The ultrasonic cleaning step immediately follows the CIS Backside Si CMP2 process in the production of 40nm Backside Illuminated (BSI) CMOS Image Sensors A1.Chemical mechanical polishing (CMP) is considered one of the dirtiest processes in wafer manufacturing, leaving a large amount of abrasive particles, metal contaminants, and chemical residues on the wafer surface P1.For BSI devices, achieving an ultra-clean, defect-free backside silicon surface is critical because this interface directly det