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

TLDR

The study examined the structural and electrical characteristics of gate stacks incorporating ZrO₂ dielectrics. ZrO₂ films were deposited by atomic layer chemical vapor deposition on various prepared substrates, and the resulting gate stacks were characterized by TEM and XPS to assess structure, composition, and interfaces. The films were polycrystalline (cubic or tetragonal) with an amorphous interfacial layer, achieving an EOT of 1.3 nm, leakage of 10⁻⁵ A/cm² at –1 V, hysteresis of 8–10 mV, and a midgap Dit of ~3×10¹¹ cm⁻² eV⁻¹, outperforming comparable SiO₂ dielectrics.

Abstract

Structural and electrical properties of gate stack structures containing ZrO2 dielectrics were investigated. The ZrO2 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 ZrO2 films were polycrystalline with either a cubic or tetragonal crystal structure. An amorphous interfacial layer with a moderate dielectric constant formed between the ZrO2 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 10−5 A/cm2 at a bias of −1 V from flatband, which is significantly less than that seen with SiO2 dielectrics of similar EOT. A hysteresis of 8–10 mV was seen for ±2 V sweeps while a midgap interface state density (Dit) of ∼3×1011 states/cm eV was determined from comparisons of measured and ideal capacitance curves.