Low temperature etching of Si in high density plasma using SF 6/O 2

Abstract

Low temperature etching of Si with SF 6 has been studied, using a DECR system and a special Helicon type plasma source. In contrast to the current understanding of low temperature etching, we did not observe a “freezing” of the lateral etching reaction, but obtained isotropic etch profiles, even at temperatures below −120° C. Anisotropic etch profiles are obtained by an addition of O 2. We therefore propose a sidewall passivation mechanism to explain the reduction of the lateral etching. Si etch rates of 5μm/min at selectivities Si/SiO 2 well above 100/1, with anisotropic profile have been obtained.