Ferroelectricity in Lu doped HfO2 layers

Doped HfO2 has become a promising candidate for non-volatile memory devices since it can beeasily integrated into existing CMOS technology. Many dopants like Y, Gd, and Sr have beeninvestigated for the stabilization of ferroelectric HfO2. Here, we report the fabrication of capacitorscomprising ferroelectric HfO2 metal-insulator-metal structures with TiN bottom and top electrodesusing the dopant Lu. Amorphous 5% Lu doped HfO2 was deposited by pulsed laser deposition andafterwards annealed to achieve the ferroelectric, orthorhombic phase (space group Pbc21). Thepolarization of the layers was confirmed by capacitance-voltage, polarization-voltage, and currentvoltagemeasurements. Depending on the anneal temperature, the remanent polarization changesand the initial state of the oxide varies. The layer exhibits initially a pinched hysteresis up to anannealing temperature of 600 °C and an unpinched hysteresis at 700 °C. The maximum polarizationis about 11 lC/cm2 which is measured after 104 cycles and stable up to 106 cycles. The influence ofthe layer thickness on the oxide properties is investigated for 10–40 nm thick HfLuO; however, athickness dependence of the ferroelectric properties is not observed. Published by AIP Publishing