Conformal Physical Vapor Deposition Assisted by Atomic Layer Deposition and Its Application for Stretchable Conductors

Physical vapor deposition (PVD) is a versatile thin-film coating technique that can deposit a wide selection of inorganic materials at low cost. However, the process is based on line-of-sight transfer, which can lead to shadowing effects and limit film uniformity over nonplanar topographies. This work describes improving conformal PVD coating on polymer nanostructures by increasing surface energy using a thin oxide interlayer deposited by atomic layer deposition (ALD). The proposed ALD-assisted PVD process allows conformal coating at low cost, and can be adopted for a wide variety of materials compatible with tradition PVD. Conformal gold films over nanostructures with 500 nm half-pitch and aspect ratio up to 1.5 are demonstrated. The film uniformity is characterized using cross-sectional electron microscopy, energy-dispersive X-ray spectroscopy, and electrical measurements, showing a clear improvement in coating uniformity with the oxide interlayer. This PVD process is then used to fabricate metallic nano-accordion structures, which can be used for stretchable conductors. The demonstrated process can improve material selection and reduce process cost of conformal coating, which can find applications in integrated circuit manufacturing, stretchable electronics, and wearable sensors.