Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
6~7
BACKGROUND O~ THE INVENTION
~he present invention relates generally to radiation sensitive
photoresist compositions and particularly to compositionS
containing aqueous alkali soluble resins together with
naphthoquinone dia~ide sensitizing agents.
It is well known in the art to produce positive photoresist
formulations such as those described in United States Patent
Nos. 3,666,473, 4,115,128 and 4,I73,470. These include alkali- - -
soluble phenol-formaldehyde novolak resins together with light-
sensitive materials, usually a substituted naphthoquinone diazide
compound. The resins and sensitizers are dissolved in an organic
solvent or mixture of solvents and are applied as a thin film or
coating to a substrate suitable for the particular application
de~sired. `-
- '-
The resin component of these photoresist formulations is soluble -;:
in aqueous alkaline solutions, but the naphthoquinone sensitizer
acts as a dissolution rate inhibitor with respect to the resin.
~pon exposure of selected areas of the coated substrate to
actinic radiation, however, the sensitizer undergoes a radiation "~
induced structural transformation and the exposed areas of the
coating are rendered more soluble than the unexposed areas. This
difference in solubility rates causes the exposed-areas of the
photoresist coating to be dlssolved when the substrate is
immersed in an alkaline developing solution while the unexposed
areas are largely unaffected, thus producing a positive relief
pattern on the substrate.
In~most instances, the exposed and developed substrate will be
subjected to treatment by a substrate-etchant solution. The
photoresist coating protects the coated areas of the substrate
from the etchant and thus the etchant is only able to etch the
~X~32~2~7
uncoated areas of the substrate, which in the case of a positive
photoresist, correspond to the areas that were exposed to actinic
radiation. Thus, an etched pattern can be created on the
substrate which corresponds to the pattern on the mask, stencil, -
template, etc., that was used to create selective exposure
patterns on the coated substrate prior to development.
The relief pattern of the photoresist on the substrate produced
,<, .~:
by the method described above is useful for various applications
including as an exposure mask or a pattern such as is employed in
the manufacture of miniaturized integrated electronic components. -
The properties of a photoresist composition which are important
in commercial practice include the photospeed of the resist,
development contrast, resist resolution, and resist adhesion.
"'.'' '
Resist resolution refers to the capabilityof a resist system to
reproduce the smallest equally spaced line pairs and intervening
spaces of a mask which is utilized during exposure with a high
degree of image edge acuity in the developed exposed spaces.
.....
In many industrial applications, particularly in the manufacture
of minaturized electronic components, a photoresist is required
to provide a high degree of resolution for very small line and
space widths (on the order of one micron or less).
The ability of a resist to reproduce very small dimension, on the
order of a micron or less, is extremely important in the
production OL large scale integrated circuits on silicon chips
and similar components. Circuit density on such a chip can only
be.increased, assuming photolithography techniques are utilized,
by increasing the resolution capabilities of the resist.
~;~B262,~
Photoresists are generally categorized as being
either positive working or negative working. In a negative
working resist composition, the imagewise light strucX areas
harden and form the image areas of the resist after removal of
the unexposed areas with a developer. In a positive working
resist the unexposed areas are the image areas. The light
struck parts are rendered soluble in aqueous alkali developers.
While negative resists are the most widely used for industrial
production o printed circuit boards, positive resists are cap-
able of much finer resolution and smaller imaging geometries.Hence positive resists are the choice for the manufacture of
densely packed integrated circuits.
In many commercial applications, it is desirable to
convert a high resolution quinone diazide type positive resist
for a negative working application.
There is interest in the field of image reversal be-
cause of the utility of this process in practical device manu-
facturing. Among the practical aspects of image reversal are
the elimination of the need for a dual set of complementary
masks to do both positive and negative imaging, greater resolu-
tion and process latitude than with positive imaging alone, re-
duction in standing wave effects, and higher thermal stability.
In this regard, several methods have been suggested for such
image reversal. See for example: "Image Reversal-. The
Production of a Negatiue Image in a Positive Photoresist" by
S.A. MacDonald et.al. p.114, IBM Research Disclosure, 1982;
"Image Reversal of Positive" Photoresist". A New Tool for
.
Advancing Integrated Circult Fabrication by E. Alling et.al.,
Journal of the Society of Photo-Imaging Engineers, Vol 539, p~
3~ 194, 1985; M.V. Buzuev et.al. "Producing a_N_gative Image on a
Positive Photoresist'i SU 1,109,708; German Patent DE 252 9054,
C2, 1975, Assigned to H. Moritz and G. Paal,
-- 4 --
~ ;
Making a Negative Image; U.S. 4,104,070, U.S. 4,576,901 and
U.S. 4,5S1,321.
Each of these disclosures suffer from several draw-
backs. A major disadvantage of current image reversal
processes is the need for an additional processing step which
involves ~reatment with either salt forming compounds or high
energy exposure sources such as electron beams or requires an
additional exposure step with actinic light. The present in-
vention provides a mechanism which involves the formation of a
catalytic amount of a radiation generated acid which cross-
links the resin in the exposed region.
The invention provides a unique chemical composition,
which when processed in a slightly modified manner to the usual
and customary method of lithographic processing, yields a
totally unexpected negative, reversed tone image from an other-
wise expected positive type photosensitizer.
Among the advantages realized by this highly desir-
able result are improvement in the relationship between
exposure energy and resulting line width, improved process
latitude, improvement in developed image resolution, substan-
tial elimination of reflective notching, enhanced photo-
sensitivity, improved thermal stability of the resulting image,
and improved adhesion between the photoresist and commonly used
substrates.
SUMMARY OF THÆ INVENTION
The invention provides a process for preparing a
negative image of a positive working photographic element which
comprises in order:
a) forming a composition which comprises
i) from about 1% to about 25% based on the weight
of the solid parts of the composition of a
photosensitive compound having the formula
~2826~7
4 ~
~S~ ORl
R2 R3
wherein R1 = 1,2 benzoquinone-2-diazide-4-sulfonyl;
1,2 naphthoquinone-2-diazide-4-sulfonyl;
or
1,2 anthraquinone-2-diazide-4-sulfonyl
R~ - H, Rs, OR6 or C - R7
R3 = H, Rs, OR6 or C - R7
11
R4 = ~, Rs, OR6 or C - R7
R6 = H, alkyl, aryl, aralkyl or R
Rs,R7 = alkyl, aryl or aralkyl
ii) from about 75% to about 99% based on the weight
of the solid parts of the composition of a
novolak, and/or polyvinyl phenol resin,
especially poly-p-vinyl phenol resin; and
iii~ from about 0.5% to about 20% based on the
weight of the solid parts of the composition of
a cross linking compound which, when in the
presence of that amount and strength of the acid
generated
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~LZ8X~Z~7
_
when said diazide is exposed to actinic
radiation, is capable of crosslinking said resin
under the application of the heating conditions
of step (e); and
iv) sufficient solvent to dissolve the foregoing
composition components; and
b~ coating said composition on a suitable substrate; and
c) heating said coated substrate at a temperature of from
about 20C to about 100C until substantially all of ~~
said solvent is dried off; and
d) imagewise exposing said composition to actinic
radiation; and
e) heating said coated substrate at a temperature of at
least about 95C to about 160C for from about 10 ! ~'.
seconds or more to crosslink said resin; and
) removing the unexposed non-image areas of said
composition with a suitable developer.
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: '`
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62~
D~TAILED DESCRIPTION OF THE PREFERR_D EMBODIMENT
As a first step in the production of the photographic
element of the present invention, one coats and dries the
foregoing photosensitive composition on a suitable substrate.
The composition contains a solvent, crosslinking agent, binding
resin and a 1,2 quinone diazide-4-sulfonyl group containing
photosensitizer. The binding resins include the classes known
as the novolaks, ployvinyl phenols and especially polyparavinyl
phenols.
The production of novolak resins, which m~y be used
for preparing photosensitive compositions, is well known in the
art. A procedure for their manufacture is described in
~hemistrY and APPlication of Phenolic Resins, Knop A. and
Scheib W., Springer Verlag, New York, 1979 in Chapter 4.
Polyvinyl phenols and especially polyparavinyl phenols are
taught in U.S. 3,869,292 and 4,439,516. Similarly, the use of
o-quinone diazides is well known to the skilled artisan as
demonstrated by Liqht Sensitive SYstems, Kosar, J ; John Wiley
~0 & Sons, New York, 1965 in Chapter 7.4. These sensitizers which
comprise a componen~ of the present resist compositions of the
present invention are preferably selected from the group of
substituted naphthoquinone diazide sensitizers which are
conventionally used in the art in positive photoreslst
formulatlons. Such sensitizlng compounds are disclosed, for
example, in United States Letters Patent Nos. 2,797,213;
3,106,465; 3,148,983; 3,130,047; 3,201,329, 3,785,825; and
3,802,885.
The photosensitizer is a 1,2 quinone diazide-4-
sulfonic acid ester of phenolic derivative. It presentlyappears that the number of fused rings is not important for
~Z~32~iZ7
this invention b~lt the position of the sulfonyl group is
important. That is, one may
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~28~27
use benzoquinones, naphthoquinones or anthraquinones as long as
the oxygen is in the 1 position, diazo i5 in the 2 po~ition and
the sulfonyl group is in the 4 position. Likew.ise the phenolic
member to which it is attached does not appear to be important.
For example it can be cumylphenol derivative as taught in UOS~
3,640,992 or it can be a mono-, di-, or tri-hydroxyphenyl alkyl
ketone or benzophenone as shown in U.S. 4,499,171.
As a generalized formula, the quinone diazides of the
present invention may be represented by:
1 0 1~
wherein R1 = 1,2 benzoquinone-2-diazide-4-sulfonyl;
1,2 naphthoquinone-2-diazide-4-sulfonyl;
or
1,2 anthraquinone-2-diaæide-4-sulfonyl
R2 = H, Rs, OR6 or C - R7
R3 = H, Rs, OR6 or C - R7
ll
R4 = H, Rs, OR6 or C - R7
R6 = H, alkyl, aryl, aralkyl or R1
R5,R7 = alkyl, aryl or aralkyl
Useful photosensitizers include (1,2)naphthoquinone-
diazide-4-sulfonyl chloride, condensed with phenolic compounds
such as hydroxy benzophenones especially trihydroxybenzophenone
and more particularly 2,3,4 trihydroxybenzophenone; 2,3,4 tri-
30 hydroxyphenyl pentyl ketone 1,2 naphthoquinone-2-diazide-4-sul-
fonic acid trisester or other alkyl phenones; 2,3,4
trihydroxy-3'-methoxy benzophenone 1,2 naphthoquinone-2-diazide-
.~,
_ g _
~2BZ~27
4-sulfonic acid trisester; 2,3,4 trihydroxy-3'-methyl
benzophenone 1,2 naphthoquinone-2~diazide-4-sulfonic acid
trisester; and 2,3,4 trihydroxybenzophenone 1,2 napthoquinone
diazide 4 sulfonic acid trisester.
The cross-linking compound is a compound, which when in
the presence of that amount and strength of the acid generated
when the diazide is exposed to actinic radiation, is capable of
cross-linking the foregoing novolak, polyvinyl phenol or
poly-p-vinyl phenol resin. This occurs upon the application of
sufficient heat to diffuse the acid to the cross-linking
component but less heat than will decompose the diazide. The
general class of such compounds are those capable of forming a
carbonium ion under the foregoing acid and heat conditions.
~ .
-- 1 0 --
627
The crosslinking compound is a compound having the gene-
ral formula
~ R10-CHR3)n-A-(CHR3~0R2)m
wherein A is B or B-Y-B and
B is a substituted or unsubstituted mononuclear
or fused polynuclear aromatic hydrocarbon or
an oxygen- or sulfur- containing heterocy-
clic aromatic compound
Y is a single bond, Cl to C~ -alkylene or
-alkylene dioxy, which chain can be interrupted
by -O-, -S-, -S02-, -CO-, -C02-, -0-C02-,
CONH2, or phenylene dioxy,
Rl and R2 are the same or different and represent
hydrogen, Cl to C6-alkyl, -cycloalkyl, substi-
tuted or unsubstituted aryl, aralkyl or acyl,
R3 is hydrogen~ Cl to C4-alkyl or substituted or
unsubstituted phenyl, - .
n means 1 to 3 and
m means O to 3, under the provision that
n + m is at least 2.
Suitable representatives of these crosslinking compounds
are, for example:
1,4-bis-hydroxymethyl-benzene,
1,3-bis-hydroxymethyl-benzene,
1,4-bis-methoxymethyl-benzene,
1,5-bis-acetoxymethyl-naphthalene,
1,4-bis-hydroxymethyl-naphthalene,
9,10-bis-methoxymethyl-anthracene,
2r5-bis-(hydroxymethyl)-furan~
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6~
~,5-bis-ethoxymethyl-thiophene,
bis-methoxymethyl-diphenylene-oxide,
bis-methoxymethyl-dimethyldiphenylene-oxide,
2,6-bis-hydroxymethyl-naphthalene,
1,4-bis-l~-hydroxymethyl)-benzene,
1 r 4-bis~ hydroxybenzyl)-benzene,
4,6-dimethyl-1,3-bis-hydroxymethyl-benzene,
2,5-dimethyl-1,4-bis-hydroxymethyl-benzene,
2,4,6-trimethyl-1,3-bis-hydroxymethyl-benzene,
2,4,6-trimethyl-1,3,5-tris-methoxymethyl-benzene,
2,3,5,6-tetramethyl-1,4-bis-acetoxymethyl-benzene,
2,4,5,6-tetramethyl-1,3-bis-ethoxymethyl-benzene,
4,4'-bis-acetoxymethyl-diphenylmethane,
4,4'-bis-methoxymethyl-diphenyl,
2-methyl-1,5-bis-acetoxymethyl-naphthalene,
2-ethyl-9,10-bis-methoxymethyl-anthracene,
4,6-diisopropyl,1,3-bis-hydroxymethyl-benzene,
4,6-diisopropyl-1,3-bis-methoxymethyl-benzene,
4,4'-bis-acetoxymethyl-diphenyl sulfone,
4,4'-bis-methoxymethyl-benzophenone,
2,6-bis-hydroxymethyl-4-chlorophenol,
2,6-bis-hydroxymethyl-4-methyl-anisole,
1,3-bis-(3-hydroxymethyl-phenoxy)-propane,
1,3-dihydroxymethyl-2-methoxy-5-n-hexyl-benzene,
1,3-dihydroxymethyl-2-ethoxy-5-ethyl-benzene,
1,3-dihydroxymethyl-2-benzyloxy-5-methoxycarbonyl-benzene,
1,3-dihydroxymethyl-2-methoxy-5-bromobenzene,
- 10 b -
~ 6~
1,3-dihydroxymethyl-2-methoxy-5-cumyl~benzene,
1,3-dihydroxymethyl-2-ethoxy-5-methylmercapto-benzene,
1,3-dihydroxymethyl-2-ethoxy-5-phenoxy-benzene,
1,3-dihydroxymethyl-2,5-diethoxy-benzene,
1,3-dihydroxymethyl-2-methoxy-5-benzyl-benzene,
1,3-dimethoxymethyl-2-methoxy S-fluorobenzene,
1,3-dimethoxymethyl-2-ethoxy-5-methoxy-benzene,
1,3-dimethoxymethyl-2-methoxy-5-phenyl-benzene,
bis-(2-(4-hydroxymethyl phenoxy)-ethyl¦-ether,
1,3-dimethoxymethyl-2-etho~y-5-bromobenzene,
1,3-diacetoxymethyl-2-ethoxy-5-tert.-butyl-benzene,
1,3-diacetoxymethyl-2-methoxy-5-phenylmercapto-benzene,
1,3-diacetoxymethyl-2-methoxy-5-chlorobenzene,
1,3-diacetoxymethyl-2,5-dimethoxy-benzene,
1,3-bis-~2-methyl-4-benzyl-6-hydroxymethyl-phenoxy)-propane,
bis-(3,5-hydroxymethyl-4-hydroxyphenyl)-methane,
dihydroxymethyl-hydroquinone dimethyl ether,
4-methoxy-3,5-bis-hydroxymethyl-diphenyl ether,
bis-(4-ethoxy-5-methyl-3-hydroxymethyl-phenyl)-sulfone,
4,4'-bis-hydroxymethyl-diphenyl ether,
4,4'-bis-acetoxymethyl-diphenyl ether,
4,4'-bis-methoxymethyl-diphenyl e~her,
~'~bis-ethoxymethyl-diphenyl ether,
2,4'-bis-methoxymethyl-diphenyl ether,
2,4,4'-tris-methoxymethyl-diphenyl ether,
2,4,2'-tris-methoxymethyl-diphenyl ether,
2,4,2',4'-tetrakis-methoxymethyl-diphenyl ether,
bis-methoxymethyl-4,4'-dimethyl-diphenyl ether,
- l,~c -
bis-methoxymethyl-2,4-dimethoxy-5-methyl-diphenyl ether,
bis-methoxyme~hyl-3,3'-dimethyl-diphenyl sulfide,
bis-methoxymethyl-2,4'-dimethoxy-diphenyl sulfide,
2,2'-bis-(4,hydroxymethyl-phenoxy)-dlethyl ether,
2,2'-dimethyl-~,4'-bis-hydroxymethyl-diphenyl ether,
1,3-bis-(4-methoxymethyl-phenoxy~-benzene,
1,3-bis-(4-methoxyme~hyl-phenoxy)-propane,
4,4'-bis-methoxymethyl-diphenyl sulfide,
2,2-bis-(4-methoxymethyl-phenyl)-propane,
4,4'-bis-phenoxymethyl-diphenyl ether,
bis-methoxymethyl-4-phenoxydiphenyl sulfide,
bis-methoxymethyl-2-isopropyl-5-methyl-diphenyl ether,
bis-methoxymethyl-3-bromo-4-methoxy-diphenyl ether,
bis-methoxymethyl-4-nitro-diphenyl ether, and
2,2'-bis-l3,5-hydroxymethyl-4-hydroxyphenyl)-propane.
A preferred compound or mixture of compounds is
selected from the group of dimethyl para-cresol,
4,4'bis-methoxy-methyl diphenyl ether r epoxy cresol novolak
resin, 2,5-bis-(hydroxymethyl)-furan, 2,5-bis(ethoxy-methyl)-
thiophene, bis(3,5-hydroxymethyl-4-hydroxyphenyl)-methane,
4,4'bis-acetoxymethyl-diphenyl ether, 1,4-bis-(~hydroxybenzyl)-
benzene, 2,6-bls-hydroxymethyl-4-methyl-anisole and 2,2 bis-
(3,5-hydroxymethyl-4-hdyroxy-phenyl)-propane. The preferred com-
pounds are dimethylol paracrescol as described in U.S. 4,404,272,
4,4'-bis-methoxymethyl diphenyl ether, and epoxy cresol novolak
resin.
- 10d-
8~7
The epoxy cresol novolak resins have the general formula O
~0 / \ 0--C~12--CH--CH2
O-CH~-CH-~H2 O--C112--CH--CH2
~-- C~2 --+~ C~2 ~
where n = 1-10
The photosensitive composition is formed by blending the
ingredients in a suitable solvent composition. In the preferred
embodiment the resin is preferably present in the overall
composition in an amount of from about 75% to about 9g% based on
the weight of the solid, i.e. non-solvent parts of tile ~`
composition. A more preferred range of resin would be from about
B0~ to about 90% and most preferably from about 82~ to about 85
by weight of the solid composition parts. The diazide is
preferably present in an amount ranging from about 1% to about
2S~ based on the weight of the solid, i.e., non-solvent parts of
the composition. A more preferred range of the diazide would be
~rom about 1~ to about 2~% and more preferably from about 10~ to
about 18% by weight of the solid composition parts. The
crosslinker is preferably present in an amount ranging from about
0.5% to about 20% based on the weight of the solid, i.e.
non-solvent parts of the composition. A more preferred range
~ould be from about 1% to about 10% and most preferably from
about 3~ to about 6% by weigh~ of the solid composi~ion parts.
In manufacturing the composition the resin, crosslinker and
diazide are mixed with such solvents as the propylene glycol
alkyl ether acetate, butyl acetate, xylene, ethylene glycol
monoethyl ether acetate, and propylene glycol rnethyl ether
acetate, among others.
1 ,~
.
.. . , . , ~ .
.
X6'~7
Additives such as colorants, dyes, anti-striation
agents, leveling agents, plasticizers, adhesion promoters, speed
enhancers, solvents and such surfactants as non-ionic surfactants
may be added to the solution o~ resin, sensitizer, cross-linker
and solvent before the solution is coated onto a substrate.
Examples of dye additives that may be used together with
the photoresist compositions of the present invention include
Methyl Violet 2B (C.I. No. 42535), Crystal Violet ~.I. 42555),
Malachite Green (C.I. No. 42000), Victoria Blue B (C.I. No.
1Q 44045) and Neutral Red (C.I. No. 50040) at one to ten percent
weight levels, based on the combined ~7eight of the solid parts of
the composition. The dye additives help provide increased
resolution by inhibiting back scattering of light o~f the sub-
strate.
Anti-striation agents may be used up to five percent
weight level, based on the combined weight of solids.
Plasticizers which may be used include, for example,
phosphoric acid tri-(~-chloroethyl)-ester; stearic acid; di-
camphor; polypropylene; acetal resins; phenoxy resins; and alkyl
~0 resins at one to ten percent weigh~ levels, based on the combined
weight of solids. The plasticizer additives improve the coating
properties of the material and enable the application of a ~ilm
that is smooth and of uniform thickness ~o the substrate.
Adhesion promoters which may be used include, for
example, ~-(3,4-epoxy-cyclohexyl)-ethyltrimethoxysilane;
pentamethyldisilane-methyl methacrylate; vinyltrichlorosilane;
and ~-amino-propyl triethoxysilane up to a 4 percent weight
level, based on the combined weight of solids.
Speed enhancers that may be used include, for example,
picric acid, nicotinic acid or nitrocinnamic acid at a weight
level of up to 20 percent, based on the combined weight of resin
and solids. These enhancers tend to increase the solubility of
'~ '
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.
Z~7
the photoresist coating in both the exposed and unexposed areas,
and thus they are used in applications when speed of development
is the overriding consideration even though some degree of
contrast may be sacrificed; i.e., while the exposed areas of the
photoresist coating will be dissolved more quickly by the
developer, the speed enhancers will also cause a larger loss of
photoresist coating from the unexposed areas.
The coatiny solvents may be present in the overall com-
position in an amount of up to 95~ by weight of the solids in the
composition.
Non-ionic surfactants that may be used include, for ex-
ample, nonylphenoxy poly(ethyleneoxy~ ethanol; octylphenoxy-
(ethyleneoxy) ethanol; and dinonyl phenoxy poly (ethyleneoxy)
ethanol at up ~o 10 percent weight, based on the combined weight
of solids.
The prepared resist solution can be applied to a sub-
strate 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 as
~0 to the percentage of solids content in order to provide coating
of the desired thickness given the type of spinnlng equipment
utilized and the amount of time allowed for the spinning process.
Suitable substrates include silicon, aluminum or polymeric
resins, silicon dioxide, doped silicon dioxide, silicon nitride,
polysilicon, tantalum, copper, ceramics and aluminium/copper mix-
tures.
The photoresist coatings produced by the above des-
cribed procedure are particularly suitable for application to
thermally oxidized silicon wafers such as are utilized in the
production of microprocessors and other miniaturized integrated
circuit components. An aluminum/aluminum oxide wafer can be used
as well. The substrate may also comprise various polymeric
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.
~ 28~6~7
resins especially transparent polymers such as polyesters.
After the resist composition solution is coated onto
the su~strate, the substrate is temperature treated at appro~i-
mately 20 to 100~C. This temperature treatment is selected in
order to reduce and control the concentration of residual sol-
vents in the photoresist while not causing substantial thermal
degradation o~ the photosensitizer. In general one desires to
minimize the concentration of solvents and thus this first
temperature treatment is conducted until substantially all of the
solvents have evaporated and a thin coating of photoresist com-
position, on the order of a micron in thickness, remains on the
substrate. This treatment is normally conducted at temperatures
in the range of from about 20C to about 100C. In a preferred
embodiment the temperature is conducted at from about 50C to
about 90C. A more preferred range is from about 70C to about
90C. This treament is conducted until the rate of change of
solvent removal becomes relatively insignificant. The tempera-
ture and time selection depends on the resist properties desired
by the user as well as equipment used and commercially desired
coating times. Commercially acceptable treatment times for hot
plate treatment are those up to about 3 minutes, more preferably
up to about 1 minute. In one example, a 30 second treatment at
90 is useful. The coating substrate can then be exposed to
actinic radiation, especially ultraviolet radiation, in any
desired pattern, produced by use of suitable masks, negatives,
stencils, templates, etc. in a manner well known to the ski]led
artisan.
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V~6~7
The resist is then subjected to a second bakiny or heat
treatment after exposure of from about 95C to about 160C, pre-
~erably 95C to 150C, more preferably 112C to 120C. This
heating treatment may be conducted with a hot plate system for
from about 10 seconds to the time necessary to cross-link the
resin. This normally ranges from about 10 seconds to 90 seconds,
more preferably from about 30 seconds to about 90 seconds and
most preferably from 15 to 45 seconds. Durations for longer than
90 seconds are possible but do not generally provide any
additional benefit. The time selected depends on the choice of
composition components and the substrate used. Heating diffuses
the generated acid to the cross-linking component. The baking
treatment also converts the diazide to a carboxylic acid
containing compound, for example indene carboxylic acid, which is
soluble in aqueous alkali solutions.
The selection of the first and second heat treatment
temperatures and first and second heat treatment times may be
selected and op~imized by the properties which are desired by the
end user. If necessary, the resist can be subjected to an addi-
tional exposure to actinic radiation without the photomask after
the second heat treatment. The exposed resist-coated substrates
are next substantially immersed in a suitable developing solu-
tion. 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 resist
coating has dissolved from the unexposed areas. Suitable devel-
opers include aqueous alkaline solutions such as those including
sodium hydroxide, and tetramethyl ammonium hydroxide as are well
known in the art.
After removal of the coated wafers from the developing
solution, an optional post-development heat treatment or bake may
be employed to increase the coating 16 adhesion and chemical
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.
~28Z6~7
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
ind~strial applications, particularly in the manufacture of
microcircuitry units on silicon/silicon dioxide-type substrates,
the developed substrates may be treated with a buffered, hydro-
fluoric acid base etching solution. The resist compositions of
the present invention are resistant to acid-base etching solu-
tions and provide effective protection for the exposed resist-
coating areas of the substrate.
The following specific examples will provide detailed
illustrations of the methods of producing and utilizing composi-
tions 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, para-
meters or values which must be utilized exclusively in order to
practice the present invention.
The following non-limiting examples serve to illustrate
the invention:
Exam~le 1
The photoresist is made up of a solution containing, 5%
of solids o~ dimethylol para-cresol, 6% of solids of 2,3,4-
trihydroxy-3'~methyl benzophenone 1,2-naphthoquinone-2-
diazide-4-sulfonic acid trisester and 89% of solids of cresol
novolac resin in propylene glycol monomethyl ether acetate.
Using this formulation silicon wafers are coated at
4,000 rpm and then soft-baked in a vented convection oven at 90C
for 30 minutes. Actinic exposure is applied using the Perkin
Elmer 220 Micralign aligner through a glass photomask containing
a resolution test pattern. Using aperature #4, the scan speeds
are varied between 200 and 400 arbitrary energy units. These
different scan speeds (each scan speed represents a different
- 16 -
iX7
experiment) corresponds to between 20 and 10 mJ/cm2 repsec-
tively as determined by an OAI radiometer ~or wavelengths between
365 and 436 nm. The photomask consists of a resolution test
pattern where single line and equal line and spaces are repre-
sented. The wid~h of these features varies between 1.0 and 3.0
~m in Q.25 ~m increments. After exposure the wafers are hard
baked sequentially on a MTI Inc. hot plate at temperatures
ranging from 110C to 150C for up to 60 seconds. A relief image
is now observable when the wafers are placed under an optical
microscope with monochromatic 520 nm illumination.
After developing the exposed and hard baked wafers in
AZ 433 MIF Developer available from the AZ Photoresists Group of
American Hoechst Corporation, Somerville, New Jersey (a 0.33N
solution of tetramethylamMonium hydroxide) in an immersion mode
process for 3 minutes with slight agitation, the wafers are
DI(deionized) water rinsed and spin dryed. If the wafers are now
examined using a scanning electron microscope at 10,000 magnifi-
cation, 1 ~m single spaces and larger geometries are clearly seen
to be completely opened.
Example 2
The photoresist is made up of a solution containing, 5%
of solids of dimethylol para-cresol, 6% of solids of 2,3,4
trihydroxy-3'-methoxy benzophenone 1,2 naphthoquinone-2-diazide-
4-sulfonic acid trisester and 89% of solids of cresol novolac
resin in propylene glycol monomethyl ether acetate.
Using this formulation silicon wafers are coated at
4,000 rmp and then soft-baked in a vented convection oven at 90C
for 30 minutes. Actinic exposure i5 applied using the Perkin
Elmer 220 Micralign aligner through a glass photomask containing
a resolution test pattern. Using aperature #4, the scan speeds
are varied between 200 and 400 arbitrary energy units. These
different scan speeds (each scan speed represents a different
'~
- 17 -
1~8Z6Z~
experiment) corresponds to between 20 and 10 mJ/cm2 respec-
tively as determined by an OAI radiometer for wavelengths between
365 and 436 nm. The photomask consists of a resolution test
pattern where single line and equal line and spaces are
represented. The width of these features varies between 1.0 and
3.0 ~m in 0.25 ~m increments. After exposure the wafers are
hard baked sequentially on a MTI Inc. hot plate at temperatures
ranging from 110C to 150~C for up to 60 seconds. A relief image
is now observable when the wafers are placed under an optical
microscope with monochromatic 520 nm illumination.
After developing the exposed and hard baked wafers in
AZ 433 MIF Developer available from the AZ Photoresists Group of
American Hoechst Corporation, Somerville, New Jersey (a 0.33N
solution of tetramethylammonium hydroxide) in an immersion mode
process for 3 minutes with slight agitation, the wafers are DI
water rinsed and spin dryed. If the wafers are now examined
using a scanning electron microscope at 10,000 magnification, 1
~m single spaces and larger geometries are clearly seen to be
completely opened.
Example 3
The photoresist is made up of a solution containing, 5%
of solids of dimethylol para-cresol, 6% of solids of 2,3,4 tri-
hydroxy phenyl pentyl ketone 1,2 naphthoquinone-2-diazide-4-
sulfonic acid trisester and 89% of solids of cresol novolac resin
in propylene glycol monomethyl ether acetate.
Using this formulation silicon wafers are coated at
4,000 rpm and then soft-baked in a vented convection oven at 90C
for 30 minutes. Actinic exposure is applied using -the Perkin
Elmer 220 Micralign aligner through a glass photomask containing
~0 a resolution test pattern. Using aperature #4, the scan speeds
are varied between 200 and 400 arbitrary energy units. These
different scan speeds (each scan speed represents a different
- 18 -
.
8~6'~:7
experiment) corresponds to between 20 and 10 mJ/cm2 respec-
tively as determined by an OAI radiometer for wavelengths between
365 and 43~ nm. The photomask consists of a resolution test
pattern where single line and equal line and spaces are repre-
sented. The width of these features varies betw2en 1.0 and 3.0
~m in 0.25 ~m increments. After exposure the wafers are hard
baked sequentially on a MTI Inc. hot plate at temperatures
ranging from 110C to 150C for up to 60 seconds. A relief ima~e
is now observable when the wafers are placed under an optical
microscope with monochromatic 520 nm illumination.
After developing the exposed and hard baked wafers in
AZ 433 MIF Developer available from the AZ Photoresists Group of
American Hoechst Corporation, Somerville, New Jersey (a 0.33N
solution of tetramethylammonium hydroxide) in an immersion mode
process for 3 minutes with sli~ht agitation, the wafers are DI
water rinsed and spin dryed. If the wafers are now examined
using a scanning electron microscope at 10,000 magnification, 1
~m single spaces and larger qeometries are clearly seen to be
completely opened.
- 19 -
~LZ826~7
The photoresist is made up of a solution containing, 5%
of solids of 4,4'-bis-methoxymethyl diphenyl ether, 6% of solids
of 2,3,4 trihydroxy benzophenone 1,2 naphthoquinone-2-diazide-4-
sulfonic acid trisester and 89~ of solids of cresol novolac resin
in propylene glycol monomethyl ether acetate.
Using this formulation silicon wafers are coated at
4,000 rpm and then soft-baked in a vented convection oven at 90~C
for 30 minutes. Actinic exposure is applied using the Perkin
Elmer 220 Micralign aligner through a glass photomask containing
a resolution test pattern. Using aperature #4, the scan speeds
are varied between 200 and 400 arbitrary energy units. These
different scan speeds (each scan speed represents a different
- 20 -
- ' :' '
lX~Z6Z~
experiment) corresponds to between 20 and 10 mJ/cm2 respec-
tively as determined by an OAI radiometer for wavelengths between
365 and 436 nm. The photomask consists of a resolution test
pattern where single line and equal line and spaces are
represented. The width of these features varies between 1.0 and
3.0 ~m in 0.25 ~m increments. After exposure the wafers are
hard baked sequentially on a MTI Inc. hot plate at temperatures
ranging from 11~C to 150C ~or up to 60 seconds. A relief image
is now observable when the wafers are placed under an optical
microscope with monochromatic 520 nm illumination.
After developing the exposed and hard baked wafers in
AZ 433 MIF Developer available from the AZ Photoresists Group of
American Hoechst Corporation, Somerville, New ~ersey (a 0.33N
solution of tetramethylammonium hydroxide) in an immersion mode
process for 3 minutes with slight agitation, the wafers are DI
water rinsed and spin dryed. If the wafers are now examined
using a scanning electron microscope at 10,000 magnification, 1
~m single spaces and larger geometries are clearly seen to be
completely opened.
~0 Example 5
The photoresist is made up of a solution containing, 5%
of solids of 4,4'-bis-methoxymethyl diphenyl ethe~, 6% of solids
of 2,3,4 trihydroxy~3'-methyl benzophenone 1,2 naphthoquinone-2-
diazide-4-sulfonic acid triester and 89% of solids of cresol
novolac resin in propylene glycol monomethyl ether acetate.
Using this formulation silicon wafers are coated at
4,000 rpm and then soft-baked in a vented convection oven at 90C
for 30 minutes. Actinic exposure is applied using the Perkin
Elmer 220 Micralign aligner through a glass photomask containing
a resolution test pattern. Using aperature ~4, the scan speeds
are varied between 200 and 400 arbitrary energy units. These
different scan speeds (each scan speed represents a different
- 21 -
~ .
experiment) corresponds to between 20 and 10 mJ/cm2 respec-
tively as determined by an OAI radiometer for wavelengths between
365 and 436 nm. The photomask consists of a resolution test pat-
tern where single line and equal line and spaces are represented.
The width of these features varies between 1.0 and 3.0 ~m in
0.~5 ~m increments. After exposure the wafers are hard baked
sequentially on a MTI Inc. hot plate at temperatures ranging from
l10C to 150C for up to 60 seconds. A relief image is now ob~
servable when the wafers are placed under an optical microscope
~ith monochromatic 520 nm illumination.
After developing the exposed and hard baked wafers in
AZ 433 MIF Developer available from the AZ Photoresists Group of
American Hoechst Corporation, Somerville, ~ew Jersey (a 0.33N
solution of tetramethylammonium hydroxide) in an immersion mode
process for 3 minutes with slight agitation, the wafers are DI
water rinsed and spin dryed. If the wafers are now examined us-
ing a scanning electron microscope at 10,000 magnification, 1 ~m
sinqle spaces and larger geometries are clearly seen to be com-
pletely opened.
Example 6
The photoresist is made up of a solution containing, 5
of solids of ~4'-bis-methoxymethyl diphenyl ether, 6% of solids
of 2,3,4 trihydroxy-3'-methoxy benzophenone 1,2 naphthoquinone-
2- diazide-4-sulfonic acid triester and 89% of solids of cresol
novolac resin in propylene glycol monomethyl ether acetate.
Using this formulation silicon wafers are coated at
4,000 rpm and then soft-baked in a vented convection oven at 90C
for 30 minutes. Actinic exposure is applied using the Perkin
Elmer 220 Micralign aligner through a glass photomask containing
a resolution test pattern. Using aperature #4, the scan speeds
are varied between 200 and 400 arbitrary energy units. These di-
fferent scan speeds (each scan speed represents a different
22 -
' .
~ ~aZ~iz7
experiment) corresponds to between 20 and 10 mJ/cm2 respec-
tively as determined by an OAI radiometer for wavelengths between
365 and 436 nm. The photomask consists of a resolution test
pattern where single line and equal line and spaces are
represented. The width of these features varies between 1.0 and
3.0 ~m in 0.25 ~m increments. After exposure the wafers are
hard baked sequentially on a MTI Inc. hot plate at temperatures
ranging from 110C to 150C for up to 60 seconds. A relief image
is now observable when the wafers are placed under an optical
microscope with monochromatic 520 nm illumination.
After developing the exposed and hard baked wafers in
AZ 433 MIF Developer available from the AZ Photoresists Group of
American Hoechst Corporation, Somerville, New Jersey (a 0.33N
solution of tetramethylammonium hydroxide) in an immersion mode
process for 3 minutes with slight agitation, the wafers are DI
water rinsed and spin dryed. If the wafers are now examined
using a scanning electron microscope at 10,000 magnification, 1
~m single spaces and larger geometries are clearly seen to be
completely opened.
Example 7
The photoresist is made up of a solution containing, 5%
of solids of 4,4'-bis-methoxymethyl diphenyl ether, 6% of solids
of 2,3,4 trihydroxy phenyl pentyl ketone-1,2 naphthoguinone-2-
diazide-4-sulfonic acid triester and 89% of solids of cresol
novolac resin in propylene glycol monomethyl ether acetate.
Using this formulation silicon wafers are coated at
~,000 rpm and then soft-baked in a vented convection oven at 90C
for 30 minutes. Actinic exposure is applied using the Perkin
Elmer 220 Micralign aligner through a glass photomask containing
a resolution test pattern. Using aperature #4, the scan speeds
are varied between 200 and ~00 arbitrary energy units. These
different scan speeds (each scan speed represents a different
- 23
8~ 7
experiment) corresponds to between 20 and 10 mJ/cm2 respec-
tively as determined by an OAI radiometer for ~ave]engths between
365 and 436 nm. The photomask consists of a resolution test
pattern where single line and equal line and spaces are
represented. The width of these features varies between 1.0 and
3.0 ~m in 0.25 ~m increments. After exposure the wafers are
hard baked sequentially on a MTI Inc. hot plate at temperatures
ranging from 110C to 150C for up to 60 seconds. A relief image
is now observable when the wafers are placed under an optical
microscope with monochromatic 520 nm illumination.
After developing the exposed and hard baked wafers in
AZ 433 MIF Developer available from the AZ Photoresists Group of
American Hoechst Corporation, Somerville, New Jersey (a 0O33N
solution of tetramethylammonium hydroxide) in an immersion mode
process for 3 minutes with slight agitation, the wafers are DI
water rinsed and spin dryed. If the wafers are now examined
using a scanning electron microscope at 10,000 magnification, 1
~m single spaces and larger geometries are clearly seen to be
completely opened.
Example 8
The photoresist is made up of a solution containing, 5
of solids of epoxy cresol novolac resin, 6% of solids of 2,3,4
trihydroxy benzophenone 1,2 naphthoquinone-2-diazide-4-sulfonic
acid triester and 89~ of solids of cresol novolac resin in
propylene glycol monomethyl ether acetate.
Using this formulation silicon wafers are coated at
4,000 rpm and then soft-baked in a vented convection oven at 90C
for 30 minutes. Actinic exposure is applied using the Perkin
Elmer 220 Micralign aligner through a glass photomask containing
a resolution test pattern. Using aperature #4, the scan speeds
are varied between 200 and 400 arbitrary energy units. These
different scan speeds (each scan speed represents a different
24 ~
experiment) corresponds to between 20 and 10 mJ/cm2 respectively
as determined by an OAI radiometer for wavelengths between 355
and 436 nm. The photomask consists of a resolution test pattern
where single line and equal line and spaces are represented. The
width of these features varies between 1. e and 3.0 ym i~ 0.25/um
increments. After exposure the wafers are hard balced
sequentially on a MTI Inc. hot plate at temperatures ranging from
110 C to 150C for up to 60 seconds. A relief image is now
observable when the wafers are placed under an optical microscope
with monochromatic 520 nm illumination.
After developing the exposed and hard baked wafers in AZ a33 MIF
Developer available from the AZ Photoresists Group of American
Hoechst Corporation, Somerville, New Jersey (a 0.33N solution of
tetramethylammonium hydroxide) in an immersion mode process for 3
~inutes with slight agitation, the wafers are DI water rinsed and
spin dryed. If the wafers are now examined using a scanning
electron microscope at 10,000 magnification, l/um single spaceS
and larger yeometries are .learly seen to be completely opened.
- . ' ''`'''''.
,.
~ ~2~7
Examples 9 - 14
The procedure of example 1 is repeated with the
modification that the photoresist is made up of a solution
containing ~9 % of solids of cresol novolak resin in propylene
glycol monomethyl ether acetate and
(~) 5 % of 2,5-bis-(hydroxymethyl)-furan and
6 % of 2,3,4 trihydroxy-3'-methyl-benzophenone-1,2-
naphthoquinone-2-diazide-4-sulfonic acid triester,
(10) S % of 2,5-bis-(ethoxymethyl)-thiophene and
6 % of 2,3,4-trihydroxy-3'-methyl-benzophenone-1,2-
naphthoquinone-2-diazide-4-sulfonic acid triester,
(11) 5 % of bis-(3,5-hydroxymethyl-4-hydroxyphenyl)-methane
and
6 % of 2,3,4-trihydroxy-3'-methyl-benzop~enone-1,2-
naphthoquinone-2-diazide-4-sulfonic acid triester
(12) 5 % of 4,4'-bis-acetoxymethyl-diphenylether and
6 % of 2,3,4-trihydroxy-benzophenone-1-2-
naphthoquinone- 2-diazide-4-sulfonic acid
triester
(13) 5 % of l~4-bis(a-hydroxybenzyl)-benzene and
6 % of 2,3,4-trihydroxy-benzophenone-1,2-
naphthoquinone- 2-diazide-4-sulfonic acid
triester
(14) 2,5 % of 2,6-bis-hydroxymethyl-4-methyl-anisole,
2,5 % of 2,2-bis-(3,5-hydroxymethyl-4-hydroxyphenyl)-
propane and
6 % of 2,3,4-trihydroxy-benzophenone-1,2-
naphthoquinone-2- diazide-4-sulfonic acid
triester.
The results are similar to those in the preceding examples.
. _, ~
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.
