Microwave Plasma-Enhanced Parylene–Metal Multilayer Design from Metal Salts

Abstract

In this paper, a new approach for the synthesis of Parylene–metal multilayers was examined. The metal layers were derived from a metal salt solution in methanol and a post-drying plasma reduction treatment. This process was designed as a one-pot synthesis, which needs a very low amount of resources and energy compared with those using electron beam sputtering processes. The Parylene coatings were obtained after reduction plasma treatments with Parylene C. Therefore, a Parylene coating device with an included plasma microwave generator was used to ensure the character of a one-pot synthesis. This process provided ultra-thin metal salt layers in the range of 1–2 nm for layer thickness and 10–30 nm for larger metal salt agglomerates all over the metal salt layer. The Parylene layers were obtained with thicknesses between approx. 4.5 and 4.7 µm from ellipsometric measurements and 5.7–6.3 µm measured by white light reflectometry. Tensile strength analysis showed an orthogonal pulling stress resistance of around 4500 N. A surface roughness of 4–8 nm for the metal layers, as well as 20–29 nm for the Parylene outer layer, were measured. The wettability for non-polar liquids with a contact angle of 30° was better than for polar liquids, such as water, achieving 87° on the Parylene C surfaces.