Understanding the impact of La dopant position on the ferroelectric properties of hafnium zirconate

Abstract

The impact of asymmetrical doping of hafnium zirconate (HZO) based capacitors is studied. By introducing Lanthanum (La) dopant at different stages of the HZO deposition process, its effect on orthorhombic phase formation and its out-of-plane preferential orientation, as reflected in remnant polarization (2P(R)), is studied using Grazing incident X-ray diffraction (GIXRD) and electrical measurements. Furthermore, tri-layer stacks were fabricated using a bottom TiO2 interfacial layer, which promotes the growth of out-of-plane oriented orthorhombic grains, and a top Nb2O5 interfacial layer, which enhances the overall content of the orthorhombic phase in the HZO layer, leading to an increase in 2P(R). Both single-layer and tri-layer asymmetrically doped capacitor stacks show improved endurance, demonstrating 2P(R) > 40 mu C/cm(2) at 10(8) cycles at 2.5 MV/ cm.