Application of CMOS sensors in radiation detection

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1 Application of CMOS sensors in radiation detection S. Ashrafi Physics Faculty University of Tabriz 1

2 CMOS is a technology for making low power integrated circuits. CMOS Complementary Metal Oxide Semiconductor MOS the MOSFET transistors Complimentary the two different types of semiconductors (N-type and P-type) CMOS is used in electronics: static RAM, digital logic circuits, micro processors, micro controllers, image sensors and particle tracking, and 2

3 Architecture of a CMOS image sensor access a pixel and read the signal value transistors photodetector 3

4 Basic functions of CMOS webcam: Optical gathering of photons (lens) Wavelength discrimination of photons (filter) Detector for photons to electrons conversion (photodiode) readout the detector Timing control, and drive electronics Signal processing electronics Analog-to digital conversion Interface electronics 4

5 Basic configuration of CMOS image sensor. M RS = reset transistor M SF = source follower transistor M SEL = select transistor An n-mosfet structure is shown: source is a PD drain is biased at V dd gate is off-state. 5

6 n MOSFET Potential profile electron density The impurity density in the source is smaller than that in the drain. Ohta

7 The operation of an APS is as follows: First, the reset transistor M RS is turned on. This resets V PD to (V dd V th ), where V th is the threshold voltage of transistor M RS. Then, M RS is turned off and the PD is electrically floated. When light is incident, the photo-generated carriers accumulate in the PD junction capacitance C PD. The accumulated charge decreases V PD according to the input light intensity. After an accumulation time of 33 msec, (at video rate), the select transistor M SEL is turned on and the output signal in the pixel is read out in the vertical output line. When the read-out process is finished, M SEL is turned off and M RS is again turned on to repeat the above process. 7

Photodetectors for CMOS image sensors behavior of minority carriers is important In p-type substrate minorities are electrons infrared (IR) penetrate up to 10 μm Diffusion of minorities to adjacent

8 Photodetectors for CMOS image sensors behavior of minority carriers is important In p-type substrate minorities are electrons infrared (IR) penetrate up to 10 μm Diffusion of minorities to adjacent photodiodes image blurring. A PD is usually operated in accumulation mode. Photocarriers are swept to the surface due to the potential well in the depletion region Ohta-2007 The potential voltage decreases voltage drop the light power 8

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10 Blooming The pixels potential well has got specified capacity. If quantity of charge is too large, then it diffuses into potential wells of surrounding pixels. 10

11 CMOS: pros & cons listing 1. Low power consumption. work at low voltage 2. Lower cost 4. Miniaturization 5. Random access of image data 6. High-speed imaging. 1. Lower Sensitivity Fill Factor Quantum Efficiency 2. Higher Noise especially under low illumination 3. Small Dynamic range Ratio: saturation signal / rms noise floor 11

12 Image sensor preparation for particle detection 3 He α p D T 12

13 Electron: range energy in Silicon 13

14 A Bayer filter over the pixel sensor array 2010-Holms 14

15 Camera Sensor Pixels with RGB Color and Infrared Blocking Filters 15

16 The back-illuminated BT sensor showed nearly 100% efficiency. computing the size, charge and coordinates of the center of each alpha cluster detected. Maneuski-2011 measurements in a light tight box 241 Am (activity 4.6 kbq) source 5.48 MeV alpha particles 16

17 Total Ionizing Dose (TID) via Dark Current (DC) analysis 1) 60 Co irradiation at room temperature 2) Sample is unbiased 3) Integration time is 3 seconds 2010-Beaumel 17

18 GeigerCam: Measuring Radioactivity with Webcams use morphological clustering to group pixels into particle impact events and analyze their energies. Thomas Auzinger,

19 Dead time The frame rate was 30 Hz, but there were only six different frames per second gathered. It could be caused by large quantity of generated charge that could not be discharged by circuits in the image sensor. The dead time of this detector is 5 cycles, which corresponds to 1/ 6 s, compared to the dead time of Geiger-Müller counters of about 10 4 s 19

20 Radon monitor electrostatic concentrator 2013-Griffin 20

21 Radon measurements: β α 2013-Griffin 21

22 Linearity & Sensitivity Sensor has a thickness of less than 10 μm 1) The excellent linearity 2) For X-rays, the blue component has higher sensitivity Kang

23 X-ray energy dependence Kang

24 Gamma-ray dose rate dependence 137 CS: 662 kev Kang

25 Other Gamma-rays Kang

26 CellRAD CellRAD is a system of software that runs on off-the-shelf unmodified Android cellphones. It uses the camera of the phone to detect gamma radiation. 26

27 Dark current distribution low dose CMOS CHARACTERISTICS Shift of distribution Due to TID Dark current spectroscopy: Second peak is related to deep-level traps 2014-Virmontois 27

28 Dark current distribution high dose Shift of distribution Due to TID Spikes are related to Displacement damages 2014-virmontois 28

29 CMOS image sensors as X-ray imagers 1 mm High-resolution X-ray micro-imaging X-ray beam monitor 2015-Castoldi 29

30 CMOS image sensors as particle beam monitors 1 up to 6 MeV proton beam Image of a single 1 MeV proton detection Castoldi 30

31 The CMOS imager: Commercial APTINA MT9V011 Fixed Pattern Noise (FPN) Suppression -5σ 2015-Perez 31

32 Response of CMOS to γ, β rays and α particles 137 Cs(γ ray): 662 kev 55 Fe: 5.90 kev or 6.5 kev X-ray 137 Cs( β ray): 514, 1176 kev 2015-Perez 32

33 Response of CMOS to neutrons 2018-Prez 33

34 Am-241 α particle E= 5485, 5443, 5388 kev phosphorus-32 β particle E max = 1711 kev 2018-Nelson 34

35 Photodiode Sensor (PD) Monolithic Active Pixel Sensor (MAPS) Improved Fill factor Complementary Sensor Active Pixel sensor (CAPS) Improved Fill factor diffusion drift 35

36 A 4-T APS structure 2008-Rao 36

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38 Disadvantages: 38

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40 Complementary active pixels sensors (CAPS) 40

41 Complementary active pixels sensors (CAPS) The main new features are that the reset transistor is replaced by a PMOS. Apply bias voltage to bulk rely on drift instead of diffusion Take care of inter-pixel isolation Avoid charge collection on parasitic wells by shielding them inside a deep n-well 41

42 Pixelated Silicon as a sensor: Keller 42

43 Pixelated Silicon Keller 43

44 Pattern Recognition: Keller 44

45 different topology shapes detected with a CCD a high-energy proton ---- or a neutron-induced reaction with three ejected evaporation particles 2014-Saoud 45

46 Conclusions: CMOS sensors are applicable to: Radiation dosimetry Particle tracking Particle identification Beam monitoring X-ray imaging CMOS sensors are available at low cost (COTS) 46

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48 References: Ohta, J. (2007). Smart CMOS image sensors and applications. CRC press. Holms, A., & Quach, A. (2010). Complementary Metal-Oxide Semiconductor Sensors. Maneuski, D., Blue, A., Hynds, D., Mac Raighne, A., & O'Shea, V. (2011). Evaluation of silicon active pixel sensors for alpha particle detection. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 659(1), Beaumel, M., Herve, D., & Van Aken, D. (2010). Cobalt-60, proton and electron irradiation of a radiation-hardened active pixel sensor. IEEE Transactions on Nuclear Science, 57(4), Auzinger, T., Habel, R., Musilek, A., Hainz, D., & Wimmer, M. (2012, August). GeigerCam: measuring radioactivity with webcams. In SIGGRAPH Posters (p. 40). 48

49 References: 49

50 Classical MAPS HV/HR-CMOS Apply bias voltage to bulk rely on drift instead of diffusion Avoid charge collection on parasitic wells by shielding them inside a deep n-well Take care of inter-pixel isolation after irradiation by suitable techniques Often a rather classical charge-sensitive amplifier with leakage current compensation is used at the expense of larger pixels New applications opening up? 50

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Fundamentals of CMOS Image Sensors

CHAPTER 2 Fundamentals of CMOS Image Sensors Mixed-Signal IC Design for Image Sensor 2-1 Outline Photoelectric Effect Photodetectors CMOS Image Sensor(CIS) Array Architecture CIS Peripherals Design Considerations