Ionization versus displacement damage effects in proton irradiated

Ionization versus displacement damage effects in proton irradiated CMOS sensors manufactured in deep submicron processV. Goiffon1 (vincent.goiffon@isae.fr)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