Our study investigates heterogeneous co-doped HfO₂ 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 HfO₂ film, influencing the preferred nucleation sites of HfO₂ during rapid thermal processing. Our findings demonstrate that the phase composition of the annealed HfO₂ film is primarily determined by heterogeneous or homogeneous crystallization processes. In cases of heterogeneous crystallization, where crystallization initiates from nuclei formed at electrode/HfO₂ 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 HfO₂ film. Additionally, we observe correlations between the texture of the HfO₂ film and the texture of the electrodes.