Study of Gate-Oxide Degradation Induced Mobility Change with Cryogenic Measurement

In this paper, n-MOSFET and p-MOSFET are stressed using Fowler-Nordheim (F-N) tunneling and substrate hot carrier injection (HCI) to induce trapped charges. The inversion mobility is extracted and deconvoluted into surface roughness, phonon, and Coulomb mobilities. Using cryogenic measurement at 4.2K, the effect of phonon scattering is removed, allowing an accurate deconvolution of surface roughness and Coulomb mobilities. It is found that besides the Coulomb mobility being degraded after stress, the effective surface roughness mobility is also degraded.