Investigation of interface traps at Si/SiO2 interface of SOI pMOSFETs induced by Fowler-Nordheim tunneling stress using the DCIV method

The changes of interface trap density and distribution at the Si/SiO2 interface in partially depleted SOI MOSFETs were investigated by direct-current current-voltage (DCIV) method before and after Fowler-Nordheim tunnelling stress condition. The equivalent density and energy level of interface trap were obtained by combining the DCIV measurement results with the theoretical calculation using the least square method. It is concluded that the interface trap density increased as applying F-N stress due to the generation of Si dangling bond and the trapped charge at the Si/SiO2 interface, and the equivalent energy level of interface trap become close to the midgap with stress time increasing. In addition, interface trap density N (IT) as a function of their energy level E (IT) can be achieved, which were typical "U-shape" curves, and the interface trap density near midgap increases obviously as the F-N stress time increasing. An effective method is proposed to evaluate the interface state of SOI devices suffered electrical stress or other damages.