Aging of silicon-based dielectric coatings deposited by plasma polymerization

Silicon-based dielectric coatings were deposited from tetravinylsilane or a mixture of tetravinylsilane with oxygen gas by pulsed plasma. The coatings in the form of a-SiC:H or a-SiOC:H alloy were stored at ambient conditions for 800 h to investigate aging effects. The SiH, SiC, and CHx species in the plasma polymer film were identified as responsible for strong oxidation of the deposited material. The increased oxygen concentration up to 19 at.% in the dielectric coatings resulted in a decrease of the refractive index. Oxygen concentrations > 10 at.% resulted in reduction of mechanical properties of dielectric coatings deposited at powers ≥ 2.5 W. Suitable deposition conditions were deduced to reduce aging effects.