Synthesis of polycarbomethylsilane derivatives and their lithographic characterization

Abstract

Bilayer resist consists of two layers, which are imaging layer and planarizing layer. Bilayer resist system has several advantages. First of all, imaging layer of the system could have relatively high absorbance. Second, anti-reflective planarizing layer diminishes defects caused by reflection like standing wave effect. Third, depth of focus problem doesn`t exist because imaging layer is thin. Finally, high aspect ratio features can be obtained by $O_₂-RIE$. In this paper, bilayer resists with polycarbomethylsilane backbone were synthesized. Polycarbomethylsilane (PCS) that is ceramic precursor and t-butyl acrylate (TBA) or allyl glycidyl ether (AGE) underwent hydrosilylation reaction under Karstedt`s catalyst. It was inferred that they were thermally stable. Absorbance of polymers was small value at 248 nm as much as they can work as a single layer resist, while they are relatively opaque at 193 nm. However they can be applied to bilayer resist as imaging layer at both wavelength because imaging layer of bilayer resist is very thin. The product polymers have silicon in backbone so that silicon content of them is remarkably high. As a result of that, $O_₂-RIE$ resistance is excellent. The $0.7\um m$ line and space pattern was obtained from only negative type resist, AGE-PCS, applying hard baked novolac resin to planarizing layer. In case of TBA-PCS the ratio of solubility changeable group was not enough to play the role perfectly. After $O_₂-RIE$ scum was remained on unexposed area, which was the typical phenomenon of the $O_₂-RIE$. Scum was removed by additional $CF_₄-RIE$, because $CF_4$ plasma can etch organic materials.