Study on possible root causes of contamination from an incoming PVA brush during post-CMP cleaning

Abstract

Generation of organic defects is one of the most critical issues that encountered during post-CMP cleaning process in sub 10 nm semiconductor device fabrication. Among the many sources for producing organic defects, we found that an incoming polyvinyl acetal (PVA) brush itself acts as a vital contaminant source and is generating the organic defects during post-CMP cleaning. To find out the residual impurities of an incoming brush, we used a new break-in process to extract the brush contaminants systematically. This method has high efficiency in capturing the insoluble particulates as well as soluble contaminants from an incoming PVA brush by using ultrasonic cleaner in DIW. The insoluble particulate contaminants were extracted completely by using ultrasonication within 10 min. The analyzed particle sizes were ranged from 0.8 to 4 mu m measured by a liquid particle counter and FE-SEM. The composition of soluble impurity was investigated by various analysis methods such as ICP-MS, LC-MS and TOF-SIMS. These results emphasize that residual impurities from an incoming PVA brush might be one of the main root causes of organic residues generated during post CMP cleaning process. It was found that the incoming brush could transfer organic contaminants like PDMS (Polydimethyl siloxane) and SDS (Sodium dodecyl sulfate) to the wafers. The proposed methodology is very effective and fast process to capture and analyze the impurities from the brush.