Parasitic BJT Read Method for High-Performance Capacitorless 1T-DRAM Mode in Unified RAM

Abstract

A high-performance unified RAM without soft programming is demonstrated on a fully depleted FinFET structure. An oxide/nitride/oxide gate dielectric is integrated in a floating-body FinFET, thereby providing the versatile functions of nonvolatile Flash memory and high-speed capacitorless 1T-DRAM. A new read method involving the utilization of a parasitic bipolar junction transistor is employed for the capacitorless 1T-DRAM mode. This manner provides nondestructive reading and a high sensing current window (Delta I(S) > 45 mu A). As the nitride traps are filled with holes before activating the capacitorless 1T-DRAM mode, an undesirable contribution of hole trapping on a threshold voltage shift, i.e., soft programming, is inhibited without sacrificing the sensing current window.