Structural and dielectric properties of amorphous ZrO2 and HfO2

TL;DR

This study uses first-principles density-functional methods to analyze the structural, vibrational, and dielectric properties of amorphous ZrO2 and HfO2, materials promising for CMOS gate insulators.

Contribution

It provides detailed theoretical models and analysis of amorphous ZrO2 and HfO2, highlighting their potential as uniform, passivating gate insulators with dielectric properties similar to crystalline phases.

Findings

Amorphous ZrO2 and HfO2 have dielectric constants comparable to their crystalline counterparts.

Realistic amorphous models were constructed using the activation-relaxation technique.

The structural and vibrational properties were characterized in detail.

Abstract

Zirconia (ZrO2) and hafnia (HfO2) are leading candidates for replacing SiO2 as the gate insulator in CMOS technology. Amorphous versions of these materials (a-ZrO2 and a-HfO2)) can be grown as metastable phases on top of a silicon buffer; while they tend to recrystallize during subsequent annealing steps, they would otherwise be of considerable interest because of the promise they hold for improved uniformity and electrical passivity. In this work, we report our theoretical studies of a-ZrO2 and a-HfO2 by first-principles density-functional methods. We construct realistic amorphous models using the ``activation-relaxation'' technique (ART) of Barkema and Mousseau. The structural, vibrational, and dielectric properties of the resulting models are analyzed in detail. The overall average dielectric constant is computed and found to be comparable to that of the monoclinic phase.