Effects of vacuum deposition conditions on ellipsometric parameters, optical constants, and reflectance of ultrapure aluminum films

This paper presents a method of controlling the ellipsometric parameters (Ψ,Δ), pseudo-optical constants (n,k), and reflectance (R) of freshly deposited aluminum films. By use of this method, values ofΔ,n, andR can be predicted from measurements of the terminal pressure/terminal deposition rate (terminal p/r ratio) prevailing during deposition of the surface region. The pseudo-optical constants and reflectances were calculated using the Ψ,Δ values. The highest-purity aluminum (99.9999%) was used and ellipsometric measurements were made immediately after removal of the films from the vacuum system. A review of existing literature on ellipsometric parameters, optical constants, and reflectance of aluminum films in the ultraviolet, visible, and infrared regions of the spectrum supports the theory that volume-oxide contamination is a primary factor affecting optical properties.