Process for making a photoactive compound and photoresist therefrom

The present invention provides for process of preparing a photoactive ester compound of high purity using a solid base catalyst, preferably an anionic exchange resin. The invention further provides for preparing and imaging a photosensitive composition comprising such a photoactive compound, a film-forming resin and a solvent composition.

BACKGROUND 
Photoresists are materials which change their solubility in a developer 
solution after the photoresist has been exposed to actinic radiation, such 
as to ultraviolet, electron or ion beam, laser or X-ray radiation. 
Photoresist compositions comprise a photoactive compound, a film forming 
polymeric resin and a solvent. The photoresist composition is applied to a 
substrate which is to be patterned and the solvent is then removed, as 
with heat, leaving the photoresist is a thin film covering the substrate. 
As a consequence of the exposure to radiation of the photoresist, a 
different solubility rate results between the exposed and unexposed 
(masked over) portions of the photoresist film which yields a surface 
relief pattern after development. Those photoresists which become more 
soluble in a developer solution in the exposed regions are referred to as 
"positive" photoresists. Those which become less soluble in the exposed 
regions are referred to as "negative" photoresists. The present invention 
deals with a class of those photoactive compounds suitable for use in 
photoresist compositions. 
Positive photoresist films may comprise an aqueous alkali soluble resin, 
such as a novolak resin or a poly(hydroxystyrene), and a photoactive 
compound. It is known to the skilled artisan to produce positive 
photoresist compositions such as those described in U.S. Pat. Nos. 
3,666,473, 4,115,128 and 4,173,470. These include water insoluble, aqueous 
alkali-soluble phenol-formaldehyde novolak resins together with 
light-sensitive materials, usually a substituted naphthoquinone diazide 
compound. The resin and photoactive compound are applied, such as by spin 
coating, spray coating, or other suitable means, from an organic solvent 
or solvent mixture onto a substrate, such as a silicon wafer or a 
chrome-plated glass plate. The developer used to process the positive 
photoresists are aqueous alkaline solutions, such as sodium metasilicate, 
potassium hydroxide, tetramethyl ammonium hydroxide and ammonium 
hydroxide. The developer removes the areas of the coated photoresist film 
that have been exposed to light or other form of irradiation so as to 
produce a relief pattern in the photoresist film. 
The application of a photosensitive film to various substrates is an 
essential step in the fabrication of integrated circuits. The substrates 
are generally silicon wafers which may have a thin oxide coating or other 
coating such as silicon nitride or aluminum. The photosensitive film is 
used to pattern the substrate in a series of steps including exposure 
(through a mask pattern), development to yield a relief pattern in the 
photoresist layer and a substrate etch step to transfer that pattern into 
the substrate material. It is essential that the mask pattern be 
accurately reproduced in the substrate etch pattern. To achieve this high 
degree of accuracy, the mask pattern must be well resolved by the 
photoresist layer. The characteristics of the photoresist compositions, 
which are important in commercial practice, include its photospeed, 
contrast, resolution (edge acuity), thermal stability of the image during 
processing, processing latitude, line width control, clean development and 
unexposed film loss. 
Not only is the performance of the photoresist critical, but also its 
quality, specifically, purity and consistency. Both soluble and insoluble 
impurities lead to yield losses during the manufacture of integrated 
circuits. Some of these impurities originate from the synthesis of the 
photoactive compound. The synthesis of the photoactive compound, typically 
those that are formed by an esterification reaction between a hydroxy 
containing compound and a halide containing compound, require a basic 
component to drive the esterification reaction. It is well known in the 
art to use soluble organic amines, such as 1,4 diazabicyclo 2,2,2! 
octane, N-methyl morpholine, triethyl amine or diethanolamine to drive the 
reaction between phenolics and diazonaphthoquinone sulfonyl chlorides, in 
the presence of a solvent. In order to obtain high degrees of 
esterification, which are desired for high resolution photoresists, 
greater than equimolar quantities of the amine are used. These amines form 
salts, and most often, chloride salts, that are difficult to remove and 
can lead to insoluble particles in the photoresist film. This patent 
discloses a method of making photoactive compounds that requires little or 
no soluble organic amines and furthermore can provide photoresist films 
with low levels of impurities, especially chloride. 
SUMMARY 
The invention provides a process for producing photoactive ester compounds 
of high purity comprising, reacting a compound containing at least one 
hydroxy group with a compound containing at least one halide group in the 
presence of a solid basic catalyst and in a solvent medium. The solid 
basic catalyst may be an anionic exchange resin. In one preferred 
embodiment less than equimolar amount of soluble organic amine is added to 
the reaction mixture, preferably less than 0.3 equivalent of the amine and 
more preferably less than 0.2 equivalent of the amine of the chloride 
concentration. The concentration of chloride contamination in the 
photoactive compound made according to the invention is preferably less 
than 100 ppm, more preferably less than 50 ppm, even more preferably less 
than 25 ppm, and most preferably less than 10 ppm. The photoactive 
compound is preferably a reaction between a multihydroxy phenolic compound 
and a diazonaphthoquinone sulfonyl chloride. 
The invention also relates to a process for making a photosensitive 
composition comprising a film-forming resin, a solvent and a photoactive 
compound of high purity produced by reacting a compound containing at 
least one hydroxy group with a compound containing at least one halide 
group in the presence of a solid basic catalyst and in a solvent medium. 
The invention further relates to a process for forming an image on a 
substrate using such a photosensitive composition. 
DESCRIPTION 
The present invention relates to a process for producing a photoactive 
ester compound, comprising reacting a compound containing at least one 
hydroxy group with a compound containing at least one halide group in the 
presence of a solid basic catalyst and in a solvent medium. The invention 
also relates to a process for making and further imaging a photosensitive 
composition comprising a film-forming resin, a photoactive ester compound 
produced by reacting a compound containing at least one hydroxy group with 
a compound containing at least one halide group in the presence of a solid 
basic catalyst and in a solvent medium. In cases where high conversions 
are required, additional organic soluble amine may be present in the 
reaction mixture at a concentration less than 0.3 equivalent. 
A photosensitive composition typically comprises an alkali-soluble, 
film-forming resin, a photoactive compound and a solvent. Resins used in 
photosensitive compositions may be novolak polymers or 
poly(hydroxystyrene) polymers. Novolak resins have been commonly used in 
the art of photoresist manufacture as exemplified by "Chemistry and 
Application of Phenolic Resins", Knop A. and Scheib, W.; Springer Verlag, 
New York, 1979 in Chapter 4. Similarly, photoactive compounds, such as, 
oquinone diazides are well known to the skilled artisan as demonstrated by 
"Light Sensitive System", Kosar, J.; John Wiley & Sons, New York, 1965 in 
Chapter 7.4. Typically, photosensitive diazides used in positive 
photoresists, are obtained by reacting hydroxyl containing compounds, 
known as ballast compounds, with 2,1-diazonaphthoquinone sulfonyl 
chlorides. Such ballast compounds are well known in the art, and examples 
of which are disclosed in U.S. Pat. Nos. 4,588,670, 4,853,315, 5,501,936, 
5,532,107 and 5,541,033, and are incorporated herein by reference. The 
esterification reaction between the hydroxyl compound and the 
2,1-diazonaphthoquinone sulfonyl chloride requires a base to drive the 
reaction. In order to avoid metal impurities in the photoactive compound, 
organic amines instead of metal carbonates, are currently being used as a 
base to catalyse the esterification reaction. The art discloses the use of 
amines soluble in organic solvents, such as -1,4 diazabicyclo 2,2,2! 
octane, N-methyl morpholine, triethyl amine and diethanolamine. However, 
it has been found that significant quantities, that is noncatalytic 
amounts, of the amine need to be used in the reaction. It is believed, 
although the applicants do not wish to be bound by the theory, that the 
amine reacts with the chloride resulting from the esterification reaction 
to form the chloride salt and thus the amine is consumed and is not 
regenerated to act as a catalyst. Therefore, at least an equimolar amount 
of amine must be used when reacting a hydroxyl containing compound with a 
chloride containing compound. However, when high degrees of esterification 
are required, that is, typically when greater than 60% of the hydroxyl 
groups are reacted with the 2,1-diazonaphthoquinone sulfonyl chloride, 
then significant amounts of the aminochloride is formed and this leads to 
unacceptably high levels of chloride in the photoresist films. Photoactive 
compounds with higher degrees of esterification are often desirable since 
they are known to give photoresists with better resolution. The salt 
formed must be removed from the reaction product, since it is known that 
these types of salts can cause contamination problems in the photoresist 
film. These salts are removed typically, by washing the photoactive 
compound with an aqueous solution, and often repeated washings are 
necessary to reduce the salt concentration. Despite these washings, 
chloride levels are not reduced to the levels desired by the industry of 
less than 100 ppm, preferably less than 50 ppm and preferably less than 10 
ppm, in the photoresist film. Residual free amine can also hinder the 
photolytic mechanism of the photoactive compound in the photoresist film. 
Thus, there is great need to reduce or eliminate organic soluble amines 
from the synthesis of the photoactive compound. 
The present invention discloses a method of esterification to form an ester 
photoactive compound, where a solid basic resin; for example, an anionic 
exchange resin, that does not dissolve in the reaction medium, is used as 
a insoluble base for catalysing the reaction between a hydroxy containing 
compound and a halide containing compound. The solid basic resin provides 
the basic site for catalyzing the esterification reaction, and 
furthermore, it has been found that the chloride levels are also reduced 
when using the solid catalyst. Once the reaction is complete the solid 
resin is removed, preferably filtered, and almost all of the halide can be 
removed from the photoactive compound. Thus, this invention describes a 
unique way of using the anion exchange resin for both providing a basic 
reaction site to drive the esterification reaction and also a process for 
reducing the contaminant levels in the photoactive compound. This results 
in a cost effective method for both the synthesis of the photoactive 
compound and also the removal of the possible sources of contaminants in 
the esterification product. 
In another embodiment of the invention a combination of a small amount of 
an organic amine soluble in the organic solvent composition of the 
reaction, and a solid basic catalyst; for example, an anionic exchange 
resin, is added to the solution of the reactants. Examples of such organic 
amines, without limitation are, 1,4 diazabicyclo 2,2,2! octane, N-methyl 
morpholine, triethyl amine or diethanolamine. This novel process helps 
achieves a high degree of esterification without excessive amounts of the 
amine salt being formed. The amine may be used at concentrations of less 
than 0.3 equivalent, preferably less than 0.2 equivalent, relative to the 
chloride functionality. The amount of the solid basic catalyst used 
depends on the composition of the reactants, type of solvent(s) and degree 
of esterification. 
The photoactive compounds of this invention are prepared by a process of 
esterification of the hydroxy compound with the diazo compound. The 
ballast compound can contain one or more hydroxy groups, preferably these 
hydroxy groups are attached to a phenyl moeity, although an aliphatic 
moeity is within the scope of this invention. Examples of such compounds 
are, without limitation, 2,3,4 trihydroxybenzophenone, 2,3,4,4' 
tetrahydroxybenzophenone, cumyl phenone, trishydroxyphenylalkane, 
oligomers of substituted phenols and formaldehyde, 4,8, dihydroxymethyl 
tricyclo(5.2.1.0)decane, and others known in the art. 
2,1-diazonaphthoquinone sulfonyl chlorides are commonly used, specific 
examples of which are, 2,1,5-diazonaphthoquinone sulfonyl chlorides, 
2,1,4-diazonaphthoquinone sulfonyl chlorides, 2,1,6-diazonaphthoquinone 
sulfonyl chlorides and mixtures of these may also be used. Other diazo 
chlorides may also be used, such as those described in U.S. Ser. No. 
08/813,167 filed Mar. 7, 1997, and Ser. No. 08/812,542 filed Mar. 7, 1997, 
and referenced herein, examples of which are, 3,diazo,2,4-quinoline 
sulfonyl chloride and 3,diazo,4-oxo coumarin sulfonyl chloride, etc. 
It is also within the scope of this invention that a photoactive ester 
compound is formed by the reaction of a 2,1-diazonaphthoquinone acid and a 
ballast compound containing at least one halide group. This esterification 
reaction can be carried in a solvent medium and in the presence of a solid 
basic catalyst as described previously, and optionally, with a less than 
0.3 equivalent of a organic soluble amine. 
The esterification reaction is carried out in an organic solvent medium. 
Solvents that may be used are those that dissolve the reactants, organic 
amine and other components, except the solid ion exchange catalyst. 
Examples of such solvents are, but are not limited to, butyrolactone, 
acetone, propylene glycol monomethyl ether, dioxane, tetrahydrofuran, or 
mixtures thereof. 
An example of a solid basic catalyst is an anionic exchange resin, which 
can be obtained commercially such as Amberlyst.RTM. 21 or Amberlyst.RTM. 
26. These resins should be of sufficient purity so that contaminants, 
largely ionic, are not reintroduced into the reaction mixture. Sometimes 
it is necessary to treat the ion exchange resins to remove almost all of 
the impurities, through several aqueous and/or solvent washing steps. The 
ion exchange resin may be treated as described in the prior art referenced 
herein, U.S. Pat. No. 5,543,263 and U.S. Ser. No. 294,453. The solid resin 
is added in amounts sufficient to effectively catalyze the reaction and 
remove the halide, preferably one to three times the concentration of the 
halide, more preferably one to two times the concentration of the halide. 
Furthermore, it has been found that use of the solid anionic catalyst 
reduces the ionic impurities compared to cases where it is not used. 
The reaction conditions, such as temperature, time and concentration of the 
components, are adjusted to give the photoactive product with the desired 
degree of esterification and purity. The temperature is generally kept 
below 45.degree. C., preferably below 30.degree. C. Upon completion of the 
esterification reaction, the solid catalyst is filtered and the 
esterification product is washed and dried under vacuum, preferably at 
35-40.degree. C. Optionally, an acid may be added after removing the solid 
catalyst, either in the form of a solvent soluble acid, such as glacial 
acetic acid, or a solid cationic exchange resin, such as Amberlyst.RTM. 
15, to quench the reaction. The treatment with the solid cationic exchange 
resin provides a further advantage in that it can then be completely 
removed by a simple process of filtration. 
Once the photoactive ester has been formed, it can be isolated by any of 
the known methods, such as precipitating from a cold aqueous methanol 
solution. The photoactive ester can further be washed with water and 
dried, thereby giving a photoactive compound of high purity that can be 
formulated into a photoresist. 
The novel photosensitive composition of this invention is formulated by 
forming an admixture of a film-forming resin, the photoactive compound of 
high purity according to the method described in this invention and a 
photoresist solvent composition. Film-forming resins can be novolak 
resins, polyhydroxystyrenes, and others known in the art. 
Suitable solvents for photosensitive compositions may include propylene 
glycol mono-alkyl ether, propylene glycol alkyl (e.g. methyl) ether 
acetate, ethyl-3-ethoxypropionate, ethyl lactate, mixtures of 
ethyl-3-ethoxypropionate and ethyl lactate, 2-heptanone, 
3-methoxy-3-methyl butanol, butyl acetate, anisole, xylene, diglyme, 
ethylene glycol monoethyl ether acetate or mixtures thereof. The preferred 
solvents are propylene glycol methyl ether acetate (PGMEA), ethyl lactate, 
2-heptanone, anisole, ethyl-3-ethoxypropionate (EEP) and 
3-methoxy-3-methyl butanol. 
In the preferred embodiment, the solid parts of the photoresist 
composition, the novolak resin and the diazonaphthoquinone, preferably 
range from 15% to about 99% resin with from about 1% to about 85% 
diazonaphthoquinone. A more preferred range of resin would be from about 
50% to about 90% and most preferably from about 65% to about 85% by weight 
of the solids photoresist components. A more preferred range of the 
diazonaphthoquinone would be from about 10% to about 50% and most 
preferably from about 15% to about 35%, by weight of the solid in the 
photoresist. In manufacturing the photoresist composition, the resin and 
the diazonaphthoquinone are mixed with the solvent, such that the solvent 
mixture is present in an amount of from about 40% to about 90% by weight 
of the overall photoresist composition. A more preferred range is from 
about 60% to about 83% and most preferably from about 65% to about 70% by 
weight of the overall photoresist composition. 
Additives such as colorants, non-actinic dyes, anti-striation agents, 
plasticizers, adhesion promoters, coating aids, speed enhancers and 
surfactants may be added to the solution of resin, photoactive compound 
and solvent system before the solution is coated onto a substrate. 
The prepared photoresist solution, can be applied to a substrate by any 
conventional method used in the photoresist art, including dipping, 
spraying, whirling and spin coating. When spin coating, for example, the 
resist solution can be adjusted with respect to the percentage of solids 
content, in order to provide coating of the desired thickness, given the 
type of spinning equipment utilized and the amount of time allowed for the 
spinning process. Suitable substrates include silicon, aluminum, polymeric 
resins, silicon dioxide, doped silicon dioxide, silicon nitride, tantalum, 
copper, polysilicon, ceramics, aluminum/copper mixtures; gallium arsenide 
and other such Group III/V compounds. 
The photoresist coatings produced by the described procedure are 
particularly suitable for application to thermally grown silicon/silicon 
dioxide-coated wafers, such as are utilized in the production of 
microprocessors and other miniaturized integrated circuit components. An 
aluminum/aluminum oxide wafer can also be used. The substrate may also 
comprise various polymeric resins, especially transparent polymers such as 
polyesters. The substrate may have an adhesion promoted layer of a 
suitable composition, such as one containing hexa-alkyl disilazane. 
The photoresist composition solution is then coated onto the substrate, and 
the substrate is treated at a temperature from about 70.degree. C. to 
about 110.degree. C. for from about 30 seconds to about 180 seconds on a 
hot plate or for from about 15 to about 90 minutes in a convection oven. 
This temperature treatment is selected in order to reduce the 
concentration of residual solvents in the photoresist, while not causing 
substantial thermal degradation of the photosensitizer. In general, one 
desires to minimize the concentration of solvents and this first 
temperature treatment is conducted until substantially all of the solvents 
have evaporated and a thin coating of photoresist composition, on the 
order of one micron in thickness, remains on the substrate. In a preferred 
embodiment the temperature ranges from about 85.degree. C. to about 
95.degree. C. The treatment is conducted until the rate of change of 
solvent removal becomes relatively insignificant. The temperature and time 
selection depends on the photoresist properties desired by the user, as 
well as the equipment used and commercially desired coating times. The 
coated substrate can then be exposed to actinic radiation, e.g., 
ultraviolet radiation, at a wavelength of from about 300 nm to about 450 
nm, x-ray, electron beam, ion beam or laser radiation, in any desired 
pattern, produced by use of suitable masks, negatives, stencils, 
templates, etc. 
The photoresist is then optionally subjected to a post exposure second 
baking or heat treatment either before or after development. The heating 
temperatures may range from about 90.degree. C. to about 120.degree. C., 
more preferably from about 100.degree. C. to about 110.degree. C. The 
heating may be conducted for from about 30 seconds to about 2 minutes, 
more preferably from about 60 seconds to about 90 seconds on a hot plate 
or about 30 to about 45 minutes by convection oven. 
The exposed photoresist-coated substrates are developed to remove the 
image-wise exposed areas by immersion in an alkaline developing solution 
or developed by spray development process. The solution is preferably 
agitated, for example, by nitrogen burst agitation. The substrates are 
allowed to remain in the developer until all, or substantially all, of the 
photoresist coating has dissolved from the exposed areas. Developers may 
include aqueous solutions of ammonium or alkali metal hydroxides. One 
preferred hydroxide is tetramethyl ammonium hydroxide. After removal of 
the coated wafers from the developing solution, one may conduct an 
optional post-development heat treatment or bake to increase the coating's 
adhesion and chemical resistance to etching solutions and other 
substances. The post-development heat treatment can comprise the oven 
baking of the coating and substrate below the coating's softening point. 
In industrial applications, particularly in the manufacture of 
microcircuitry units on silicon/silicon dioxide-type substrates, the 
developed substrates may be treated with a buffered, hydrofluoric acid 
base etching solution. The photoresist compositions of the present 
invention are resistant to acid-base etching solutions and provide 
effective protection for the unexposed photoresist-coating areas of the 
substrate.

The following specific examples will provide detailed illustrations of the 
methods of producing and utilizing compositions of the present invention. 
These examples are not intended, however, to limit or restrict the scope 
of the invention in any way and should not be construed as providing 
conditions, parameters or values which must be utilized exclusively in 
order to practice the present invention. 
EXAMPLES 
Cleaning of Amberlyst.RTM. 21 
The anionic ion exchange resin, Amberlyst.RTM. 21, was soaked for 2 hours 
and was cleaned by passing deionized water through a column of 
Amberlyst.RTM. 21 until the effluent was clear, followed by 10% ammonium 
hydroxide and further rinsed until the deionized water passing through the 
column was neutral. This cleaned Amberlyst.RTM. 21 was dried for use in 
the following Examples. 
Cleaning of Amberlyst.RTM. 15 
Amberlyst 15 beads (100 ml) as received were soaked for 2 hours in 500 ml 
of deionized water (DI) water. After the 2 hour soaking the beads were 
placed in a glass column. DI water was passed through the column until the 
effluents ran clear. Six bed volumes of 10% (electronic grade) 
hydrochloric acid were passed through the column with a 10 minutes 
residence time for each bed volume. Finally a large volume of DI water was 
passed through the column until the conductivity of the water going into 
the column was the same as the effluents leaving the column. At this point 
the beads were considered ready for use and dried. 
Example 1 
A mixture of tris-(4-hydroxyphenyl)ethane (THPE) (13.5 g, 0.044 moles), 
2,1,4-diazo naphthoquinone sulfonyl chloride (14.9 g, 0.055 moles), 
2,1,5-diazo naphthoquinone sulfonyl chloride (20.3 g, 0.075 moles), 
gamma-butyrolactone (200 ml) and acetone (100 ml) was stirred gently at 
25.degree. C. until about 90% of the starting materials were in solution. 
To this mixture was added, over 15 minutes, a solution of 
1,4-diazabicyclo(2,2,2-)octane (Dabco) (2 g, 0.018 moles and 0.14 
equivalent of chloride), gamma-butyrolactone (60 ml) and acetone (30 ml). 
A cleaned Amberlyst.RTM. 21 resin (65 g) was then added over one hour, 
while keeping the reaction temperature below 30.degree. C. The reaction 
mixture was stirred for one hour. The Amberlyst.RTM. 21 resin was 
filtered. Glacial acetic acid (2 ml) was added and stirred for one hour. 
The final solution was filtered and added to a mixture of deionized (DI) 
water (800 ml) and methanol (200 ml), maintained at 15-20.degree. C., 
while stirring. The slurry was stirred for 30 minutes and filtered. The 
product was dried and washed with DI water until the conductivity of the 
wash liquor was less than 1 .mu.Siemens(.mu.LS). The compound was dried in 
a vacuum oven at 35-40.degree. C. until the water content was less than 
1%. The degree of esterification, that is, the amount of hydroxy groups 
that reacted with the chloride to form the ester, was determined by high 
pressure liquid chromatography to be 85% and the total chloride level as 
measured by silver nitrate assay was less than 10 ppm. 
Example 2 (Comparative) 
A mixture of tris-(4-hydroxyphenyl)ethane (THPE) (6.2 Kg, 20.2 moles), 
2,1,4-diazo naphthoquinone sulfonyl chloride (36.8 Kg, 25.2 moles), 
2,1,5-diazo naphthoquinone sulfonyl chloride (10.1 Kg, 37.5 moles), 
gamma-butyrolactone (27.1 l) and acetone (13.7 l) was stirred gently at 
25.degree. C until about 90% of the starting materials were in solution. 
To this mixture was added, over 30-40 minutes, a solution of 
1,4-diazabicyclo(2,2,2-)octane (Dabco) (7.4 Kg, 66.1 moles), 
gamma-butyrolactone (24.3 l) and acetone 12.1 l). The mixture was stirred 
for an hour and the temperature maintained at 30.degree. C. The final 
solution was filtered. Glacial acetic acid (3.2 Kg) was added and stirred 
for one hour. The acidified solution was filtered. The solution was added 
to a mixture of deionized (DI) water (756 l) and methanol (81 l), 
maintained at 15-20.degree. C., while stirring. The slurry was stirred for 
30 minutes and filtered. The product was dried and washed with DI water 
until the conductivity of the wash liquor was between 3-5 .mu.S. The 
compound was dried in a vacuum oven at 35-40.degree. C. until the water 
content was less than 1%. The degree of esterification was determined by 
high pressure liquid chromatography to be 99% and the total chloride level 
as measured by silver nitrate assay was 170 ppm. 
Example 3 
A mixture of tris-(4-hydroxyphenyl)ethane (THPE) (13.5 g, 0.044 moles), 
2,1,4-diazo naphthoquinone sulfonyl chloride (14.9 g, 0.055 moles), 
2,1,5-diazo naphthoquinone sulfonyl chloride (20.3 g, 0.075 moles), 
gammabutyrolactone (90 ml) and acetone (45 ml) was stirred gently at 
25.degree. C. until about 90% of the starting materials were in solution. 
A washed Amberlyst.RTM. 21 resin (65 g) was then added over one hour, 
while keeping the reaction temperature below 30.degree. C. The reaction 
mixture was stirred for one hour. The Amberlyst.RTM. 21 resin was 
filtered. Glacial acetic acid (2 ml) was added and stirred for one hour. 
The final solution was filtered. The solid was added to a mixture of 
deionized (DI) water (800 ml) and methanol (200 ml), maintained at 
15-20.degree. C., while stirring. The slurry was stirred for 30 minutes 
and filtered. The product was dried and washed with DI water until the 
conductivity of the wash liquor was less than 1 .mu.S. The compound was 
dried in a vacuum oven at 35-40.degree. C. until the water content was 
less than 1%. The degree of esterification was determined by high pressure 
liquid chromatography to be 27%. 
Example 4 
A mixture of trihydroxybenzophenone (13.5 g, 0.054 moles), 2,1,4-diazo 
naphthoquinone sulfonyl chloride (39.3 g, 0.14 moles), 2,1,5-diazo 
naphthoquinone sulfonyl chloride (4.3 g, 0.016 moles), gamma-butyrolactone 
(300 ml) was stirred gently at 25.degree. C. until about 90% of the 
starting materials were in solution. To this mixture was added, over 15 
minutes, a solution of N-methyl morpholine (3.5 g, 0.035 moles and 0.22 
equivalent of chloride) and gamma-butyrolactone (60 ml). A cleaned 
Amberlyst.RTM. 21 resin (80 g) was then added over one hour, while keeping 
the reaction temperature below 30.degree. C. The reaction mixture was 
stirred for one hour. The Amberlyst.RTM. 21 resin was filtered. Glacial 
acetic acid (2 ml) was added and stirred for one hour. The final solution 
was filtered. The solid was added to a mixture of deionized (DI) water 
(600 ml) and methanol (120 ml), maintained at 15-20.degree. C., while 
stirring. The slurry was stirred for 30 minutes and filtered. The product 
was dried and washed with DI water until the conductivity of the wash 
liquor was less than 1 .mu.S. The compound was dried in a vacuum oven at 
35-40.degree. C. until the water content was less than 1%. The degree of 
esterification was determined by high pressure liquid chromatography to be 
97% and the total chloride level as measured by silver nitrate assay was 
17 ppm. 
Example 5 (Comparative) 
A mixture of trihydroxybenzophenone (12.5 g, 0.054 moles), 2,1,4-diazo 
naphthoquinone sulfonyl chloride (39.3 g, 0.14 moles), 2,1,5-diazo 
naphthoquinone sulfonyl chloride (4.3 g, 0.016 moles), gamma-butyrolactone 
(300 ml) was stirred gently at 25.degree. C. until about 90% of the 
starting materials were in solution. To this mixture was added, over 15 
minutes, a solution of N-methyl morpholine (18 g, 0.18 moles) and 
gamma-butyrolactone (60 ml). The mixture was stirred for an hour and the 
temperature maintained at 30.degree. C. Glacial acetic acid (4 ml) was 
added and stirred for one hour. The final solution was filtered. The solid 
was added to a mixture of deionized (DI) water (600 ml) and methanol (600 
ml), maintained at 15-20.degree. C., while stirring. The slurry was 
stirred for 30 minutes and filtered. The product was dried and washed with 
DI water until the conductivity of the wash liquor was less than 1 .mu.S. 
The compound was dried in a vacuum oven at 35-40.degree. C. until the 
water content was less than 1%. The degree of esterification was 
determined by high pressure liquid chromatography found to be 97% and the 
total chloride level as measured by silver nitrate assay was 100 ppm. 
Example 6 
A mixture of paracresol/formaldehyde resin (72 g, 0.1 moles), 2,1,5-diazo 
naphthoquinone sulfonyl chloride (64.6 g, 0.24 moles) and acetone (500 ml) 
was stirred gently at 25.degree. C. until about 90% of the starting 
materials were in solution. To this mixture was added, over 15 minutes, a 
solution of triethylamine (2.6 g, 0.026 moles) and acetone (500 ml). A 
washed Amberlyst.RTM. 21 resin (80 g) was then added over one hour, while 
keeping the reaction temperature below 30.degree. C. The reaction mixture 
was stirred for one hour. The Amberlyst.RTM. 21 resin was filtered. 
Glacial acetic acid (2 ml) was added and stirred for one hour. The final 
solution was filtered. The solid was added to a mixture of deionized (DI) 
water (2400 ml) and methanol (600 ml), maintained at 15-20.degree. C., 
while stirring. The slurry was stirred for 30 minutes and filtered. The 
product was dried and washed with DI water until the conductivity of the 
wash liquor was less than 1 .mu.S. The compound was dried in a vacuum oven 
at 35-40.degree. C. until the water content was less than 1.0%. The resin 
was found to be esterified by high pressure liquid chromatography and the 
total chloride level as measured by silver nitrate assay was 70 ppm. 
Example 7 (Comparative) 
A mixture of paracresol/formaldehyde resin (25% solids) (225 g acetone and 
75 g, 0.1 mole resin), 2,1,5-diazo naphthoquinone sulfonyl chloride (64.6 
g, 0.24 moles) and acetone (500 ml) was stirred gently at 25.degree. C. 
until about 90% of the starting materials were in solution. To this 
mixture was added, over 15 minutes, a solution of triethylamine (26.0 g, 
0.257 moles) and acetone (50 ml). The mixture was stirred for an hour and 
the temperature was maintained at 30.degree. C. Glacial acetic acid (4 ml) 
was added and stirred for one hour. The final solution was filtered. The 
solid was added to a mixture of deionized (DI) water (1200 ml) and 
methanol (250 ml), maintained at 15-20.degree. C., while stirring. The 
slurry was stirred for 30 minutes and filtered. The product was dried and 
washed with DI water until the conductivity of the wash liquor was less 
than 1 .mu.S. The compound was dried in a vacuum oven at 35-40.degree. C. 
until the water content was less than 1%. The resin was found to be 
esterified by high pressure liquid chromatography with a similar degree of 
esterification as Example 6 and the total chloride level as measured by 
silver nitrate assay was 5000 ppm. 
Example 8 
A mixture of paracresol/formaldehyde resin (300 g of a 25% solution in 
acetone) and 2,1,5-diazo naphthoquinone sulfonyl chloride (64.6 g, 0.24 
mole) was stirred gently at 25.degree. C. until about 90% of the starting 
materials were in solution. To this mixture was added, over 15 minutes, a 
solution of triethylamine (2.6 g, 0.026 mole and 0.1 equivalent of 
chloride) and acetone (50 ml). A washed Amberlyst.RTM. 21 resin (80 g) was 
then added over one hour, while keeping the reaction temperature below 
30.degree. C. The reaction mixture was stirred for one hour. The 
Amberlyst.RTM. 21 resin was filtered. Half the solution was passed through 
a 200 ml prewashed Amberlyst.RTM. 15 column which had been conditioned 
with acetone. The solution was held for 1 hour and filtered. The filtered 
solution was added to a mixture of deionized (DI) water (750 ml) and 
methanol (750 ml), maintained at 15-20.degree. C., while stirring. The 
slurry was stirred for 30 minutes and filtered. The product was dried and 
washed with DI water until the conductivity of the wash liquor was less 
than 1 .mu.S. The compound was dried in a vacuum oven at 35-40.degree. C. 
until the water content was less than 1.0%. The resin was found to be 
esterified by high pressure liquid chromatography and the total chloride 
level as measured by silver nitrate assay was 11 ppm. 
Example 9 
A solution of photoresist was made with 23.4 weight % cresol/formaldehyde 
resin, 5.9 weight % pyrogallol/acetone resin, 6.4 weight % photoactive 
compound from Example 6, 0.0086 weight % of FC430 (available from 3M Co., 
3M Center Building 233, St. Paul, Minn. 55144) and 64.3 weight % of ethyl 
lactate. 
The photoresist was spin coated onto silicon wafers and soft-baked at 
100.degree. C. for 90 seconds to give a film thickness of 1.2 micrometers. 
The samples were image-wise exposed with a G-Line stepper and 
post-exposure baked at 100.degree. C. for 90 seconds. The samples were 
developed with AZ.RTM. MIF-32 developer (available from AZ.RTM. Electronic 
Materials, Clariant Corp., 70 Meister Ave., Somerville, N.J. 08876) using 
a 87 seconds spray/puddle 21.6.degree. C. cycle. Good quality images were 
obtained on the wafers.