Design of CMOS active pixels based on finger-shaped PPD

• 作 者: Feng Li Ruishuo Wang Liqiang Han Jiangtao Xu
• 机 构: Tianjin Key Laboratory of Imaging and Sensing Microelectronic Technology, School of Microelectronics
• 出 处: 半导体学报（英文版）
• 发表日期: 2020年10期
• 关键词: CMOS active pixel full well capacity full depletion

To improve the full-well capacity and linear dynamic range of CMOS image sensor,a special finger-shaped pinned photodiode (PPD) is designed.In terms of process,the first N-type ion implantation of the PPD N buried layer is extended under the transfer gate,thereby increasing the PPD capacitance.Based on TCAD simulation,the width and spacing of PPD were precisely adjusted.A high full-well capacity pixel design with a pixel size of 6 x 6μm2 is realized based on the 0.18μm CMOS process.The simulation results indicate that the pixel with the above structure and process has a depletion depth of 2.8μm and a charge transfer efficiency of 100％.The measurement results of the test chip show that the full-well capacity can reach 68650e-.Compared with the conventional structure,the proposed PPD structure can effectively improve the full well capacity of the pixel.