UV Assisted Densification of PerHydroPoIySilazane (PHPS) based Spin-On glass in High Aspect Ratio Gap Fill Structure

Abstract

Broad band Ultraviolet (UV) radiation of spin coated PerHydroPoIySilazane (PHPS) films prior to steam anneal is shown to improve density of final SiO2 inside high aspect ratio ( 7:1) gap fill structure. Post-steam anneal wet etch rate improvements of up to 18% in blanket films and up to 26% in the ≥7:1 aspect ratio gap fill structure have been obtained for UV treated films relative to control (steam annealed only films). UV dose plays a critical role in determining the final film densification. However, PHPS film becomes moisture sensitive post-UV exposure. The UV treated films show instability in presence of moisture and react/self-convert into Si02. The rate of moisture absorption and conversion depend on the UV dose and the Q time between UV and steam anneal. Presence of moisture adversely impacts the final wet etch rate of the oxide. Careful choice of UV dose and implementation of Q time between UV and steam anneal are critical to get full entitlement from UV.