Charge balance effect on the phase stability and reliability in doped HfO2-ZrO2 superlattice films for further DRAM capacitors: A first-principles study

A dielectric material with a higher permittivity and a lower leakage is required to meet the demands of three-dimensional (3D) dynamic random access memory (DRAM). Current morphotropic phase boundary (MPB) behavior exhibits a higher permittivity but relatively high leakage. In this work, we propose a feasible approach to achieve MPB and low leakage by the charge balance effect in the doped HfO2-ZrO2 superlattice system. Our first-principles calculations reveal that the synergy effect of doping and oxygen vacancies can achieve lower phase transition barriers between polar and nonpolar phases, suggesting the formation of more MPB regions. Especially for Y dopant, it is more preferred due to the smallest transition barrier. Additionally, defect states arising from oxygen vacancies can be passivized at the charge balance state to enable large bandgap, suppressing leakage currents. This work provides a potential solution for a dielectric material with a higher permittivity and a lower leakage, paving the way for future 3D DRAM capacitors.