SOI 1T-DRAM cells with variable channel length and thickness: Experimental comparison of programming mechanisms

Several concepts of capacitor-less single-transistor (1T) DRAM have recently been proposed to overcome the scaling limitations of bulk DRAMs. In this study, we focus on the comparison of two programming mechanisms of 1T-DRAMs: the impact ionization (II), the most common mechanism to store charges in the body of the cell, and the meta-stable dip (MSD) effect. The impact of the gate length and channel thickness reduction on both the II and the MSD programming mechanisms has been investigated using dynamic measurements on conventional Fully Depleted SOI (FDSOI) transistors. In the absence of any customization of technology and device architecture, it is found that MSD programming is superior and demonstrates higher resilience to the MOSFET scaling. These promising performances arise from the dynamic coupling between the front and back gates and from the use of low drain bias.