Low frequency noise degradation in ultra-thin oxide (15/spl Aring/) analog n-MOSFETs resulting from valence-band tunneling

The abnormal increase of low frequency flicker noise in analog n-MOSFETs with gate oxide, in the valence band tunneling domain, is investigated. In 15/spl Aring/ oxide devices, valence-band electron tunneling from Si substrate to poly-gate occurs at a positive gate voltage and results in the splitting of electron and hole quasi Fermi-levels in the channel. The excess low frequency noise is attributed to electron and hole recombination at interface traps between the two quasi Fermi-levels. The trap capture and emission times in the valence band tunneling domain are extracted from random telegraph signals. The dependence of measured trap times on gate voltage is consistent with our proposed model.