Hironori Fujisawa

Abstract Superior ferroelectric properties of Al-doped HfO₂ (HAO) thin films are demonstrated using flash lamp annealing (FLA). This annealing approach is a low-thermal-budget treatment that features short annealing times at the millisecond timescale. We first clarified the annealing conditions with respect to optimum ferroelectricity. The results show that 5-millisecond annealing at 1000 °C is sufficient for adequate crystallization, achieving a high 2P_r value of 17.3 μC cm⁻². By adjusting the cooling rate on the millisecond timescale during crystallization annealing, a high cooling rate of 182 °C ms⁻¹ exhibited a superior 2P_r value of 16.6 μC cm⁻², in contrast to a slow cooling rate of 12 °C ms⁻¹, which yielded a 2P_r value of 10.2 μC cm⁻². The results indicate that the control of the cooling rate is crucial for achieving an optimum 2P_r value, illustrating the potential of FLA for forming high-quality ferroelectric thin films.

Abstract We report the use of a low-thermal-budget annealing technique; flash lamp annealing (FLA), which provides an extremely short annealing time in the millisecond range, on the ferroelectric properties of Al-doped HfO₂ (HAO) films. HAO annealed at 1000 °C with 5 ms shows a higher remanent polarization value of 24.9 μC cm⁻² compared to rapid thermal annealing (RTA), without degradation of endurance. GIXRD shows a stronger peak intensity originating from the orthorhombic (o-) phase and is observed when using FLA, indicating the formation of a larger amount of the o-phase. We believe that this is a consequence of the low thermal budget of FLA, and that specifically FLA can minimize the relaxation of the compressive stress in the TiN electrodes, inducing a high tensile stress to the HAO films and therefore an enhancement of o-phase formation. These results indicate that FLA is a promising annealing method for HAO crystallization due to the enhancement of o-phase formation.