A Breakthrough Method for the Effective Conditioning of PVA Brush Used for Post-CMP Process

Abstract

Polyvinyl acetal (PVA) brush cleaning is one of the most important processes in the post chemical mechanical planarization (CMP) cleaning process. However, PVA brush could be severely contaminated due to strong direct contact with a large amount of abrasive particles during the long-time post CMP cleaning, and the particles on the brush can be easily transported to the next wafer substrate. In this study, we tested four different types of conditioning processes to remove the particles from the brush to increase the cleaning efficiency of post CMP process and comparatively evaluated using FE-SEM. The physical scrubbing method showed higher cleaning efficiency than the chemically dipping method, but some abrasive particles remained on the non-contacted surface. The flow-through method using pH 11 showed the higher removal ability than pH 3 and 7 due to strong repulsive force between silica abrasive particle and PVA brush, but some abrasive particles remained due to non-uniform flow of chemicals. The ultrasonication method with DIW was found to be very effective to remove the particles completely from the brush without damage. Consequently, the new developed conditioning process provides an environmentally friendly and cost effective alternative conditioning process to the existing conditioning process of contaminated PVA brushes.