A CMOS-compatible morphotropic phase boundary

Abstract

Morphotropic phase boundaries (MPBs) show substantial piezoelectric and dielectric responses, which have practical applications. The predicted existence of MPB in HfO2–ZrO2 solid solution thin film has provided a new way to increase the dielectric properties of a silicon-compatible device. Here, we present a new fabrication design by which the density of MPB and consequently the dielectric constant ϵ r of HfO2–ZrO2 thin film was considerably increased. The was controlled by fabrication of a 10 nm [1 nm Hf0.5Zr0.5O2 (ferroelectric)/1 nm ZrO2 (antiferroelectric)] nanolaminate followed by an appropriate annealing process. The coexistence of orthorhombic and tetragonal structures, which are the origins of ferroelectric (FE) and antiferroelectric (AFE) behaviors, respectively, was structurally confirmed, and a double hysteresis loop that originates from AFE ordering, with some remnant polarization that originates from FE ordering, was observed in P–E curve. A remarkable increase in ϵ r compared to the conventional HfO2–ZrO2 thin film was achieved by controlling the FE–AFE ratio. The fabrication process was performed at low temperature (250 °C) and the device is compatible with silicon technology, so the new design yields a device that has possible applications in near-future electronics.