In this overview article several MEMS applications of poly-SiGe are discussed: thermal applications, the application as a capping layer for MEMS wafer-level packaging and the use as MEMS structural layer for processing MEMS devices on top of CMOS. For all these applications also different deposition processes have been developed: chemical vapor deposition at reduced pressure (RPCVD), at low pressure (LPCVD) and with plasma enhancement (PECVD). Special techniques to reduce the processing temperature to the absolute minimum are reviewed as well: the use of hydrogenated microcrystalline SiGe, of metal-induced crystallization and of laser annealing. The latter methods are important when one wants to process SiGe MEMS above advanced CMOS with low-permittivity dielectrics.

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This paper describes two novel processes for depositing poly-SiGe films at CMOS-compatible temperatures (1450°C). A range of deposition temperatures is investigated to ensure compatibility with different CMOS generations. While the multilayer process investigates temperatures ranging between 42O-45O0C, the microcrysfalline SiCe deposition has been made possible at temperatures as low as 300°C. These films are optimized to obtain low stress and stress gradient values suitable for MEMS structural layers.Low SiGe-AI contact resistivity on the order of 10.' n.cm' and film resistivity as low as 1 &.cm were achieved as well.

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