DRY SILICON ETCHING FOR MEMS

Silicon etching is an essential process step for the fabrication of micro-electro-mechanical systems (MEMS). As we enter the on-chip integrated sensor era, the sensing elements are typically defined after circuit fabrication. This has benefits in permitting the use of a standard technology such as CMOS and also in minimising the wafer processing after fabricating the often fragile MEMS structures. Structure definition in silicon must be carried out by dry etching when profile anisotropy is required (independent of crystal orientation), particularly for high aspect ratios. Although a variety of plasma etch tools and dry etch approaches have been reported in the literature, none have been capable of meeting the majority of MEMS dry etching needs. This paper presents a novel anisotropic silicon etch process which overcomes the limitations of other techniques and is fast becoming recognised as an enabling technology for a wide range of applications in MEMS fabrication.