Reduced Leakage and Enhanced Endurance via an ITO Oxygen Reservoir Layer in HZO Ferroelectric Capacitors

This work proposes a simple, BEOL compatible strategy to improve endurance of Hf_0.5Zr_0.5O₂ (HZO) ferroelectric capacitors by inserting indium tin oxide (ITO), a conductive metal oxide as a passivation interlayer. Without electrode replacement, ITO interlayer serves as an oxygen reservoir at the interface between the top tungsten (W) electrode and HZO. By tailoring the O₂ flow of 0.5 sccm (Oxygen-Poor) and 2 sccm (Oxygen-Rich) during ITO sputter deposition, the W/ITO/HZO/W capacitors exhibit more than 250x enhanced endurance, sustaining nearly 10⁹ switching cycles, without sacrificing the remanent polarization compared to the ITO-free W/HZO/W capacitors. X-ray Photoelectron Spectroscopy (XPS) reveals oxygen vacancy (V_O) compensation at the top interface, confirming the oxygen-reservoir role of the ITO interlayer. Furthermore, by analyzing leakage current and dead-layer formation of the capacitors with ITO deposited in different oxygen flow rate, we outline a strategy for enhancing the reliability of hafnium-based ferroelectric devices.