Design of Current-Mode CMOS Image Sensor Based on Standard 0.18μm CMOS Process With on Pixel Colour Separation

In this paper, the design of a current mode CMOS image sensor pixel in standard 0.18 μm TSMC RFCMOS process is presented. The proposed photodiode has been achieved by using Deep NWell layer. Taking advantages of buried NWell, three diode junctions: N+/P-Well, DNWell/P-Well, DNWell/Psub have been achieved that are used as blue, green and red detectors, respectively. In the photodiode RGB curve, the peaks have been accured at wavelengths of 440 nm, 500 nm and 620 nm. In this way, the colours have been well separated in standard CMOS process with no additional cost, compared to other methods. For the pixel circuit of CMOS Image sensor, three high swing cascade current mirrors which are suitable to operate at lower voltages have been used. By Using this pixel circuit in CMOS image sensors, there is no need to use costly methods of colour detection (for example; colour filters on the pixel). In addition, the complexity of the process and the chip area is decreased.