A new highly selective sacrificial layer technology for SiC MEMS

Abstract

A new sacrificial layer technology for the fabrication of silicon carbide (SiC) based micro electro mechanical systems (MEMS) is described using silicon germanium (SiGe) as sacrificial material. An extremely high etch selectivity between SiC and SiGe of up to 1:1000000 was achieved when using chlorine trifluoride (ClF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) as etchant in a dry plasmaless etch process. This enormous selectivity enables the fabrication of free standing SiC microstructures like combs or membranes with a strongly reduced need for perforation patterns, which are typical for silicon dioxide sacrificial layers etched selectively to silicon by hydrofluoric acid (HF) in liquid or vapour phase. Only few and small openings are necessary to fully release large SiC structures with the sacrificial layer technology presented, therefore allowing higher degrees of design freedom for MEMS compared to traditional release technologies.