Low temperature and high quality atomic layer deposition HfO<inf>2</inf> coatings

Abstract

Low temperature high quality thermal atomic layer deposition (ALD) HfO 2 process has been developed and characterized using different oxidant sources—water, water-ozone, and ozone. Despite a low deposition temperature of 170 °C, the coatings are shown to be exhibit high optical quality, good barrier properties, environmentally stable, low impurity concentration, and other desirable material properties. The water-based process was shown to produce the highest quality coatings in terms of density, purity and stoichiometry. Using various complimentary characterization techniques on hafnia coatings deposited atop silicon, including X-ray reflectivity (XRR); ultraviolet-visible reflectometry; time-of-flight secondary ion mass spectroscopy (TOF-SIMS); and X-ray photoelectron spectroscopy (XPS) measurements, the coatings are shown to be of high quality. The developed ALD hafnia processes have exceptionally good control over layer thickness with uniformed coatings reproducibly demonstrated on 150 mm silicon wafers. Due to the exceptionally low extinction coefficient, ALD hafnia coatings of varying thickness were measured atop silicon to study the coatings anti-reflectivity behavior in the mid-ultraviolet region. The anti-reflectance performance of these single-layer coatings compares to or exceeds the performance of other reported single layer coatings. Importantly, unlike other coating technologies these ALD coatings are guaranteed to be continuous, pinhole-free and dense despite being thin (< 15nm).