Supercritical drying for nanostructure fabrication

Abstract

Supercritical drying has been developed for the fabrication of nanostructures made of silicon or resist. Pattern collapse, which is a very serious problem in the fabrication of fine patterns, is related to the spacing, the aspect ratio and the surface tension of rinse solution. Among them, reducing the surface tension is the most effective way to suppress pattern collapse, because it does not affect pattern size. The use of supercritical carbon dioxide, which has no surface tension, as a final rinse, has enabled the formation of fine silicon patterns without collapse. For resists, preventing water contamination is the key to suppressing pattern deformation during supercritical drying. On the other hand, for water-rinsed resist systems, the use of a surfactant, which acts as a bridge between rinse water and supercritical fluid, is the most important technique that makes supercritical resist drying feasible. Thus, a drying technique that produces resist patterns without collapse or deformation has been developed; and a special dryer, which holds one wafer on a hot holder, has been constructed.