LIGHT-SENSITIVE COMPOUNDS AND PHOTORESISTS CONTAINING THE SAME

COMPOSES PHOTOSENSIBLES ET PHOTORESISTANCES QUI LES RENFERMENT

English Abstract

ABSTRACT
This invention relates to low molecular weight light-sensitive
polymeric substances and their preparation in which, in the presence of a
common solvent, a mixture of p-azidobenzoic acid or an esterifiable deriva-
tive thereof and a p-nitrobenzoic acid which may be substituted in the
ortho- and/or meta-positions with an alkyl group containing from 1 to 4
carbon atoms, or an esterifiable derivative thereof are reacted with an
epoxide resin. The products obtained have improved properties such as
radiation sensitivity, light resolution and edge definition.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of preparing low molecular weight light-sensitive
polymeric compounds comprising reacting, in the presence of a common solvent,
a mixture of p-azidobenzoic acid or an esterifiable derivative thereof and
a p-nitrobenzoic acid which may be substituted in the ortho- and/or meta-
positions with an alkyl group containing from 1 to 4 carbon atoms, or an
esterifiable derivative thereof, with an epoxide resin as represented by
the general formula:
<IMG>
(I)
in which formula R represents hydroxypropylene or the hydrocarbon nucleus of
a dihydric phenol which is free from functional groups other than phenolic
hydroxy groups or a 1,2-propylene oxide derivative thereof; and n is 0, 1,
2 or 3.
2. A method according to claim 1 in which the mixture comprising p-
azidobenzoic acid or an esterifiable derivative thereof and p-nitrobenzoic
acid, if desired substituted in the ortho- and/or meta-positions with an
alkyl group containing from 1 to 4 carbon atoms or an esterifiable derivative
thereof, contains up to 75% by weight p-nitrobenzoic acid.
3. A method according to claim 2, in which the mixture contains p-
azidobenzoic acid and p-nitrobenzoic acid in the proportions of between
3 : 1 parts by weight to 1 : 2 parts by weight.
4. A method according to claim 1, in which the epoxide resin has a
molecular weight of between 340 - 1500.
5. A method according to claim 4, in which the epoxide resin has a
14

molecular weight of between 340 - 750.
6. A method according to claim 4, in which the epoxide resin is a
novolak resin with a molecular weight in the range of 600 - 1500.
7. A method according to claim 1, in which the epoxide resin is
prepared by reacting 2 to 4 moles of epichlorohydrin with one mole of
bisphenol A under an inert atmosphere with the gradual addition of 2 moles
of sodium hydroxide, separating the epoxide product and reacting the epoxide,
in the presence of a common solvent, with a mixture containing p-azidobenzoic
acid or an esterifiable derivative thereof and p-nitrobenzoic acid, if
desired substituted in the ortho- and/or meta-positions with an alkyl group
containing not more than 4 carbon atoms, or an esterifiable derivative
thereof at a temperature of less than 200°C.
8. h method according to claim 7, in which the reaction was carried
out at a temperature of between 130 - 150°C.
9. A method according to claim 6, in which a novolak resin is
prepared by reacting one mole of phenol with 0.8 mole of formaldehyde in
the presence of an acid catalyst at 100 C, separating the product by removing
the water produced when the desired degree of polymerization is reached
ant reacting the novolak resin with epichlorohydrin to form terminal
reactive epoxide groups on the novolak resin nucleus, separating the reaction
product and reacting the product, in the presence of a common solvent, with
a mixture of p-azidobenzoic acid or an esterifiable derivative thereof and
p-nitrobenzoic acid, if desired substituted in the ortho- and/or meta-
positions with an alkyl group containing not more than 4 carbon atoms or an
esterifiable derivative thereof, in the mole ratio of one mole of the resin
to 3 to 4 moles of the mixture.

10. A method according to claim 9, in which the mixture contains
1 mole of p-azidobenzoic acid and from 0.3 to 3 moles of p-nitrobenzoic
acid.
11. A method according to claim 1, in which the common solvent is an
organic solvent such as 1,4-dioxane or toluene.
12. A method according to claim 1 wherein R is selected from the group
consisting of p,p'-dihydroxydiphenyl, p,p'-dihydroxydiphenyl methane,
p,p'-dihydroxydiphenylmethylmethane, p,p'-dihydroxydibenzyl, and p,p'-di-
hydroxydiphenyldimethyl methane.
13. Light-sensitive polymers as represented by the general formula:
<IMG>
(III)
<IMG>
a 1,2-propylene oxide, a p-azidobenzoxy or a p-nitrobenzoxy derivative
thereof, in which formula R1 represents hydroxypropylene or the hydrocarbon
nucleus of a dihydric phenol which is free from functional groups other than
phenolic hydroxy groups, X represents a N3 or a N02 group, with the proviso
that the mixture of the polymers at least contain one molecule in which one
X is a N2 group and at least one molecule in which one X is a N02 group,
and n is 0, 1, 2 or 3,
14. Light-sensitive polymeric compounds according to claim 13 which
contain an average of not more than 75% N02 groups.
15. Light-sensitve polymeric compounds according to claim 13 which
contain at least one terminal or cross-linked nitrilo radical ?-N=) per
molecule.
16

16. Light-sensitive polymeric compounds according to claim 13, in
which R' is the hydrocarbon nucleus of p,p'-dihydroxydiphenyldimethyl
methane.
17. Light-sensitive polymeric compounds according to claim 13, in
which n is 0.
18. Light-sensitive compositions comprising a polymer according to
claim 13 mixed with, dissolved or dispersed in an inert carrier.
19. Light-sensitive compositions according to claim 18 in which the
composition is dissolved in a suitable organic solvent and, if desired, an
inert carrier.
20. Light-sensitive compositions according to claim 18, comprising a
light-sensitizing agent.
21. Light-sensitive coatings when coated on a substrate comprising a
polymeric compound according to claim 13 or a light-sensitive composition
according to claim 17.
22. Light-sensitive composition according to claim 20 in which the
sensitizing agent is 5-nitroacenenaphthene.
17

Description

~:']~1 B ~3 r,> ~1 0
~EEN/l.~`VD
8 . 1 . 1 975
4~98
"Novel Light-sensitive Compounds and Photoresists -
containing the same".
This invention relates to light-sensitive
p~lymeric compounds and is concerned ~ith an improvement : :
to the invention of our United Kingdom Specificati.on
No. 1,.330,263.
The said specification describes and claims
a method of preparing low molecular weight light~
sensitive polymeric compounds, which method comprises -
,
reac~ing, in the presence of a common solvent, p-azidobenzoic ~:.
acid or an esterifiable derivative thereof with an ;~:
, .. .
epoxide resin as represented by the general. formula I:
./ O~ ~ ~ OE
CH2 CH - CH2- -O -. R - O - CH2 - CH - CH2- O - R - O
, ~ .,
0~ ~ ~
. ~ : CH2 CH~- CH2 tI]
~, . . .
in whioh ~ormula R represents hydroxypropylene or the ;
hydrocarbon nucleus of a dihydric phenol which lS free~
from functional groups other than phenolic hydroxy groups,
: such as ~ -dihydroxydiphenyl~ ~p~-dihydroxy- .:
. . diphenyl methane, p,p~-dihydroxydlphenylmethylmethane,
: p~-dihydroxydibenzyl, and p,~-dihydroxydiphenyl~
dimethyl methane; or a 1,2-propylene oxide derivative : .
~thereof; and n is 0, 1, 2 or 3. ~
!;~ '
: ` . ' . '

3 3,~
8. 1 . 1975
1044398
- The present invention is particularly concerned
with a new class of light-sensitive polymeric compounds
which are derivatives of a reaction product obtained
by reacting a mixture of p-azidobenzoic acid or an ~-
esterifiable derivative thereof and a possib].y substituted
~-nitrobenzoic acid or an esterifiable derivative thereof
with the aforementioned epoxide resin.
From said U.K. Specification No. 1,330,263
light-sensitive polymers are known which can be represented
by the general formula:
, ` ''~
O OH OH
N3 ~ C-O-CH2-CH-CH~ -O-R'-O-CH2-lH-CH2 ~ ~~ 2 ~
- . n ~ .
- ' ' .: . ~ : '.
-CH-CH -O-C ~ N
¦ 2 11 ~ 3 II
OH
'
or 1,2-propylene oxide or p-azidobenzoxy derivatives there~o~,
in which formula R' represents hydroxypropylen~, or the
hydrocarbon nucleus of a dihydric phenol which is free
from functional groups other than phenolic hydroxy groups,
and n is:0, 1,~2 or 3.
We have discov,ered that some of the p-azidobenzoxy
groups present ln thë mixturë of polymers represent~d by ~ormula
~1 II may be replQced by ~-nitrobenzoxy groups and that,
~UD~ xpectedly, the propertiès, especlally~the light
resolution and edge definition, of these polymeric coinpounds
,~.. . : : , -
,

l'HB 321~C)8
8.1.1975
~ 4398 :: -
are grreatly improved. The p-nitrobenzoxy-substituted
polymers are also sensitive to relatively narrow
ranges of wave-lengths of light, particularly in the
short-wave or ultra-violet range. Thus, the polymeric
compounds of the present invention have greatly ,
redhced defects due to aberration on exposure to
light through masks with very fine apertures. Further- -
more, the compounds of the invention have the
. advantage that they can be processed under normal
lighting conditions without, for example, use of
special lights such as yellow lamps. ~ `
According to the present invention there
- is provided a method of preparing low molecular weight
light-sensitive polymeric compounds comprising reacting,~
in the presence of a common solvent, a mixture of
p-azidobenzoic acid or an esterifiable derivative
thereof and a p-nitrobenzoic acid ~hich may be substituted :
in the ortho- and/or meta-positions wlth an alky~
group containing from 1 to 4 carbon~atoms, or an
esterifiable derivative thereof~ wlth an epoxide
resin as represented by the general formula:
CM2 - CH - CE ~ 0 - R - 0 - CM2 - ~M - GH2 ~ - R
/\ - ' ` .i
-0 - C~I2 - CH - CH2
in which formula R represents hydroxypropylene or the
hydrocàrbon nuoleus of a dihydric phenol which is free
- from functional groups o*her than phenollc hydroxy groups,
.. ~ :

PHB 3~l08
8.1.1975
1~)44398
such as ~,p~:ihydroxydiphenyl, p,pl-dihydroxy-
diphenyl methane, p,~'-dihydroxydiphenylmethylmethane,
p,p~-dihydrox~dibenzyl, and p,p'-dihydroxydiphenyldimeth~Tl
methane; or a 1,2-propylene oxide derivative thereor;
and n is 0, 1, 2 or 3.
An example of an epoxide resin according
to the above formula whereby R represents a 1,2-
propylene oxide derivative of the nucleus of a dihydric
phenol and n = O, is represented by the formula
CH2 - CH-CHz-O- ~
~ CH2 H
CH 2 - CH--CH 2- 0~ 0--CH2 -cH - CH2
:
- The molecular weight of such a epoxidised
novol~k resin monomer is 645.
. When R has the above given meaning and n - 1 the
molecular weight is 1063. At n = 2 the molecular weight
amounts 1481.
Upon reaction of the epoxidised novolak resin
represented above wlth a mixture Or p-azidobenzoic acid and
p-nitrobenzoic acid the following compound will result:
O OH CH2-l OH O
ZO X-~-(~-O-CH2-CH-oH2-o-~ ~-o-CHz-CH-CH2-o-c-~3-x
CH H
O OH ~2 ~ 2 OH O
X- ~ ~C-O-CH2-CH-CH2-0- ~ ~ -0-CH2-CH-CH2-0-C ~ ~ X
'
:~ wherein X stands for a N3- or N02 group.
~. . : ' "
_, _

P11~3 3,~
8. 1. 19'75
1~4398
. .
The p-nitrobenzoic acid compounds or
esterif`iable ~1erivatives thereof may be sub~tituted
in the ortho- and/or meta-positions with one or
more alkyl groups containing from 1 to 4 carbon atoms, ~or
example, o-methyl p-nitrobenzoic acid, o-ethyl ~-nitro-
benzoic acid, o-propyl ~-nitrobenzoic acid, o butyl
p-nitrobenzoic acid, m-methyl p-nitrobenzoic acid,
m-ethyl p-nitrobenzoic acid, m-propyl ~-nitrobenzoic -
acid, m-butyl p-nitrobenzoic acid, o,~'-dimethyl
p-nitroben~oic acid, o,o'-diethyl p-nitrobenzoic acid,
o,o!_dipropyl p-nitrobenzoic acid, o,o'-dibutyl
p-nitrobenzoic acid, m,m'-dimethyl p-nitrobenzoic acid,
m,m'-diethyl p-nitrobenzoic acid, m,m'-dipropyl
p-nitrobenzoic acid, m,m'-dibutyl P-nitrobenzoic acid,
o~o',m,m'-tetramethyl ~-nitrobenzoic acid, o,o',m,m'-tetra-
- -:
ethyl p-nitrobenzoic acid, o,o'-diethyl-m,m'-dimethyl
~-nitrobenzoic acid, o,o',m-trimethyl ~-nitrobenzoic acid, `
o,m,m'-triethyl p-nitrobenzoic acid.
Preferably, the mixture comprising
P-azid~benzoic acid or an esterifiable derivative thereof
and p-nitrobenzoic acid, if desired substituted in the
ortho- and/or meta-positions with an alkyl group containing ! "
~rom 1 to 4 carbon atoms or an esterifiable derivative
thereof~contains up to 75~ by weight ~-nitrobenzoic acid.
In an alternative embodiment the mixture
contains ~-azidobenzoic acid and p-nitrobenzoic acid
in the proportions of between 3 : 1 parts by weight
to 1 : 2 parts by weight.
The epoxide resin may contain two reactive
terminal epoxide groups and also may ha~e a molecular
...
... . -
. :

Pll~ ~21Jo8
8.1.1975
~044398
weight of between 340 - 1500, especially between
340 - 750. Wllen the epoxide resin is a novolak resin
the molecular weight range is pre~erably between
600 - 1500.
Suitable ep,oxide resins may be prepared
by reacting 2 to 4 moles of epichlorohydrin with one
mole of bisphenol A under an'inert atrnosphere with the
gradual addition of 2 moles of sodium hydroxide. The
epoxide product may then be separated and reacted
in the presence of a common solvent such as toluene
with a mixture containing ~-azidobenzoic acid or
an es~terifiable derivative thereof and ~-nitrobenzoic
ac'id, if desired substituted in the ortho- and/or
meta-positions with an alkyl group containing not more
than 4 carbon atoms, or an esterifiable derivative
thereof at a temperature of less than 200C and
preferably between 130 - 150C.
A suitable novolak resin may be prepared
by reacting one mole of phenol with o.8 moles~of
.~ormaldehyde in the presence of an acid catalys* at ~'
100C, separating the product by removing the water
produced when the desired degree of polymerisation '
is reached. The novolak resin may then be reacted wlth
epichlorohydrin to form terminal reactive epoxide groups
on the novolak resin nucleus. The reaction product '-'
i9 separated and it is reacted in the presence of ~ ,
a common solvent such as toluene with a mixture o~
~-azidobenzo~c acid or an esterifiable derivative
thereof and ~-nitrobenz'oic acid, if desired substituted
~ .
-7- '

1?111~ ~ _108
8 . 1 . 1 97 5
~44398 :
in the ortho- and/or meta-positions with an alkyl
group contai~ing not more than 4 carbon atoms or an
esterifiable derivative thereof, in the mole ratio of
one mole of the resin to 3 to 4 moles of the mixture. :~
Preferably, the mixture contains 1 mole of
p-azidobenzoic acid and from 2 to 3 moles of ~-nitrobenzoi.c
acid, and the common solvent is an organic solvent such
as 1,4-dioxane or toluene.
According to a further aspect of the present
invention there is provided light-sensitive polymers as
represented by the general formula:
X- ~ ~-0-CHz-CH-CH2~ o-R'-o-CH2-CH-CH73 0-R 0 CH2
. n
~,
f 2 11 ~ -X . III
OH
a 1?2-propylene oxide, a p-azidobenzoxy or a ~-nitrobenzoxy :
derivative thereof, in which formula R' represents hydroxy-
propylene or the hydrocarbon nucleus of a dihydric phenol -
which is free from functional groups other than phenolic
hydroxy groups, X represents a N3 or a N02 group,
with the proviso that! a mixture of the polymers at least contain
lone molecùle in which one X is a N3 group, and at least one :
molecule in which one X is a N02 group, and n is 0, 1, 2 or 3.
Light-sensitive polymeric compounds according
to the invention preferably do not contain, on an averag~e, more
than 75% N02 groups. Thus~ the distribution of the N02 groups -
among the mo]ecules in a mixture of differing molecular
', :'' '.
~, 8

8.1.1975
1~44398
weights may range fro~ specific molecules wllich have ~ -
three azido groups replaced by nitro groups, to specific
moleculcs whicll have two, one or even no azido groups
replaced by nitro groups. However, the majority of the
molecules in a 66.6~ substitution have two a~ido
groups replaced by nitro groups. Altsrnatively, the
majority of the molecules may have only one azido group
replaced by a nitro group in a 33.3~ substitution. If
desired a homo~enous fraction of any one molecular species
may be made by molecular separation techniques.
The light-sensitive polymeric cornpounds may
have at least one terminal or cross-linked nitrilo
radical per molecule. Particularly suitable polymeric
compounds are represented by Formula III, in which
formula R~ is the hydrocarbon nucleus of p,p~ -dihydroxy-
diphenyldimethylmethane, where n is 0, 1, 2 or 3 and
preferably n is 0.
Epoxide resins of th- type represented by
Formula I may be prepared by reacting acetone and 2 mole
equivalents of phenol to give bisphenol A, followed
by reacting with epichlorohydrin in the manner described
in specificatiorl No. 1,330,263. Alternatively, the
epoxide resins prepared from glycerol, bisphenol F
or a long-chain bisphenol derived from cashew-nut oil
may be used, followed by epoxidation with epichlorohydrin.
Similarly, the epoxide resins may be prepared from novolak
reslns in the manner de~cribed in ~pecification No. 1,330,263.
The epoxide resin monomer may be dissolved
separately in a solvent which is also a solvent common
to both p-azidobenzoic acid or an esterifiable derivati~e
,.

~-- PT13 ~408
8.1.1975
lr~44398
thereof and p-nitrobenzoic acid or an esterifiable
derivative thcreof. Preferably, a solution of the
mixture of ~-azidobenzoic acid and p-nitrobenzoic acid
is prepared and this solution is added to a solution ~
the epoxide resin and the reaction between the reagents
is effected by refluxing the mixture for up~; to 8 hours. -
The polymers produced according to the present
invention ha~e a relatively low molecular weight which
is controlled by the molar proportions of the reagents
used and the degree to which the reaction is allowed
to proceed,
~hese low molecular weight polymers may be
dissolved in organic solvents to form solutions.
Preferablyf the solvents used for forming solutions of
the polymers are ketones, such as cyclohexanone, acetone, ~ -
methyl-ethyl ketone, 1,4-dioxane; esters, such as
ethyl acetate, propyl acetate, butyl acetate, methyl
glycoacetate; and mixtures of these and other solvents.
If desired, the solvents may be diluted with hydrocarbons, ;
suoh as xylene and/or dipolar aprotic solvents such
as dimethyl formamide, dimethyl acetamide and N-methyl
pyrrolidone.
In general, the solubility of the polymers
in an organic solvent decreases with increasing molecular
.
2~ weights. As the molecular weight of the -N3 group and the
-N02 group are simllar, i.e. in the ratio of 42 : 46,
nnd each group represent~ only a small proportion of
the total molecular weight of the polymer, substitution
Or -N3 groups by -N02 groups does not materially change
the solubilities of the respective polymers.

:
l~rll3 3? '~
8.1.1975
~044398'
Light-sensitive compounds may be incorporated in-to
compo9itions of the polymer:ic compound~ according to tlle
invention. The light-sensitive compounds may be incorporated
into the polymeric composition either during the prepara-tion
of the polymer or a composition thereof, or subsequently,
for example, when applyi~g a polymeric composition to the
surface of a substrate.
One particularly suitable light-sensitive
compound is 5-nitroacenaphthene. Other suitable light-
sensitive compounds are Michler's ketone;~,p-tetraethyldiaminodiphenylketone; p,p-tetramethyl-
diaminodiphenylketone; p,p-dimethylaminobenzophenone;
1,2-benzanthraquinone; ~-chloroanthraquinone; 9,10-anthra-
quinone; 4-nitro-2-chloro aniline; 2,6-dichloro-4-nitro
analine; 2,4,6-trinitro aniline; 5-nitro-2-amino toluene;
and P-nitrodiphenyl.
By way of illustration, certain preferred
processes embodying the invention will now be described
in more detail in the ensuing speoi~ic Examples:
EXAMPLE I
20.~ grams of epoxide-novolak resin, available
as Bakelite resin ERR 0100 with a moleoular weight range ~ :
between 1000 and 2000, were placed in a 500 ml flask with -
200 ml o~ dioxane and stood overnight to dissolve the
resin. The following day, 5.6 g p-nitrobenzoic acid,
10.8 g p-a~ldobenzoic acid and 2 ml benzyl trimethyl
ammonium hydroxide were added. The solution was then
- refluxed (in a glyceiine bath at approximately 140C)
~or 7 hours; allowed to cool to room temperature; and
. .
-~ . : . .

Tl3 ~,21l~)8
8.1.1975
1044398 :
..
poured into 6~o ml of methanol in a one-litre beaker,
A brown resin precipitated and, after standing 2 hours
to settle the precipitate, the l-iquid was decan-ted,
leaving the resin at the bottom of the beaker. The
resin weighed 28 grams and was dissolved in 70 ml of
cyclohexanone.
EX~MPLE II
2.5 g of a sensitiserj 5-nitroacenaphthene,
were dissolved in the cyclohexanone mixture obtained
from Example I.
EXAMPLE III -
The solution obtained from Examples I and II
were then applied to the silicon d~oxide oxidised
surfaces of silicon slices by spinning at~600 r.p.m.
and the coated slices were heated at 70C for 20 minutes
on a hot plate. Each coated slice was then exposed -
through a photomask to ultra-violet light (intensity
5 milliwatts per sq.cm.) for various times, and developed
for 2-3 minutes in cyclohexanone, followed by a
15-second rinse in methanol. The optimum exposure
time-was found to be 10 seconds. In a comparative test,
the optimum exposure time ~or a polymeric layer of
equal thicknes~ of resist produced from p-azidobenzoic
acid and epoxide-novolak resin without ~-nitro groups
and sensitised by Michler's ketone was found to be
90 second~., showing that the addition of nitro-benzoic
aoid to the reactlon mixture giv~s a llght-sensitive
polymeric product nine times more sensitive. The addition
of 5-nitroacenaphthene to the solution of the polymeric
': ' ~''
-12-

.
1~J
c3.1.1975
~4439~
procluct obtained from p-azldobenzoic acid ancl
epoxide-novolak resin did not give an optirl~um
exposure time of less than 90 seconds.
. .
~ 13-