BSI CMOS Sensor Backside Microstructures for Higher Quantum Efficiency

The patent applies curvature by forming microstructures (such as microlenses or curved surface features) on the semiconductor layer to replace the flat planar surface. These curved microstructures refract and focus incident light more effectively, reducing reflection losses and improving light absorption by the photodiodes, thereby enhancing quantum efficiency while maintaining manufacturing feasibility through standard photolithography and etching processes

The patent introduces a textured or porous-like microstructure pattern on the semiconductor layer surface. This creates multiple interfaces and scattering centers that trap light more effectively, increasing the optical path length and absorption probability. The microstructures act as light-trapping elements that reduce reflection without requiring complex materials, maintaining ease of manufacture through conventional semiconductor processing

The patent segments the semiconductor layer surface into multiple discrete microstructures (such as an array of microlenses or textured regions) rather than using a single complex structure. Each microstructure is simple in form but collectively they provide the light-trapping function. This segmentation allows the complex optical function to be achieved through repetition of simple units, reducing overall device complexity while maintaining high quantum efficiency

The patent optimizes key parameters of the microstructures (such as height, radius, spacing, and curvature) to achieve maximum light-trapping efficiency with minimal structural complexity. By carefully selecting parameters like microstructure pitch matching the wavelength of light or height optimized for total internal reflection, the patent achieves high quantum efficiency with simple geometric forms that can be manufactured using standard process parameters