Engineering ferroelectric interfaces: Delta-doping and millisecond flash lamp annealing for enhancing polarization properties in TiN/Al:HfO2/TiN capacitors

Abstract

We identify two key strategies for enhancing polarization properties: the engineering of delta-doped interfacial layers and the application of millisecond-scale flashlamp annealing (FLA), using TiN/Al:HfO2 (HAO)/TiN ferroelectric capacitors. The delta-doped Al2O3 layer remains stably localized at the interfaces even after high-temperature annealing at 1000 °C for 5 ms. This interfacial localization between the electrodes and HAO films significantly influences both the polarization behavior and the crystallization characteristics. Delta doping at the top electrode interface yields a remanent polarization (2Pr) value approximately 10% higher than that observed by doping at the bottom interface. This enhancement is attributed to the position-dependent formation of oxygen vacancies (Vo), which vary with the location of the delta-doped layer. Grazing incidence x-ray diffraction analysis reveals that delta doping at the top interface promotes the formation of ferroelectric orthorhombic phases more effectively than in undoped structures. Furthermore, a peak angle analysis of HAO films indicates that capacitors with top interface delta doping exhibit higher diffraction angles compared to those without doping, suggesting an increased tensile stress exists within the HAO layer. FLA treatment further amplifies this tensile stress relative to rapid thermal annealing, thereby contributing to improved ferroelectric properties. These findings underscore the importance of both interfacial delta doping and low-thermal-budget FLA treatment in achieving enhanced ferroelectric performance and highlight their potential for the fabrication of high-performance ferroelectric devices.