Mechanism of PVA Brush Loading with Ceria Particles during Post-CMP Cleaning Process

Abstract

Brush scrubbing is a well-known post CMP cleaning process. Interaction between PVA brush and the particles removed during the process must be considered while designing a cleaning process. In this work, the effect of cleaning solution pH was investigated in terms of particle removal from the wafer and subsequent loading to the PVA brush nodule. Higher cleaning of particles from wafer was observed for pH 2 and 12 cleaning solutions and poor cleaning for pH 7 cleaning solution. In contrast, the brushes were loaded heavily for pH 7 compared to pH 2 and 12. Higher electrostatic attraction between oppositely charged PVA and ceria surfaces provided higher ceria particles loading to PVA brush in acidic and neutral cleaning solutions. This particle loading to PVA brush can further effect cleaning efficiency as well as cross-contamination.