Optimize The Cleaning Process of Tungsten Contact Cmp to Avoid Copper Wire Bridges and Improve Product Yield

摘要

After tungsten contact CMP, Ti residue defect was found, and as defect count increased, CP fail bin count also increased. After the deposition of the M2 NDC film, VC inspection with negative charging mode was used to scan, and the DVC defect of the ring map was found. Combined with FIB slice analysis, this DVC is the bridge of the M1 Cu line caused by Ti residue. Through inline scan data and various split experimental analysis, it is found that residue source comes from P3 process, and defects are more likely to occur when CMP stops on multi-film; In the cleaner unit, NH4OH can effectively remove defects, but at the end of lifetime in brush2, with the accumulation of wafer count, there will be accumulation of residue source on brush2 and it will stick to the surface of wafer and cause secondary pollution of wafer. By improving the cleaning ability of NH4OH and the self-cleaning ability of brush2 in BB2 module, the occurrence probability of defect was significantly reduced and the yield was improved.