Chemical-Mechanical Planarization (CMP) plays an important role when the metal line scales of integrated circuit (IC) are getting small. CMP is utilizing the chemical reaction and mechanical polishing to reach the planarization requirement of wafer surface. When a CMP process finished, the slurry residues and the fragments of consumable parts (e.g., polishing pad) would be attached on the wafer surface, which needs another cleaner procedure to remove the residues. However, the cleaner procedure may also suffer scratch issue on the wafers surface. This study is employing the statistic method to analysis the factor that caused wafer scratch of CMP process, and tries to find the optima process parameter for defect improvement.