Degradation of time dependent variability due to interface state generation

摘要

Although only a few defects will be present in the gate dielectric of deeply-downscaled CMOS devices, their relative impact may become intolerable [1]. An individual charged defect can significantly alter the channel current ID of a nm-sized FET, causing VTH fluctuations (RTN) and time dependent ΔVTH variability. Based on detailed understanding of atomistic devices, random dopant fluctuation (RDF) was identified as the main source of both time-zero variability and giant RTN fluctuations in ultra-scaled devices [2–3]. In order to reduce variability, the industry is moving to low doped channel devices [4]. Here we show that the adverse role of RDF is taken over by charged interface states. In addition to that, stress during operation induces interface state generation, which in turn causes VTH drift and further increases RTN amplitudes and time-dependent ΔVTH variability.