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Acrylate polymers, which have increased sensitivity in the deep UV (below 300 nanometers) range, contain an aromatic molecule within three carbon atoms of the carbonyl group.
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Deep UV Resists
Acrylate polymers, which have increased sensitivity in the deep UV (below
300 nanometers) range, contain an aromatic molecule within three carbon atoms
of the carbonyl group.
Of the chemical functional species absorbing lower than 300 nanometers, the
ketone or acrylate groups are very important. However, polymethyl methacrylate,
a well known electron-beam resist, is still not very sensitive in the 200-300
nanometer range. Even with an intense 2,500 watt mercury-xenon source,
exposure times of 2.5 hours are needed for one-micron-thick resist films.
We have found that having an aromatic molecule within three carbon atoms
of the carbonyl group in an acrylate polymer enhances the speed and sensitivity
of the resist film so that exposure times can be reduced to .25 hour. Exposure by
deep UV provides better resolution. Examples of suitable chemical structures
are polyphenyl methacrylate and polybenzyl methacrylate. The presence of the
aromatic group also increases the plasma etch resistance of the resist film. The
pendant aromatic group can have substituents, such as NH(2), Cl, Br, I, lower
alkyl groups, aromatic groups and NO(2), including various combinations of