CMOS Image Sensor Reflective Layers for Light Sensitivity

The patent applies local quality by positioning reflective layers at specific locations (side surfaces of the light receiving unit) to reflect light locally back to the photodiode. This localized reflection compensates for the reduced light intensity at peripheral regions caused by the shortened back focal length, thereby improving the peripheral brightness ratio without increasing overall device size.

The patent converts the harmful effect of light incident at large angles (which causes brightness ratio deterioration) into a beneficial effect by using reflective layers to redirect this oblique light back onto the photodiode. The reflective layers transform the previously wasted oblique incident light into useful light that contributes to the signal, thereby improving photosensitivity and peripheral brightness ratio.

The reflective layers convert the harmful effect of reduced light gathering area (due to smaller pixel size) into a benefit by capturing light that would otherwise miss the photodiode and reflecting it back. This is particularly effective for oblique incident light, which becomes a useful resource that compensates for the reduced photodiode area in high-resolution sensors.

The patent changes the optical path parameters by introducing reflective surfaces that alter the light trajectory. This allows light to reach the photodiode through multiple paths (direct and reflected), effectively increasing the light gathering ability without changing the physical pixel size, thereby maintaining high resolution while improving light sensitivity.

The patent extracts the light condensing function from the micro-lens structure and implements it using reflective layers formed through existing CMOS fabrication processes. By removing the need for separate micro-lens fabrication steps and using standard reflective layer deposition techniques, the solution maintains photosensitivity improvement while reducing manufacturing complexity.

The patent uses a simplified approach by forming reflective layers that copy the essential light-directing function of micro-lenses but through a more manufacturable process. The reflective layers are formed using standard semiconductor fabrication techniques (sputtering, evaporation, or CVD) that are already integrated into CMOS production, avoiding the need for additional micro-lens fabrication steps.