Double junction photodiode for X-ray CMOS sensor IC

Chaoqun Xu; Ying Sun; Yan Han; Dazhong Zhu

doi:10.1088/1674-4926/35/7/074011

J. Semicond. > 2014, Volume 35 > Issue 7 > 074011

SEMICONDUCTOR DEVICES

Double junction photodiode for X-ray CMOS sensor IC

Chaoqun Xu, Ying Sun, Yan Han and Dazhong Zhu

+ Author Affiliations

Corresponding author: Sun Ying, Email:suny@zju.edu.cn

DOI: 10.1088/1674-4926/35/7/074011

Abstract: A CMOS compatible P⁺/N_well/P_sub double junction photodiode pixel was proposed, which can efficiently detect fluorescence from CsI(Tl) scintillation in an X-ray sensor. Photoelectric and spectral responses of P⁺/N_well, N_well/P_sub and P⁺/N_well/P_sub photodiodes were analyzed and modeled. Simulation results show P⁺/N_well/P_sub photodiode has larger photocurrent than P⁺/N_well photodiode and N_well/P_sub photodiode, and its spectral response is more in accordance with CsI(Tl) fluorescence spectrum. Improved P⁺/N_well/P_sub photodiode detecting CsI(Tl) fluorescence was designed in CSMC 0.5 μm CMOS process, CTIA (capacitive transimpedance amplifier) architecture was used to readout photocurrent signal. CMOS X-ray sensor IC prototype contains 8×8 pixel array and pixel pitch is 100×100 μm². Testing results show the dark current of the improved P⁺/N_well/P_sub photodiode (6.5 pA) is less than that of P⁺/N_well and P⁺/N_well/P_sub photodiodes (13 pA and 11 pA respectively). The sensitivity of P⁺/N_well/P_sub photodiode is about 20 pA/lux under white LED. The spectrum response of P⁺/N_well/P_sub photodiode ranges from 400 nm to 800 nm with a peak at 532 nm, which is in accordance with the fluorescence spectrum of CsI(Tl) in an indirect X-ray sensor. Preliminary testing results show the sensitivity of X-ray sensor IC under Cu target X-ray is about 0.21 V·m²/W or 5097e^-/pixel@8.05 keV considering the pixel size, integration time and average energy of X-ray photons.

Key words: double junction photodiode, indirect X-ray sensor, CMOS X-ray sensor IC, fluorescence detection

References

[1]	Chavanelle J, Parmentier M. A CsI(Tl)-PIN photodiode gamma-ray probe. Nucl Instrum Methods Phys Res A, 2003, 504(1-3): 321 doi: 10.1016/S0168-9002(03)00761-7
[2]	Kah D H, Bae J B, Hyun H J, et al. Fabrication and performance test of a silicon photo-strip detector coupled with a crystal scintillator. Instrum Methods Phys Res A, 2011, 628(1-3): 256 http://linkinghub.elsevier.com/retrieve/pii/S0168900210015202
[3]	Silva J, Lanceros-Mendez S, Minas G, et al. CMOS X-ray image sensor array. Electronics, Circuits and Systems, 2007: 1067 doi: 10.1109/ICECS.2007.4511178
[4]	Kudin A M, Borodenko Y A, Grinyova B V, et al. CsI(Tl) + photodiode scintillation assemblies for γ -ray and proton detectors. Instruments and Experimental Techniques, 2010, 53(1): 39 doi: 10.1134/S0020441210010057
[5]	Miller S R, Gaysinskiy V, Shestakova I, et al. Recent advances in columnar CsI(Tl) scintillator screens. Proceedings of SPIE-Penetrating Radiation Systems and Applications Ⅶ, 2005, 5923-59230F: 1
[6]	Tabet M. Double sampling techniques for CMOS image sensors. PhD dissertation, University of Waterloo, Dept. Elect. Compt. Eng. , Waterloo, Ontario, Canada, 2002
[7]	Yamazaki T, Court L, Kameshima T. Sensor gain and noise requirements for fluoroscopic applications. Proceedings of SPIE-Physics of Medical Imaging, 2001, 2(25): 489 http://proceedings.spiedigitallibrary.org/pdfaccess.ashx?url=/data/conferences/spiep/35044/489_1.pdf
[8]	Valais I, Nikolopoulos D, Kalivas N, et al. A systematic study of the performance of the CsI:Tl single-crystal scintillator under X-ray excitation. Nucl Instrum Methods Phys Res A, 2007, 571(1/2): 343 http://linkinghub.elsevier.com/retrieve/pii/S0168900206018936
[9]	Murari K, Etienne-Cummings R, Thakor N, et al. Which photodiode to use: a comparison of CMOS-compatible structures. IEEE Sensors Journal, 2009, 9(7): 752 doi: 10.1109/JSEN.2009.2021805
[10]	Liu L N, Chen C, Liu C H. Numerical simulation of spectral response for 650 nm silicon photo detector. Semicond Photonics Technol, 2010, 2(9): 82
[11]	Dash W C, Newman R. Intrinsic optical absorption in single-crystal germanium and silicon at 77 K and 300 K. Phys Rev, 2007, 4(99): 145 http://adsabs.harvard.edu/abs/1955PhRv...99.1151D
[12]	Wu C Y, Shih Y C, Lan J F, et al. Design, optimization, and performance analysis of new photodiode structure s for CMOS active-pixel-sensor (APS) imager applications. IEEE Sensors Journal, 2004, 4(1): 135 doi: 10.1109/JSEN.2003.820361
[13]	Cheng H Y, King Y C. An ultra-low dark current CMOS image sensor cell using n/sup⁺/ring reset. IEEE Electron Device Lett, 2002, 23(9): 538 doi: 10.1109/LED.2002.802587
[14]	Liu C, Emadi A, Wu H W, et al. A CMOS 128-APS linear array integrated with a LVOF for high sensitivity and high-resolution micro-spectrophotometry. Proceedings of SPIE-The International Society for Optical Engineering, 2010, 7726: 772616 http://repository.tudelft.nl/islandora/object/uuid:ef511dec-c68d-4104-9861-b3ddc25b14d3/datastream/OBJ/download
[15]	Wang Xu, Yang Hongyan, Yuan Ying, et al. A low noise multi-channel readout IC for X-ray cargo inspection. Journal of Semiconductors, 2013, 34(4): 045011 doi: 10.1088/1674-4926/34/4/045011
[16]	Xu Jiangtao, Yao Suying, Li Binqiao, et al. Design, analysis, and optimization of a CMOS active pixel sensor. Chinese Journal of Semiconductor, 2006, 27(9): 1548 http://www.oalib.com/paper/1521963
[17]	Turchetta R, Berst J D, Casadei B, et al. A monolithic active pixel sensor for charged particle tracking and imaging using standard VLSI CMOS technology. Nuclear Instruments and Methods in Physics Research A, 2001, 458: 677 doi: 10.1016/S0168-9002(00)00893-7

Fig. 1. Schematic drawing of the three photodiode structures. (a) P⁺/N_well. (b) N_well/P_sub. (c) P⁺/N_well/P_sub.

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Fig. 2. Diagrammatic sketch of PN junction photodiode.

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Fig. 3. Diagrammatic sketch of P⁺/ N_well/P_sub photodiode.

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Fig. 4. Simulated spectral response of P⁺/N_well, N_well/P_sub and P⁺/N_well/P_sub photodiodes.

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Fig. 5. Schematic of the improved P⁺/N_well/P_sub photodiode structure.

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Fig. 6. Dark current of three photodiodes.

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Fig. 7. Photocurrent against reverse bias voltage under 100 lux illuminance.

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Fig. 8. Photocurrent against light intensity of improved P⁺/N_well/P_sub photodiode.

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Fig. 9. Response of improved P⁺/N_well/P_sub photodiode to monochromatic light.

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Fig. 10. Pixel architecture of CTIA APS.

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Fig. 11. Microphotograph of the chip. A: Pixel array, B: CDS circuit and buffer, C: Controlling sequence, D: Clock and biasing circuit, E: Testing photodiode structure.

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Fig. 13. Sensitivity measurement of the assembled CMOS X-ray sensor.

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Fig. 12. Conceptual illustration of the assembled X-ray sensor array.

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Table 1. Typical values of minority lifetime in silicon.

Table 2. Comparison of the three photodiodes.

Table 3. Testing results under X-ray excitation.

Table 4. Main parameters of the sensor.

[1]	Chavanelle J, Parmentier M. A CsI(Tl)-PIN photodiode gamma-ray probe. Nucl Instrum Methods Phys Res A, 2003, 504(1-3): 321 doi: 10.1016/S0168-9002(03)00761-7
[2]	Kah D H, Bae J B, Hyun H J, et al. Fabrication and performance test of a silicon photo-strip detector coupled with a crystal scintillator. Instrum Methods Phys Res A, 2011, 628(1-3): 256 http://linkinghub.elsevier.com/retrieve/pii/S0168900210015202
[3]	Silva J, Lanceros-Mendez S, Minas G, et al. CMOS X-ray image sensor array. Electronics, Circuits and Systems, 2007: 1067 doi: 10.1109/ICECS.2007.4511178
[4]	Kudin A M, Borodenko Y A, Grinyova B V, et al. CsI(Tl) + photodiode scintillation assemblies for γ -ray and proton detectors. Instruments and Experimental Techniques, 2010, 53(1): 39 doi: 10.1134/S0020441210010057
[5]	Miller S R, Gaysinskiy V, Shestakova I, et al. Recent advances in columnar CsI(Tl) scintillator screens. Proceedings of SPIE-Penetrating Radiation Systems and Applications Ⅶ, 2005, 5923-59230F: 1
[6]	Tabet M. Double sampling techniques for CMOS image sensors. PhD dissertation, University of Waterloo, Dept. Elect. Compt. Eng. , Waterloo, Ontario, Canada, 2002
[7]	Yamazaki T, Court L, Kameshima T. Sensor gain and noise requirements for fluoroscopic applications. Proceedings of SPIE-Physics of Medical Imaging, 2001, 2(25): 489 http://proceedings.spiedigitallibrary.org/pdfaccess.ashx?url=/data/conferences/spiep/35044/489_1.pdf
[8]	Valais I, Nikolopoulos D, Kalivas N, et al. A systematic study of the performance of the CsI:Tl single-crystal scintillator under X-ray excitation. Nucl Instrum Methods Phys Res A, 2007, 571(1/2): 343 http://linkinghub.elsevier.com/retrieve/pii/S0168900206018936
[9]	Murari K, Etienne-Cummings R, Thakor N, et al. Which photodiode to use: a comparison of CMOS-compatible structures. IEEE Sensors Journal, 2009, 9(7): 752 doi: 10.1109/JSEN.2009.2021805
[10]	Liu L N, Chen C, Liu C H. Numerical simulation of spectral response for 650 nm silicon photo detector. Semicond Photonics Technol, 2010, 2(9): 82
[11]	Dash W C, Newman R. Intrinsic optical absorption in single-crystal germanium and silicon at 77 K and 300 K. Phys Rev, 2007, 4(99): 145 http://adsabs.harvard.edu/abs/1955PhRv...99.1151D
[12]	Wu C Y, Shih Y C, Lan J F, et al. Design, optimization, and performance analysis of new photodiode structure s for CMOS active-pixel-sensor (APS) imager applications. IEEE Sensors Journal, 2004, 4(1): 135 doi: 10.1109/JSEN.2003.820361
[13]	Cheng H Y, King Y C. An ultra-low dark current CMOS image sensor cell using n/sup⁺/ring reset. IEEE Electron Device Lett, 2002, 23(9): 538 doi: 10.1109/LED.2002.802587
[14]	Liu C, Emadi A, Wu H W, et al. A CMOS 128-APS linear array integrated with a LVOF for high sensitivity and high-resolution micro-spectrophotometry. Proceedings of SPIE-The International Society for Optical Engineering, 2010, 7726: 772616 http://repository.tudelft.nl/islandora/object/uuid:ef511dec-c68d-4104-9861-b3ddc25b14d3/datastream/OBJ/download
[15]	Wang Xu, Yang Hongyan, Yuan Ying, et al. A low noise multi-channel readout IC for X-ray cargo inspection. Journal of Semiconductors, 2013, 34(4): 045011 doi: 10.1088/1674-4926/34/4/045011
[16]	Xu Jiangtao, Yao Suying, Li Binqiao, et al. Design, analysis, and optimization of a CMOS active pixel sensor. Chinese Journal of Semiconductor, 2006, 27(9): 1548 http://www.oalib.com/paper/1521963
[17]	Turchetta R, Berst J D, Casadei B, et al. A monolithic active pixel sensor for charged particle tracking and imaging using standard VLSI CMOS technology. Nuclear Instruments and Methods in Physics Research A, 2001, 458: 677 doi: 10.1016/S0168-9002(00)00893-7

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Received: 29 October 2013 Revised: 28 February 2014 Online: Published: 01 July 2014

Article Navigation > Journal of Semiconductors > 2014 > 35(7): 074011

Chaoqun Xu, Ying Sun, Yan Han, Dazhong Zhu. Double junction photodiode for X-ray CMOS sensor IC[J]. Journal of Semiconductors, 2014, 35(7): 074011. doi: 10.1088/1674-4926/35/7/074011 ****C Q Xu, Y Sun, Y Han, D Z Zhu. Double junction photodiode for X-ray CMOS sensor IC[J]. J. Semicond., 2014, 35(7): 074011. doi: 10.1088/1674-4926/35/7/074011.

Citation:

Chaoqun Xu, Ying Sun, Yan Han, Dazhong Zhu. Double junction photodiode for X-ray CMOS sensor IC[J]. Journal of Semiconductors, 2014, 35(7): 074011. doi: 10.1088/1674-4926/35/7/074011 ****

C Q Xu, Y Sun, Y Han, D Z Zhu. Double junction photodiode for X-ray CMOS sensor IC[J]. J. Semicond., 2014, 35(7): 074011. doi: 10.1088/1674-4926/35/7/074011.

Citation:

Chaoqun Xu, Ying Sun, Yan Han, Dazhong Zhu. Double junction photodiode for X-ray CMOS sensor IC[J]. Journal of Semiconductors, 2014, 35(7): 074011. doi: 10.1088/1674-4926/35/7/074011 ****

C Q Xu, Y Sun, Y Han, D Z Zhu. Double junction photodiode for X-ray CMOS sensor IC[J]. J. Semicond., 2014, 35(7): 074011. doi: 10.1088/1674-4926/35/7/074011.

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Double junction photodiode for X-ray CMOS sensor IC

DOI: 10.1088/1674-4926/35/7/074011

Department of Information Science and Electronic Engineering, Institute of Microelectronics and Optoelectronics, Zhejiang University, Hangzhou 310027, China

Funds:

the Natural Science Foundation of Zhejiang Province Y1100287

Project supported by the National Natural Science Foundation of China (No. 61076075) and the Natural Science Foundation of Zhejiang Province (No.Y1100287)

the National Natural Science Foundation of China 61076075

More Information

Corresponding author: Sun Ying, Email:suny@zju.edu.cn
Received Date: 2013-10-29
Revised Date: 2014-02-28
Published Date: 2014-07-01

Abstract

Abstract

A CMOS compatible P⁺/N_well/P_sub double junction photodiode pixel was proposed, which can efficiently detect fluorescence from CsI(Tl) scintillation in an X-ray sensor. Photoelectric and spectral responses of P⁺/N_well, N_well/P_sub and P⁺/N_well/P_sub photodiodes were analyzed and modeled. Simulation results show P⁺/N_well/P_sub photodiode has larger photocurrent than P⁺/N_well photodiode and N_well/P_sub photodiode, and its spectral response is more in accordance with CsI(Tl) fluorescence spectrum. Improved P⁺/N_well/P_sub photodiode detecting CsI(Tl) fluorescence was designed in CSMC 0.5 μm CMOS process, CTIA (capacitive transimpedance amplifier) architecture was used to readout photocurrent signal. CMOS X-ray sensor IC prototype contains 8×8 pixel array and pixel pitch is 100×100 μm². Testing results show the dark current of the improved P⁺/N_well/P_sub photodiode (6.5 pA) is less than that of P⁺/N_well and P⁺/N_well/P_sub photodiodes (13 pA and 11 pA respectively). The sensitivity of P⁺/N_well/P_sub photodiode is about 20 pA/lux under white LED. The spectrum response of P⁺/N_well/P_sub photodiode ranges from 400 nm to 800 nm with a peak at 532 nm, which is in accordance with the fluorescence spectrum of CsI(Tl) in an indirect X-ray sensor. Preliminary testing results show the sensitivity of X-ray sensor IC under Cu target X-ray is about 0.21 V·m²/W or 5097e^-/pixel@8.05 keV considering the pixel size, integration time and average energy of X-ray photons.
- double junction photodiode,
- indirect X-ray sensor,
- CMOS X-ray sensor IC,
- fluorescence detection

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References(17)

References

[1]	Chavanelle J, Parmentier M. A CsI(Tl)-PIN photodiode gamma-ray probe. Nucl Instrum Methods Phys Res A, 2003, 504(1-3): 321 doi: 10.1016/S0168-9002(03)00761-7
[2]	Kah D H, Bae J B, Hyun H J, et al. Fabrication and performance test of a silicon photo-strip detector coupled with a crystal scintillator. Instrum Methods Phys Res A, 2011, 628(1-3): 256 http://linkinghub.elsevier.com/retrieve/pii/S0168900210015202
[3]	Silva J, Lanceros-Mendez S, Minas G, et al. CMOS X-ray image sensor array. Electronics, Circuits and Systems, 2007: 1067 doi: 10.1109/ICECS.2007.4511178
[4]	Kudin A M, Borodenko Y A, Grinyova B V, et al. CsI(Tl) + photodiode scintillation assemblies for γ -ray and proton detectors. Instruments and Experimental Techniques, 2010, 53(1): 39 doi: 10.1134/S0020441210010057
[5]	Miller S R, Gaysinskiy V, Shestakova I, et al. Recent advances in columnar CsI(Tl) scintillator screens. Proceedings of SPIE-Penetrating Radiation Systems and Applications Ⅶ, 2005, 5923-59230F: 1
[6]	Tabet M. Double sampling techniques for CMOS image sensors. PhD dissertation, University of Waterloo, Dept. Elect. Compt. Eng. , Waterloo, Ontario, Canada, 2002
[7]	Yamazaki T, Court L, Kameshima T. Sensor gain and noise requirements for fluoroscopic applications. Proceedings of SPIE-Physics of Medical Imaging, 2001, 2(25): 489 http://proceedings.spiedigitallibrary.org/pdfaccess.ashx?url=/data/conferences/spiep/35044/489_1.pdf
[8]	Valais I, Nikolopoulos D, Kalivas N, et al. A systematic study of the performance of the CsI:Tl single-crystal scintillator under X-ray excitation. Nucl Instrum Methods Phys Res A, 2007, 571(1/2): 343 http://linkinghub.elsevier.com/retrieve/pii/S0168900206018936
[9]	Murari K, Etienne-Cummings R, Thakor N, et al. Which photodiode to use: a comparison of CMOS-compatible structures. IEEE Sensors Journal, 2009, 9(7): 752 doi: 10.1109/JSEN.2009.2021805
[10]	Liu L N, Chen C, Liu C H. Numerical simulation of spectral response for 650 nm silicon photo detector. Semicond Photonics Technol, 2010, 2(9): 82
[11]	Dash W C, Newman R. Intrinsic optical absorption in single-crystal germanium and silicon at 77 K and 300 K. Phys Rev, 2007, 4(99): 145 http://adsabs.harvard.edu/abs/1955PhRv...99.1151D
[12]	Wu C Y, Shih Y C, Lan J F, et al. Design, optimization, and performance analysis of new photodiode structure s for CMOS active-pixel-sensor (APS) imager applications. IEEE Sensors Journal, 2004, 4(1): 135 doi: 10.1109/JSEN.2003.820361
[13]	Cheng H Y, King Y C. An ultra-low dark current CMOS image sensor cell using n/sup⁺/ring reset. IEEE Electron Device Lett, 2002, 23(9): 538 doi: 10.1109/LED.2002.802587
[14]	Liu C, Emadi A, Wu H W, et al. A CMOS 128-APS linear array integrated with a LVOF for high sensitivity and high-resolution micro-spectrophotometry. Proceedings of SPIE-The International Society for Optical Engineering, 2010, 7726: 772616 http://repository.tudelft.nl/islandora/object/uuid:ef511dec-c68d-4104-9861-b3ddc25b14d3/datastream/OBJ/download
[15]	Wang Xu, Yang Hongyan, Yuan Ying, et al. A low noise multi-channel readout IC for X-ray cargo inspection. Journal of Semiconductors, 2013, 34(4): 045011 doi: 10.1088/1674-4926/34/4/045011
[16]	Xu Jiangtao, Yao Suying, Li Binqiao, et al. Design, analysis, and optimization of a CMOS active pixel sensor. Chinese Journal of Semiconductor, 2006, 27(9): 1548 http://www.oalib.com/paper/1521963
[17]	Turchetta R, Berst J D, Casadei B, et al. A monolithic active pixel sensor for charged particle tracking and imaging using standard VLSI CMOS technology. Nuclear Instruments and Methods in Physics Research A, 2001, 458: 677 doi: 10.1016/S0168-9002(00)00893-7

Double junction photodiode for X-ray CMOS sensor IC

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