Wavelength- and thickness-independent optical coatings for integrated circuit metallization layers

Abstract

Detailed measurements have been made of the optical properties of sputtered tantalum silicide films on aluminum layers used in integrated circuit fabrication. This new multicomponent conductor (TaSix on aluminum), which is currently in use because of its exceptional electrical, physical, and chemical properties, was also found to have superior optical properties compared to aluminum alone. The addition of the thin silicide layers reduces both the total hemispherical and diffuse reflectance properties by up to 45% over the 265–800-nm wavelength range with almost no dependence on film thickness. Unlike other optical coatings used on metal layers in integrated circuit manufacturing, the silicide films do not need to be removed after photolithography and pattern transfer processes are completed: aluminum wire bonding from the completed circuit (with silicide coating) to the package is highly reliable and reproducible.