The Process Simulation And Optimization Of CMOS Image Sensor Pixel

Before the1980s, the CCD image sensor holds the absolute dominance in the market.With the rapid development of semiconductor technology, especially for reducing CMOStechnology feature sizes, the performance of the CMOS image sensor is improvedcontinuously. Based on the structure of the CCD image sensor, CMOS image sensors also usetheir own advantages to develop the direction of low cost, high compatibility and integratedon-chip system. As the PPD-4T pixel structure has become one of the main CMOS imagesensor pixel structures, the optimization of PPD-4T pixel that based on the CMOS technologyhas become a hot spot.Firstly, the photo-electric conversion principle of CMOS image sensor is introduced inthis work. We also analyze and compare the three main CMOS image sensor pixel structures.Thereafter, combining a standard CMOS technology process, the detailed technologyprocesses of the main structures of the PPD-4T pixel are described. Further, on the basis oftechnology process fabricating the PPD-4T pixel, the schemes for improving the lightcollection efficiency and the charge transfer efficiency of the pixel are proposed, and thesimulation software is used to carry out hybrid simulation tests. In the PPD light collectionefficiency, it is proved that the light collection efficiency can be improved by using twoN-type impurity implantations to increase the N doped region, and a P-type impurityimplantation and two N-type impurity implantations to form the PPD mult-junction. And inthe charge transfer efficiency, the potential of the PPD is improved and speed of the chargetransfer is accelerated by increasing the N dopant concentration of the potential barrier. Thegradient potential within the channel is formed and the charge transfer efficiency is improvedby adjusting the thickness of the gate oxide layer and the channel doping concentration in theelectric potential barrier for the optimization of the charge transfer channel.Finally, the effects of different positions of PPD-4T pixel are analyzed and the reason ofthe effects are given in the single particle incident environment. The investigations forradiation hardening of the pixel are significant in the future.