In-Situ Ellipsometry Aided Rapid ALD Process Development and Parameter Space Visualization

Abstract

Process development in atomic layer deposition (ALD) is a time-consuming process requiring optimization of pulse/purge times and temperature for controlling growth rates. For example, a new precursor for ceria ALD process using Ce(iPrCp)2(N-iPr-amd) takes tens of experiments for optimization [Golalikhani et al. J. Vac. Sci. Technol 36.5 (2018): 051502]. Against this backdrop, we report a powerful methodology of sequential pulsing aided by in situ ellipsometry, which is used to arrive at an optimal ceria ALD process in 10 experimental runs, requiring less than a day. We have performed saturation pulse experiments of precursor and oxidizer on a silicon surface monitored using in situ ellipsometry. This approach generates a time-temperature-thickness 3D map and makes it convenient to visualize the optimal pulse/purge times and a temperature 'valley' for the process. In situ ellipsometry data from saturation pulse experiments were correlated with adsorption isotherms. The film's growth rate deposited in the ALD temperature window was ~ 2 Å/cycle; the deposited film was further characterized using XPS, XRD, UV-Vis, and AFM. The growth rate is augmented by AI/ML algorithms that can introduce explainability between process parameters and film properties.