Composite grid structure to reduce cross talk in back side illumination image sensors

A semiconductor structure for back side illumination (BSI) pixel sensors, the semiconductor structure comprising:

• a semiconductor substrate arranged over a back-end-of-line (BEOL) metallization stack and accommodating photodiodes;
• a composite grid arranged over the semiconductor substrate and comprising a dielectric grid and a conductive grid, wherein the dielectric and conductive grids border and collectively define openings overlying corresponding ones of the photodiodes;
• and
• color filters arranged in the openings and having top surfaces that are vertically offset from a top surface of the composite grid.

A semiconductor structure for back side illumination (BSI) pixel sensors, the semiconductor structure comprising:

• a semiconductor substrate arranged over a back-end-of-line (BEOL) metallization stack and accommodating photodiodes;
• a composite grid arranged over the semiconductor substrate and comprising a dielectric grid, a conductive grid, and a hard mask grid, wherein the hard mask grid is arranged over the dielectric grid and has sidewalls aligned with sidewalls of the dielectric grid, and wherein the dielectric, conductive, and hard mask grids collectively define openings overlapping corresponding ones of the photodiodes;
• a dielectric layer conformally lining the composite grid;
• and
• color filters arranged in the openings and having top surfaces vertically offset from a top surface of the composite grid by more than a thickness of the dielectric layer.