Physics-based 1/ f noise model for MOSFETs with nitrided high- κ gate dielectrics

Abstract A physics-based low frequency noise model has been developed for MOSFET devices with nitrided high- κ gate dielectric materials. The new model is built upon the correlated carrier number and surface mobility fluctuations theory, where the original Unified Model was modified to take into account the multilayered structure of the high- κ gate dielectrics, and the resultant charge carrier tunneling process in terms of a two-step cascaded barrier instead of a single step barrier. The new model eliminates the discrepancies previously reported for the dielectric trap density values extracted from noise data using the original Unified Model for flicker noise. The dielectric trap density, typically taken as an average or spatially uniform in the dielectric and constant with respect to energy, is replaced here with an exponential expression dependent on the band-gap energy along with a spatial distribution of the traps in the high- κ layer. Thus, due to the energy dependence of the trap density, bending of the energy bands induces an additional non-uniformity in the spatial trap distribution. Implementation of this expression also provides the much needed flexibility in simulating realistic trap profiles in high- κ materials. Here, MOSFETs with nitrided dielectrics were considered for the noise experiments, as nitridation presents many advantages for the electrical and thermal characteristics of the gate insulator. Variable temperature low frequency noise and mobility measurements have been performed on MOSFETs with nitrided high- κ dielectric. Phonon scattering was found to have a profound effect on the mobility behavior, but no consequence on the low frequency noise characteristics. The low frequency noise data obtained on devices with different interfacial layer thicknesses and different regions of transistor operation was successfully compared with the predictions of the newly developed Multi Stack Unified Noise (MSUN) Model over a temperature range of 172–300 K.

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