Radiation damage to electronic devices Radiation damage to electronic devices

for LHC and Super-LHC experimentsfor LHC and Super-LHC experiments

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Presented by Julien MekkiIES, University Montpellier II, France

CERN, Geneva, Switzerland

SeminarIPNL – Lyon – France

14th January 2011

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OutlineOutline I. Introduction

II. Packaging effect on RadFET sensors for the radiation monitoringproject

III. Forward biased p-i-n diodes used as dosimeters

IV. Perspectives and outlook on future studies

V. Conclusion

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Who am I ?Who am I ?Actual position

Assistant professor at University of Montpellier 2 – CERN USER.

Study of silicon detector performances for LHC and Super-LHC experiments.

PhD in Electronics (Nov. 2009) – (CERN, Université Montpellier 2)

Characterization and performance optimization of radiation monitoring sensors for high

energy physics experiments at the CERN LHC and Super-LHC

Master thesis in Science and Technology (2006) (CNES, EADS Astrium)

Radiation hardness of electronic components used for space applications.

February 2011:

Senior fellow at CERN – Emerging Energy Technologies department

Project: Radiation to electronics (R2E)

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CERN TechnologiesCERN Technologies Three keys technologies at CERN

Accelerating particle beams Detecting particles

Large-scale computing (Grid)Concorde(15 Km)

Balloon (30 Km)

CD stack with 1 year LHC data!(~ 20 Km)

Mt. Blanc(4.8 Km)

GRID

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CMS

The The LLarge arge HHadron adron CCollider (LHC)ollider (LHC)

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The The LLarge arge HHadron adron CCollider (LHC)ollider (LHC)

7 TeV

7 TeV

Mixed radiation fieldHadrons (n, p, k+,k-, π+, π-)

Leptons (e-, e+, μ-, μ+)

Photons

Intense close to the interaction point

General design principle

Sub-detectors:

1) Inner detectors → Trackers

2) Calorimeters → Energy deposited

3) Muon gas chamber

ATLAS

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Radiation monitoring project – Why ?Radiation monitoring project – Why ?

The effect of radiation on electronic and detector components → Major issue

All equipments → Affected by radiation damage

LHC experiments are designed to operate for 10 years.

→ Radiation level survey needed for damage and failure analysis.

Different radiation field parameters have to be monitored… Different

sensitivity and range are required… Different small active devices have been

investigated !

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Radiation monitoring project – What ?Radiation monitoring project – What ?

r (cm) Z (cm)Dose

(Gy/y)

Annual Фeq

(×1013(neq/cm2))

A 20-30 80-90 17382 2.9

B 40-50 340-350 5625 2

C 80-90 340-350 1249 1

Ionization effectTID (Total Ionizing Dose)

e.g. accumulation of charge in SiO2 : damage to microelectronic components

Unit Gray: 1 Gy = 1 Joule released in 1 kg of matter = 1 J/kg

Non-Ionizating effectNIEL (Non Ionizing Energy Loss)

causing e.g. crystal defects in semiconductor crystals: silicon detector damage

Unit: 1 MeV neutrons/ cm2 “equivalent fluence” (Фeq)

In space (Geostationary orbit) 10-30 Gy/y

ATLAS

Ideal: Measure the full radiation spectrum (particle type, energy and intensity at all locations)

→ Impossible (there is no such device)

Luminosity: 1034 cm-2.s-1

Many radiation sensors tested, only few of them was selected and installed in the LHC experiments

2 major issues:

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Radiation monitoring project – How ?Radiation monitoring project – How ?

2 types of RadFET:250 nm oxyde thickness → REM,UK1600 nm oxyde thickness → LAAS, France

BPW34 Commercial Silicon p-i-n diodes

Measure of the 1-MeV Фeq

Measure of the TID

Many radiation sensors tested, only few of them was selected and installed in the LHC experiments

2 major issues:

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Radiation monitoring project – How ?Radiation monitoring project – How ?

2 types of RadFET:250 nm oxyde thickness → REM,UK1600 nm oxyde thickness → LAAS, France

BPW34 Commercial Silicon p-i-n diodes

Measure of the 1-MeV Фeq

Measure of the TID

Packaging can induce possible dose enhancement in the measurements.

The only freedom remaining in the design is the chip carrier cover.

But, like the chip carrier, it has an effect on the TID measurement.

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Packaging effect on Packaging effect on

RadFET sensors for the RadFET sensors for the

radiation monitoring projectradiation monitoring project

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RadFETs GeneralRadFETs General(1) e-/h+ pair generation;

(2) e-/h+ pair recombination;

(3) e- / h+ transport;

(4) hole trapping;

(5) Interface state.

Build-up of charge in SiO2

increase of the p-MOS Threshold Voltage integrated

Dose Measurement

Exposure: “zero bias”Readout: iDS

VGS TID∝

γ-neutron Irradiation

Chip carrier was placed into the reactor core Various materials and thicknesses Measurement: dose

Slight increase of TID was measured for thicknesses exceeding 1 mm.

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Ref : F. Ravotti. Phd thesis, University Montpellier II, France.

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Packaging Effect on RadFET sensorsPackaging Effect on RadFET sensors

How the RadFETs response is influenced by the cover ?

and also ….

How much dose is deposited by different particles with different energies in the RadFETs ?

RadFET response studied using the simulation toolkit:

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What is What is

C++ based / Object Oriented Toolkit for the simulation of particle interactions with matter.

Geant4 provides the possibility to describe accurately an experimental setup. (Geometry and Materials)

GEometry ANd Tracking

The program provides the possibility of generating physics events and efficiently track particles through the simulated detector.

The interactions between particles and matter must be simulated by taking into account all possible physics processes, for the whole energy range.

Geant4 ModelGeant4 Model

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Packaging

REM-TOT-500

LAAS-1600

Without cover With ceramic cover

Chip carrier has been hit perpendicularly in the front side.

Result of the simulation is the total energy deposited by primary and secondary

particles.

First set of simulation:→ Full dies size are taken as sensitive volume

Second set of simulation:→ sensitive volume: thin oxide Layer (SiO2)

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Packaging comparisonPackaging comparison

Results for Pions:

Charged hadrons are dominated by pions close to the interaction point.

Most important contribution on the total energy deposited in a mixed field.

Low energy pions are absorbed in the cover.

Simulation have been carried out for all particles and energies present in the LHC radiation field.

RadFET sensors in the ATLAS detectorRadFET sensors in the ATLAS detector

Provide information about the TID in the LHC experiments

260 µm cover has been investigated and compared to uncovered RadFETs

2 locations are taken as example:Inner detector (1)Liquid Argon Calorimeter (2)

Estimation of the total energy deposited in the RadFETs as well as the cover effect for each particle type.

1

2

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% of the total number

of particles

Annual dose without cover in

units of kGy/year and

(contribution %)

Annual dose with cover in units

of kGy/year and

(contribution %)

Dose enhancement (%)

(260µm /no-cover)

Protons 1.2 1.73×100 (26.7) 1.65×100 (22.9) -4.3

Photons 54.9 2.46×10-2 (0.4) 8.29×10-2 (1.1) 237.1

Electrons 5.9 1.13×100 (17.4) 1.34×100 (18.4) 19.4

Pions 10.8 2.89×100 (44.7) 3.39×100 (46.4) 17.2

Neutrons 25.2 3.17×10-2 (0.5) 3.72×10-2 (0.5) 17.2

Muons 1.9 6.66×10-1 (10.3) 7.42×10-1 (10.5) 11.5

Total dose enhancement: 12.1±1 % 

About 45 % of the energy is deposited by pions.

Significant dose enhancement for photons due to secondary particles.

Photons deposit less than 2 % of the overall energy.

Detailed results for the Inner Detector :

ResultsResults

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ResultsResults

Pions: Pions are charged hadrons: heavy particles

Mass 270 times higher than e-.

Energy deposited → Bragg peak

Photons: Secondary particles (e-, e+)

→ Compton, pair production effects

→ Photonuclear absorption (α)

Energy deposited in the medium (MeV.cm-2.g-1)

Depth (cm) Bragg peak

Compton e-Alpha (e-; e+)

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ResultsResults

Results for the Liquid Argon Calorimeter:

Total Dose enhancement = 23.6 ± 2.4%

Pions represent 0.1 % of particles → contribution to dose ≈ 7 %

Protons deposit about 35% of the overall energy

(represent only 0.08 % of particles, but mass 1800 times higher than e-.)

Annual dose values in the covered and uncovered RadFET sensors for both locations.

Inner Detector Liquid Argon Calorimeter

Simulated TID (SiO2)Without cover With cover Without cover With cover

6.5 kGy/year 7.3 kGy/year 5 Gy/year 6.1 Gy/year

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Conclusion of this studyConclusion of this study Dose enhancement as TID was simulated using Geant4 for all particles and energies

present within the LHC radiation field.

Understanding of each particle and energy influence.

260 µm thick Alumina cover can alter the measured dose up to 25 %.

The choice of RadFET packages is thus important for measuring the TID in High Energy Physics Experiments.

Study published in J. Mekki et al, IEEE TNS, vol. 56, no. 4, pp. 2061-2069, 2009.

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Forward biased p-i-n diodes Forward biased p-i-n diodes

used as dosimetersused as dosimeters

2 major issues:

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Radiation Monitoring at the LHC ExperimentsRadiation Monitoring at the LHC Experiments

2 types of RadFET:250 nm oxide thickness → REM,UK1600 nm oxide thickness → LAAS, France

BPW34 Commercial silicon p-i-n diodes

Measure of the 1-MeV Фeq

→ 108 ≤ Фeq ≤ 1014 -1015 neq/cm2 for LHC

Measure of the TID

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p-i-np-i-n diodes (NIEL) diodes (NIEL)

Displacement damage in high Si-

base

Resistivity increases vs Фeq

FORWARD BIASFORWARD BIAS

Fixed IF VF Фeq

VF = (material parameters, geometry [W], readout current [J], pulse length)

VF

iF

BPW34 p-i-n diode:

Thickness ≈ 300 µm,

Area = 2.65×2.65 mm2,

ρ ≈ 2.7 kΩ.cm

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Hadron sensitivity range from 2×1012 to 4×1014 neq/cm2.

Perspectives for the future Super-LHC: Luminosity and radiation level (×10). Detectors will be exposed to fluences up to 1016 1-MeV equivalent neutrons.

A solution to measure very high fluences has to be found

Readout protocol for LHCReadout protocol for LHCBPW34 diodeBPW34 diode

FORWARD BIASFORWARD BIAS

Fixed Readout Current IF VF Фeq

IF = 1 mA with a short duration pulse

F. Ravotti et al., IEEE TNS, vol. 55, no. 4,pp. 2133-2140, 2008

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First studyFirst study

New readout protocol

Different current steps of 50ms pulse duration

Current used: 10µA – 100µA – 1mA – 5mA – 10mA – 15mA – 25mA

Increase of bulk resistivity with Фeq

Thyristor - like behavior (F. Ravotti et al, IEEE TNS, vol. 55, no. 4, pp. 2016-2022, 2008.)

Self-heating of the diode

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Detailed study of the detectors behaviorSecond StudySecond Study

Modifications of the electrical properties of the material

Development of 2 tests benches for the detector characterization

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2 differents regimes can be distinguished:2 differents regimes can be distinguished:

At low fluences:At low fluences:

1)1) At low voltages a At low voltages a linear linear regionregion can be observed. can be observed.

2)2) As VAs VF F increases: linear increases: linear

region → region → sharp increase of sharp increase of IIFF..

Second study(1/2)Second study(1/2) I-V curves fI-V curves from rom very low voltages very low voltages (=1mV), (=1mV), to high voltages.to high voltages.

Up to Up to 6.26×106.26×1015 15 nneqeq/cm/cm22 (60% of the expected Super-LHC fluences)(60% of the expected Super-LHC fluences)

First regime:First regime:

For

war

d cu

rren

t (A

)

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Rise of IF vs Фeq increases up to ≈ 1 × 1013 neq/cm2

Second regime:Second regime:

Second study (2/2)Second study (2/2)

1)1) For For ФФeq eq > 1 × 10 > 1 × 10 13 13 nneqeq/cm/cm22, I-V , I-V

characteristics are linear at low voltages.characteristics are linear at low voltages.

2)2) With further increase of the radiation With further increase of the radiation level, this linear behaviour level, this linear behaviour extend to extend to higher Vhigher VFF..

For

war

d cu

rren

t (A

)

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New formulation (1/3) New formulation (1/3) This new formulation is based on the This new formulation is based on the relaxation material theoryrelaxation material theory

Relaxation materials have a large density of g-r centers near ERelaxation materials have a large density of g-r centers near Egg/2./2.

Recombination pins the fermi level at minimum conductivityRecombination pins the fermi level at minimum conductivity

Maximum resistivity:

ipn nq 2/1max )(2

1

(see references in my PhD thesis)(see references in my PhD thesis)

http://jmekki.web.cern.ch/jmekki/2009-11-27-Thesis-Mekki.pdf

For

war

d cu

rren

t (A

)

Фeq

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New formulation (2/3)New formulation (2/3) Relaxation materials were experimentally fitted as :

For For IIF F > 1mA> 1mA, possibility to have thyristor-like behavior, possibility to have thyristor-like behavior11 and/or self-heating effect. and/or self-heating effect.

1F. Ravotti et al., IEEE TNS, vol. 55, no. 4,pp. 2133-2140, 2008

eqV 0cteG max0

00 exp

V

VVGI

For

war

d cu

rren

t (A

)

For

war

d cu

rren

t (A

)

IF ≥ 1mA

IF ≤ 1mA

FIT

Фeq = 6.3×1014 neq/cm2 Фeq = 6.3×1015 neq/cm2

IF ≥ 1mAIF ≤ 1mA

FIT

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New formulation (3/3)New formulation (3/3) At the LHC experiments, BPW34FS diodes are operated in forward bias.

A new formulation to predict and monitor values of VF versus Фeq:For Фeq ≥ 1×1013 neq/cm2

For IF ≤ 1mA

Based on:

IF = 1 mA

IF = 100 μA

IF = 10 μA

00

0 VG

ILambertWVV F

FLambertW(x) function is the inverse function of:

)()( xexxf

cteG max0

eqV 0

00 exp

V

VVGI FFF

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Qualitative evaluation of the Qualitative evaluation of the temperature dependencetemperature dependence

Temperature Coefficient < 0

ni increases with T°, so ρmax decreases when T° increases.

ipn nq 2/1max )(2

1

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Conclusion of this studyConclusion of this study Effects on radiation damage up to 6.3×1015 neq/cm2 on the OSRAM BPW34FS silicon

p-i-n diode have been studied.

Comparison with relaxation materials.

New formulation to predict VF versus Фeq for:

Фeq ≥ 1×1013 neq/cm2

IF ≤ 1mA

Sensitivity is increased, and Фeq measurement range can be expanded when diode is measured at lower temperature.

Summary:

Allow to extend the existing readout protocol. (IF = 1 mA)

Permit to predict radiation response for expected SLHC fluences.

Study published in J. Mekki et al, IEEE TNS, vol. 57, no. 4, pp. 2066-2073, 2010.

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Perspectives and outlook on Perspectives and outlook on

future studiesfuture studies

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Perspectives and outlookPerspectives and outlook

BPW34 p-i-n diode can be used for monitoring LHC and Super-LHC fluences from 2×1012 neq/cm2.

2 possibility already exists:

→ Pre-irradiation allows to measure Фeq > 8×109 neq/cm2.

→ CMRP diode (Thickness = 1 mm; Area = 1.2 mm2, ρ ≈ 10 kΩ.cm):

1×108 < Фeq (neq/cm2 ) < 2×1012

With the intention to develop our specific dosimeter

→ An investigation on custom made devices (high resistivity silicon detector)

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Silicon DetectorsSilicon Detectors

Tested devices were made from n-type FZ and MCz silicon wafers.

Geometry dependence on the detector’s radiation response has been evaluated.

→ 2 different active area: 2.5×2.5 cm2 and 5×5 cm2

→ 2 different thicknesses: 300 µm and 1000 µm

Outcome:

The device thickness is the main parameter which influence

their radiation response.

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Silicon DetectorsSilicon DetectorsReadout Current

Detector A

(300 µm)

Detector B

(1000 µm)

100 µA 9.1×109 cm-2/mV 3.2×108 cm-2/mV

1 mA 4.2×109 cm-2/mV 1.9×109 cm-2/mV

Sensitivity is increased by a factor ≈ 25

Thick detector

Thin detector

Study published in J. Mekki et al, IEEE TNS, vol. 57, no. 6, pp. 3483-3488, 2010.

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Silicon DetectorsSilicon DetectorsReadout Current

Detector A

(300 µm)

Detector B

(1000 µm)

100 µA 9.1×109 cm-2/mV 3.2×108 cm-2/mV

1 mA 4.2×109 cm-2/mV 1.9×109 cm-2/mV

Sensitivity is increased by a factor ≈ 25

Фeq = 2×1010 neq/cm2

Thick detector

Фeq = 2×1012 neq/cm2

Thin detector

Фeq ≈ 8×1012 neq/cm2

Thick detector

Study published in J. Mekki et al, IEEE TNS, vol. 57, no. 6, pp. 3483-3488, 2010.

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General ConclusionGeneral Conclusion Monitor the LHC radiation field: 2 devices

→ RadFET (TID)

→ p-i-n diodes (Фeq)

RadFETs:

Evaluation of packaging configurations

Evaluation of the TID and package impact on a real LHC experiment.

→ Dose enhancement up to 25 %

p-i-n diodes:

New formulation for monitoring very high fluences (Super-LHC).

At low temperature → expand to higher fluences

Custom made devices :

Sensitivity for low Фeq can be improve using thicker p-i-n diodes or detectors.

Thank you for your attentionThank you for your attention

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Thank you for your attentionThank you for your attentionThe Atlas Detector

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Normal readout protocol:

Wait for temperature stabilization inside the diode after each measurement:

Outcome:Problem for measuring at high injection level due to self-heating.

VF at IF = 100µA

VF at IF = 10µA

50ms 50ms 50ms 50ms 50ms

VF at IF = 10µA VF at IF = 10µA

VF at IF = 1mAVF at IF = 25mA

50 ms

Measurement

VF1 at IF = 10µA VF2 at IF = 10µA

• After measurement VF2 < VF1 (self-heating)

• Wait intil VF2=VF1

Self heating

Self heating

Self heating effect Self heating effect

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Summary of the relaxation materials theory (1/3)Summary of the relaxation materials theory (1/3)

Relaxation theory occurs when the material has high resistivity, and contains defects due to impurities or damage which enhance the G-R rate.

Definition of the dielectric relaxation time:

Time to restore charge neutrality to a region when excess carrier are suddently introduced.

When excess carriers are injected across the PN junction, at the instant of injection (t=0), there will be an excess charge (Δn,p) , so that charge neutrality is disturbed.

It is assumed to be the bulk equivalent of a RC time constant :

τD = ρεε0

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Summary of the relaxation materials theory (2/3)Summary of the relaxation materials theory (2/3)

Example: Injection of minority carriers in the n side (Δp):

p(x)

x

p0

Δp

n(x)

x

n0

Diffusion of holes (gradient of holes)

At t = 0 → there are excess holes but no excess e-

e- (Δn) are attracted in this region by drift because of the field induce by Δp.

p(x)

x

p0

Δp

n(x)

x

n0

Δn

Δn flow in from the contact to neutralize Δp

This neutralization occurs in a dielectric relaxationtime (τD).

While neutrality is quickly established, Δp diffuse slowly and recombine with e- so that there is still excess charges in the material : The conventionnal carrier lifetime τ0

Resistivity is decreased by the enhancement of carrier in the material.

In conventionnal lifetime material, neutrality is restored before excess carrier recombine. τ0 >> τD

The np product is equal to: np = ni2×exp[(Фn-Фp)/kT]; Фn and Фp are the quasi-fermi levels for e- and h+ , and is

dependent on the applied voltage.(V = Фn-Фp)

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Summary of the relaxation materials theory (3/3)Summary of the relaxation materials theory (3/3)

For irradiated diodes, the material becomes highly recombinative do to high density of recombination centers.

Minority carrier injection increases the resistivity since the concentration of minority and majority carriers is reduced by recombination. τD = ρεε0 increases. τD >> τ0

Injected minority carrier lead to a depletion of majority carriers through the g-r centers activity. Therefore the carrier equilibrium is rapidly reached → no possible to influence it by externally applied voltage.

Recombination pins the fermi level at minimum conductivity (defect near Eg/2)Recombination pins the fermi level at minimum conductivity (defect near Eg/2)

→ np = ni2 as for the steady-state condition in lifetime diode.

Maxiumum resistivity of Silicon : Maxiumum resistivity of Silicon :

ipn nq 2/1max )(2

1

kT

qVn

kT

qnnp i

npi exp

)(exp 22

in n

n

q

kTln

ip n

p

q

kTln

q

Ei