16 - Removal of Particles by Chemical Cleaning

Abstract

Particle removal is strongly dependent on the particle interactions with the substrate and surrounding liquid. Depending on the solution pH, substrate composition and particle aging, the intermolecular interactions are governed to varying degrees by van der Waals, covalent, and electrostatic forces. Industry standards are needed to accurately compare particle removal techniques; for the particle challenge wafers examined here, >90% particle removal efficiency required 1 and 2.5 A ° silicon oxide losses for dry- and wet-deposited Si3N4 particles, respectively. Material loss requirements for the 45 nm technology node as indicated in the 2005 ITRS roadmap suggest that further process development is required to maintain high particle removal efficiency with ≤ 0.3A ° material loss per cleaning step without the use of megasonics. Current market drivers require that process chemistries address both particle and metal removal within the same process step without degrading electrical device performance through irreversible chemical additive adsorption. The process mixture physical and chemical properties (e.g., pH, solubility, etchselectivity) and the method of dispensing (e.g., spray, immersion) are critical factors in optimizing particle removal for advanced semiconductor device manufacturing.