Accurate Evaluation of High-k HZO/ZrO₂ Films by Morphotropic Phase Boundary

Abstract

This study evaluates HfxZr1-xO2 (HZO)-based high-k dielectrics, where dielectric constant (k) is significantly enhanced through structural engineering. The investigation focuses on their dielectric characteristics by pulse operation for DRAM applications. HZO/ZrO2 (HZZ) films with different superlattice structures display different dielectric behaviors, including ferroelectricity, morphotropic phase boundary (MPB), and anti-ferroelectricity. The HZZ film at the MPB condition exhibits exceptionally high k value of 62 even at voltage of 1 V, which is attributed to the abundance of phase boundaries facilitating phase transition in the superlattice structure. Conversely, the HZZ films with ferroelectric and anti-ferroelectric properties exhibit lower-than-expected k values compared to capacitance measurement, due to overestimation caused by polarization switching. Furthermore, the HZZ film at the MPB condition demonstrates robust endurance above 1012 cycles (k>45 @1015 cycles, extrapolation). These findings highlight the potential of HZZ films at the MPB to replace conventional DRAM capacitors, offering superior dielectric properties.