Dual-layer metal-grid polarizer for polarization image sensor in 65-nm CMOS technology

We demonstrate an image sensor pixel with dual-layer metal grid polarizer with extinction ratio over 80 in 65-nm standard CMOS technology. By recent advanced CMOS technology, it is feasible to design sub-wavelength metal layer patterns in the visible wavelengths. Fine metal grid has high polarization characteristics. Its extinction ratio depends on the grid pitch. Thus, high extinction ratio can be realized by using deep sub-micron CMOS technology. As the grating pitch decreases, extinction ratio becomes high. On the other hand, multiple metal layers can be designed in usual CMOS technology. It is expected that improvement of extinction ratio is also achieved by utilizing this feature. In this work, we compare the extinction ratios of dual-layer polarizers with different spacing and demonstrate high extinction ratio can be achieved by optimizing the spacing.