Comparison of pulsed and continuous-wave deposition of thin films from saturated fluorocarbon/H-2 inductively coupled rf plasmas

Thin films are prepared by plasma polymerization using inductively coupled continuous-wave (CW) and variable duty cycle pulsed rf plasmas. The effects of hydrogen addition (0-97.5%) on thin films deposited from CW saturated fluorocarbon (CF4 and C2F6) plasmas are examined. Variable duty cycle, pulsed C2F6 rf plasmas are employed for comparison to the CW results. Film properties are determined using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Deposition rates and contact angles are also measured for all films. Analysis using these techniques indicates a strong dependence of the bulk and surface structure on the hydrogen content of the feed in the CW systems. Significantly different film chemistry and deposition rates are observed in the pulsed systems. For the pulsed systems, film composition is dependent on duty cycle and relative pulse on and off times. Using an optimum duty cycle of 3% results in a less cross-linked fluorocarbon polymer, with primarily CF2 species in the bulk film and CF3 surface termination.