# Particle Deposition and Removal in Wet Cleaning Processes for ULSI Manufacturing

## Abstract

Particle deposition on wafer surfaces in solutions can be described by the well-documented principles of colloid science. Particle concentration, solution pH, and ionic strength in solutions are all important factors which determine the number of particles which deposit on wafer surfaces immersed in liquids. Maximum particle deposition is observed in high ionic strength acidic solutions and is reduced as solution pH increase. Particle removal efficiencies in various solutions were also investigated NH<inf>4</inf>OH-H<inf>2</inf>O<inf>2</inf>-H<inf>2</inf>O solutions were optimized in NH<inf>4</inf>OH content around the ratio of 0.05:1:5 (0.05 part NH<inf>4</inf>OH, 1 part H<inf>2</inf>O<inf>2</inf>, 5 parts H<inf>2</inf>O). Wafer damage as measured by surface micro-roughness was not increased during NH<inf>4</inf>OH-H<inf>2</inf>O<inf>2</inf>-H<inf>2</inf>O treatment using this ratio. © 1992 IEEE