Influence of back-gate stress on the back-gate threshold voltage of a LOCOS-isolated SOI MOSFET

摘要

The performance of a LOCOS-isolated SOI MOSFET heavily depends on its back-gate characteristic,which can be affected by back-gate stress. A large voltage stress was applied to the back gate of SOI devices forat least 30 s at room temperature, which could effectively modify the back-gate threshold voltage of these devices.This modification is stable and time invariant. In order to improve the back-gate threshold voltage, positive substratebias was applied to NMOS devices and negative substrate bias was applied to PMOS devices. These results suggestthat there is a leakage path between source and drain along the silicon island edge, and the application of large backgatebias with the source, drain and gate grounded can strongly affect this leakage path. So we draw the conclusionthat the back-gate threshold voltage, which is directly related to the leakage current, can be influenced by back-gatestress.