Improvement of chemical, physical, and electrical properties of parylene-D deposited by chemical vapor deposition by controlling the parameters process

Abstract

The effect of chemical vapor deposition (CVD) parameters on the surface morphology and the molecular structure of parylene-D (also called poly-dicloro-xylylene or PPX D) films were investigated. Relevant process parameters are defined by the sublimation temperature, pyrolysis temperatures, growth rate, and time of the deposition process. The sublimation temperatures strongly affects the layer growth rate which increases by a factor of about 4 as the temperature increases from 120 to 160 °C. The sublimation temperature at which the parylene-D cannot be deposit is estimated to be 105 °C. The present CVD experimental parameters have shown that appropriate sublimation temperatures can yield a controlled growth of the layer thickness ranging from tens of nanometers up to at least 8 μm with a good control of the amorphous and the crystalline amounts. Nearly amorphous parylene-D is obtained when sublimation temperatures are height. However, the crystallinity is increased considerably when the dimer Tsub is decreased. A decrease in the surface roughness is achieved by reducing the Tsub and the deposition rate. These experimental conditions giving rise to dense and transparent parylene-D films. The pyrolysis temperatures favorite growing of globules at the surface compared to the sublimation temperatures. The size of the globules increases from 1.3 μm for Tpyr. = 650 °C to 13.7 μm for Tpyr. = 690 °C. It inferred also that the crystallinity content and the crystalline size decrease by increasing the pyrolysis temperatures. Electrical properties are very influenced by the CVD-processing parameters especially by modifying the pyrolysis temperature. Using these optimized conditions, state-of-the-art parylene-D films with promising properties are reproducibly processed. These results significantly expand the range of processing variables compatible with large applications domains.