Fluoroaromatic polymers

It can be seen diat all resists have high sensitivity to 157-nm exposure. The hydrocarbon-based resist has about twice the sensitivity of its IfflP analog, which can be explained by noting that the HOST-based polymer has almost twice the absorbance of the fluoroaromatic polymer. It is also observed that the HFIPS/BOM based resist has an higher smisitivity, 14.6 mJ/cm versus 22.7 mJ/cm. This is consistent with the prediction of higher sensitivity made by observing the thermal deconqrosition of the two polymers in the presence of camphorsulfonic acid uhere BOM polymer showed thermal deconqx>sition at a lower temperature than the MOM polymer (vide supra). 

The time to strip the fluoroaromatic polymers and the HOST/TBA polymer, was determined based on the 157 nm absorbance of the polymer and the plasma etch rate. It is shown gnqihically in Figures 9 and 10. Tte y-intercept of the two gr hs represents the thickness of a polymer film with an qitical density (O.D.) of 0.4, and the sl< of die gnqihs is e plasma etch rate of the polynia. An O.D. of 0.4 is often used as the maximum absorbance that is tolerable for a... 

An alternative approach to 157 nm resist development was presented, employing fluoroaromatic polymers, that represent an evolutionary step in resist materials development. Both partially blocked and copolymers of 4-hexafluoro-isopropanol styrene have been synthesized and characterized. Both absorb less than 4/C at 157 nm. Both the acetals and die t-B(X blocking groups lower the absorbance further and the 100% blocked HFIP/BOM has an extrapolated O.D. of 2.06/D. Thermal properties were also measured and shown to te dependent upon the degree of blocldng as is the case in PHS-based resists. 

The market for fluoroaromatics, with fluorine atoms as ring substituents, has expanded considerably over the past 20 years, driven not only by the need for intermediates in pharmaceutical and crop protection products but also for the manufacture of monomers for high-performance aromatic polymers. Although a range of possible methods have been described for the introduction of fluorine into the aromatic ring, only three are currently established for... 

Several of the synthesized polymers were formulated with a photoacid generator (di-t-butylphenyl iodonium nonaflate) and a base (tetrabutyl ammonium lactate) in ethyl lactate. Projection lithography was performed on a 0.60 NA 157-nm micro-stepper with both a binary and phase shift mask. A critical assumption in pursuing the fluoroaromatic approach toward the developmmit of 157-nm r ists is the ability of these resists to show imaging... 

The plasma etch rates for the fluorocarbon polymers were determined under two rqiresentative plasma etch processes, an oxide etch and a poly etcL The fluoroaromatic acetals are a significant inqnovement over the fluoroaromatic ester etch rates. The most promisii fiuoroaromatic acetal is the HFIP/BOM copolymer in which plasma etch rates are comparable or superior to those of the ESCAP polymer under typical oxide or poly etch conations. When film removal time is used as the figure of merit in evaluating plasma etch resistance, the HFIP/BOM polymer provides over a two-fold inqrrovement in plasma etch resistance over die ESCAP polymer. 

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