Radiation Damage in Silicon Detectors - CERN...2014/01/02 · Michael Moll - CERN EP-TA1-SD Seminar - 14.2.2001 - 4 - Primary Damage PKA - Primary Knock on Atom Simulation (Fig.:

Radiation Damage in Silicon Detectors- An introduction for non-specialists -

Michael MollMichael Moll

CERN EP - GenevaCERN EP - Geneva

ROSE CollaborationROSE Collaboration (CERN RD48(CERN RD48))

ROSE - Research and DevelopmentROSE - Research and Developmenton Silicon Detectors for Future Experimentson Silicon Detectors for Future Experiments

http://www.cern.ch/rd48http://www.cern.ch/rd48

CERN EP-TA1-SD Seminar 14.2.2001

Michael Moll - CERN EP-TA1-SD Seminar - 14.2.2001 - 2 -

Outline♦ Motivation - The challenge of LHC-experiments

♦ Radiation induced changes in silicon detector properties• Increase of leakage current

• Change of effective doping concentration (depletion voltage)

• Decrease of charge collection efficiency

♦ Radiation hard silicon detectors• Oxygen enriched silicon

♦ Damage projections for LHC operation

♦ Microscopic defects in silicon

♦ Relation between microscopic and macroscopic

properties of the damage

♦ Summary and Outlook


Motivation

♦ Promising new physical results arerelated to some very rarely producedparticles

• High event rate (109/s at LHC), verygood spatial resolution and fast signalread out required, can be fulfilled withsilicon detectors, however:

♦ Detectors and electronics will beharshly irradiated !

• ATLAS - Inner Detector:Φeq up to 3×1014cm-2

per operational year

• 10 years of operationhave to be guaranteed

0 10 20 30 40 50 60R [cm]

1012

1013

1014

1015

Φeq

[cm

-2] total Φeq

neutrons Φeq

pions Φeq

other chargedhadrons Φeq

SCT - barrelSCT - barrelPixelPixel

3x1014cm-23x1014cm-2

SCT - barrelSCT - barrel

PixelPixel

ATLAS - Inner Detector

⇒⇒⇒⇒ What is the impact on silicon detectors ?What is the impact on silicon detectors ?

⇒⇒⇒⇒ How can we make silicon radiation harder ?How can we make silicon radiation harder ?


Primary Damage♦ PKA - Primary Knock on Atom

♦ Simulation (Fig.: van Lint 1980)(Fig.: van Lint 1980)

• 50 KeV PKA(average recoil energy for PKA produced by 1 MeV neutrons)

♦ Displacement threshold in Silicon:• Single lattice atom (Frenkel pair):

Ed ≈≈ 25 eV• Defect cluster

EC ≈≈ 5 keV

♦ Neutrons (elastic scattering)• En > 185 eV for single displacement• En > 35 keV for cluster

♦ Electrons• Ee > 255 keV for single displacement• Ee > 8 MeV for cluster

♦ 60Co-gammas• Compton Electrons with max. Eγγ ≈≈1 MeV (no cluster production)


10-10 10-9 10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 100 101 102 103 104

particle energy [MeV]

10-5

10-4

10-3

10-2

10-1

100

101

102

103

104

D(E

) / (

95 M

eV m

b)

neutronsneutrons

pionspions

protonsprotons

electronselectrons

100 101 102 103 104

0.4

0.60.8

1

2

4

neutronsneutrons

pionspions

protonsprotons

Displacement damage functions

♦ NIEL - Non Ionizing Energy Loss♦ NIEL - Hypothesis:

• Damage parameters scale with the NIEL(Be careful, does not hold for all particles / damage parameters, see later)

For Silicon: 100 MeVmb = 2.14 keVcm2/g


Testing Structures - Simple Diodes

♦ Very simple structures in order to concentrate on the bulk features• Typical thickness: 300µm

• Typical active area: 0.5 × 0.5 cm2

♦ Openings in front and back contact• optical experiments with lasers or LED

♦ Different producers used (by the ROSE Collaboration)• ITE (Warsaw), Sintef(Oslo), MPI-Halbleiterlabor Munich, ELMA (Moscow), Canberra (Olen,Belgium),

Diotec (Radosina, Slovakia), Schottky-diodes (Hamburg), ST Microelectronics (Catania, Italia), CIS (Erfurt)

Example: Test structure from ITE


Standard Measurements♦♦ IrradiationIrradiation

•• MeVMeV neutronsneutrons – Reactor, Be(d,n) or T(d,n) – Reactor, Be(d,n) or T(d,n)

•• 10MeV, 23 10MeV, 23 GeVGeV protonsprotons•• 192 192 MeV MeV pionspions

•• 6060Co-Co-gammasgammas

♦♦ Measurements Measurements ⇒⇒⇒⇒ Extracted ParametersExtracted Parameters• C/V at room temperature ⇒⇒⇒⇒ depletion voltage Udep ∝∝ Neff

• I/V at room temperature ⇒⇒⇒⇒ current at depletion voltage I(Udep)

• DLTS (Deep Level Transient Spectroscopy) ⇒⇒⇒⇒ microscopic defect parameters• TSC (Thermally Stimulated Currents) ⇒⇒⇒⇒ microscopic defect parameters

♦♦ Annealing ExperimentsAnnealing Experiments• Isothermal annealing studies at 20°C…120°C

• Isochronal annealing studies 20°C…400°C

⇒⇒⇒⇒ Temperature dependent modeling ⇒⇒⇒⇒ Damage Scenarios for HEP-Experiments

Understanding of microscopic defect kinetics ⇒⇒⇒⇒ Defect Engineering


Radiation induced changes in detector properties

♦ Change of depletion voltage• Due to defect levels that are charged in the depleted region

⇒⇒ most problematic !

♦ Increase of leakage current• Bulk current due to generation/recombination levels

♦ Decrease of charge collection efficiency• Due to damage induced trapping centers


ST Microelectronics - standard diodes

♦ Different orientations (<111> and <100>) and resistivities

♦ CV measurements before irradiation

1 5 10 50 100 500bias voltage[V]

101

5

102

Cap

acita

nce

[pF]

W333-A3 (GR3477) : <111> 1KW330-A3 (GR3476) : <100> 1KW336-A3 (GR3474) : <111> 2KW335-A3 (GR3473) : <100> 2KW339-A4 (GR3475) : <111> >5K

Standard silicon : ST - Microelectronics test structures before irradiation

M.Moll | 01-S GS -S TD -CV -BEF OR E-IRR


10-1 100 101 102 103

Φeq [ 1012 cm-2 ]

1

510

50100

5001000

5000

Ude

p [V

] (d

= 3

00µm

)

10-1

100

101

102

103

| Nef

f | [

1011

cm

-3 ]

≈ 600 V≈ 600 V

1014cm-21014cm-2

"p - type""p - type"

type inversiontype inversion

n - typen - type

[Data from R. Wuns torf 92]

Neff - effective doping concentration• Neff positive - n-type silicon (e.g. Phosphorus doped - Donor)

• Neff negative - p-type silicon (e.g. Boron doped - Acceptor)

• |Neff| proportional to depletion voltage and 1/(device thickness)22effNd

Vdep∝


Systematic analysis of annealing dataExample: oxygen enriched silicon after 24 GeV/c proton irradiation

Instead of depletion voltage plot thechange in the effective space charge ∆∆Neff

5 101 5 102 5 103 5 104 5 105

annealing time at 60oC [min]

0.0

5.0.1012

1.0.1013

1.5.1013

2.0.1013

∆Nef

f [1/

cm3 ]

0.0

5.0.1012

1.0.1013

1.5.1013

2.0.1013

10.3.1014 p/cm2

6.2.1014 p/cm2

4.2.1014 p/cm2

3.4.1014 p/cm2

2.0.1014 p/cm2

1.2.1014 p/cm2

5.9.1013 p/cm2

2.9.1013 p/cm2

1.6.1013 p/cm2

24 GeV/c proton irradiation

( ) ( )tNNtN eqeffeffeqeff ,, 0 Φ−=Φ∆


1 10 100 1000 10000


0

2

4

6

8

10

∆ N

eff [

1011

cm-3

]

NY,∞ = gY Φeq

NC

NC0

gC Φeq

Na = ga ΦeqNa = ga Φeq

Annealing behavior of Neff - Hamburg model -( ) ( )tNNtN eqeffeffeqeff ,, 0 Φ−=Φ∆ ∆Neff = Change of Neff with respect

to Neff 0 (value before irradiation)

long term reverse annealing:

second order parameterization(with Ny,∞=gy×Φeq).gives best fitBut: τy independent of Φeq⇒⇒ underlying defect reaction based on first order process!

+−⋅= ∞

yYY t

NNτ/1

11,

stable damage:

incomplete „donor removal“ + introduction of stable acceptors

( )( ) eqCeqCOC gcNN Φ⋅+Φ⋅−−⋅= exp1

short term annealing:

first order decay of acceptors introducedproportional to Φeq during irradiation

∑

−××Φ=i i

aieqatgN τexp

( ) ( ) ( ) ( )tNNtNtN eqYeqCeqaeqeff ,,, Φ+Φ+Φ=Φ∆


1011 1012 1013 1014 1015

Φeq [cm-2]

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

α [1

0-17 A

/cm

]

n-type FZ - 10 to 20 KΩcmn-type FZ - 7 KΩcmn-type FZ - 4 KΩcmn-type FZ - 3 KΩcm

n-type FZ - 780 Ωcmn-type FZ - 420 Ωcmn-type FZ - 130 Ωcmn-type FZ - 110 Ωcmn-type CZ - 140 Ωcmp-type EPI - 2 and 4 KΩcm

p-type EPI - 380 Ωcm

Increase of Leakage Current

♦ Damage parameter αα• definition:

• measured after 80min at 60C: αααα80/6080/60 = (3.99 ± 0.03)10 = (3.99 ± 0.03)10-17-17 A/cm A/cm

• used for fluence (NIEL) calibration

1011 1012 1013 1014 1015

Φeq [cm-2]

10-6

10-5

10-4

10-3

10-2

10-1

∆I /

V

[A/c

m3 ]

n-type FZ - 7 to 25 KΩcmn-type FZ - 7 to 25 KΩcmn-type FZ - 7 KΩcmn-type FZ - 7 KΩcmn-type FZ - 4 KΩcmn-type FZ - 4 KΩcmn-type FZ - 3 KΩcmn-type FZ - 3 KΩcm

n-type FZ - 780 Ωcmn-type FZ - 780 Ωcmn-type FZ - 410 Ωcmn-type FZ - 410 Ωcmn-type FZ - 130 Ωcmn-type FZ - 130 Ωcmn-type FZ - 110 Ωcmn-type FZ - 110 Ωcmn-type CZ - 140 Ωcmn-type CZ - 140 Ωcm

p-type EPI - 2 and 4 KΩcmp-type EPI - 2 and 4 KΩcm

p-type E PI - 380 Ωcmp-type E PI - 380 Ωcm

♦ Increase of leakage currentindependent of:

• Conduction type (p or n), resistivity• oxygen and carbon content• crystal orientation <111>, <100>

♦ Temperature dependence:

cooling strongly reduces current

−∝ Tk

EI

B

g

2exp

eqVI

Φ⋅∆

=α


101 102 103 104 105 106

time [ min ]

1 hour 1day 1 month 1 year

0

2

4

6

8

10

α [

10-1

7 A/c

m ]

(α∞)

21oC21oC

49oC49oC60oC60oC

80oC80oC106oC106oC

W unstorf (92) α∞=2.9x10 -17A/cmW unstorf (92) α∞=2.9x10 -17A/cm

Annealing of leakage current

♦♦ Annealing at RT (21°C):Annealing at RT (21°C):• good agreement with previous parameterization ((WunstorfWunstorf 92, 92, parameters for non inverted detectors))

♦♦ Annealing at higher temperature (long term at RT):Annealing at higher temperature (long term at RT):• new parameterization:

• exponential term: activation energy: EA = 1,11eV , ν = 1.2×1013 s-1

correlated with defect at EC-0.46eV (DLTS)• logarithmic term: acceleration factor θ(T) ∝ exp(1.3 eV / kB T) ⇒ no saturation value ! (no αα∞∞)

( ) ( ))/)(ln()(/exp),( 0011 ttTTttT ⋅⋅−+−⋅= θβαταα


The ROSE Collaboration CERN-RD48(R&D On Silicon for future Experiments)

1995: formed by the Co-Spokespersons: F.Lemeilleur (CERN, now retired), G.Lindström (Hamburg, now retired), S.Watts (Brunel,London)

2000: Final report to LEB - Oxygenated silicon will be used for the pixel detectors of ATLAS/CMS 38 HEP- and Semiconductor groups (125 persons), 7 associated companies and many observers

For detailed information: http://cern.ch/rd48

Objectives:•develop radiation hard detectors whichensure operation for the whole lifetime ofthe Large Hadron Collider (LHC)experimental program

•interact with industry both for growingand defect engineering the appropriatedetector grade material as for processingdiodes in the most optimal way

•exchange know how with the LHCexperiments both as to the experimentaldemands as to recommendations fromresults of the ROSE-studies

Standardand

new material

Macroscopic parameters

Material characterization(PL, IR, DLTS, SIMS,..)

Defect kinetics(Need [O],[C],[P],[B],[Sn],..)

Defect characterization(DLTS, TSC, PL, TCT,..)

Device model

Defect engineering strategy :


Oxygen and Carbon- the key ingredients -

♦ DOFZ - Diffusion Oxygenated Float Zone Silicon• Controlled introduction of oxygen, easily included in manufacturing process,

low cost

1 01 5

1 01 6

1 01 7

1 01 8

1 01 5

1 01 6

1 01 7

Ox

yg

en

Co

nc

en

tra

tio

n -

[O

] (

cm

-3)

Carbon concentrat ion - [C] (cm- 3

)

CFZ Po lovod ice

ITME Ep i tax ia l

Two growth ra tes

MACOM Ep i tax ia l

Po lovod ice CZ

D O F Z

Standard FZ

O F Z / J E T I T M E

O F Z / G a s

Po lovod ice


0 30 60 90 120 150depth [µm]

1016

5

1017

5

[O] [

atom

s/cm

3 ] 9d 1200oC 9d 1200oC12h 1100oC12h 1100oC 6h 1100oC 6h 1100oC

Oxygen diffusion

♦ DOFZ - Diffusion Oxygenated Float Zone• Profiles measured by SIMS (Secondary Ion Emission Spectroscopy)

• Open question: Which is the minimum diffusion time/ oxygen concentration needed to get the beneficial effect ?


Leakage Current Annealing - Oxygenated Silicon

♦ Damage parameter αα: independent of ΦΦeq ,

used for fluence (NIEL) calibration

♦ Oxygenated and Standard Silicon show same annealing

1011 1012 1013 1014 1015

Φeq [cm-2]

10-6

10-5

10-4

10-3

10-2

10-1

∆I /

V

[A/c

m3 ]

n-type FZ - 7 to 25 KΩcmn-type FZ - 7 to 25 KΩcmn-type FZ - 7 KΩcmn-type FZ - 7 KΩcmn-type FZ - 4 KΩcmn-type FZ - 4 KΩcmn-type FZ - 3 KΩcmn-type FZ - 3 KΩcm

n-type FZ - 780 Ωcmn-type FZ - 780 Ωcmn-type FZ - 410 Ωcmn-type FZ - 410 Ωcmn-type FZ - 130 Ωcmn-type FZ - 130 Ωcmn-type FZ - 110 Ωcmn-type FZ - 110 Ωcmn-type CZ - 140 Ωcmn-type CZ - 140 Ωcm

p-type EPI - 2 and 4 KΩcmp-type EPI - 2 and 4 KΩcm

p-type EPI - 380 Ωcmp-type EPI - 380 Ωcm

100 5 101 5 102 5 103 5 104 5 105

annealing time at 60oC [minutes]

0

1

2

3

4

5

6

α(t)

[10-1

7 A/c

m]

1

2

3

4

5

6

oxygen enriched silicon [O] = 2.1017 cm-3oxygen enriched silicon [O] = 2.1017 cm-3

parameterisation for standard silicon parameterisation for standard silicon

eqV

I

Φ⋅∆

=α

80 min 60°°C

80 min 60°°C


Influence of Carbon and Oxygen concentration24 GeV/c proton irradiation

Compared to standard silicon:

♦ High Carbon ⇒⇒⇒⇒ less radiation tolerant♦ High Oxygen ⇒⇒⇒⇒ more radiation tolerant

ββSt = 0.0154

ββ[O] = 0.0044 ÷÷0.0053

ββ[C] = 0.0437

0

1E+12

2E+12

3E+12

4E+12

5E+12

6E+12

7E+12

8E+12

9E+12

1E+13

0 1E+14 2E+14 3E+14 4E+14 5E+14

Proton fluence (24 GeV/c ) [cm-2]

|Nef

f| [c

m-3

]

0

100

200

300

400

500

VFD

for

300

µµm

thic

k de

tect

or [V

]

Standard (P51)O-diffusion 24 hours (P52)O-diffusion 48 hours (P54)O-diffusion 72 hours (P56)Carbon-enriched (P503)

Carbonated

Standard

Oxygenated


Oxygen and standard silicon- Particle dependence -

♦ Strong improvement for pions and protons

♦ Almost no improvement for neutrons

23 GeV protons - 192 MeV pions - reactor neutrons

0 0.5 1 1.5 2 2.5 3 3.5Φeq [1014cm-2]

1

2

3

4

5

6

7|N

eff|

[1012

cm

-3]

100

200

300

400

Vde

p [V

] (

300µ

m)

neutronsneutrons

neutronsneutronspionspionsprotonsprotons

pionspionsprotonsprotons

oxygen rich FZ

standard FZstandard FZ


1 10 100 1000 10000


0

2

4

6

8

10

∆ N

eff [

1011

cm-3

]

NY,∞ = gY Φeq

NC

NC0

gC Φeq

Na = ga ΦeqNa = ga Φeq

Annealing behavior of Neff - Hamburg model -( ) ( )tNNtN eqeffeffeqeff ,, 0 Φ−=Φ∆ ∆Neff = Change of Neff with respect

to Neff 0 (value before irradiation)

long term reverse annealing:

second order parameterization(with Ny,∞=gy×Φeq).gives best fitBut: τy independent of Φeq⇒⇒ underlying defect reaction based on first order process!

+−⋅= ∞

yYY t

NNτ/1

11,

stable damage:

incomplete „donor removal“ + introduction of stable acceptors

( )( ) eqCeqCOC gcNN Φ⋅+Φ⋅−−⋅= exp1

short term annealing:

first order decay of acceptors introducedproportional to Φeq during irradiation

∑

−××Φ=i i

aieqatgN τexp

( ) ( ) ( ) ( )tNNtNtN eqYeqCeqaeqeff ,,, Φ+Φ+Φ=Φ∆


Systematic analysis of annealing dataExample: oxygen enriched silicon after 24 GeV/c proton irradiation

Instead of depletion voltage plot thechange in the effective space charge ∆∆Neff

5 101 5 102 5 103 5 104 5 105


0.0

5.0.1012

1.0.1013

1.5.1013

2.0.1013

∆Nef

f [1/

cm3 ]

0.0

5.0.1012

1.0.1013

1.5.1013

2.0.1013

10.3.1014 p/cm2

6.2.1014 p/cm2

4.2.1014 p/cm2

3.4.1014 p/cm2

2.0.1014 p/cm2

1.2.1014 p/cm2

5.9.1013 p/cm2

2.9.1013 p/cm2

1.6.1013 p/cm2

24 GeV/c proton irradiation

( ) ( )tNNtN eqeffeffeqeff ,, 0 Φ−=Φ∆

Michael Moll - CERN EP-TA1-SD Seminar - 14.2.2001 - 23 -100 5 101 5 102 5 103 5 104


0.0

0.2

0.4

0.6

0.8

1.0

NY/N

Y∞

oxygenated FZoxygenated FZ


24 GeV/c proton irradiation24 GeV/c proton irradiationnormalised reverse annealingnormalised reverse annealing

τY = 50 minτY = 50 min

τY = 220 minτY = 220 min

Extraction of damage parameters

♦ 24 GeV/c proton irradiatedO-enriched diodes

♦ gc improved by a factor of 3♦ saturation of reverse annealing

♦ delayed reverse annealing

Reverseannealing

amplitude NY

Stable damageparameter NC

0 1 2 3 4 5 6 7Φeq [1014 cm-2]

0

0.2

0.4

0.6

0.8

1

1.2

NC [

1013

cm

-3]



24 GeV/c proton irradiation24 GeV/c proton irradiation

gc=5.61 10-3cm -1gc=5.61 10-3cm -1

gc=1.93 10-2cm-1gc=1.93 10-2cm-1

0 1 2 3 4 5 6 7Φeq [101 4 cm-2]

0

0.5

1

1.5

2

2.5

NY [

101

3 cm

-3]


24 GeV/c proton irradiation24 GeV/c proton irradiation


Reverseannealing time

constant τY


Damage Projection - ATLAS Pixel Detector - B-Layer (4cm)

0 1 2 3 4 5 6 7 8 9 10

time [years]

500

1000

1500

2000

Vde

p (20

0µm

) [V

]

500

1000

1500

2000

oxygenated silicon

standard silicon

operation vol tage: 600Voperation vol tage: 600V

♦ Radiation level: nnnn ΦΦΦΦeqeq(year) = 3.5 (year) = 3.5 ×××× 10 101414 cm cm-2 -2 (full luminosity)(full luminosity) >> 85% charged hadrons 85% charged hadrons

♦ Three scenario: nnnn 1 year = 1 year = 100 days beam (-7100 days beam (-7°°°°C)C) (1) 3 (1) 3 days 20days 20°°°°C and 14 days 17C and 14 days 17°°°°CC

(2) 30(2) 30 days 20days 20°°°°CC (3) 60(3) 60 days 20days 20°°°°CC

Rest of the year: no beam (-7Rest of the year: no beam (-7°°°°C)C)


0 1 2 3 4 5 6 7 8 9 10time [years]

100

200

300

400

Vde

p (3

00µm

) [V

]

100

200

300

400

oxygenated silicon

standard silicon

Damage Projection - Strip Detector - 30 cm♦ Radiation level: nnnn ΦΦΦΦeqeq(10years) = 2 (10years) = 2 ×××× 10 101414 cm cm-2-2

≈≈≈≈ 50% charged hadrons 50% charged hadrons

♦ Scenario: nnnn 1 year = 1 year = 100100 days beam (-7days beam (-7°°°°C)C) 14 14 days 20days 20°°°°CC 251251 days no beam (-7days no beam (-7°°°°C)C)

Dashed line - 2 days 20°C and14 days 14°C warm-up


Warning: Variation of “standard material”

♦ Strong variation of standard silicon

♦ Reproducible results for oxygenated silicon

0 1 2 3 4 5 6 7 8 9 10Φproton [1014 cm-2]

0

2

4

6

8

10

12

|Nef

f| [1

012cm

-3]

100

200

300

400

500

600

700

800

Vde

p [V

] (30

0 µm

)

oxygenated FZ

standard FZ silicon


Summary (1/4) - Leakage Current♦♦ NIELNIEL - Non Ionizing Energy Loss - Non Ionizing Energy Loss

• NIEL - Hypothesis (damage parameters scale with NIEL) has to be used very carefully ! (e.g. not valid for changes in Vdep of oxygenated and standard silicon detectors)

♦♦ DevicesDevices used for investigations used for investigations• Very simple diodes in order to concentrate on the bulk damage effects

♦♦ Macroscopic Damage Effects - Macroscopic Damage Effects - Leakage CurrentLeakage Current• Strong increase of leakage current after irradiation ⇒ Cooling of detectors necessary

• Leakage current damage parameter αα - material independent (no impurity, resistivity or conduction type dependence)

- scaling with NIEL for fast neutrons, pions and protons

• Leakage current annealing after irradiation same for all type of materials

• 60Co-gamma irradiation: No leakage current (bulk current!) annealing observed at room temperature !


Summary (2/4) - Depletion Voltage

♦♦ Macroscopic Damage Effects - Macroscopic Damage Effects - Depletion Voltage Depletion Voltage -- ((NNeffeff))

• In general the space charge becomes more negative after irradiation (type inversion).The initial n-type silicon inverts to a quasi "p-type" siliconThe main depletion zone evolves from the back electrode (n+) after type inversion

• Changes in Neff consists of three basic components (neutrons, pions, protons):- Short term or beneficial annealing (Decrease of depletion voltage for inverted detectors)- Stable damage (No change in time after irradiation)- Reverse annealing (Increase of depletion voltage for inverted detectors)

• 60Co-gamma irradiation: No beneficial and no reverse annealing !

• Determination of all damage parameters (Hamburg model + many isothermal annealingexperiments) allows for the simulation of damage projections in the LHC experimentsunder various operational conditions.

• Annealing experiments (macroscopic parameters - Vdep, α) isothermal and isochronal givealready some very useful hints about the microscopic defects / defect reactions underlyingthe change of the macroscopic parameters !


Summary (3/4) - Microscopic Defects

♦♦ Damage at the Microscopic LevelDamage at the Microscopic Level• DLTS and TSC measurements reveal many electrical active defects

• Most of the defects are not charged in the space charge region (no influence on Vdep !!)

• Comparison between 60Co-gamma and neutron/proton irradiated silicon allows fordetermination between point defects and defects related to defect clusters.

• Annealing experiments (isochronal and isothermal) reveal correlation's between singledefects and macroscopic parameters - reverse annealing and leakage current annealing

• Defect introduction rates and defect parameters can be used for the modeling of the overalldefect kinetics in the silicon (including fluence ranges where DLTS technique is notapplicable any more)

♦♦ Defect kinetics modelingDefect kinetics modeling• Modeling of the defect kinetics suggests that oxygen rich silicon is radiation harder

(V2O-model)• Model can explain experimental data for gamma irradiated silicon

(change of depletion voltage)

• Model gives qualitatively the macroscopic findings for hadron irradiated silicon detectors(depletion voltage). However, all models are so far incomplete.


Summary (4/4) - Oxygenated Silicon♦♦ Oxygen enriched silicon - technological resultsOxygen enriched silicon - technological results

• Oxygen enrichment by diffusion is most effective / less cost intensive method

• Detectors produced on oxygen enriched silicon do not show any change in detector propertiesbesides the improved radiation hardness (surface properties, performance beforeirradiation,etc.)

• Diffusion technology has been successfully transferred to several silicon detectormanufacturers (SINTEF, Micron, ST, CiS) and full-scale microstrip detectors produced

♦♦ Oxygen enriched silicon - scientific resultsOxygen enriched silicon - scientific results• Effective doping changes can be improved by oxygenation of the material

(factor 3 for stable damage parameter gc). Such improvement is only observed when theradiation environment contains a significant charged particle component.

• Reverse annealing saturates at high fluences (2×1014p/cm2) for oxygen enriched silicon.Time constant for the process is larger by a factor of 2-4 allowing detectors to remain atroom temperature for longer periods during maintenance periods: additional safety margin.

♦♦ Many open questions – Further work on oxygenated/standard Silicon needed !Many open questions – Further work on oxygenated/standard Silicon needed !•• The proton – neutron puzzle: Violation of NIEL ?

• Why does the reverse annealing saturate in oxygenated silicon ?

• Which defect is responsible for the differences observed after proton and neutron irradiation ? (V2O ? )

• …more open questions and details……see ROSE status reports ….


The ROSE Collaboration

Visit our web-site for…

… more information … status reports, preprints, … publications, …related conferences, etc….

http://cern.ch/rd48

Remember, today isValentines Day !

A good day for ROSES ?

Documents

Radiation Damage in Silicon Detectors - CERN...2014/01/02 · Michael Moll - CERN EP-TA1-SD Seminar - 14.2.2001 - 4 - Primary Damage PKA - Primary Knock on Atom Simulation (Fig.: