  Here, we optimized the annealing temperature of HZO/TiN thin film
heterostructure via multiscale analysis of remnant polarization,
crystallographic phase, minimum ferroelectric domain size, and average grain
size. We found that the remnant polarization was closely related to the
relative amount of the orthorhombic phase whereas the minimum domain size was
to the relative amount of the monoclinic phase. The minimum domain size was
obtained at the annealing temperature of 500$^\cird$C while the optimum remnant
polarization and capacitance at the annealing temperature of 600$^\circ$C. We
conclude that the minimum domain size is more important than the sheer
magnitude of remnant polarization considering the retention and fatigue of
switchable polarization in nanoscale ferroelectric devices. Our results are
expected to contribute to the development of ultra-low-power logic transistors
and next-generation non-volatile memory devices.
