Interface engineering via Ti scavenging interlayer for enhanced ferroelectricity in ultrathin Hf0.5Zr0.5O2 films

The formation of a non-ferroelectric TiO x N y interfacial layer at the TiN/Hf 0.5 Zr 0.5 O 2 (HZO) interface can induce a depolarization field, thus limiting the performance of HfO 2 -based ferroelectrics. Previous studies have reported that the electrical properties of TiO x N y , including its effective capacitance and conductivity, strongly depend on the oxygen-to-nitrogen composition ratio. In this study, a Ti interlayer was employed as an oxygen-scavenging layer to control the oxygen concentration in the TiO x N y interfacial layer, and its effect on the ferroelectric properties of the HZO films was systematically investigated. Electrical measurements as a function of Ti thickness revealed that the remanent polarization increased with Ti thickness, whereas thicker Ti layers increased leakage current and degraded endurance. First-order reversal curve analysis and time-dependent switching measurements showed that the Ti interlayer facilitated homogeneous and fast polarization switching, suggesting reduced local field distortion associated with interfacial charge trapping. With an optimized 2-nm-thick Ti interlayer, the remanent polarization of HZO films was significantly enhanced while maintaining stable endurance up to 10 9 switching cycles. The effectiveness of the Ti scavenging strategy became more pronounced as the HZO thickness decreased, demonstrating that interfacial modulation plays a critical role in suppressing the severe ferroelectric degradation observed in ultrathin HZO films. These results establish Ti scavenging as an effective strategy for overcoming the scalability limitations of ferroelectric HZO. The proposed approach provides a practical pathway toward scalable, low-power HZO-based ferroelectric devices.