High-resolution fluorocarbon-based resist for 157-nm lithography

Lithography at 157nm represents the next evolutionary step in optical lithography and is clearly seen as the likely successor to 193nm lithography. If successful, the photoresists used for this technology must be initially capable of 100nm resolution and be extendable to less than 70nm. As with the transition to shorter wavelengths in the past, the photoresist materials developed for longer wavelengths appear to be too absorbent for practical use as a traditional high resolution single layer resist imageable with 157nm radiation. The high 157nm absorbance of polyacrylate, polycyclic, and polyhydroxystyrene copolymer resists, will force the coated resist thickness to be under 100nm. It has been shown that some fluorine-functionalized polymers are more transparent in this spectral region than pure hydrocarbon polymers. This has led us to investigate the use of fluorocarbon polymers in resists specially designed for 157nm lithography. We have synthesized and evaluated a number of unique 4-hexafluoroisopropanol1 styrene based polymer systems that yield resists in which the 157nm absorbance ranges from 3.0 to 4.0micrometers . Resists of this type are potentially capable of imaging at resist thickness of 150nm. Examples of the high performance imaging capability of our resist design are shown to have imaging capability of 150nm with 0.50NA microstepper and 40nm employing interference lithography.