Reliability of Surface MEMS Structures Fabricated Using Standard CMOS Back-End-Of-Line Processes

Reliability of surface MEMS fabricated with standard CMOS back-end-of-line (BEOL) processes was investigated by several film analyses and by monitoring change in MEMS properties after standard pressure cooker test (PCT). A significant change in MEMS characteristics was observed after PCT for samples with SiN passivation layer thinner than 100nm, while for passivation layer thicker than 150nm, no change was observed. A large shift in film stress after PCT and results from TDS (Thermal Desorption Spectroscopy) and XRR (X-ray reflectometry) suggested that this is due to water release from SiO2 film used in the structure.