Optical function of atomic layer deposited alumina (0.5–41.0 nm) from 191 to 1688 nm by spectroscopic ellipsometry with brief literature review

Abstract

Atomic layer deposition (ALD) is widely used in the semiconductor industry to provide atomic level control over film thicknesses and layer conformality. Here, the authors report the thermal (332 °C) ALD of thin amorphous alumina films (0.5–41.0 nm) deposited using water and trimethylaluminum precursors. Alumina deposition was optimized by varying the dose and purge times for both precursors with an eye toward obtaining uniform film thicknesses and constant growth per cycle. Films were characterized by x-ray photoelectron spectroscopy and spectroscopic ellipsometry (from 191 to 1688 nm). The subsequent workup of the SE data was based on a multisample analysis. It considered Cauchy and Sellmeier functions and accounted for surface roughness. This modeling yielded an optical function for ALD alumina over the measured wavelength range. The authors recommend the optical function determined from the Sellmeier model.