Toward High 2Pr in Al:HfO2 Capacitors at Low Thermal Budgets: The Interplay of Crystallinity, Phase, and Ferroelectricity

Al-doped HfO₂ (HAO) has demonstrated improved ferroelectric stability; however, its relatively low remnant polarization (2P_r) at reduced annealing temperatures significantly limits practical application. This limitation primarily stems from a low ferroelectric phase fraction and insufficient crystallinity. To address this challenge, we systematically investigated the interplay among processing parameters, ferroelectric phase content, and film crystallinity. Guided by these insights, we optimized HAO films processed at low annealing temperatures by tuning key parameters, including Al doping concentration, oxidant, film thickness, and electrode material. Within an annealing temperature range of 500 °C to 700 °C, the optimized capacitors exhibited markedly enhanced 2P_r values. Notably, a record-high 2P_r of 37.5 μC/cm² was achieved at 500 °C, representing an 80.3% increase over the previously reported benchmark of 20.8 μC/cm². These findings underscore the pivotal role of processing-driven control over phase composition and crystallinity in enhancing the ferroelectric performance of HAO films, offering a promising pathway for their integration into next-generation electronic devices.