Backside Illuminated Image Sensor Metal Grid Isolation

The patent extends the isolation structure (metal grid and doped regions) into the depth dimension of the substrate, not just laterally. By creating deep isolation structures that penetrate through the substrate thickness, the patent achieves effective separation of adjacent pixels in the vertical dimension, preventing crosstalk while maintaining small pixel footprints in the lateral plane.

The patent employs a composite isolation approach combining multiple materials and mechanisms: metal grid structures for electrical isolation, p-type and n-type doped regions for electrical field control, and shallow trench isolation materials for physical separation. This multi-material composite strategy addresses both electrical and optical crosstalk simultaneously.

The metal grid structures serve multiple functions simultaneously: they provide electrical isolation between pixels, act as mechanical support for overlying layers, and function as part of the isolation architecture. This multi-functionality reduces the need for separate dedicated isolation components, simplifying the overall device structure despite the enhanced isolation requirements.

The patent combines the isolation function with the substrate structure itself by integrating metal grids and doped regions directly into the substrate architecture. Rather than adding separate isolation layers on top of the substrate, the isolation features are merged with the substrate's structural elements, reducing overall device complexity.