Understanding the Floating-Body Effect Simulation and Optimization in 3D-DRAMs

Abstract

In this paper we study the physics and simulation of the floatingbody effect (FBE) in advanced DRAM technologies, such as 4F2 and 3D DRAMs. Our results highlight that this effect is modulated by the bitline voltage transition speed and, therefore, proper transient TCAD simulations in the nanoseconds regime must be carried out to accurately describe the FBE. We also show how the DRAM transistor can be optimized, by means of TCAD-driven Multi-Objective Optimization, for write/read speed and retention including FBE minimization. Finally, we highlight the role of statistical variability, induced by random dopants and discrete traps, in enhancing leakage and FBE and how this can affect the transistor optimization directions.