In the fabrication of 40nm Backside Illuminated (BSI) CMOS Image Sensors T1, the Pre Litho Cleaning step within the ILD 6 module serves as a critical surface preparation phase.Situated immediately after the deposition of the ILD 6 stack (including the Wafer Bonding Layer) and prior to the Metal 8 (DBI Pad) Trench Photo step, this wet process ensures a pristine surface for photolithography P4.Unlike earlier pre-litho cleans (e (Engineering Practice).g., steps #7, 13) that prepare intermediate met