Poly-para-xylylene thin films: A study of the deposition chemistry, kinetics, film properties, and film stability

Poly-para-xylylene, or parylene, thin films are chemically vapor deposited (CVD), conformal, pin-hole free polymeric thin films. They have found many industrial uses since there invention in 1947 and continue to find new applications in micro-electronics, biotechnology, and micro-electro-mechanical systems. In this study the deposition chemistry, deposition kinetics, film properties, and film stability were investigated.; A differentially pumped quadrupole mass spectrometer was used to analyze the vapor species present during the CVD process. The identity of dimer contamination and its impact on the CVD process and film properties was studied. The quantitative conversion of dimer to monomer was investigated and it was found that conversion begins at around 385°C and by 565°C 100% conversion is obtained.; The kinetics of the CVD process was analyzed for a range of substrate temperatures and chamber pressures. A new kinetic model based on a two-step adsorption was developed and fit the kinetic data well. This model should be appropriate for use with all parylene family polymers.; Many of the properties of the films deposited in this study were analyzed. This includes a detailed study of surface morphology using atomic force microscopy which shows the interface width increases as a power law of film thickness. Other properties analyzed were the thermal stability, electrical properties, index of refraction, birefringence, hardness, and elastic modulus.; The effect of ultraviolet (UV) radiation of λ ≥ 250 nm on the thermal stability, electrical, and optical properties of thin parylene films was studied. The thermal stability and electrical properties of UV treated films were seen to deteriorate as the radiation dose increased.; The stability of parylene thin films receiving plasma etching was analyzed. The dielectric constant, dissipation factor, and leakage current of plasma etched thin parylene films were investigated and found to be stable for the range of chemistries and processing parameters investigated.