Ferroelectric scandium-doped aluminum nitride (Al_1-xSc_xN) is of considerable research interest because of its superior ferroelectricity. Studies indicate that Al_1-xSc_xN may suffer from a high leakage current, which can hinder further thickness scaling and long-term reliability. In this work, we systematically investigate the origin of the leakage current in Al_0.7Sc_0.3N films via experiments and theoretical calculations. The results reveal that the leakage may originate from the nitrogen vacancies with positively charged states and fits well with the trap-assisted Poole-Frenkel (P-F) emission. Moreover, we examine the cycling behavior of ferroelectric Al_0.7Sc_0.3N-based FeRAM devices. We observe that the leakage current substantially increases when the device undergoes bipolar cycling with a pulse amplitude larger than the coercive electric field. Our analysis shows that the increased leakage current in bipolar cycling is caused by the monotonously reduced trap energy level by monitoring the direct current (DC) leakage under different temperatures and the P-F emission fitting.

This study presents an investigation into the stress effect on the leakage current in ferroelectric Al0.7Sc0.3N films by experiments and density functional theory (DFT) computations. The experiments are based on 8-in. 100 nm Al0.7Sc0.3N films obtained from pulsed DC co-sputter deposition technology, which exhibit non-uniform compressive in-plane stress across the wafers and similar distributions of leakage current, suggesting close dependence between each other. DFT computations revealed that stress affects leakage current in two ways: the level of traps introduced by nitrogen vacancy and the formation energy of nitrogen vacancy in Al0.7Sc0.3N. By considering both factors, the leakage current of Al0.7Sc0.3N films increases with larger compressive in-plane stress, as observed in the experimental results. Additionally, the DFT calculation results indicated that the leakage current is more sensitive to compressive stress compared to the tensile, and the minimum leakage current can be obtained with neutral in-plane stress. These findings provide a guideline for stress engineering to optimize the AlScN-based ferroelectric devices.

In this work, 10 nm scandium-doped aluminum nitride (AlScN) capacitors are demonstrated for the construction of the selector-free memory array application. The 10 nm Al_0.7Sc_0.3N film deposited on an 8-inch silicon wafer with sputtering technology exhibits a large remnant polarization exceeding 100 µC/cm² and a tight distribution of the coercive field, which is characterized by the positive-up-negative-down (PUND) method. As a result, the devices with lateral dimension of only 1.5 μm show a large memory window of over 250% and a low power consumption of ~40 pJ while maintaining a low disturbance rate of <2%. Additionally, the devices demonstrate stable multistate memory characteristics with a dedicated operation scheme. The back-end-of-line (BEOL)-compatible fabrication process, along with all these device performances, shows the potential of AlScN-based capacitors for the implementation of the high-density selector-free memory array.

In this letter, we report the KrF excimer laser annealing for achieving high-performance ferroelectric Hf0.5Zr0.5O2(HZO). The laser anneals the target device layer effectively with a high heating/cooling rate without overheating under-layer deep structures. The impact of laser fluence, number of pulses, and pulse duration on the ferroelectricity in HZO was carefully studied through numerical simulation and experiment. The remnant polarization $2{P}_{\text {r}}$ of $22~\mu \text{C}$ /cm2, a coercive field of ~1 MV/cm, and a cycling endurance of > $10^{{8}}$ were achieved in the 8 nm ferroelectric HZO thin film annealed by the laser with an ultra-low laser fluence of ~84 mJ/cm2 and 20 pulses. Benefiting from the large beam size of KrF excimer laser, the laser annealing is practical for obtaining stable wafer-scale ferroelectric HZO within a short time.