Crystalline phase control of ferroelectric HfO2 thin film via heterogeneous co-doping

Our study investigates heterogeneous co-doped HfO<inf>2</inf> thin films integrated into metal-ferroelectric-metal stacks, achieved by incorporating multiple layers doped with various species during the atomic layer deposition process. This approach creates an artificial crystallization temperature gradient across the HfO<inf>2</inf> film, influencing the preferred nucleation sites of HfO<inf>2</inf> during rapid thermal processing. Our findings demonstrate that the phase composition of the annealed HfO<inf>2</inf> film is primarily determined by heterogeneous or homogeneous crystallization processes. In cases of heterogeneous crystallization, where crystallization initiates from nuclei formed at electrode/HfO<inf>2</inf> interfaces, grains predominantly crystallize in the orthorhombic phase. Conversely, grains are more likely to crystallize in the monoclinic phase if they originate from nuclei formed at the center of the HfO<inf>2</inf> film. Additionally, we observe correlations between the texture of the HfO<inf>2</inf> film and the texture of the electrodes.