Physical and chemical effects in low temperature etching of memory devices

Advanced memory devices are integrated in vertical direction, and critical etching challenges must be addressed to advance the technology roadmap. Among the enabling applications are vertical etching of SiO₂ and SiN with high aspect ratio as well as lateral or isotropic etching of these films with high selectivity. In this talk we will focus on plasm etching of high aspect ratio structures in SiO₂, SiN, stacks of these materials. Recently, HF is used in high aspect ratio plasma etching of SiO₂, SiN and multilayer stacks of these films at wafer temperatures below room temperatures (1,2). The elementary surface reactions bare some resemblance with the vapor etching analogues (1-3). Mechanism specific to plasma etching with this new process includes sidewall passivation, neutral transport, and the role of ions in the etching reaction. The underlaying chemical effects will be explained using molecular dynamics and density functional theory.



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