Hafnium–zirconium oxide interface models with a semiconductor and metal for ferroelectric devices

Density functional theory (DFT) is employed to investigate ferroelectric (FE) hafnium–zirconium oxide stack models for both metal–insulator–metal (MIM) and metal–insulator–semiconductor (MIS) structures. The role of dielectric (DE) interlayers at the ferroelectric interfaces with metals and semiconductors and the effects of thickness scaling of FE and DE layers were investigated using atomic stack models. A high internal field is induced in the FE and DE layers by the FE polarization field which can promote defect generation leading to limited endurance. It is also shown that device operation will be adversely affected by too thick DE interlayers due to high operating voltage. These DFT models elucidate the underlying mechanisms of the lower endurance in experimental MIS devices compared to MIM devices and provide insights into the fundamental mechanisms at the interfaces.