Fabrication of silicon-based MEMS capacitive microphone structure with thin starting wafer

In this work, silicon-based MEMs capacitive microphone was designed and fabricated on 150 mm CMOS Line. 400 um thin wafer was used as starting wafer, which can greatly reduce process integration complexity accompany with the reduced cost. Low-stress poly film was used as back-plate and membrane. CMOS BEOL Al film was used as PAD for the back-plate and membrane. To make better control of wafer bowing induced by thinner wafer and in-film stress, optimized integration scheme and module process were developed. CV test was done to check the wafer-level microphone performance. From the CV data, C0 (initial capacitance at 0 V) is about 4.8 pF, and pull-in voltage is about 13.5 V. A fast wafer-level reliability test was done to check the structure/process performance. From the data comparison between initial values and values after cycles of stressed pulse, the process can meet the device requirements.