Analysis of X-Ray Photo-Charge Induced Speckles in a Radiation Hardened CMOS Image Sensor

an author's https://oatao.univ-toulouse.fr/23025

Allanche, Timothé and Goiffon, Vincent and Rizzolo, Serena and Paillet, Philippe and Chabane, Aziouz and Duhamel, Olivier and Muller, Cyprien and Magnan, Pierre and Clerc, Raphael and Marin, Emmanuel and Boukenter, Aziz and Ouerdane, Youcef and Girard, Sylvain Analysis of X-Ray Photo-Charge Induced Speckles in a Radiation Hardened CMOS Image Sensor. (2017) In: Radiation and Its Effects on Components and Systems (RADECS 2017), 2 October 2017 - 6 October 2017 (Genève, Switzerland).

T. Allanche, V. Goiffon, S. Rizzolo, C. Muller, P. Paillet, O. Duhamel, P. Magnan, A. Chabane, F.Corbière, S.Rolando, R. Clerc, E. Marin, A. Boukenter, Y. Ouerdane and

S. Girard

t.allanche@univ-st-etienne.fr

Analysis of X-Ray Photo-charge Induced Speckles in a

Radiation Hardened CMOS Image Sensor

Thanks to the studies about permanent, single effects and transient effect on CMOS Image Sensor (CIS), their hardness to radiation is increasing, allowing to use CIS in radiation environments associated with higher dose rates. It then

becomes mandatory to study the induced photo-current to quantify and predict the generated speckles and the image quality degradation with respect to the selected CIS operation conditions.

0 _1x104 2x104 3x104 4x104 5x104 6x104 7x104 20 40 60 80 1x103 2x103 3x103 4x103 5x103 0 1000 2000 a)

Number of

Px

Photo generated electrons (e-)

3krad/h 77.5krad/h 1500krad/h 300krad/h 400krad/h 750krad/h 1Mrad/h 20Mrad/h b)

Photo generated electrons (e-)

3krad/h 77.5krad/h

Main results

Set-Up

 Evolution Gaussian-like shape with an

increasing standard deviation until saturation.

 The evolution of the generated

photo-current is almost linear with the dose rate We irradiated a CMOS Image Sensor with

X-rays, to measure the induced photo-current. We studied the effect of :

 Energies up to 120 keV

 Dose rates from 3krad/h to 30Mrad/h

 Integration time from 0.135ms to 13.5ms

Conclusion

 Development of a set-up in order

to quantify the induced

photo-current.

 Highlighting the effects of each

parameter: dose rate, integration

time…

 The integration time and sensitive

volume have to be small to

minimize the photo-current.

 Simulation has to be improved to

consider all operation cases

100 101 102 103 104 100 101 102 103 104 105 t _nt=0.135ms t_int=1.35ms t_int=13.5ms Aver

age generated electrons (e-)

Dose rate (krad/h)

Pixel saturation  Image at 77.5krad/h 13.5ms

𝐸

_{𝐷 𝑡𝑜𝑡}

=

𝐷 ∗ 𝑡

𝑖𝑛𝑡

∗ 𝑉

𝑃𝑥

∗ 𝜌

𝑆𝑖

𝑒𝑉

𝐸

_𝐷

= 𝐸

_𝐷

+ (1 − exp 𝜇 𝐸 𝑡

_𝑃𝑥

𝜌

_𝑆𝑖

𝐸

𝑛

_𝑒−

=

𝐸

𝐷

3.6

𝑄

𝑒𝑓𝑓

Stops when 𝑬_𝑫 = 𝑬_{𝑫 𝒕𝒐𝒕𝒂𝒍} is reached

This deposited energy generates

𝑛_𝑒− electrons.

Determination of the deposited energy 𝐸_{𝐷 𝑡𝑜𝑡} for a

given total dose.

Generated e- 0 20 40 60 80 100 120 140 0 20 40 60 80 100 120 140 160 Ph oton fl ux den sity

Photon energy (KeV)

140kV 120kV 100kV 80kV Tungsten tube 10-0

A photon is randomly chosen with a given energy E following the X–ray spectrum

density and calculate its deposit energy 𝐸_𝐷

Simulation

103 104 105 106 107 101 102 103 104 Measurement t_int=0.135ms Simulation t_int=0.135ms Measurement t_int=1.35ms Simulation t_int=1.35ms Measurement t_int=13.5ms Simulation t_int=1.35ms

Photo generated electrons per

Px (e-)