Extraction of individual water related species contribution to the global diffusion coefficient of moisture in silicon dioxide through Fourier transform infrared OH band spectral deconvolution

Abstract

The moisture uptake kinetics and mechanisms were studied in a plasma-enhenced chemical vapor deposition (PECVD) silicon dioxide film using Fourier-Transform Infrared Spectroscopy (FTIR) characterizations. The increase of absorbance in the OH stretching region, resulting from the exposure to moisture, was monitored and modeled using Fick’s diffusion law, yielding an apparent diffusion coefficient of 1.4 $\pm$ 0.2 $\times$ 10⁻¹⁴ cm${}^2$/s. Deconvolutions of the spectrum were performed assuming mixed Gaussian-Lorentzian models to highlight the contribution of the different OH species in the moisture ingress process. The findings support a diffusion process through multiple pathways where physiosorbed and chemisorbed water concurrently exist.