Diagnostics And Control Of High-Density Etching Plasmas

Abstract

AbstractAdvanced diagnostics of high-density inductively coupled plasmas (ICPs) are presented supporting the following three proposals of innovative etching modes: First, pulsed plasma etching mode can suppress charge-up on high-aspect-ratio micro-patterns. In order to understand the mechanism, time-resolved measurements of electrons, chlorine atoms and negative ions in a pulsed chlorine ICP are performed. As a result of electron cooling and negative ion yield in afterglow, electrons are found to be accelerated toward a rf-biased electrode, thus neutralizing positive surface charges on that. Second, downstream etching mode using C4F8 gas enables high etch selectivity of SiO2 to Si. The reason for this is qualitatively discussed using comprehensive measurements of spatial distributions of CF3, CF2, CF and F densities in CF4 and C4F8 plasmas. Third, hot wall etching mode also enables high selectibity etching in fluorocarbon plasmas. Radical diagnostics reveal that wall heating dramatically modifies the radical composition of both CF4 and C4F8 plasmas, and it improves the etch selectivity and reproducibility.