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

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 & SIM;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.

Automated summary

Developing the ALD process for cerium oxide using in situ ellipsometry was achieved in ten experiments in less than a day. This method efficiently determined the optimal deposition conditions, generating a contour visualization of the parameter space.