In a Backside Illuminated (BSI) CMOS Image Sensor, the active photodiode array receives light from the wafer backside, necessitating the exposure of frontside-routed bond pads through the thinned silicon substrate (Engineering Practice).Following the preliminary backside planarization and photolithography steps, the Si Etch step is executed to selectively remove the bulk silicon overlying the terminal metal pads A1.This process creates a deep via or trench structure that physically breaches the