Modeling and Simulation of Advanced Floating Body Z-ram Memory Cells

A modeling approach to study advanced floating body Z-RAM memory cells is developed. In particular, the scalability of the cells is investigated. First, a Z-RAM cell based on a 50 nm gate length double-gate structure corresponding to state of the art technology is studied. A bi-stable behavior essential for Z-RAM operation is observed even in fully depleted structures. It is demonstrated that by adjusting the supply source-drain and gate voltages the programming window can be adjusted. The programming window is appropriately large in voltage as well as in current. We further extend our study to a Z-RAM cell based on an ultra-scaled double-gate MOSFET with 12.5 nm gate length. We demonstrate that the cell preserves its functionality by providing a wide voltage operating window with large current differences. An appropriate operating window is still observed at approximately 25-30% reduced supply voltage, which is an additional benefit of scaling. The relation of the obtained supply voltage to the one anticipated in an ultimate MOSFET with quasi-ballistic transport is discussed.