J. Semicond. > 2023, Volume 44 > Issue 11 > 114104, doi: 10.1088/1674-4926/44/11/114104

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Incomplete charge transfer in CMOS image sensor caused by Si/SiO2 interface states in the TG channel

Xi Lu1, §, Changju Liu2, 3, §, Pinyuan Zhao1, Yu Zhang1, , Bei Li3, Zhenzhen Zhang1 and Jiangtao Xu2,

+ Author Affiliations

 Corresponding author: Yu Zhang, zy2009@hdu.edu.cn; Jiangtao Xu, xujiangtao@tju.edu.cn

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Abstract: CMOS image sensors produced by the existing CMOS manufacturing process usually have difficulty achieving complete charge transfer owing to the introduction of potential barriers or Si/SiO2 interface state traps in the charge transfer path, which reduces the charge transfer efficiency and image quality. Until now, scholars have only considered mechanisms that limit charge transfer from the perspectives of potential barriers and spill back effect under high illumination condition. However, the existing models have thus far ignored the charge transfer limitation due to Si/SiO2 interface state traps in the transfer gate channel, particularly under low illumination. Therefore, this paper proposes, for the first time, an analytical model for quantifying the incomplete charge transfer caused by Si/SiO2 interface state traps in the transfer gate channel under low illumination. This model can predict the variation rules of the number of untransferred charges and charge transfer efficiency when the trap energy level follows Gaussian distribution, exponential distribution and measured distribution. The model was verified with technology computer-aided design simulations, and the results showed that the simulation results exhibit the consistency with the proposed model.

Key words: CMOS image sensor, charge transfer, interface state traps



[1]
Fossum E R, Hondongwa D B. A review of the pinned photodiode for CCD and CMOS image sensors. IEEE J Electron Devices Soc, 2014, 2, 33 doi: 10.1109/JEDS.2014.2306412
[2]
Takayanagi I, Kuroda R. HDR CMOS image sensors for automotive applications. IEEE Trans Electron Devices, 2022, 69, 2815 doi: 10.1109/TED.2022.3164370
[3]
Liu B K, Li Y D, Wen L, et al. Displacement damage effects in backside illuminated CMOS image sensors. IEEE Trans Electron Devices, 2022, 69, 2907 doi: 10.1109/TED.2021.3124991
[4]
Lee Y S, Kim H J. High-speed multilevel binary imaging CMOS image sensor for object feature extraction. IEEE Sens J, 2022, 22, 15934 doi: 10.1109/JSEN.2022.3189653
[5]
Marcelot O, Panglosse A, Martin-Gonthier P, et al. TCAD calibration at cryogenic temperatures for CMOS image sensor simulations. IEEE Trans Electron Devices, 2022, 69, 6188 doi: 10.1109/TED.2022.3207120
[6]
Rizzolo S, Goiffon V, Estribeau M, et al. Influence of pixel design on charge transfer performances in CMOS image sensors. IEEE Trans Electron Devices, 2018, 65, 1048 doi: 10.1109/TED.2018.2790443
[7]
Han L Q, Yao S Y, Theuwissen A J P. A charge transfer model for CMOS image sensors. IEEE Trans Electron Devices, 2016, 63, 32 doi: 10.1109/TED.2015.2451593
[8]
Fossum E R. Charge transfer noise and lag in CMOS active pixel sensors. IEEE Workshop CCD’s Adv. Image Sensors, 2003, 11
[9]
Han L Q, Yao S Y, Xu J T, et al. Analysis of incomplete charge transfer effects in a CMOS image sensor. J Semicond, 2013, 34, 054009 doi: 10.1088/1674-4926/34/5/054009
[10]
Capoccia R, Boukhayma A, Jazaeri F, et al. Compact modeling of charge transfer in pinned photodiodes for CMOS image sensors. IEEE Trans Electron Devices, 2018, 66, 160 doi: 10.1109/TED.2018.2875946
[11]
Yang C, Peng G L, Mao W, et al. Novel CMOS image sensor pixel to improve charge transfer speed and efficiency by overlapping gate and temporary storage diffusing node. Chin Phys B, 2021, 30, 018502 doi: 10.1088/1674-1056/abc53f
[12]
Wang X Y, Gao Y Q, Gao Z Y, et al. Charge transfer potential barrier model of a pinned photodiode in CMOS image sensors. IEEE Sens J, 2022, 22, 4036 doi: 10.1109/JSEN.2021.3139091
[13]
Khan U, Sarkar M. Analysis of charge transfer potential barrier in pinned photodiode of CMOS image sensors. IEEE Trans Electron Devices, 2021, 68, 2770 doi: 10.1109/TED.2021.3071331
[14]
Liu L, Guo Y, Li B K, et al. Analytical modeling of potential barrier for charge transfer in pinned photodiode CMOS image sensors. IEEE Trans Electron Devices, 2022, 69, 5637 doi: 10.1109/TED.2022.3200636
[15]
Hu C Z, Zhang B, Xin Y Z, et al. Analytical modeling of charge behavior in pinned photodiode for CMOS image sensors. IEEE Sens J, 2023, 23, 14295 doi: 10.1109/JSEN.2023.3278307
[16]
Xu J T, Wang R S, Han L Q, et al. Analysis and modeling of spill back effect in high illumination CMOS image sensors. IEEE Sens J, 2020, 20, 3024 doi: 10.1109/JSEN.2019.2956594
[17]
Xu Y. Fundamental characteristics of a pinned photodiode CMOS pixel. Ph. D. dissertation, Dept. Microelectron. Comput. Eng., Delft Univ. Technol., Delft, the Netherlands, 2015
[18]
Fowler B , Liu X. Charge transfer noise in image sensors. International Image Sensor Workshop (IISW), 2007, 2
[19]
Bonjour L E, Blanc N, Kayal M. Experimental analysis of lag sources in pinned photodiodes. IEEE Electron Device Lett, 2012, 33, 1735 doi: 10.1109/LED.2012.2217474
[20]
Khan U, Sarkar M. Dynamic capacitance model of a pinned photodiode in CMOS image sensors. IEEE Trans Electron Devices, 2018, 65, 2892 doi: 10.1109/TED.2018.2831719
[21]
Liu E, Zhu B, Luo J. The physics of semiconductors. Beijing: House of Electronics Industry, 2011
[22]
Mohsen A M, McGill T C, Daimon Y, et al. The influence of interface states on incomplete charge transfer in overlapping gate charge-coupled devices. IEEE J Solid-State Circuits, 1973, 8, 125 doi: 10.1109/JSSC.1973.1050361
[23]
Han L Q, Xu J T. Long exposure time noise in pinned photodiode CMOS image sensors. IEEE Electron Device Lett, 2018, 39, 979 doi: 10.1109/LED.2018.2839711
[24]
Xia C Y, Zhang Y, Lu X M, et al. Dynamic model of FWC dependent on the energy-level distribution of interface-state traps in pinned photodiodes. IEEE Trans Electron Devices, 2021, 68, 1682 doi: 10.1109/TED.2021.3056019
[25]
Ayobi A, Mirnia S N. Influence of Gaussian disorder and exponential traps on charge carriers transport and recombination in single layer polymer light-emitting diodes based on PFO as emitting layer. Opt Quantum Electron, 2019, 51, 1 doi: 10.1007/s11082-018-1712-9
Fig. 1.  (Color online) Four-transistor pixel structure of the PPD CIS.

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Fig. 2.  (Color online) VTG time sequence diagram, semiconductor energy band diagram, and charge trapping effect during charge transfer. (a) Time sequence diagram of VTG during charge transfer. (b) Energy band diagram of the semiconductor in the TG region at VTG-Low. (c) Process of electron capture by interface states in phase Ⅰ. (d) Energy band diagram of the semiconductor in the TG region at VTG-High. (e) Process of electron emission by interface states in phase Ⅲ.

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Fig. 3.  (Color online) Different trap energy level distributions. (a) 1−8 sets of measured distribution data of Si/SiO2 interface state. (b) 9−16 sets of measured distribution data of Si/SiO2 interface state. (c) 17−24 sets of measured distribution data of Si/SiO2 interface state. (d) 25−32 sets of measured distribution data of Si/SiO2 interface state.

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Fig. 4.  (Color online) Variations in NTrapped with the mean value E0 under Gaussian and exponential distributions.

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Fig. 5.  (Color online) Variations in CTE with the mean value E0 under Gaussian and exponential distributions.

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Fig. 6.  (Color online) Variations in NTrapped with different variances ES under Gaussian and exponential distributions.

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Fig. 7.  (Color online) Variations in CTE with different variances ES under Gaussian and exponential distributions.

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Fig. 8.  (Color online) The variations in $ N_{\text{Trapped}} $ with trap charge density Nit.

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Fig. 9.  (Color online) The variations in $ \text{CTE} $ with trap charge density Nit.

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Table 1.   Parameters of the mathematical model.

Parameters Description Value
NA Doping concentration of the p-type substrate 1015 cm-3
ND Doping concentration of the n-well 1017 cm-3
NA+ Doping concentration of the top pinning layer 1020 cm-3
NC Effective state density of conduction band 2.8 × 1019 cm-3
vt Thermal velocity 107 cm/s
q Unit charge 1.6 × 10-19 C
K Boltzmann constant 1.38 × 10-23 J/K
T Temperature 300 K
LTG Length of the TG 0.7 μm
LPPD Length of the pinned photodiode 2 μm
ATG Area of the TG 0.7 μm2
tfall Time required for the TG to drop from VTG-High to VTG-Low 1 ns
Nmax The coefficient of Gaussian and exponential distribution 5 ×1010 cm−2·eV-1
n Electron density of Si semiconductor 1015 cm-3
$ {\text{σ}}_{\text{n}} $ Electron capture cross-section 10-15 cm-2
DownLoad: CSV
[1]
Fossum E R, Hondongwa D B. A review of the pinned photodiode for CCD and CMOS image sensors. IEEE J Electron Devices Soc, 2014, 2, 33 doi: 10.1109/JEDS.2014.2306412
[2]
Takayanagi I, Kuroda R. HDR CMOS image sensors for automotive applications. IEEE Trans Electron Devices, 2022, 69, 2815 doi: 10.1109/TED.2022.3164370
[3]
Liu B K, Li Y D, Wen L, et al. Displacement damage effects in backside illuminated CMOS image sensors. IEEE Trans Electron Devices, 2022, 69, 2907 doi: 10.1109/TED.2021.3124991
[4]
Lee Y S, Kim H J. High-speed multilevel binary imaging CMOS image sensor for object feature extraction. IEEE Sens J, 2022, 22, 15934 doi: 10.1109/JSEN.2022.3189653
[5]
Marcelot O, Panglosse A, Martin-Gonthier P, et al. TCAD calibration at cryogenic temperatures for CMOS image sensor simulations. IEEE Trans Electron Devices, 2022, 69, 6188 doi: 10.1109/TED.2022.3207120
[6]
Rizzolo S, Goiffon V, Estribeau M, et al. Influence of pixel design on charge transfer performances in CMOS image sensors. IEEE Trans Electron Devices, 2018, 65, 1048 doi: 10.1109/TED.2018.2790443
[7]
Han L Q, Yao S Y, Theuwissen A J P. A charge transfer model for CMOS image sensors. IEEE Trans Electron Devices, 2016, 63, 32 doi: 10.1109/TED.2015.2451593
[8]
Fossum E R. Charge transfer noise and lag in CMOS active pixel sensors. IEEE Workshop CCD’s Adv. Image Sensors, 2003, 11
[9]
Han L Q, Yao S Y, Xu J T, et al. Analysis of incomplete charge transfer effects in a CMOS image sensor. J Semicond, 2013, 34, 054009 doi: 10.1088/1674-4926/34/5/054009
[10]
Capoccia R, Boukhayma A, Jazaeri F, et al. Compact modeling of charge transfer in pinned photodiodes for CMOS image sensors. IEEE Trans Electron Devices, 2018, 66, 160 doi: 10.1109/TED.2018.2875946
[11]
Yang C, Peng G L, Mao W, et al. Novel CMOS image sensor pixel to improve charge transfer speed and efficiency by overlapping gate and temporary storage diffusing node. Chin Phys B, 2021, 30, 018502 doi: 10.1088/1674-1056/abc53f
[12]
Wang X Y, Gao Y Q, Gao Z Y, et al. Charge transfer potential barrier model of a pinned photodiode in CMOS image sensors. IEEE Sens J, 2022, 22, 4036 doi: 10.1109/JSEN.2021.3139091
[13]
Khan U, Sarkar M. Analysis of charge transfer potential barrier in pinned photodiode of CMOS image sensors. IEEE Trans Electron Devices, 2021, 68, 2770 doi: 10.1109/TED.2021.3071331
[14]
Liu L, Guo Y, Li B K, et al. Analytical modeling of potential barrier for charge transfer in pinned photodiode CMOS image sensors. IEEE Trans Electron Devices, 2022, 69, 5637 doi: 10.1109/TED.2022.3200636
[15]
Hu C Z, Zhang B, Xin Y Z, et al. Analytical modeling of charge behavior in pinned photodiode for CMOS image sensors. IEEE Sens J, 2023, 23, 14295 doi: 10.1109/JSEN.2023.3278307
[16]
Xu J T, Wang R S, Han L Q, et al. Analysis and modeling of spill back effect in high illumination CMOS image sensors. IEEE Sens J, 2020, 20, 3024 doi: 10.1109/JSEN.2019.2956594
[17]
Xu Y. Fundamental characteristics of a pinned photodiode CMOS pixel. Ph. D. dissertation, Dept. Microelectron. Comput. Eng., Delft Univ. Technol., Delft, the Netherlands, 2015
[18]
Fowler B , Liu X. Charge transfer noise in image sensors. International Image Sensor Workshop (IISW), 2007, 2
[19]
Bonjour L E, Blanc N, Kayal M. Experimental analysis of lag sources in pinned photodiodes. IEEE Electron Device Lett, 2012, 33, 1735 doi: 10.1109/LED.2012.2217474
[20]
Khan U, Sarkar M. Dynamic capacitance model of a pinned photodiode in CMOS image sensors. IEEE Trans Electron Devices, 2018, 65, 2892 doi: 10.1109/TED.2018.2831719
[21]
Liu E, Zhu B, Luo J. The physics of semiconductors. Beijing: House of Electronics Industry, 2011
[22]
Mohsen A M, McGill T C, Daimon Y, et al. The influence of interface states on incomplete charge transfer in overlapping gate charge-coupled devices. IEEE J Solid-State Circuits, 1973, 8, 125 doi: 10.1109/JSSC.1973.1050361
[23]
Han L Q, Xu J T. Long exposure time noise in pinned photodiode CMOS image sensors. IEEE Electron Device Lett, 2018, 39, 979 doi: 10.1109/LED.2018.2839711
[24]
Xia C Y, Zhang Y, Lu X M, et al. Dynamic model of FWC dependent on the energy-level distribution of interface-state traps in pinned photodiodes. IEEE Trans Electron Devices, 2021, 68, 1682 doi: 10.1109/TED.2021.3056019
[25]
Ayobi A, Mirnia S N. Influence of Gaussian disorder and exponential traps on charge carriers transport and recombination in single layer polymer light-emitting diodes based on PFO as emitting layer. Opt Quantum Electron, 2019, 51, 1 doi: 10.1007/s11082-018-1712-9

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    Received: 16 August 2023 Revised: 18 September 2023 Online: Accepted Manuscript: 01 November 2023Uncorrected proof: 08 November 2023Published: 10 November 2023

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      Article Navigation >  Journal of Semiconductors  > 2023  >  44(11): 114104
      Xi Lu, Changju Liu, Pinyuan Zhao, Yu Zhang, Bei Li, Zhenzhen Zhang, Jiangtao Xu. Incomplete charge transfer in CMOS image sensor caused by Si/SiO2 interface states in the TG channel[J]. Journal of Semiconductors, 2023, 44(11): 114104. doi: 10.1088/1674-4926/44/11/114104 X Lu, C J Liu, P Y Zhao, Y Zhang, B Li, Z Z Zhang, J T Xu. Incomplete charge transfer in CMOS image sensor caused by Si/SiO2 interface states in the TG channel[J]. J. Semicond, 2023, 44(11): 114104. doi: 10.1088/1674-4926/44/11/114104Export: BibTex EndNote
      Citation:
      Xi Lu, Changju Liu, Pinyuan Zhao, Yu Zhang, Bei Li, Zhenzhen Zhang, Jiangtao Xu. Incomplete charge transfer in CMOS image sensor caused by Si/SiO2 interface states in the TG channel[J]. Journal of Semiconductors, 2023, 44(11): 114104. doi: 10.1088/1674-4926/44/11/114104

      X Lu, C J Liu, P Y Zhao, Y Zhang, B Li, Z Z Zhang, J T Xu. Incomplete charge transfer in CMOS image sensor caused by Si/SiO2 interface states in the TG channel[J]. J. Semicond, 2023, 44(11): 114104. doi: 10.1088/1674-4926/44/11/114104
      Export: BibTex EndNote
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      Incomplete charge transfer in CMOS image sensor caused by Si/SiO2 interface states in the TG channel

      doi: 10.1088/1674-4926/44/11/114104
      • 1.

        School of Electronics and Information, Hangzhou Dianzi University, Hangzhou 310018, China

      • 2.

        Tianjin Key Laboratory of Imaging and Sensing Microelectronic Technology, School of Microelectronics, Tianjin University, Tianjin 300072, China

      • 3.

        Chongqing Optoelectronics Research Institute, Chongqing 400060, China

      More Information
      • Author Bio:

        Xi Lu received the B.E. degree from the School of Electrical Engineering and Automation, Tianjin Polytechnic University, Tianjin, China, in 2020. She is currently pursuing the master’s degree with the School of Electronic Information, Hangzhou Dianzi University, Hangzhou, China. Her current research interests include CMOS image sensor and pixel design

        Changju Liu is from Chonqing Optoelectronics Research Institute, Chongqing, China, he received the M.S. degree in 2007 from University of Electronic Science and Technology of China. His research activities are focused on CCD/CMOS image sensor and optoelectronic integrated devices

        Pinyuan Zhao received the B.E. degree from the School of Electronic Information, Anhui University of Technology, Anhui, China, in 2021. She is currently pursuing the master’s degree with the School of Electronic Information, Hangzhou Dianzi University, Hangzhou, China. Her current research interests include CMOS image sensor design especially on pixel design

        Yu Zhang received the M.S. degree in circuit and system from Tianjin University, Tianjin, China, in 2006 and the Ph.D. degree in Microelectronics and solid state electronics from Tianjin University, Tianjin, China, in 2009. Since July 2009, she has been with the School of Electronics and Information, Hangzhou Dianzi University, and currently is full professor of this university. Her research interests are noise model and VLSI realization of CMOS image sensor

        Bei Li received his bachelor's degree in 2002 from NorthWest University. He is a senior engineer of Chonqing Optoelectronics Research Institute, Chongqing, China. His research focuses on wafer test

        Zhenzhen Zhang received the B.E. degree from the School of Electronic Information, Xi'an Shiyou University of Technology, Xi'an, China, in 2020. She is currently pursuing the master’s degree with the School of Electronic Information, Hangzhou Dianzi University, Hangzhou, China. Her current research interests include signal processing

        Jiangtao Xu received the B.E. degree from Tianjin University in 2001, the M.S. and Ph.D. degrees from the School of Electronic Information and Engineering, Tianjin University, in 2004 and 2007, respectively. From 2007 to 2010, he was a Lecturer. From 2010 to 2018, he was an Associate Professor with Tianjin University. Since 2018, he has been a full Professor with the School of Microelectronics. His research interests are in CMOS image sensor chip and system

      • Corresponding author: zy2009@hdu.edu.cn; xujiangtao@tju.edu.cn
      • Received Date: 2023-08-16
      • Revised Date: 2023-09-18
        • Available Online: 2023-11-01

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