Comparison of breakdown characteristics of DeNMOS devices with various drain structures

In this work, OFF-state breakdown characteristics of shallow trench isolation (STI)-type drain extended NMOS (DeNMOS) devices with different drain structures are studied and compared. The drain structures include deep-drain structure and structures with heavy doping on STI-sidewall regions. These devices show improved ON-state resistance without degrading breakdown voltage. Devices with higher doping underneath the drain diffusion region exhibit stronger bipolar triggering and higher snapback in their breakdown characteristics, thereby sustaining higher drain current levels before device failure. The devices with heavy doping only on the STI-sidewall show intermediate snapback characteristics between conventional and deep-drain devices in the breakdown region. Therefore, this work provides physical insights into the impact of different drain doping profiles on low-voltage I-V characteristics and high current drain breakdown characteristics of STI-DeMOS devices for different drain doping profiles.