Method of preventing cross talk

A method of preventing cross talk of light in an optic sensor apparatus, the optic sensor apparatus being formed on a semiconductor wafer, the semiconductor wafer comprising a substrate, a plurality of metal-oxide semiconductor (MOS) transistor sensors positioned on the substrate, and a plurality of insulators positioned on the substrate, and each insulator positioned between each two MOS transistor sensors, the method comprising:

• forming a dielectric layer on the semiconductor wafer covering the MOS transistor sensors and the insulators;
• forming a plurality of trenches in the dielectric layer, each trench being through the surface of the dielectric layer to the surface of each of the insulator;
• forming a barrier layer covering the surface of the dielectric layer, the walls within the trenches, and the bottoms within the trenches;
• forming a metal layer on the barrier layer, and filling the trenches;
• and
• performing a chemical mechanical polishing (CMP) process to remove both portions of the barrier layer and portions of the metal layer outside the trenches;
• wherein the metal layer within the trenches is used to prevent cross talk of light in the optic sensor apparatus.