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Design of CMOS active pixels based on finger-shaped PPD

Feng Li1, Ruishuo Wang1, Liqiang Han2 and Jiangtao Xu1,

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 Corresponding author: Jiangtao Xu, Email: xujiangtao@tju.edu.cn

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Abstract: 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.

Key words: CMOS active pixelfull well capacityfull depletion



[1]
Bigas M, Cabruja E, Forest J, et al. Review of CMOS image sensor. Microelectron J, 2006, 37(5), 433 doi: 10.1016/j.mejo.2005.07.002
[2]
Luo B, Yang F X, Yan L. Key technologies and research development of CMOS image sensors. IITA International Conference on Geoscience and Remote Sensing, 2010, 322
[3]
Fontaine R. Innovative technology elements for large and small pixel CIS devices. Proc International Image Sensor Workshop (IISW), 2013, 1
[4]
Wang X D, Ye T. Comparative research and future tendency between CMOS and CCD image sensor. Electron Des Eng, 2010, 18(11), 184
[5]
Jan B, Erik J M, Wilco K, et al. Recent developments on large-area CCDs for professional applications. International image sensor workshop. Proc International Image Sensor Workshop (IISW), 2015, 1
[6]
Velichko S, Hynecek J, Johnson R, et al. CMOS global shutter charge storage pixels with improved performance. IEEE Trans Electron Devices, 2015, 63(1), 1 doi: 10.1109/TED.2015.2443495
[7]
Solhusvik J, Kuang J, Lin Z, et al. A comparison of high dynamic range CIS technologies for automotive applications. Proc International Image Sensor Workshop, 2013, 1
[8]
Freedman S D, Boussaid F. A high dynamic range CMOS image sensor with a novel pixel-level logarithmic counter memory. IEEE International Conference on Knowledge-Based Engineering and Innovation (KBEI), 2015, 14
[9]
Takayanagi I, Yoshimura N, Mori K, et al. An 87 dB single exposure dynamic range CMOS image sensor with a 3.0 μm triple conversion gain pixel. Proc International Image Sensor Workshop (IISW), 2017, 30
[10]
Wang R G, Yin Y X, Liang L, et al. A high dynamic range CMOS image sensor with dual charge transfer phase. IEEE International Conference on Solid-State and Integrated Circuit Technology (ICSICT), 2016, 1369
[11]
Yu J T, Li B Q, Yu P P, et al. Two-dimensional pixel image lag simulation and optimization in a 4-T CMOS image sensor. J Semicond, 2010, 31(9), 094011 doi: 10.1088/1674-4926/31/9/094011
[12]
Lofthouse-Smith D D, Soman M R, Allanwood E A H, et al. Image lag optimisation in a 4T CMOS image sensor for the JANUS camera on ESA's JUICE mission to Jupiter. Int Soc Opt Photonics, 2018, 10709, 107091J doi: 10.1117/12.2313686
[13]
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(3), 1048 doi: 10.1109/TED.2018.2790443
[14]
Orly Y P, Ran G, Yosi S D. A random access photodiode array for intelligent image capture. IEEE Trans Electron Devices, 1991, 38(8), 1772 doi: 10.1109/16.119013
[15]
Iltgen K, Bendel C, Benninghoven A. Optimized time-of-flight secondary ion mass spectroscopy depth profiling with a dual beam technique. J Vac Sci Technol A, 1997, 15(3), 460 doi: 10.1116/1.580874
[16]
Park Y H. Image sensor having self-aligned and overlapped photodiode and method of making same. US Patent 7180151, 2007
[17]
Li Z H. Research on image sensor with ultra wide dynamic range. PhD Thesis, Jilin University, 2016
[18]
Cao X, Gäbler D, Lee C, et al. Design and optimisation of large 4T pixel. Proc Int Image Sensor Workshop (IISW), 2015, 112
[19]
Han L Q. Study on the charge transfer mechanism and noise of CMOS active pixel. PhD Thesis, Tianjin University, 2016
[20]
Oike Y, Akiyama K, Hung L D, et al. An 8.3M-pixel 480 fps global-shutter CMOS image sensor with gain-adaptive column ADCs and 2-on-1 stacked device structure. IEEE Symposium on VLSI Circuits, 2016, 1
[21]
Lim W, Hwang J, Kim D, et al. A low noise CMOS image sensor with a 14-bit two-step single-slope ADC and a column self-calibration technique. IEEE International Conference on Electronics, Circuits and Systems (ICECS), 2015, 51
[22]
Yeh S, Hsieh C. Novel single-slope ADC design for full well capacity expansion of CMOS image sensor. IEEE Sens J, 2013, 13(3), 1012 doi: 10.1109/JSEN.2012.2227706
[23]
Xu R, Ng W C, Yuan J, et al. A 1/2.5 inch VGA 400 fps CMOS image sensor with high sensitivity for machine vision. IEEE J Solid-State Circuits, 2014, 49(10), 2342 doi: 10.1109/JSSC.2014.2345018
Fig. 1.  N buried layer structure of PPD.

Fig. 2.  (Color online) 2D TCAD simulation of depletion region in traditional cubic PPD.

Fig. 3.  (Color online) The finger-shaped PPD and its top view.

Fig. 4.  (Color online) Under the basic ion implantation process conditions, the potential distribution in (a) initial phase, (b) after illumination phase, (c) transfer phase, (d) post-transition phase.

Fig. 5.  (Color online) Under the basic ion implantation process conditions: (a) the potential distribution in transfer phase, (b) the potential curve on the charge transfer path.

Fig. 6.  (Color online) Potential and depletion region distribution with different single-finger PPD widths.

Fig. 7.  (Color online) The number of electrons in PPD based on TCAD 2D simulation.

Fig. 8.  (Color online) Depletion zone and potential distribution with different PPD spacing.

Fig. 9.  (Color online) The number of electrons in PPD based on TCAD 2D simulation. (a) Using the process conditions of Fig. 2. (b) Using the process conditions of Fig. 8(d).

Fig. 10.  (Color online) The special finger-shaped PPD structure proposed in this paper: (a) three-dimensional structure, (b) sectional structural view, (c) 2D device simulation diagram.

Fig. 11.  (Color online) Pixel layout and the main layout level of PPD-TG-FD. (a) 2 × 2 pixel unit. (b) Layout of PPD-TG-FD.

Fig. 12.  Photoresponse with different single-finger spacing.

Fig. 13.  (Color online) FWC with different spacing (Before widening N1).

Fig. 14.  (Color online) The measurement results of test chip: (a) photoresponse of the pixel using the proposed PPD structure, (b) PTC of the pixel using the proposed PPD structure.

Table 1.   Vpin, NFWC and depletion depth (W) with different d.

d (μm)0.60.70.80.91.0
Vpin (V)1.0571.2151.4081.6461.863
NFWC (e)30944335551667257966
W (μm)2.8422.7922.8452.8452.845
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Table 2.   Vpin with different PPD spacing.

Spacing (μm)1.41.31.21.11.00.9
Vpin (V)1.3821.4151.4241.4381.506Not fully depleted
DownLoad: CSV

Table 3.   Performance comparison between the pixel test results with a PPD of finger shape and related literature.

ParameterThis workRef. [20]Ref. [21]Ref. [22]Ref. [23]
Technology0.18 μm CMOS90 nm CMOS0.13 μm CMOS0.18 μm CMOS0.18 μm CMOS
Pixel size (μm2)6.00 × 6.005.86 × 5.865.60 × 5.605.60 × 5.606.50 × 6.50
FWC (e-)686503045023000474506400
DownLoad: CSV
[1]
Bigas M, Cabruja E, Forest J, et al. Review of CMOS image sensor. Microelectron J, 2006, 37(5), 433 doi: 10.1016/j.mejo.2005.07.002
[2]
Luo B, Yang F X, Yan L. Key technologies and research development of CMOS image sensors. IITA International Conference on Geoscience and Remote Sensing, 2010, 322
[3]
Fontaine R. Innovative technology elements for large and small pixel CIS devices. Proc International Image Sensor Workshop (IISW), 2013, 1
[4]
Wang X D, Ye T. Comparative research and future tendency between CMOS and CCD image sensor. Electron Des Eng, 2010, 18(11), 184
[5]
Jan B, Erik J M, Wilco K, et al. Recent developments on large-area CCDs for professional applications. International image sensor workshop. Proc International Image Sensor Workshop (IISW), 2015, 1
[6]
Velichko S, Hynecek J, Johnson R, et al. CMOS global shutter charge storage pixels with improved performance. IEEE Trans Electron Devices, 2015, 63(1), 1 doi: 10.1109/TED.2015.2443495
[7]
Solhusvik J, Kuang J, Lin Z, et al. A comparison of high dynamic range CIS technologies for automotive applications. Proc International Image Sensor Workshop, 2013, 1
[8]
Freedman S D, Boussaid F. A high dynamic range CMOS image sensor with a novel pixel-level logarithmic counter memory. IEEE International Conference on Knowledge-Based Engineering and Innovation (KBEI), 2015, 14
[9]
Takayanagi I, Yoshimura N, Mori K, et al. An 87 dB single exposure dynamic range CMOS image sensor with a 3.0 μm triple conversion gain pixel. Proc International Image Sensor Workshop (IISW), 2017, 30
[10]
Wang R G, Yin Y X, Liang L, et al. A high dynamic range CMOS image sensor with dual charge transfer phase. IEEE International Conference on Solid-State and Integrated Circuit Technology (ICSICT), 2016, 1369
[11]
Yu J T, Li B Q, Yu P P, et al. Two-dimensional pixel image lag simulation and optimization in a 4-T CMOS image sensor. J Semicond, 2010, 31(9), 094011 doi: 10.1088/1674-4926/31/9/094011
[12]
Lofthouse-Smith D D, Soman M R, Allanwood E A H, et al. Image lag optimisation in a 4T CMOS image sensor for the JANUS camera on ESA's JUICE mission to Jupiter. Int Soc Opt Photonics, 2018, 10709, 107091J doi: 10.1117/12.2313686
[13]
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(3), 1048 doi: 10.1109/TED.2018.2790443
[14]
Orly Y P, Ran G, Yosi S D. A random access photodiode array for intelligent image capture. IEEE Trans Electron Devices, 1991, 38(8), 1772 doi: 10.1109/16.119013
[15]
Iltgen K, Bendel C, Benninghoven A. Optimized time-of-flight secondary ion mass spectroscopy depth profiling with a dual beam technique. J Vac Sci Technol A, 1997, 15(3), 460 doi: 10.1116/1.580874
[16]
Park Y H. Image sensor having self-aligned and overlapped photodiode and method of making same. US Patent 7180151, 2007
[17]
Li Z H. Research on image sensor with ultra wide dynamic range. PhD Thesis, Jilin University, 2016
[18]
Cao X, Gäbler D, Lee C, et al. Design and optimisation of large 4T pixel. Proc Int Image Sensor Workshop (IISW), 2015, 112
[19]
Han L Q. Study on the charge transfer mechanism and noise of CMOS active pixel. PhD Thesis, Tianjin University, 2016
[20]
Oike Y, Akiyama K, Hung L D, et al. An 8.3M-pixel 480 fps global-shutter CMOS image sensor with gain-adaptive column ADCs and 2-on-1 stacked device structure. IEEE Symposium on VLSI Circuits, 2016, 1
[21]
Lim W, Hwang J, Kim D, et al. A low noise CMOS image sensor with a 14-bit two-step single-slope ADC and a column self-calibration technique. IEEE International Conference on Electronics, Circuits and Systems (ICECS), 2015, 51
[22]
Yeh S, Hsieh C. Novel single-slope ADC design for full well capacity expansion of CMOS image sensor. IEEE Sens J, 2013, 13(3), 1012 doi: 10.1109/JSEN.2012.2227706
[23]
Xu R, Ng W C, Yuan J, et al. A 1/2.5 inch VGA 400 fps CMOS image sensor with high sensitivity for machine vision. IEEE J Solid-State Circuits, 2014, 49(10), 2342 doi: 10.1109/JSSC.2014.2345018
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    Received: 25 December 2019 Revised: 13 January 2020 Online: Accepted Manuscript: 10 April 2020Uncorrected proof: 21 April 2020Published: 01 October 2020

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      Feng Li, Ruishuo Wang, Liqiang Han, Jiangtao Xu. Design of CMOS active pixels based on finger-shaped PPD[J]. Journal of Semiconductors, 2020, 41(10): 102301. doi: 10.1088/1674-4926/41/10/102301 F Li, R S Wang, L Q Han, J T Xu, Design of CMOS active pixels based on finger-shaped PPD[J]. J. Semicond., 2020, 41(10): 102301. doi: 10.1088/1674-4926/41/10/102301.Export: BibTex EndNote
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      Feng Li, Ruishuo Wang, Liqiang Han, Jiangtao Xu. Design of CMOS active pixels based on finger-shaped PPD[J]. Journal of Semiconductors, 2020, 41(10): 102301. doi: 10.1088/1674-4926/41/10/102301

      F Li, R S Wang, L Q Han, J T Xu, Design of CMOS active pixels based on finger-shaped PPD[J]. J. Semicond., 2020, 41(10): 102301. doi: 10.1088/1674-4926/41/10/102301.
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      Design of CMOS active pixels based on finger-shaped PPD

      doi: 10.1088/1674-4926/41/10/102301
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      • Corresponding author: Email: xujiangtao@tju.edu.cn
      • Received Date: 2019-12-25
      • Revised Date: 2020-01-13
      • Published Date: 2020-10-04

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