The ability to reproduce a high quality image depends strongly on the image sensor light sensitivity and selectivity, which in turn depend on the optical properties of the pixel. The optical efficiency of a CMOS image sensor pixel is calculated using a geometrical-optics phase-space approach and predictions are validated with measurements made using a CMOS digital pixel sensor.
Next, following the trend of increased integration in CMOS image sensors, light filters using patterned metal layers are placed on top of each pixel’s photodetector. To demonstrate wavelength selectivity, integrated color pixels with 1D and 2D patterned metal layers are prototyped in a standard 180-nm CMOS technology. The transmittance of several designs is found to exhibit wavelength selectivity in the visible range. Numerical electromagnetic field simulation of 1D patterned metal layers results in good agreement with measurements. Finally, electromagnetic field simulations are used to predict the transmittance for more elaborate designs.