Evaluation of STI degradation using temperature dependence of leakage current in parasitic STI MOSFET

Shallow trench isolation (STI) has become the most promising isolation scheme for ULSI applications. However, the trench isolation suffers from dislocations and oxidation induced stacking faults. Such faults are typically located near trench edges. These STI faults increase the junction leakage current and may turn-on the parasitic STI MOSFET resulting in significant leakage current through the trench isolation. In this paper we analyze the mechanism of parasitic STI MOSFET formation and investigate the temperature dependence of its leakage current. Simulation results show that the value of drain current of parasitic STI MOSFET can be used for evaluation of STI degradation. The abnormal temperature dependence of the parasitic drain current with floating body can be used as a faulty STI indicator.