Tungsten atomic layer deposition on polymers

• Published in: Thin solid films 2008-07, Vol.516 (18), p.6175-6185
• Main Authors: Wilson, C.A., McCormick, J.A., Cavanagh, A.S., Goldstein, D.N., Weimer, A.W., George, S.M.
• Format: Article
• Language: English
• Subjects: Aluminum oxide; Atomic layer deposition; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Electrical properties of specific thin films; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Nucleation; Physics; Polymers; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Theory and models of film growth; Thin film structure and morphology; Tungsten; Vapor phase epitaxy; growth from vapor phase
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2007.11.086

Tungsten (W) atomic layer deposition (ALD) was investigated on a variety of polymer films and polymer particles. These polymers included polyethylene, polyvinyl chloride, polystyrene, polycarbonate, polypropylene and polymethylmethacrylate. The W ALD was performed at 80 °C using WF 6 and Si 2H 6 as the gas phase reactants. W ALD on flat polymer films can eventually nucleate and grow after more than 60 AB cycles. X-ray photoelectron spectroscopy studies of W ALD on polystyrene after 50 AB cycles suggested that tungsten nanoclusters are present in the W ALD nucleation regime. The W ALD nucleation is greatly facilitated by a few cycles of Al 2O 3 ALD. W ALD films were grown at 80 °C on spin-coated polymers on silicon wafers after 10 AB cycles of Al 2O 3 ALD. The W ALD film was observed to grow linearly with a growth rate of 3.9 Å per AB cycle on the polymer films treated with the Al 2O 3 ALD seed layer. The W ALD films displayed an excellent, mirror-like optical reflectivity. The resistivity was 100–400 µΩ cm for W ALD films with thicknesses from 95–845 Å. W ALD was also observed on polymer particles after W ALD in a rotary reactor. Without the Al 2O 3 ALD seed layer, the nucleation of W ALD directly on the polymer particles at 80 °C required > 50 AB cycles. In contrast, the polymer particles treated with only 5 AB cycles of Al 2O 3 ALD were observed to blacken after 25 AB cycles of W ALD. W ALD on polymers may have applications for flexible optical mirrors, electromagnetic interference shielding and gas diffusion barriers.