In the LS_GRID (Light Shield Grid) module of a 40nm Backside Illuminated (BSI) CMOS Image Sensor, the metal grid physically isolates adjacent pixels to suppress optical and electrical crosstalk (Engineering Practice).Preceding this step, the main grid metal, typically tungsten (W), has been patterned via the W Etch process (Engineering Practice).The underlying Titanium Nitride (TiN) film, which exhibits a low electrical resistivity of 20-25 µΩ·cm, serves as an adhesion and diffusion barrier laye