LOW-TEMPERATURE ETCHING OF SI IN HIGH-DENSITY PLASMA USING SF6 O-2/

Low temperature etching of Si with SF6 has been studied, using a DECR system and a special Helicon type plasma source. In contrast to the cu rrent understanding of low temperature etching, we did not observe a ' 'freezing'' of the lateral etching reaction, but obtained isotropic et ch profiles, even at temperatures below -120-degrees-C. Anisotropic et ch profiles are obtained by an addition of O2. We therefore propose a sidewall passivation mechanism to explain the reduction of the lateral etching. Si etch rates of 5 mum/min at selectivities Si/SiO2 well abo ve 100/1, with anisotropic profile have been obtained.