CMOS Image Sensor Superlattice Crosstalk Reduction

The semiconductor structure is segmented into multiple alternating layers of different materials (e.g., SiGe and Si) forming a superlattice. Each layer is thin and has specific compositional characteristics. This segmentation creates a periodic modulation of the conduction band that enhances carrier mobility through reduced effective mass and increased velocity, while maintaining manufacturability through established epitaxial growth techniques.

The patent employs composite material structures where alternating layers of silicon-germanium (SiGe) and silicon (Si) are grown epitaxially. The SiGe layers provide tensile strain to the Si channels, while the Si layers provide compressive strain. This composite approach creates a superlattice with engineered band structures that significantly improve charge carrier mobility compared to conventional homogeneous semiconductor materials.

The superlattice structure acts as an intermediary barrier between adjacent pixels in the CMOS image sensor. The alternating SiGe/Si layers create potential wells and barriers that confine charge carriers within specific pixel regions, preventing carrier diffusion into neighboring pixels. This intermediary structure effectively reduces crosstalk while maintaining pixel isolation functionality.

The superlattice introduces local variations in material composition and strain characteristics at the pixel boundaries. The SiGe layers provide localized tensile strain regions that create potential barriers, while Si layers provide compressive strain regions. This local quality variation creates an energy landscape that confines carriers to their respective pixels, reducing crosstalk without requiring extensive lateral isolation structures.