Electrical and materials properties of ZrO2 gate dielectrics grown by atomic layer chemical vapor deposition

Abstract

Structural and electrical properties of gate stack structures containing ${\mathrm{ZrO}}_{\mathrm{2}}$ dielectrics were investigated. The ${\mathrm{ZrO}}_{\mathrm{2}}$ films were deposited by atomic layer chemical vapor deposition (ALCVD) after different substrate preparations. The structure, composition, and interfacial characteristics of these gate stacks were examined using cross-sectional transmission electron microscopy and x-ray photoelectron spectroscopy. The ${\mathrm{ZrO}}_{\mathrm{2}}$ films were polycrystalline with either a cubic or tetragonal crystal structure. An amorphous interfacial layer with a moderate dielectric constant formed between the ${\mathrm{ZrO}}_{\mathrm{2}}$ layer and the substrate during ALCVD growth on chemical oxide-terminated silicon. Gate stacks with a measured equivalent oxide thickness (EOT) of 1.3 nm showed leakage values of ${10}^{\text{−5}}\hspace{0.5em}{\mathrm{A/cm}}^{\mathrm{2}}$ at a bias of −1 V from flatband, which is significantly less than that seen with ${\mathrm{SiO}}_{\mathrm{2}}$ dielectrics of similar EOT. A hysteresis of 8–10 mV was seen for ±2 V sweeps while a midgap interface state density ${\mathrm{(D}}_{\mathrm{it}})$ of ${\text{∼3×10}}^{11}$ states/cm eV was determined from comparisons of measured and ideal capacitance curves.