A Novel Ferroelectric Superlattice Based Multi-Level Cell Non-Volatile Memory

We demonstrate a novel ferroelectric (FE) superlattice based multi-level cell (MLC) memory, which outperforms previous multi-state FE memory implemented using partial polarization switching, from the standpoint of device-to-device variation. We show that the FE superlattice consisting of alternate FE and dielectric (DE) thin layers provides a scalable approach for MLC implementation because: 1) the superlattice constructs controlled layer-by-layer polarization switching in the constituent FE layers; 2) the number of FE layers equals the number of stored bits; and, finally, (3) the switching of all the domains in a given coercive field (E_C) distribution associated with one isolated peak suppresses the variation induced by partial polarization switching. Based on these, we experimentally demonstrate a 2-bit/cell FE superlattice memory and simulate a 3-bit/cell memory with excellent device-to-device variation.