Characterization of fluorocarbon thin films deposited by ICP and PP

Abstract

Fluorine-containing hydrophobic thin films have been treated in this study with a mixture of fluorocarbon precursors like C2F6, C3F8, and c-C4F8 and the unsaturated hydrocarbons of C2H2 using inductively coupled plasma (ICP) and pulsed plasma (PP) deposition. Process parameters for plasma polymerization such as gas ratio, gas pressure, plasma power, pulse frequency, and processing time were investigated. Surface analytical instruments such as time-of-flight secondary ion mass spectrometry (TOF-SIMS) and x-ray photoelectron spectroscopy (XPS) were used to provide useful information about the surface composition and the chemical structure of the fluorocarbon films. Film thickness and surface morphology were also observed by using FE-SEM and AFM. Water contact angle measurements and FE-SEM results show that the ICP technique provides coarser grained films and more hydrophobic surfaces as well as a higher deposition rate compared to the PP technique. TOF-SIMS and XPS analyses indicate that the ICP technique produced more fluorine-containing functional groups, including CF2 and CF3, than the PP technique. From the curve-fitted XPS results, it is clear that fluorocarbon films grown using the ICP technique exhibited less cross-linking and higher CF2 concentrations than those grown using the PP technique.