Design of CMOS active pixels based on finger-shaped PPD

Feng Li, Ruishuo Wang, Liqiang Han, Jiangtao Xu*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review


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 × 6 μm2 is realized based on the 0.18 μm CMOS process. The simulation results indicate that the pixel with the above structure and process has a depletion depth of 2.8 μm 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.

Original languageEnglish
Article number102301
JournalJournal of Semiconductors
Issue number10
Publication statusPublished - 2020


  • CMOS active pixel
  • Full depletion
  • Full well capacity


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