Oxide Edge Trap Density Extraction in Silicon Nanowire MOSFET From Tunnel Current Noise Measurement in Gated Diode Like Arrangement

摘要

Edge traps in the gate oxide of silicon nanowire MOSFETs have been extracted from tunnel current noise measurement in a gated diode like arrangement. We have found that, low frequency noise in tunnel current results from collective response of the edge traps available within the gate oxide surrounding band-to-band generation (BTBG) region of silicon nanowire, and when the BTBG region is accessed by favorable terminal biases. From detail modeling of the phenomenon, we derived a closed form expression of the tunneling current noise power spectral density (PSD) employing which oxide edge trap density in nanowire MOSFET had been extracted through its fit with the experimental noise PSD data. We furthermore validated our model for different BTBG biases, and contrasted our result with the bulk oxide trap density in identical MOSFET, while the latter was separately estimated from the gate current noise PSD measurement. Mismatch between the oxide bulk trap and edge trap concentrations has been found, whereby actual edge trap density remains otherwise hidden from the widely employed gate current noise measurement technique. It is because, the present scheme improves the resolution of the extracted oxide edge trap concentration in surrounded gate MOSFET owing to constricted tunnel current flow near the corner of the gate which imposes selectivity on the oxide edge traps