A Model for the Chemical Vapor Deposition of Poly(para-xylylene) (Parylene) Thin Films

• Published in: Chemistry of materials Vol. 14; no. 5; pp. 1945 - 1949
• Main Authors: Fortin, J. B, Lu, T.-M
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 20.05.2002
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Polymerization; Preparation, kinetics, thermodynamics, mechanism and catalysts; Chemisorption; Kinetic model; Pyrolysis; Gas polymerization; Xylene polymer; Dimer; Deposition rate; Kinetics; Experimental study; Chemical vapor deposition; Comparative study; Thin film
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/cm010454a

A kinetic model is developed for the chemical vapor deposition of poly(para-xylylene), or parylene, thin polymer films. The growth process is modeled as a multistep process that includes physisorption of monomer on the surface and subsequent chemisorption. The chemisorption step is equivalent to a propagation reaction between the monomer and a radical chain end, and each chemisorption produces a new chemisorption site. The sticking coefficient of the monomer as a function of substrate temperature is extracted from the measured data using the model and is determined to be 2.0 × 10-5 at 60 °C, increasing to 1.4 × 10-3 at −60 °C. The heat of physisorption for the monomer is also extracted from the experiment, and the value found (75 kJ/mol) is reasonable when compared to those of other similar molecules. The model fits experimental kinetic data well for a large range of pressures and temperatures, and it should be appropriate for use with all parylene-family polymers.