Transition metals for selective chemical vapor deposition of parylene-based polymers

A novel method for realizing selective growth of parylene-N and parylene-C synthesized by chemical vapor deposition is presented. Exposure of surfaces to transition metals, metal salts, and organometallic complexes, such as t hose of iron, ruthenium, platinum, palladium, copper, and silver, is found to inhibit polymer deposition on the substrate. The maximum thickness of th e selectively grown polymer films is dependent on the monomer delivery rate to the surface and metal inhibitor used, and for lower growth rates on sur faces patterned with iron, structures 1.4 mu m and 4.1 mu m in thickness ar e realized for parylene-N and parylene-C, respectively. The selectively dep osited polymer films show no overgrowth onto the metallized areas of the su bstrate and the slope of the feature sidewalls is steeper than 1.1.mu m/mu m. Once polymer nucleation finally occurs on the metal films, the morpholog y of the deposited polymer layer reflects the effectiveness of the metal in preventing polymer deposition. For substrates with Little effect on polyme r deposition the film morphology consists of uniformly distributed small no dules reflecting multiple polymer nucleation sites on the surface. When the metal initially inhibits polymer growth, the morphology has significantly larger grains, indicating fewer nucleation sites. Possible mechanisms under lying the selective growth are discussed.