per 
cent by weight, based on the total solids content of the resist. The upper 
limit is expediently about 30 per cent by weight. A content of from 10 to 
20 per cent by weight is very highly suitable. 
The choice of radiation-sensitive acid generator is not crucial in the 
present invention, and it is therefore generally possible to employ any 
compounds known for this purpose. The person skilled in the art will make 
the choice, for example, on the basis of the radiation with which he would 
like to cure the resist. 
Radiation-sensitive acid generators which are suitable for the invention 
include, for example, halogen compounds which form hydrohalic acid on 
irradiation. Examples of compounds of this type are described in U.S. Pat. 
Nos. 3,515,552, 3,536,489, 3,779,778. 
Other radiation-sensitive components of the negative resist composition 
according to the invention are onium compounds, such as iodonium or 
sulfonium salts. Such compounds are described in "UV-Curing, Science and 
Technology", in particular p. 13 ff. (editor: S. P. Pappas, Technology 
Marketing Corp., 642 Westover Road, Stanford, Conn., USA, 1985) and form 
the subject-matter of many patent specifications, for example U.S. Pat. 
Nos. 4,058,400, 4,058,401 and 4,069,055. 
It is also possible to employ diaryliodosyl salts. Such compounds are 
described, for example, in EP-A-106 797. 
It is furthermore possible to use sulfoxonium salts as the 
radiation-sensitive compounds. Aliphatic sulfoxonium salts which absorb in 
the deep UV region are described, for example, in EP-A-0 164 314. 
A further group of suitable radiation-sensitive acid generators comprises 
metallocene salts, which are described, inter alia, in Canadian Patent No. 
1,285,686. 
It is furthermore possible to employ compounds which liberate sulfonic 
acids on exposure to actinic radiation. Examples of such compounds are 
described in GB-A-2 120 263, EP-A-0 037 152 and U.S. Pat. No. 4,371,605. 
These compounds also include oxime sulfonate compounds, as described, for 
example, in EP-A-0 139 609 and EP-A-0 241 423. Specific photoinitiators of 
this type are the oxime sulfonates of the formula III 
##STR5## 
in which 
Ar is an unsubstituted aryl group or an aryl group which has one or more 
chlorine, bromine, hydroxyl, C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 
perfluoroalkyl or C.sub.1 -C.sub.4 alkoxy substituents, X is an oxygen or 
sulfur atom, R.sub.1 is hydrogen, C.sub.1 -C.sub.4 alkyl or a phenyl group 
which is unsubstituted or substituted by chlorine, bromine, C.sub.1 
-C.sub.4 alkyl or C.sub.1 -C.sub.4 alkoxy substituents, and R.sub.2 is 
hydrogen or C.sub.1 -C.sub.4 alkyl. In this formula, Ar is preferably an 
aryl group of the formula 
##STR6## 
X is an oxygen atom, R.sub.1 is a C.sub.1 -C.sub.4 alkyl or phenyl 
radical, and R.sub.2, R.sub.3 and R4, independently of one another, are 
hydrogen, chlorine or methyl. The use of these photoinitiators, for 
example .alpha.-(4-toluenesulfonyloxyimino)-4-methoxybenzyl cyanide, is 
very highly suitable for exposure using radiation from the region of the 
mercury I line (wavelength 365 nm). 
Preference is given to photo-induced acid formers which liberate sulfonic 
acids or halogen acids on irradiation, in particular iminosulfonates. The 
content of radiation-sensitive acid generators in the resists according to 
the invention should be from about 0.1 to 20 per cent by weight, based on 
the total solids content of the resist, large variations being possible 
due to the many suitable types of acid generators. 
Examples of suitable compounds which reduce the solubility of the resist in 
aqueous alkaline solution in the presence of the acid formed on 
irradiation of the acid generator are known acid-curable resins, for 
example acrylic, polyester, alkyd, melamine, urea, epoxy and phenolic 
resins or mixtures thereof. Acid-curable resins like these are generally 
known and are described, for example, in Ullmann's Encyclopadie der 
technischen Chemie [Ullmann's Encyclopaedia of Industrial Chemistry] 4th 
Edn., Vol. 15 (1978), pp. 613-628. 
Particularly preferred acid-curable resins (crosslinking agents) are amino 
resins, for example unetherified or etherified melamine, urea, guanidine 
or biuret resins, in particular methylated melamine resins or butylated 
melamine resins, corresponding glycolurils and urones. Resins here are 
taken to mean both conventional technical-grade mixtures, which generally 
also include oligomers, and pure and highly pure defined compounds. 
Hexamethoxymethylmelamine (formula IV) and tetramethoxymethylglycoluril 
(formula V) and N,N'-dimethoxymethylurone (formula VI) are the most 
preferred acid-curable resins; 
##STR7## 
The proportion of this component can vary within broad limits. If an 
additional film-forming polymeric binder is present, this proportion is 
generally from 2 to 30 per cent by weight, based on the solids content of 
the resist. 
An additional film-forming polymeric binder is necessary at least in cases 
where the acid-curable compound cannot itself function as binder for the 
resist composition. Particularly suitable materials here are 
alkali-soluble phenolic resins, for example novolaks, derived from an 
aldehyde, for example acetaldehyde or furfuraldehyde, but in particular 
from formaldehyde, and a phenol, for example unsubstituted phenol, mono- 
or di-chlorine-substituted phenol, such as p-chlorophenol, mono- or 
di-C.sub.1 -C.sub.9 alkyl-substituted phenol, such as o-, m- or p-cresol, 
the various xylenols, p-tert-butylphenol, p-nonylphenol, p-phenylphenol, 
resorcinol, bis(4-hydroxyphenyl)methane or 
2,2-bis(4-hydroxyphenyl)propane. Also suitable are homopolymers and 
copolymers based on ethylenically unsaturated phenols, for example 
homopolymers of vinyl- and 1-propenyl-substituted phenols, such as 
p-vinylphenol and p-(1-propenyl)phenol, or copolymers of these phenols 
with one or more ethylenically unsaturated materials, for example 
styrenes. The amount of binder is generally between 30 and 90 per cent by 
weight or preferably between 40 and 80 per cent by weight, based on the 
solids content of the resist. 
Of course, it is generally also possible to replace individual substances 
by mixtures of a plurality of representatives of the individual components 
described above. 
A specific embodiment of the negative resist according to the invention 
comprises from 40 to 87 per cent by weight, in particular from 52 to 77 
per cent by weight, of a phenolic resin as binder, preferably of a novolak 
or polyvinylphenol, from 5 to 25 per cent by weight, in particular from 5 
to 20 per cent by weight, of a substance selected from 
hexamethoxymethylmelamine (formula IV), tetramethoxymethylglycoluril 
(formula V) and N,N'-dimethoxymethylurone (formula VI), either in highly 
pure or technical-grade form, from 0.1 to 10 per cent by weight, in 
particular from 1 to 10 per cent by weight, of a compound which forms 
sulfonic acids or halogen acids on irradiation, and from 5 to 25 per cent 
by weight, in particular from 10 to 25 per cent by weight, of a 
polyhydroxyl compound from the group consisting of 
1,1,2,2-tetrakis(4-hydroxyphenyl)ethane; 
1,2,2,3-tetrakis(4-hydroxyphenyl)propane, 
1,3,3,5-tetrakis(4-hydroxyphenyl)pentane and the compound of the formula 
II already shown above. An example of a highly suitable resist would 
comprise from 60 to 75 per cent by weight of novolak resin, for example an 
m-cresol or m/p-cresol novolak, from 7.5 to 17.5 per cent by weight of 
hexamethoxymethylmelamine, from 12.5 to 17.5 per cent by weight of the 
polyhydroxyl compound of the above formula III and from 0.5 to 5 per cent 
by weight of .alpha.-(4-toluenesulfonyloxyimino)-4-methoxybenzyl cyanide 
as photo-induced acid generator. 
In addition to the said constituents, the photoresist compositions 
according to the invention may also contain one or more additives 
conventional for negative resists in the amounts customary to a person 
skilled in the art, for example flow-control agents, wetting agents, 
adhesives, thixotropic agents, dyes, pigments, fillers, solubility 
accelerators, sensitizers, etc. 
The present invention also relates to a process for producing images which 
comprises the following steps: 
1.) production of a coating comprising one of the photoresists described 
herein on a substrate; 
2.) imagewise exposure of the coated substrate by the projection exposure 
method; if desired warming, and 
3.) development with the aid of an aqueous alkaline developer. 
For application, the compositions must generally also contain a solvent. 
Examples of suitable solvents are ethyl lactate, 3-methoxymethyl 
propionate, 3-ethoxyethyl propionate, ethyl pyruvate, 2-heptanone, diethyl 
glycol dimethyl ether, cyclopentanone, cyclohexanone, 
.gamma.-butyrolactone, ethyl methyl ketone, 2-ethoxyethanol, 2-ethoxyethyl 
acetate and in particular 1-methoxy-2-propyl acetate. The solvents may 
also be a mixture, for example of two or more of said solvents. The choice 
of solvent and concentration depends, for example, on the type of 
composition and on the coating method. 
The solution is applied evenly to a substrate by known coating methods, for 
example by spin-coating, dip-coating, knife coating, curtain coating, 
brushing, spraying and reverse-roll coating. It is also possible to apply 
the photosensitive layer to a temporary, flexible support and then to coat 
the final substrate by layer transfer (lamination). 
The application rate (coating thickness) and the type of substrate (layer 
carrier) depend on the desired application area. The layer thickness can 
in principle be in the range from about 0.1 .mu.m to more than 100 .mu.m. 
Possible areas of application of the composition according to the invention 
are as photoresists for electronics, the production of printing plates, 
such as offset printing plates or screen-printing plates, in chemical 
milling and in particular as microresists in the production of integrated 
circuits. The layer supports and processing conditions are correspondingly 
various. 
In the use as microresists for integrated and highly integrated circuits, 
which is preferred, the layer thicknesses are generally between 0.1 and 10 
.mu.m, preferably between 0.5 and 5 .mu.m, in particular between 0.5 and 
1.5 .mu.m. 
The compositions according to the invention are outstandingly suitable as 
coating compositions for substrates of all types, including wood, 
textiles, paper, ceramic, glass, plastics, such as polyester, for example 
polyethylene terephthalate, polyolefins or cellulose acetate, in 
particular in the form of films, but in particular for the coating of 
metals, such as Ni, Fe, Zn, Mg, Co or in particular Cu or Al and of Si, 
silicon oxides or nitrides, or other substrates which are conventional in 
the semiconductor industry, to which an image is to be applied by 
imagewise exposure. 
After the coating, the solvent is generally removed by warming, giving a 
layer of the photoresist on the support. The drying temperature must of 
course be below the temperature at which certain components of the resist 
could cure thermally. For drying, the temperatures should in general not 
exceed from 80 to 130.degree. C. 
The resist coating is then exposed imagewise through a photomask containing 
a predefined pattern. 
The photosensitivity of the negative resists according to the invention 
extends, depending on which radiation-sensitive acid generator is 
employed, from the UV region (about 200 nm) to about 600 nm and thus 
covers a very wide range, so that as light sources per se a large number 
of the most varying types can be used. Both point light sources and 
sheet-like emitters (lamp carpets) are suitable. Examples are carbon arc 
lamps, xenon arc lamps, mercury vapour lamps, for example medium- and 
high-pressure mercury lamps, if desired doped with metal halides 
(metal-halogen lamps), fluorescent lamps, argon incandescent lamps, 
electronic flash lamps and photographic flood lamps. The distance between 
the lamp and the image material according to the invention can vary 
depending on the application and lamp type and strength, for example 
between 2 cm and 150 cm. 
If desired, sensitizers can also be added to the photoresists in order to 
increase the spectral sensitivity in a certain wavelength region. These 
sensitizers include, for example, Michler's ketone, benzophenones, 
phenothiazines, thioxanthones and aromatic hydrocarbons, such as 
anthracene, substituted anthracenes, pyrene and perylene. 
Before development, a certain time is generally necessary to allow the 
components of the resist composition to react. In order to accelerate this 
reaction and thus the formation of a sufficiently differentiated 
solubility between the exposed and unexposed areas of the resist coating 
in the developer, the coating is preferably warmed before development. The 
warming can also already have been carried out during exposure or can 
begin during exposure. Preferred temperatures are between 60.degree. and 
150.degree. C. The duration depends on the warming method and can, if 
necessary, easily be optimized by the person skilled in the art with the 
aid of a few routine experiments. It is generally between a few seconds 
and several minutes. For example, from 10 to 300 seconds are highly 
suitable if a hotplate is used, and from 1 to 30 minutes if a convection 
oven is used. 
The layer is then developed, the non-exposed, more soluble parts of the 
coating being removed. Gentle agitation of the workpiece, gentle brushing 
of the coating in the developer bath or spray development may accelerate 
this process step. For development, conventional aqueous alkaline 
developers of resist technology, for example, can be used. Such developers 
contain, for example, sodium hydroxide, potassium hydroxide, the 
corresponding carbonates, bicarbonates, silicates or metasilicates, but 
preferably metal-free bases, such as ammonia or amines, for example 
ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, 
methyldiethylamine, alkanolamines, for example dimethylethanolamine, or 
triethanolamine, or quaternary ammonium hydroxides, for example 
tetramethylammonium hydroxide or tetraethylammonium hydroxide. The 
developer solutions are generally up to 0.5N, but are generally diluted in 
a suitable manner before use. For example, solutions having a normality of 
from about 0.1 to 0.3 are highly suitable for use. The choice of the 
particular developer depends on the type of photoresist, in particular on 
the nature of the binder used or of the photolysis products formed. The 
aqueous developer solutions may also, if desired, contain relatively small 
amounts of wetting agents and/or organic solvents. Typical organic 
solvents which can be added to the developer liquids are, for example, 
cyclohexanone, 2-ethoxyethanol, toluene, acetone, isopropanol and mixtures 
of two or more of these solvents. A typical aqueous/organic developer 
system is based on Butylcellosolve.RTM./water.

EXAMPLE 1 
A first resist (resist 1) is prepared from 22.1 g of polyvinylphenol 
(PHM-C, manufacturer Maruzen Chemicals), 8.9 g of melamine resin 
(Cymel.RTM.303, manufacturer Cyanamid) and 2,6 g of tribromomethyl phenyl 
sulfone (manufacturer Sumitomo), and 0.5 g of phenothiazine as sensitizer 
and 66 g of diglyme (diethylene glycol dimethyl ether) as solvent. 
A further three resists (2,3 and 4) are prepared, in each case from 18.7 g 
of polyvinyl-phenol (PHM-C), 8.9 g of melamine resin Cymel.RTM.303, 2.6 g 
of tribromomethyl phenyl sulfone, 0.5 g of phenothiazine, 66 g of diglyme 
and in the case of resist 2 in addition 3.4 g of the compound of the 
formula II (TRISP-PA, manufacturer Mitsui Petrochemicals), in the case of 
resist 3 in addition 3.4 g of 1,2,2,3-tetrakis-(4-hydroxyphenyl)propane 
and in the case of resist 4 in addition 3.4 g of 
1,1,2,2-tetrakis(4-hydroxyphenyl)ethane. 
After microfiltration (0.2 .mu.m), the resist solutions are in each case 
spin-coated onto a silicon wafer in such a way that a resist film with a 
thickness of 1.05 .mu.m is obtained after drying for 60 seconds at 
100.degree. C. on a hotplate. Exposure of the wafers is carried out by 
means of radiation having a wavelength of 365 nm using a 5:1 projection 
exposure unit (ASM L PAS 5000/50 Stepper, NA 0.48) in steps, where either 
the exposure dose is changed by 10 mJ/cm.sup.2 from one step to the next 
or the system is defocused by 0.3 .mu.m compared with the ideal focusing 
and the exposure dose is varied in total between 20 and 220 mJ/cm.sup.2 
and the defocusing between +1.5 .mu.m and -1.5 .mu.m compared with the 
ideal setting. The resist film is then heated for 60 seconds at 
110.degree. C. on a hotplate and subsequently developed for 90 seconds in 
aqueous 2.38% tetramethylammonium hydroxide (TMAH) solution. 
The maximum resolution for the most accurate focusing and the focusing 
latitude, ie. the total range in .mu.m by which the focusing can vary 
compared with the ideal setting without a deviation of the resist 
structures by more than 0.05 .mu.m (.+-.10%) compared with their nominal 
dimensions occurring, is determined by electron microscopy. The values are 
shown in Table 1. 
TABLE 1 
______________________________________ 
Maximum resolution, 
Focusing latitude 
l/s* 
Resist [.mu.m] [.mu.m] 
______________________________________ 
1 1.5-1.8 0.40(zero comparison) 
2 &gt;2.1 0.35 
3 &gt;2.1 0.35 
4 &gt;2.1 0.35 
______________________________________ 
*lines and spaces 
It can be seen that the negative resists according to the invention 
(resists 2, 3 and 4) have a focusing latitude which is greater by more 
than 15% than resist 1, which does not contain a compound of the formula 
I. In addition, the maximum resolution and the sensitivity are increased. 
EXAMPLE 2 
Resist 5 is prepared by dissolving 4.7 g of m-cresol novolak, 1.2 g of 
hexa(methoxymethyl)melamine and 0.15 g of 
.alpha.-(4-toluenesulfonyloxyimino)-4-methoxybenzyl cyanide (prepared by 
the procedure published in EP-A-0 241 423) in 14 g of diglyme. Resist 
solutions 6, 7 and 8 are obtained analogously from 1.2 g of 
hexa(methoxymethyl)melamine and 0.15 g of 
.alpha.-(4-toluenesulfonyloxyimino)-4-methoxybenzyl cyanide and m-cresol 
novolak (4.4 g in the case of resist 6, 4.2 g in the case of resist 7 and 
4.0 g in the case of resist 8) with addition of various amounts of the 
compound of the above formula II (0.3 g corresponding to 5 per cent by 
weight of the total solids content in the case of resist 6, 0.6 g, 
corresponding to 10 per cent by weight of the total solids content in the 
case of resist 7, and 0.9 g, corresponding to 15 per cent by weight of the 
total solids content in the case of resist 8) and 14 g of diglyme. 
The resist solutions are applied and exposed as described in Example 1. 
After heating for 60 seconds at 110.degree. C. on a hotplate, the resists 
are developed by means of 0.262N TMAH solution. 
Table 2 shows the results for maximum resolution and focusing latitude 
determined by electron microscopy. 
TABLE 2 
______________________________________ 
Maximum resolution, 
Focusing latitude 
l/s* 
Resist [.mu.m] [.mu.m] 
______________________________________ 
5 &lt;1.5 0.40(zero comparison) 
6 1.5 0.40 
7 1.8 0.35 
8 &gt;1.8 0.35 
______________________________________ 
*lines and spaces 
Zero comparison without using a compound of the formula (I). 
EXAMPLE 3 
Resist 9 is prepared from 9.7 g of m-cresol novolak, 2.5 g of 
hexa(methoxymethyl)melamine, 0.2 g of a radiation-sensitive acid generator 
of the formula 
##STR8## 
and 27.6 g of diglyme, and resist 10 is prepared from 8.5 g of m-cresol 
novolak, 2.5 g of hexa(methoxymethyl)melamine, 0.2 g of the acid generator 
from resist 9, 27.6 g of diglyme and 1.2 g of the compound of the above 
formula II. 
After microfiltration (0.2 .mu.m), the two resist solutions are in each 
case spin-coated onto a silicon wafer in such a way that a resist film 
with a thickness of 1.5 .mu.m is obtained after drying for 60 seconds at 
100.degree. C. on the hotplate. Exposure of the wafer is carried out by 
means of a GCA-6400 (NA 0.38) G-line stepper (wavelength 436 nm) in steps, 
where either the exposure dose is changed by 5 mJ/cm.sup.2 from one step 
to the next or the system is defocused by 0.3 .mu.m compared with the 
ideal focusing and the exposure dose is varied in total between 20 and 160 
mJ/cm.sup.2 and the defocusing between +3 .mu.m and -3 .mu.m relative to 
the ideal setting. The resist film is then heated for 60 seconds at 
105.degree. C. on the hotplate and subsequently developed for 90 seconds 
in aqueous 2.38% tetramethylammonium hydroxide (TMAH) solution. 
The maximum resolution for the most accurate focusing and the focusing 
latitude, ie. the total range in .mu.m by which the focusing can vary 
compared with the ideal setting without a deviation of the resist 
structures by more than .+-.10% compared with their nominal dimensions 
occurring, is determined by electron microscopy. 
TABLE 3 
______________________________________ 
Maximum resolution, 
Focusing latitude 
l/s* 
Resist [.mu.m] [.mu.m] 
______________________________________ 
9 2.4 0.85(zero comparison) 
10 3.0 0.70 
______________________________________ 
*lines and spaces 
In addition to the focusing latitude, the maximum resolution here is also 
about 20% better.