This Post CMP Cleaning step immediately follows the Tungsten (W) Chemical Mechanical Planarization (CMP) of the Lower Vertical Grid in the 40nm BSI CMOS Image Sensor flow A3.The preceding CMP process inevitably leaves behind an array of contaminants on the wafer surface, including residual abrasive particles, organic slurry additives, and metallic impurities P1.If not rigorously removed, these defects will critically degrade the optical and electrical integrity of the device, interfering with th