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Ionization versus displacement damage effects in proton irradiated CMOS sensors manufactured in deep submicron processV. Goiffon1 ([email protected])P. Magnan1, O. Saint-pé2, F. Bernard3, G. Rolland31 Université de Toulouse, ISAE, 2 EADS Astrium, 3 CNES
Test chip :• 0.18 µm CMOS CIS technology• Dedicated photodiode doping profiles• Shallow trench isolations (STI)• 128 x 128 pixel array, 3T, 10µm pitch• Larges photodiodes (>104 µm²)• Other test structures (MOSFETs, Gated-diodes…)Proton irradiation :• Facilities : KVI, UCL, Isotron• Energies : 7.4 to 200 MeV• Fluences : 5 x 109 to 3 x 1011 H+/cm²
0 1000 2000 3000 40000
20
40
60
80
100
120
140
Diode perimeter (µm)
Rev
erse
cur
rent
at 2
.4V
(fA
)
Peripheral dark current
IC1, 8.8×109 H+/cm2, 50MeV
IC2, 1.5×1010 H+/cm2, 100MeV
IC3, 2.4×1010 H+/cm2, 184MeVIC1 no irrad.IC2 no irrad.IC3 no irrad.
0 0.5 1 1.5 2 2.5 30
50
100
150
200
Reverse voltage (V)
Rev
erse
cur
rent
(fA
)
2000x5µm2 photodiode dark currents
IC1, 8.8×109 H+/cm2, 50MeV
IC2, 1.5×1010 H+/cm2, 100MeV
IC3, 2.4×1010 H+/cm2, 184MeVIC1 no irrad.IC2 no irrad.IC3 no irrad. A
+
Proton irradiations only induce large dark current increases … …dominated by the perimeter contribution…
…due to ionizing dose induced STI trapped charges and
interface states.
Effects on large photodiodes
Overview
Experimental
Effects on CMOS sensors Perspectives
• No photoresponse degradation , no voltage shift, no gain reduction
No sign of electric field enhancement at the Si-STI interface
Displacement damages still play a significant role in uniformity
degradation
• Photodiode hardened against ion-izing dose effect could conse-quently reduce proton irradiation effects
• In-pixel gated photodiode (B. Hancock, Proc. SPIE 4306, 2001) seems promising
• Multi level random telegraph signals will be studied in detail
0 10 20 30 40 50 601
1.5
2
2.5
3
3.5
4x 10
-15
Time (s)
Dar
k cu
rren
t (A
)
Proton induced RTS
0 1 2 3 4 5 60
0.2
0.4
0.6
0.8
1
Dark current (fA)
Act
ivat
ion
ener
gy (
eV)
Activation energies after 50 MeV 8.8×109 H+/cm2
pixel valuemean value
Displacement damages effects on mean dark current are negligible…
… in front of ionizing dose : peripheral STI is responsible
Goal : Study of proton irradiation effects on CMOS sensorsmanufactured in a deep submicron technology dedicated to imaging applications
Test structures : pixel array + isolated large photodiodes
Main result : Proton irradiations mainly induce dark current increases due to ionizing interactions
101
102
103
10-16
10-15
10-14
Displacement damage dose (TeV/g)
Dar
k cu
rren
t inc
reas
e (A
)
Dark current increase vs. displacement damage dose
MeasurementComputed displacement contribution
101
102
10-16
10-15
10-14
Ionizing dose (Gy)
Dar
k cu
rren
t inc
reas
e (A
)
Dark current increase vs. ionizing dose
Proton irrad.Proton irrad. without hot pixels60Co irrad. (worst case)
0 1 2 3 4 5 610
0
101
102
103
Dark current (fA)
Pix
el c
ount
50 MeV 8.8x109 H+/cm2
MeasurementsIonizing dose estimation