In a 40nm Backside Illuminated (BSI) CMOS Image Sensor, light enters from the backside, necessitating the thinning of the silicon substrate (Engineering Practice).To connect the sensor to external circuitry, bond pads located in the front-side metallization must be accessed from the backside P1.Following backside silicon thinning and initial surface treatments, this specific lithography step, Bond Pad Opening 3 - Photo, defines the mask for the deep backside via trench A1.Unlike earlier intermed