Interconnect Issues for Integrated MEMS Technology

This paper reviews recent progress toward the monolithic, modular integration of microelectromechanical devices (MEMS) with electronics. The interconnect metallurgy poses a thermal budget limit on the processes that can be used to build the MEMS structures after the electronics are completed. In addition, the metal interconnect and inter-metal dielectric layers must be protected during the removal of sacrificial material to release the microstructures. Polycrystalline silicon germanium (poly-SiGe) is a promising structural material, with mechanical properties similar to polycrystalline silicon, which can be conformally deposited by low pressure chemical vapor deposition at temperatures compatible with modern multi-level interconnect technologies. Ideally, it should be possible to form a low-resistance and lowparasitic-capacitance contact directly between poly-SiGe and an underlying metal interconnect. Initial specific contact resistance measurements between p-type poly-SiGe and TiN/Al are reported.