A novel sacrificial layer technology based on highly selective etching of silicon-germanium in CLF3

This paper introduces a new sacrificial layer and etching technology for the surface-micromachining of MEMS. Poly crystalline silicon-germanium (SiGe) is used as sacrificial material in combination with poly-Si as active functional layer. Applying a new plasmaless dry etching technique based on ClF₃-gas, SiGe can be etched with an extremely high selectivity of up to 5000:1 with respect to silicon. This technique opens new opportunities for enhanced design freedom, increased underetching ranges and speed, and offers full compatibility to most dielectric and metal materials, and to monolithic integration with electronic circuitry on the same chip.