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 those of iron, ruthenium, platinum, palladium, copper, and silver, is found to inhibit polymer deposition on the substrate. The maximum thickness of the selectively grown polymer films is dependent on the monomer delivery rate to the surface and metal inhibitor used, and for lower growth rates on surfaces patterned with iron, structures 1.4 μm and 4.1 μm in thickness are realized for parylene-N and parylene-C, respectively. The selectively deposited polymer films show no overgrowth onto the metallized areas of the substrate and the slope of the feature sidewalls is steeper than 1.1.μm/μm. Once polymer nucleation finally occurs on the metal films, the morphology of the deposited polymer layer reflects the effectiveness of the metal in preventing polymer deposition. For substrates with little effect on polymer deposition the film morphology consists of uniformly distributed small nodules 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 underlying the selective growth are discussed.