Polysilanes: solution photochemistry and deep UV lithography

Abstract

Soluble polysilane derivatives (i.e., materials containing catenated chains of substituted silicon atoms in the polymer backbone) represent a new class of radiation sensitive materials for which a number of new applications have recently appeared. The spectroscopic properties of the polysilanes are unusual and interesting. All of these materials absorb strongly in the ultraviolet, which suggests extensive sigma delocalization along the polymer backbone. Amorphous alkyl polysilanes absorb strongly from 300-325 nm, while aryl substituents directly attached to the backbone cause substantial red shifts in the absorption spectra. The latter is a true electronic substituent effect. The absorption spectra also depend to some extent on the polymer molecular weight. The absorption characteristics also depend strongly on the backbone conformation with the planar zigzag conformation the most red shifted of all. Recently reported soluble poly(diarylsilanes) are the most red shifted of all the polysilanes, apparently due to a combination of electronic and conformation effects.