application of cmos sensors in radiation...
TRANSCRIPT
Application of CMOS sensors in radiation detection
S. Ashrafi
Physics FacultyUniversity of Tabriz
1
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 …
CMOS is a technology for making low power integrated circuits.
2
Architecture of a CMOS image sensor
photodetector
tran
sisto
rs
access a pixeland read the signal value
3
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
Basic configuration of CMOS image sensor.
MSF = source follower transistor
MSEL = select transistor
An n-MOSFET structure is shown:MRS = reset transistor
source is a PD
drain is biased at Vdd
gate is off-state.
5
Potential profile
Ohta-2007
The impurity density in the sourceis smaller than that in the drain.
electron density
n MOSFET
6
The operation of an APS is as follows:
First, the reset transistor MRS is turned on. This resets VPD to (Vdd −Vth), where Vth is the threshold voltage of transistor MRS.
Then, MRS is turned off and the PD is electrically floated.
When light is incident, the photo-generated carriers accumulate in the PD junction capacitance CPD. The accumulated charge decreases VPD according to the input light intensity.
After an accumulation time of 33 msec , (at video rate), the select transistor MSEL 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, MSEL is turned off and MRS 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 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
• The potential voltage decreases
• voltage drop ∝ the light powerOhta-2007
8
9
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
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
2. Higher Noise
3. Small Dynamic range
Fill Factor × Quantum Efficiency
especially under low illumination
Ratio: saturation signal / rms noise floor
11
α3He
p
TD
Image sensor preparation for particle detection
12
Electron: range – energy in Silicon
13
A Bayer filter over the pixel sensor array
2010-Holms
14
Camera Sensor Pixels with RGB Color and Infrared Blocking Filters
15
computing the size, charge and coordinates of the center of each alpha cluster detected.
measurements in a light tight box 241Am (activity 4.6 kBq) source 5.48 MeV alpha particles
The back-illuminated BT sensor showed nearly 100% efficiency.
Maneuski-2011
16
Total Ionizing Dose (TID) –via Dark Current (DC) analysis
1) 60Co irradiation at room temperature2) Sample is unbiased 3) Integration time is 3 seconds 2010-Beaumel
17
Thomas Auzinger, 2012
GeigerCam: Measuring Radioactivity with Webcams
use morphological clustering to group pixels into particle impact events and analyze their energies.
18
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
Radon monitor
2013-Griffin
electrostatic concentrator
20
2013-Griffin
β
α
Radon measurements:
21
Linearity & Sensitivity
Kang 2016
2) For X-rays, the bluecomponent has higher sensitivity
1) The excellent linearity
Sensor has a thickness of less than 10 μm
22
X-ray energy dependence
Kang 2016
23
Gamma-ray dose rate dependence 137CS: 662 keV
Kang 2016
24
Other Gamma-rays
Kang 2016
25
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.
CellRAD
26
Dark current distribution – low dose
CMOS CHARACTERISTICS
Dark current spectroscopy: Second peak is related to deep-level traps
Shift of distributionDue to TID
2014-Virmontois
27
Dark current distribution – high dose
Shift of distributionDue to TID
Spikes are related to Displacement damages
2014-virmontois
28
CMOS image sensors as X-ray imagers
High-resolution X-ray micro-imaging X-ray beam monitor
2015-Castoldi
1 mm
29
CMOS image sensors as particle beam monitors
1 up to 6 MeV proton beam
Image of a single 1 MeV proton detection.
2015-Castoldi
30
Fixed Pattern Noise (FPN) Suppression
2015-Perez
-5σ
The CMOS imager: Commercial APTINA MT9V011
31
55Fe: 5.90 keV or 6.5 keV X-ray
137Cs(γ –ray): 662 keV
137Cs( β–ray): 514, 1176 keV
Response of CMOS toγ, β – rays and α particles
2015-Perez 32
2018-Prez
Response of CMOS to neutrons
33
phosphorus-32 β particleEmax= 1711 keV
Am-241 α particleE= 5485, 5443, 5388 keV
2018-Nelson
34
PhotodiodeSensor(PD)
MonolithicActive Pixel Sensor (MAPS)
ComplementarySensor Active Pixel sensor(CAPS)
ImprovedFill factor
diffusion
ImprovedFill factor
drift
35
2008-Rao
A 4-T APS structure
36
37
Disadvantages:
38
39
Complementary active pixels sensors (CAPS)
40
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
The main new features are that the reset transistor is replaced by a PMOS.
Complementary active pixels sensors (CAPS)
41
Pixelated Silicon as a sensor:
Keller
42
Pixelated SiliconKeller
43
Pattern Recognition:
Keller
44
a neutron-induced reaction with three ejected evaporation particles
2014-Saoud
a high-energy proton---- or----------
different topology shapes detected with a CCD
45
Conclusions:
CMOS sensors are applicable to:
Radiation dosimetry
Particle tracking
X-ray imaging
Particle identification
Beam monitoring
CMOS sensors are available at low cost (COTS)
46
47
Ohta, J. (2007). Smart CMOS image sensors and applications. CRC press.
References:
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), 328-332.
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), 2056-2065.
Auzinger, T., Habel, R., Musilek, A., Hainz, D., & Wimmer, M. (2012, August). GeigerCam: measuring radioactivity with webcams. In SIGGRAPH Posters (p. 40).
48
References:
49
“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 adeep n-well■ Take care of inter-pixel isolation after irradiation by suitable techniques■ Often a rather classical charge-sensitive amplifier with leakage currentcompensation is used at the expense of larger pixels■ New applications opening up?
50
51
52