A Silicon Nitride Based Shallow Trench Isolation with Side-Gate for CMOS Integration with MEMS Components for System-On-Chip Applications

Abstract

ABSTRACTWe have developed a hydrofluoric acid (HF) resistant, composite shallow trench isolation (STI) process for MOSFETs utilizing silicon nitride as isolation material for on-chip integration of micro-electro-mechanical (MEMS) resonators and CMOS devices. Peripheral leakage currents in silicon nitride isolated MOSFETs are suppressed by employing an independently controlled polysilicon side-gate, surrounding the active area of the devices. Electrostatic control of the threshold voltage at the device periphery alleviates the need for edge implants, resulting in increased thermal budget. Compatibility with HF release processes and high temperature anneal cycles allows integration of MEMS components in close proximity to CMOS devices for system-on-chip applications. nMOSFET devices fabricated using this composite STI process show excellent device characteristics.