Impact of dark current on pinned photo-diode capacitance of CMOS image sensor in low illumination regime

Abstract

Applications for quanta and space sensing both depend on efficient low-light imaging. To precisely optimize and design image sensor pixels for these applications, it is crucial to analyze the mechanisms behind dark current generation, considering factors such as temperature, trap cross-section and trap concentration. The thresholds for these generating effects are computed using optoelectrical technology computer aided design (TCAD) simulations, and the ensuing changes in pinned photo-diode (PPD) dynamic capacitance are observed. Various generation models along with an interfacial trap model are used to compare PPD capacitance fluctuations during light and dark environments. With the use of this comparison study, current compact models of complementary metal oxide semiconductor (CMOS) image sensors can be modified to accurately capture the impacts of dark current in low-light conditions. The model developed through this study demonstrates a deviation of only 6.85% from the behavior observed in physical devices. These results not only enhance our understanding of dark current generation mechanisms but also offer practical applications by improving the performance and accuracy of image sensors.

References

[1] Ma J, Chan S, Fossum E R. Review of quanta image sensors for ultralow-light imaging[J]. IEEE transactions on electron devices, 2022, 69(6): 2824-2839. Bibcode: ,

[2] Antonsanti A. Probing dark current random telegraph signal in a small pitch vertically pinned photodiode CMOS image sensor after proton irradiation[J]. IEEE transactions on nuclear science, 2022, 69(7): 1506-1514. Bibcode: ,

[3] Ao J, Gao Z, Gao J, et al. . A dynamic photoresponse model for a pinned photodiode in CMOS image sensors[J]. Optoelectronics letters, 2022, 18(6): 419-424. Bibcode: ,

[4] Suharwerdi M, Qazi G. Dark current in pinned photodiode CMOS image sensors: a pre-fabrication physics-based model[J]. Optical and quantum electronics, 2023, 55: 581.

[5] Mcgrath D. Dark current limiting mechanisms in CMOS image sensors[J]. Electronic imaging, 2018, 30(11): 3541-3548.

[6] Tan J, Buttgen B, Theuwissen A J P. Analyzing the radiation degradation of 4-transistor deep submicron technology CMOS image sensors[J]. IEEE sensors journal, 2012, 12(6): 2278-2286. Bibcode: ,

[7] Goiffon V. Pixel level characterization of pinned photodiode and transfer gate physical parameters in CMOS image sensors[J]. IEEE journal of the electron devices society, 2014, 2(4): 65-76.

[8] Capoccia R, Boukhayma A, Jazaeri F. Compact modeling of charge transfer in pinned photodiodes for CMOS image sensors[J]. IEEE transactions on electron devices, 2019, 66(1): 160-168. Bibcode: ,

[9] Shi J. A room-temperature polarization-sensitive CMOS terahertz camera based on quantum-dot-enhanced terahertz-to-visible photon upconversion[J]. Nature nanotechnology, 2022, 17: 1288-1293. Bibcode: ,

[10] Khan U, Sarkar M. Dynamic capacitance model of a pinned photodiode in CMOS image sensors[J]. IEEE transactions on electron devices, 2018, 65(7): 2892-2898. Bibcode: ,

[11] Hu C, Zhang B, Xin Y, et al. . Analytical modeling of charge behavior in pinned photodiode for CMOS image sensors[J]. IEEE sensors journal, 2023, 23(13): 14295-14303. Bibcode: ,

[12] Zhang K. 4T complementary metal oxide semiconductor image sensor charge transfer efficiency optimization[J]. Journal of nanoelectronics and optoelectronics, 2023, 18(4): 428-434.

[13] Marcelot O. Dark current sharing and cancellation mechanisms in CMOS image sensors analyzed by TCAD simulations[J]. IEEE transactions on electron devices, 2017, 64(12): 4985-4991. Bibcode: ,

[14] Dan M. Dark current model for the time of low noise & photon counting[C]. 2021 International Image Sensor Workshop (IISW), September 20–23, 2021 Online

[15] Abarca A, Theuwissen A. A CMOS image sensor dark current compensation using in-pixel temperature sensors[J]. Sensors, 2023, 23: 9109. Bibcode: ,

[16] Marcelot O. Exploration of pinned photodiode radiation hardening solutions through TCAD simulations[J]. IEEE transactions on electron devices, 2019, 66(8): 3411-3416. Bibcode: ,

[17] Pierret R F Advanced semiconductor fundamentals[M], 2003 2nd ed. New York Prentice Hall

[18] Khan U, Sarkar M. Analysis of charge transfer potential barrier in pinned photodiode of CMOS image sensors[J]. IEEE transactions on electron devices, 2021, 68(6): 2770-2777. Bibcode: ,

[19] Chao C Y, Chen Y, Chou K, et al. . Extraction and estimation of pinned photodiode capacitance in CMOS image sensors[J]. IEEE journal of the electron devices society, 2014, 2(4): 59-64.

[20] Yue X, Fossum E R. Design and characterization of a burst mode 20 Mfps low noise CMOS image sensor[J]. Sensors, 2023, 23: 6356. Bibcode: ,