Device physics of capacitive MEMS

Using interferometric modulator (IMOD) MEMS-based technology as a typical example, we give an overview of key device concepts of capacitive micro-electro-mechanical systems (MEMS). We discuss basic electromechanical physics of the device, both in the ideal case of no charging in the dielectric and the more realistic scenario with charging. The dielectric stack is a critical element of capacitive MEMS. A significant part of the paper is dedicated to the role of the dielectric and electronic transport effects during device operation. The similarities and differences between dielectrics in MEMS and gate oxides in semiconductor MOS and MIM structures are highlighted. Several experimental techniques to study charge transport in the MEMS dielectric stack are reviewed following a discussion on how the dynamics of these electronic effects can be modeled. Finally, we comment on the importance of surface and interfaces on MEMS performance and reliability as well as fundamental studies of their properties.