Angled physical vapor deposition techniques for non-conformal thin films and three-dimensional structures
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lasmonics, Photonics, and Metamaterials Research Letter
Angled physical vapor deposition techniques for non-conformal thin films and three-dimensional structures Zhuoxian Wang*, School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA Paul R. West*, School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA; Intel Corporation, Hillsboro, OR 97124, USA Xiangeng Meng, Nathaniel Kinsey, Vladimir M. Shalaev, and Alexandra Boltasseva, School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA Address all correspondence to Alexandra Boltasseva at [email protected] (Received 7 October 2015; accepted 20 January 2016)
Abstract The field of nanophotonics has experienced a dramatic development in recent years, which requires ample candidate structures to achieve desirable functionalities. For many novel device designs in emerging field of transformation optics, optical metamaterials, and others, non-uniform and non-conformal thin films as well as three-dimensional (3D) structures are necessary to achieve advanced functionalities. Here, we report several techniques utilizing angled physical vapor deposition to obtain unique and complex 3D structures such as films with tapered thickness on planar substrates, tapered or uniform films on curved surfaces, and 3D nanorod arrays. These structures could enrich the existing practical design space for applications in nanophotonics and nanoelectronics.
Introduction Physical vapor deposition (PVD) is a well-established and widely used technique for depositing thin films. Upon evaporation, the vaporized source material travels in a “line-of-sight” manner from the source crucible to the substrate. Because the substrate is typically oriented perpendicular to the source in conventional systems, this deposition process generally provides relatively uniform, planar layers of the deposited material. Thus, current manufacturing technologies are almost exclusively limited to top-down, two-dimensional processes unless more complex, multi-step fabrication approaches are used. However, as nanofabrication technologies advance, there is an increasing desire to create films and structures that are quasi-3D and fully 3D for various electrical and optical devices.[1–4] Angled PVD is one of the most promising approaches that can be exploited to allow fabrication of such structures. By adjusting the substrate angle, the line-of-sight deposition allows for the creation of drastically different, non-uniform, and nonconformal structures.[5] In the limiting case of a large angle range, when the substrate is fixed at an angle close to 90° (commonly known as glancing angle deposition or GLAD), a conventional thin-film formation process is transformed into preferential deposition on random nucleation sites formed during the early stages of deposition.[6–8] Continued deposition atop these nucleation sites can, for exampl
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