Poly(ferrocenyldimethylsilanes) for reactive ion etch barrier applications

The behavior of poly(ferrocenyldimethylsilane) (PFS) under reactive ion etching conditions was investigated. Due to the presence of iron and silicon in the main chain, the polymer was found to be relatively stable toward oxygen plasma etching compared to common organic polymers. Depending on the conditions employed, the etching rate ratio for poly(isoprene) vs poly(ferrocenyldimethylsilane) ranged from 20:1 to 50:1. During etching, a thin iron- and silicon-containing oxide layer was formed at the surface of the organometallic polymer. The oxide layer was characterized by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) using depth profiling. Iron was found to be more resistant toward removal by oxygen plasma compared to silicon. Iron in the polymer also makes it resistive to CF4/O-2 etching. A regular pattern consisting of parallel lines of PFS on a solid substrate was obtained by micromolding in capillaries (MIMIC) (a microcontact printing technique), which could be transferred into the underlying substrate. Under the conditions employed, silicon and silicon nitride substrates were etched at approximately 20 nm/min, whereas no thickness decrease was observed for the poly(ferrocenyldimethylsilane) film, even after etching times exceeding 10 min.