Reproducible e-Beam Deposition of High-Quality Aluminum Thin Films on Silicon

Student’s name: Wyatt Thomas Home Institution: Virginia Tech NNCI Site: MONT @ Montana State University REU Principal Investigator: Dr. Wataru Nakagawa – Department of Electrical Engineering, Montana State University REU Mentor: Wataru Nakagawa Abstract: Wire grid polarizers are an important component of many optical devices. An important fabrication step of wire grid polarizers is using a physical vapor deposition (PVD) method for applying a thin metallic layer over the substrate. Although manufacturing procedures are the crucial step to high-quality components, PVD is an unpredictable process with inherent uncertainties in many research facilities. In this research project, we investigate the effect of different fabrication parameters of electron beam evaporation in an Angstrom Engineering EvoVac of aluminum onto flat and patterned silicon on surface quality and reproducibility. Important fabrication variables such as deposition rate, substrate velocity, and substrate temperature were systematically altered to discover the optimal recipe for smooth aluminum thin films. These samples were characterized through scanning electron microscopy (SEM), atomic force microscopy (AFM), and profilometry. We found that 1500 Å aluminum samples deposited at 30 Å/s with the stationary substrate held at room temperature yield reproducible films with acceptably low surface roughness that can be used in the fabrication of wire grid polarizers.