Device physics of ferroelectric memories

Abstract

A status report is given on high-dielectric (usually ferroelectric) thin-films of fine-grained ceramics utilized for ferroelectric memories, including active memory elements in nonvolatile random access memories (NV-RAMs), passive capacitors in dynamic random access memories (DRAMs), and ferroelectric gates in ferroelectric field-effect transistors (FEMFETs) configured for non-destructive read-out (NDRO) memories. Emphasis is upon breakdown fields, leakage current, fatigue, and retention. Both the Ba_xSr_1-xTiO₃ (BST) family and the SrBi₂Ta₂O₉ family of layer-structure perovskites are discussed. The review ends with a list of unsolved physics questions about ferroelectric thin films that will be helpful in further engineering developments.