<i>In situ</i> ellipsometry aided rapid ALD process development and parameter space visualization of cerium oxide nanofilms

Abstract

Process development in atomic layer deposition (ALD) is often time-consuming, requiring optimization of saturation curves and temperature windows for controlled deposition rates. Any ALD process should be self-limiting in nature, exhibiting a temperature window of nominal deposition and a linear deposition rate. Meeting these criteria usually requires several ALD experiments, followed by film characterization, which are generally time, cost, and labor-intensive. Against this backdrop, we report a methodology using in situ ellipsometry to rapidly develop the ALD process for cerium oxide using Ce(iPrCp)2(N-iPr-amd) and water. The entire optimized process was realized in ten experiments of sequential pulsing as a function of temperature, requiring less than a day. In the traditional approach, tens of experiments and ex situ characterization may be required. The approach reported here generated a contour visualization of the time-temperature-thickness parameter space delineating the optimal deposition conditions. The cerium oxide deposition rate deposited in the ALD temperature window was ∼0.15 nm/cycle; the deposited film was further characterized using x-ray photoelectron spectroscopy, x-ray diffraction, and atomic force microscopy to probe the film composition and quality further.