Radical Behavior in Inductively Coupled Fluorocarbon Plasma for SiO2 Etching

Silicon dioxide etching in an inductively coupled plasma (ICP) using a multispiral coil (MSG) has been studied on the basis of CFx (x = 1, 2) radical measurement employing a laser-induced fluorescence (LIF) technique. Fundamental radical behaviors in the MSC-ICP including a pulsed operation have been investigated for CF4 gas chemistry; radical composition and distribution are strongly dependent on chamber wall conditions and on the pulse modulation period as well as the time-averaged ICP power, because of dissociation and extinction kinetics. Moreover, radical behaviors in fluorocarbon plasmas including C4F8 and CHF3 have been examined in relation to the SiO2 etching characteristics. The dependence of radical densities on gas chemistry and on ICP power in the MSC-ICP has been characterized and has been found to correlate with the SiO2 etch rate and selectivity to Si. The results demonstrate that the control of radical behavior is crucial in realizing selective SiO2 etching using the MSC-ICP.