Can silicon operate beyond 10Can silicon operate beyond 101515 n/cmn/cm22 ??DEFECT ENGINEERING DEFECT ENGINEERING –– Oxygen Oxygen Dimer SiDimer Si

S. J. Watts, C. Da Via', A. Karpenko, A. Kok, Brunel University UK

OUTLINEOUTLINE

11-- BACKGROUNDBACKGROUND22-- KEY ISSUE KEY ISSUE –– signal efficiency in irradiated detectorssignal efficiency in irradiated detectors33-- SOLUTIONSSOLUTIONS

aa OPERATING CONDITIONS OPERATING CONDITIONS ( T, Forward/Reverse Bias ? )( T, Forward/Reverse Bias ? )bb DEFECT ENGINEERING DEFECT ENGINEERING ( ( Dimer Dimer oxygenated oxygenated SiSi))cc DEVICE ENGINEERING ( e.g. 3D Sherwood Parker)DEVICE ENGINEERING ( e.g. 3D Sherwood Parker)

44-- CONCLUSIONSCONCLUSIONS

qqV is weighting potentialV is weighting potentialVVxx

VVcc

Signal = q xSignal = q x PPqcqc(x) x CORR x ((x) x CORR x (VVcc –– VVxx))

Drift Time = d/Drift Time = d/µµEE

ττTT = ( = ( NNTTσσVVth th ) ) --11

tteffeff and and µµ varyvarywith temperaturewith temperature

PPqiqi = 1 = 1 –– PPqcqc

PPqi qi prop. 1/prop. 1/tteffeff

RAMO’sRAMO’s theorem + trappingtheorem + trapping

0

0.02

0.04

0.06

0.08

0.1

10-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

0.001

50 100 150 200 250 300 350

Signal density = 1016 cm-3, Trap density = 1015 cm-3

Pqi

Time C

onstant (s)

Temperature ( K)

Vacancy-Oxygenτ

τ

e

τ

τ

T

c

ττcc = (n= (nss σ σ vvthth) ) --11

ττTT = (N= (NTT σσ vvthth) ) --11

ττee prop. exp(prop. exp(∆∆E/E/kTkT))

1/1/ττ = 1/= 1/ττee + 1/+ 1/ττcc

Same theory as usedSame theory as usedin in CCD’sCCD’s

For depletion case (Reverse Bias)For depletion case (Reverse Bias)T < 200K Trapping ControlledT < 200K Trapping ControlledT > 200K Emission ControlledT > 200K Emission Controlled

For Forward BiasFor Forward BiasAlways Trapping ControlledAlways Trapping Controlled

0

0.05

0.1

0.15

0.2

0.25

100 150 200 250 300

Pqi

Temperature (K)

VO

V2

Cluster

Neutron

Proton

NT

= 1015 cm-3

For electron trapping For electron trapping –– ttDD = 10 ns= 10 nsConclusionConclusion

NIEL ViolationNIEL Violation

Charged hadrons worseCharged hadrons worse

Aside :Aside :PPqiqi = (= (ττ//ττTT) x (1 ) x (1 ––exp(exp(--ttDD//ττ))))Same in Same in CCDsCCDs

Introduction rates ( cmIntroduction rates ( cm--1 1 ) ) nn ppVOVO 0.60.6 0.96 0.96 V2 + ClusterV2 + Cluster 1.21.2 1.2 1.2

0

1

2

3

4

5

6

7

8

50 100 150 200 250 300 350

k = (

t eff x

Fluen

ce )-1

( 10

-16 ns

-1 cm

2 )

Temperature (K)

Protons

Neutrons

Data from 220K to 300K from -

Kramberger et al.ROSE TN01-01 Submitted to NIMA

Electron Trapping - calculation scaled to Kramberger data at 250K

Note:Note:

Kramberger Kramberger et al.et al.See NIEL ViolationSee NIEL Violationn/p trapping NOT the n/p trapping NOT the same for same equiv.same for same equiv.1 1 MeV MeV n n fluencefluence..

Conclusion:Conclusion:VO causes this differenceVO causes this difference

NOTE : Below 200K this parameter is the same forNOTE : Below 200K this parameter is the same forForward and Reverse biasForward and Reverse bias

0

500

1000

1500

2000

2500

50 100 150 200 250 300 350

FOR FLUENCE = 1014 cm-2

E = 104 V cm-1

Eff

ectiv

e Tr

appi

ng L

engt

h ( m

icro

ns)

Temperature (K)

Neutron

Neutron

Proton

Proton

Electrons

Holes

10

15

20

25

30

2 106

4 106

6 106

8 106

1 107

1.2 107

50 100 150 200 250 300 350

teffnteffnh

VdeVdh

Eff

ectiv

e Tr

appi

ng T

ime

(ns) D

rift Velocity (cm

s-1)

Temperature (K)

E = 104 V cm-1 ( 1V/micron)

1014 n cm-2

neutronsneutrons

Data for neutron and protons for effective trapping time 220KData for neutron and protons for effective trapping time 220K--300K from300K fromKrambergerKramberger et alet al

VOVO

LLeffeff == ττeffeff xx VVdriftdrift

EFFECTIVE DRIFT LENGTHEFFECTIVE DRIFT LENGTH

SIGNAL FORMATION SIGNAL FORMATION -- RAMO'S THEOREMRAMO'S THEOREM

IMPORTANCE OF THE WEIGHTING POTENTIALIMPORTANCE OF THE WEIGHTING POTENTIAL

PADS AND SEGMENTED DETECTORS ARE VERY DIFFERENTPADS AND SEGMENTED DETECTORS ARE VERY DIFFERENT

Holes Holes ElectronsElectrons

0

0.2

0.4

0.6

0.8

1

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035

1E14 ncm-2 200KSig

nal e

/ Sig

nal h

/ Sig

nal T

otal

Distance (cm)

p+ n+

CO

LLEC

TION

ELE

CTR

OD

E

Weighting Potential

PAD DETECTOR

Signal e

Signal h

Signal Total

0

0.2

0.4

0.6

0.8

1

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035

1E15 n cm-2 200K

Sig

nal e

/ Sig

nal h

/ Sig

nal T

otal

Distance (cm)

p+ n+

CO

LLEC

TION

ELE

CTR

OD

E

STRIP DETECTOR

Weighting Potential

Signal h

Signal e

Signal Total

0

20

40

60

80

100

0 1 1015 2 1015 3 1015 4 1015 5 1015 6 1015

200K Simulation 104 V/cm 300 Micron detector

PAD e+h

STRIP e+h

STRIP e+h n+

"CC

E"

Fluence n cm-2

PROTONS

Note:Note:Pad results samePad results samewhether you collectwhether you collectAt n+ or p+ contactAt n+ or p+ contact

CONCLUSION CONCLUSION –– collect electrons !!!!!collect electrons !!!!!If one can remove VO then we should do betterIf one can remove VO then we should do better

SOLUTIONS (b) DEFECT ENGINEERING SOLUTIONS (b) DEFECT ENGINEERING -- O DIMERO DIMER

OOii

OOii

SiSiSiSi

HIGH TEMPERATURE 60Co γ IRRADIATIONAT T > 350 0C VO BECOMES MOBILE AND CAUSES OXYGEN TO CLUSTER

QUASI CHEMICAL REACTIONS:

V+Oi => VOi

VOi + Oi => VO2i

I + VO2i => O2i

SiSiSiSi

OOi SiSii

OXYGEN INTERSTITIALOXYGEN INTERSTITIAL OXYGEN DIMEROXYGEN DIMER

Method variation on L. Lindstroem work

VOVO ----------------> VO> VO22 NEUTRALNEUTRALVV22OO ----------------> V> V22OO22 NEUTRALNEUTRAL

EXPECT CHANGE IN MACROSCOPIC EFFECTSEXPECT CHANGE IN MACROSCOPIC EFFECTSSHOULD IMPROVE CCE FOR ELECTRONSSHOULD IMPROVE CCE FOR ELECTRONS

ALSO ALSO –– OO2i2i diffuses very rapidly. Possibility of lowdiffuses very rapidly. Possibility of low--temp diffusion For DOFZ !!!!temp diffusion For DOFZ !!!!

-7 10 11

-6 10 11

-5 10 11

-4 10 11

-3 10 11

-2 10 11

-1 10 11

0

1 1011

100 150 200 250 300

366D309D

Con

cent

ratio

n (c

m-3

)

Temperature (K)

E(170)0

4 1011

8 1011

1.2 10 12

1.6 10 12

100 150 200 250 300

309D

Con

cent

ratio

n ( c

m-3

)

Temperature (K)

H(200)

H(144)

H(80?)

DEFECTS IN “DIMERED” MATERIAL

309D Oxygenated and “309D Oxygenated and “dimereddimered””366D Standard and “366D Standard and “dimereddimered””

Electron (E) or Hole (H) trap Energy Level (eV) Identification

E(170) Ec - 0.32 Probably VOH [11]

H(200) Ev + 0.36 CiOi (0/+) Charge state [1]

H(144) Ev + 0.2 Unknown

H(80?) Approx. Ev + 0.1 Not fully resolved. Unknown.

EXPERIMENTAL RESULTS EXPERIMENTAL RESULTS IV and NIV and Neffeff AFTER AFTER 2424GeV/c pGeV/c p−−irradiationirradiation

0.0 100

5.0 1011

1.0 1012

1.5 1012

2.0 1012

2.5 1012

3.0 1012

3.5 1012

4.0 1012

0 5 1013 1 1014 1.5 1014 2 1014 2.5 1014 3 1014 3.5 1014 4 1014

S

SD

O

OD

Nef

f (cm

-3)

Fluence (protons/cm2)

24 GeV/c proton irradiation - CERN scenario

0.0 100

2.0 10-3

4.0 10-3

6.0 10-3

8.0 10-3

1.0 10-2

1.2 10-2

1.4 10-2

0 5 1013 1 1014 1.5 1014 2 1014 2.5 1014 3 1014 3.5 1014 4 1014

S

SD

O

OD

Vol

ume

curr

ent (

Acm

-3)

Fluence (p/cm2)

309

366

Oxygenation shows normal improvement Leakage current looks the same in all samples.α~ 3E-17 A cm-1

0.0

50.0

100.0

150.0

200.0

250.0

0 10 20 30 40 50 60 70 80

94K FORW ARD BIAS - PAD DETECTOR

309p

309pd

x-ra

y pe

ak p

ositi

on (A

U)

Voltage (V)

309p Oxygenated309pd Oxygenated + Dimered

4 1014 24 GeV/c protons/cm2

Small improvement Small improvement –– do not expect anything spectaculardo not expect anything spectacularat this at this fluence fluence –– also a PAD detectoralso a PAD detector

5.0 1011

6.0 1011

7.0 1011

8.0 1011

9.0 1011

1.0 1012

1.1 1012

1.2 1012

1.3 1012

80 100 120 140 160 180

Nef

f [cm

-3]

T [K]

CONTROL OF THE SPACE CHARGECONTROL OF THE SPACE CHARGEWITH TEMPERATUREWITH TEMPERATURE

Phosphorus doping levelPhosphorus doping level

energy level occupancy ~ eenergy level occupancy ~ e-- ∆∆E/E/kTkT

MCA2us shapingX-ray source

detector

Li N

Temperature 85K to 300K

241Am

T [K]T [K]

NNef

f ef

f [c m[cm

-- 33]]

depleted

p+ n+

undepleted

X-RAY source

1x101x1014 14 n/cmn/cm2 2 > type inverted : > type inverted : --veve SCSC

CC DaDa ViaViaTo be publishedTo be published

++veve SCSC

0 .0

2 0 0 .0

4 0 0 .0

6 0 0 .0

8 0 0 .0

1 0 0 0 .0

1 2 0 0 .0

1 4 0 0 .0

1 6 0 0 .0

0 0 .0 0 5 0 .0 1 0 .0 1 5 0 .0 2 0 .0 2 5 0 .0 3 0 .0 3 5

1 2 0 K1 4 0 K1 6 0 K1 8 0 K

-E [V

/cm

]

D is ta n c e [ c m ]

ELECTRIC FIELD DISTRIBUTIONELECTRIC FIELD DISTRIBUTIONVERSUS TEMPERATURE AFTER 1E14 n/cmVERSUS TEMPERATURE AFTER 1E14 n/cm22

p+ n+

OXYGEN DIMERED SILICON OXYGEN DIMERED SILICON AFTER 24GeV/c PROTON IRRADIATIONAFTER 24GeV/c PROTON IRRADIATION

i

1.1x101.1x101111 p/cmp/cm22 4x104x1014 14 p/cmp/cm22

Radiation induced trapsRadiation induced trapsDLTS spectraDLTS spectra

SC after reverse annealingSC after reverse annealingMeasurements at 220K Measurements at 220K

-2.5 1011

-2 1011

-1.5 1011

-1 1011

-5 1010

0

5 1010

100 150 200 250 300

366p309p366Dp309Dp

Con

cent

ratio

n (c

m-3

)

Temperature (K)

E(90)E(170)

E(225)

~3y~3y50.0

100.0

150.0

200.0

250.0

300.0

0 200 400 600 800 1 103 1.2 10

309p366p366pd309pd

depl

eton

vol

tage

(V)

annealing time (min)

T=220

Anneal at 80 Anneal at 80 ooC C –– Equiv. to about 13 yr RTEquiv. to about 13 yr RT

Depletion voltages in various samples before and after annealing

Material VDep

300KVolts Note 1

VDep 223K ∆V RA

300KVolts Note 3

∆V RA

223KVolts Note 4

Standard 288 200 975 65

Oxygenated 189 100 740 40

Standard Dimered 288 90 - 0 to 10

OxygenatedDimered

180 100 - 40

Volts Note 2

Note 1: Inferred from CV measurement at room temperature Note 2: Inferred from x-ray count-rate measurement as function of voltage at 223K.Note 3: Calculated using Hamburg parameterisation of standard and oxygenated silicon.Note 4: Inferred from x-ray count-rate measurement as function of voltage.

TEMPERATURE DEPENDENCE OF DEPLETION VOLTAGE

Occupancy prop. Exp(∆E/kT)

SRH ∆E = Eg - 2ET

Inter-Centre Charge Transfer (ICT) ∆E = Eg - 2ET + ED

For V2 ∆E = -0.28 eV SRH, ∆E = -0.08 eV ICTEEgg

EETT

EETT

EEgg

EEDD

Temp. Dependence of RA part of depletion voltage = -0.2 eV

Temp. Dependence of Non -RA part of depletion voltageApprox -0.06 eV (depends on material )

CORRELATION BETWEEN RA - CLUSTER INTRO. RATE & TEMPDEPENDENCE OF DEPLETION VOLTAGE (PRIOR TO RA)

0

10

20

30

40

50

60

70

-0.1

-0.09

-0.08

-0.07

-0.06

-0.05

-0.04

-0.03

-0.02

0.8 1 1.2 1.4 1.6 1.8 2

Max

. Dep

letio

n V

olta

ge C

hang

e (V

olts

)

Activation E

nergy (eV) - S

ee Caption

Introduction Rate for E(225) DLTS Peak (cm -1)

SD

O & OD

S

ReverseReverseAnnealingAnnealing

BADBAD

GOODGOOD

Temp. Temp. DependenceDependenceof space chargeof space charge

Slow Slow VVdepchange with Tchange with T

FastFast VVdepdepchange with Tchange with T

Prior to RAPrior to RA

dep

CobaltCobalt--60 Irradiation Measure Minority Carrier Lifetime60 Irradiation Measure Minority Carrier LifetimeExpect VO to be important in standard Expect VO to be important in standard SiSi

3400

3600

3800

4000

4200

4400

4600

0 2 1013 4 1013 6 1013 8 1013 1 1014 1.2 1014

Minority Carrier Lifetime in differnt samples

1/tau S1/tau SD

1/ta

u (s

-1)

Fluence (gamma cm-2)

1Krad = 2.25E12 1Krad = 2.25E12 γγcmcm--22

1/1/ττ = 1/= 1/ττ00 + + φφ/K/Kττ

ττ00

KKττ

S S SDSD287287µµss 258258µµss

(1.0+/(1.0+/--0.1)0.1)*1E11*1E11

(2.0+/(2.0+/--0.2)0.2)*1E11*1E11

Units Units γγscmscm--22

Steps: 0, 15, 30, 45 Steps: 0, 15, 30, 45 KradKrad

Factor 2 better for standard Factor 2 better for standard dimered dimered siliconsilicon

VERY PRELIMINARY CONCLUSIONS VERY PRELIMINARY CONCLUSIONS FOR DIMER OXYGENATED SILICONFOR DIMER OXYGENATED SILICON

Evidence Evidence

•• That charge trapping has been improvedThat charge trapping has been improved•• That reverse annealing is suppressed in low [O] That reverse annealing is suppressed in low [O] dimered Sidimered Si•• Reverse annealing seems to be correlated with E(225) “cluster” Reverse annealing seems to be correlated with E(225) “cluster” peakpeak•• That space charge temperature dependence is different in low [OThat space charge temperature dependence is different in low [O] ] dimered Sidimered Si•• Temperature dependence of depletion voltage BEFORE RA correlatTemperature dependence of depletion voltage BEFORE RA correlated to theed to thesize of voltage change after RA !!!size of voltage change after RA !!!•• Better damage parameter for minority carrier lifetime in low [OBetter damage parameter for minority carrier lifetime in low [O] ] dimered Sidimered Siafter gamma irradiation.after gamma irradiation.

LOT OF THINGS TO DO YETLOT OF THINGS TO DO YET

NB: First look at how reverse annealing amplitude varies with teNB: First look at how reverse annealing amplitude varies with temperature.mperature.This may help to identify the defect causing RAThis may help to identify the defect causing RALots of possibilities Lots of possibilities OOii to Oto O2i2i to Oto O3i3i during processing. during processing. Low [O] and high [O] materialLow [O] and high [O] material