Capacitor-less, Long-Retention (> 400s) DRAM Cell Paving the Way towards Low-Power and High-Density Monolithic 3D DRAM

Abstract

We report for the first time a fully 300-mm stacking-compatible capacitor-less DRAM cell with >400s retention time by integrating two IGZO-TFTs in a 2T0C configuration. We optimize the single IGZO-TFT performances by engineering the materials surrounding the IGZO layer and the transistor layout parameters. We thus introduce a novel IGZO-TFT device and demonstrate a scaled transistor (W = 70 nm, L = 45 nm) with optimal Vth reproducibility on 300-mm wafers. By integrating the IGZO-TFTs in a 2T0C configuration, we systematically assess reproducible long retention time for different transistor dimensions, thanks to the extremely low extracted IGZO-TFT off-current (similar to 3x10(-19)A/mu m).