Evidence of single domain switching in hafnium oxide based FeFETs: Enabler for multi-level FeFET memory cells

Recent discovery of ferroelectricity in HfO₂ thin films paved the way for demonstration of ultra-scaled 28 nm Ferroelectric FETs (FeFET) as non-volatile memory (NVM) cells [1]. However, such small devices are inevitably sensible to the granularity of the polycrystalline gate oxide film. Here we report for the first time the evidence of single ferroelectric (FE) domain switching in such scaled devices. These properties are sensed in terms of abrupt threshold voltage (VT) shifts leading to stable intermediate VT levels. We emphasize that this feature enables multi-level cell (MLC) FeFETs and gives a new perspective on steep subthreshold devices based on ferroelectric HfO₂.