Transport behavior of atomic layer deposition precursors through polymer masking layers: Influence on area selective atomic layer deposition

Sorption and diffusion of precursors through polymer layers were considered as limitations to the successful implementation of a polymer film-based masking approach to area selective atomic layer deposition techniques (ASALDT). Quartz crystal microbalance studies were used to estimate solubility and diffusivity of ALD precursors through supported thin polymer films at elevated temperatures. Specifically, measurements have been performed to estimate the solubility of water in polyhydroxystyrene, polymethylmethacrylate (PMMA), and hexafluoroisopropylalcohol polynorbornene. In addition, diffusion coefficients and solubilities of titanium tetrachloride (TiCl4) and titanium isopropoxide [Ti(ipr)(4)] through PMMA have also been determined. The results suggest that polymer films exhibit insignificant water uptake at high temperature (similar to 160 degrees C) and, hence, sorption of water into polymer films does not pose limitations to polymer masking-based ASALDT. Diffusion coefficient measurements of metal precursors account for the role of precursor size in determining the minimum polymer masking layer thickness for a successful ASALDT process. (C) 2007 American Vacuum Society.