Characterization and modeling of negative bias temperature instability in P-MOSFETs

Abstract

It has been the intent of this work to investigate negative bias temperature instability (NBTI) in p-MOSFETS with ultra-thin nitrided gate oxides experimentally and theoretically. A systematic study on NBTI has been carried out and the understanding of NBTI mechanism is further enhanced. Firstly, a simple NBTI characterization technique of measuring a single-point saturation drain current has been proposed to minimize the unfavorable NBTI recovery during measurement. With this method, the measurement time can be largely reduced. This method gives a closer-to-real threshold voltage shift and thus yields a more reliable power-law factor. Subsequently, since NBTI has become a key device reliability challenge for advanced CMOS technology nodes, an NBTI in-line test methodology has been developed to monitor NBTI during the device development phase. Moreover, NBTI recovery is experimentally examined, and a combined empirical model for NBTI recovery within the modulated measurement time frame has been proposed to describe the entire process of NBTI recovery in a wide time range. A comprehensive study on the modeling of NBTI has been conducted. An analytical reaction-diffusion (R-D) model within the framework of the standard R-D model has been developed. This model can well describe NBTI in a wide time scale covering the three regimes of reaction, transition and diffusion. A power-law factor of ~1 is experimentally observed for the nitrided gate oxide, which shows clear evidence of the existence of the reaction-limited regime for NBTI. The analytical R-D model