Elimination of Low Yield with 3–9 O’clock Signature through Optimization of CMP Cleaner unit Brush Gap

Tungsten Chemical and Mechanical Polishing (CMP) is a necessary process in the ever-shrinking technology for the next generation semiconductor devices fabrication. In a manufacturing environment it is not only critical to control the wafer planarization removal rate and uniformity but also to evaluate the post process performance by examining the polished wafer surface for defects, micro-scratches, contamination, oxide erosions and dishing issues. It is an on-going challenge to improve wafer yield by eliminating these inline issues and introducing continuous improvement program (CIP) to detect and resolve them in order to reduce or eliminate the exposure to customers.In this paper we will delve into the thought process on how the low yield issue associated with the tungsten process step was resolved by enhancing the detection method both inline and following the tungsten CMP scan step, and by optimizing of the tool's cleaner module unit brush gap to resolve the line streak signature. The subsequent elimination of the 3-9 o'clock low yield signatures only manage to unravel after an improvement sensor was installed to detect the actual wafer rpm at the brush unit during cleaning step.