Low temperature etching of Si and PR in high density plasmas

Low temperature etching of Si with SF6 has been studied using 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 even at temperature below - 120°C. However anisotropic etch profiles are obtained by an addition of O2. We therefore propose a sidewall mechanism to explain the reduction of the lateral etching. Si etch rates of 5 μm/min with Si to SiO2 selectivities well above 150:1, and anisotropic profiles have been obtained. Using the same experimental set-up we investigated the etching of photoresist (PR) in a pure O2 plasma. PR etch rates and profiles have been characterized as a function of pressure, ion energy and temperature. PR etch rate of 2.5 μm/min with anisotropy ≥0.95 have been achieved.