ABSTRACT
In very small electronic devices, the alternate capture and emission of carriers at an individual defect site located at the interface of Si:SiO2 of a MOSFET (metal–oxide–semiconductor fieldeffect transistor) generates discrete switching in the device conductance referred to as a random telegraph signal (RTS) or random telegraph noise (RTN). Accurate and physical models for random telegraph noise fluctuations (RTF) [1] are essential to predict and optimize circuit performance during the design stage [2]. Currently, such models are not available for circuit simulation. The compound between RTF and other sources of variation, such as random dopant fluctuations (RDF), further complicates the situation especially in extremely scaled CMOS (complementary metal–oxide–semiconductor) design. In the vicinity of a trap site, the electrostatic short-range Coulomb forces that exist between trap-inversion electrons–depletion ions modify the electrostatic surface potential in the channel from source to drain in a spatially random and discrete manner. Accurate replication of these multiple peaks and valleys of the surface potential is critical to be accounted for by the analytical models for inversion conditions and when spatial inhomogeneity exists due to the interface trap, inversion carriers, and depletion region dopant ions [3]. This aspect is not presently 16accounted for by most analytical device models, including the dopant number fluctuation [4] and the percolation theory model [5]. It will be shown that these two analytical models fail to account for the large threshold voltage fluctuations that are observed for source-side trap positions in the channel by 3D EMC device simulation [6] of a 45 nm MOSFET. Therefore, a new model is proposed. This new model, for the first time, highlights the carrier mobility fluctuations resulting from source side trap positions with the spatially variant short-range interaction force causing potential inhomogeneities and random spikes in the surface potential barrier near the source.
