textAdvances in microelectronic devices have relied heavily on improved
photolithographic imaging capabilities. The resolution limit of optical
lithography can be improved by lowering the wavelength of exposure light. The
latest reduction in exposure wavelength is from 193 nm to 157 nm. The focus of
this work is the synthesis, copolymerization studies and lithographic imaging
capabilities of 2-trifluoromethylacrylates. Model calculations and gas phase
absorbance measurements of model compounds first suggested that these
materials would provide suitable transparency at the 157 nm wavelength. Methyl
2-trifluoromethylacrylate was synthesized and aniocically polymerized and
variable angle spectroscopic ellipsometry showed that this material had an
absorbance that was 1,000 times more transparent than its non-fluorinated
analogue. A variety of relatively transparent resist materials based on a 2-
trifluoromethylacrylate backbone were synthesized by anionic polymerization,
and these materials were successfully imaged at 157 nm. While 2-
trifluoromethylacrylates do not undergo homopolymerization with radical
initiators, they do radically copolymerize with various norbornenes. Interestingly,
these materials exhibit a 2:1 (2-trifluromethacrylate:norbornene) monomer
incorporation. This phenomenon was exploited to produce a number of relatively
transparent materials that produced positive-tone structures when imaged at the
157 nm wavelength. Kinetic studies were performed to show that the
copolymerizations of 2-trifluormethacrylates and norbornene derivatives deviate
from the terminal model and follow the penultimate model. Competitive reaction
studies using the “mercury method” were performed to demonstrate that
substitution of a trifluoromethyl group can indeed effect the reactivity of a
propagating radical, lending support to the proposed penultimate model. The
structure of the 2-trifluoromethylacrylate propagating radical will also be
investigated by electron spin resonance spectroscopy.Chemistry and BiochemistryChemistr
