Frank Hönniger, Institute for Experimental Physics Student Seminar, 10th April 2006 1 Developement of Radiation Hard Silicon for Tracking Detektors Student

1Frank Hönniger, Institute for Experimental Physics

Student Seminar, 10th April 2006

Developement of Radiation Hard Silicon for Tracking Detektors

Student Seminar, 10. April 2006

Frank HönnigerUniversity of Hamburg,

Institut für Experimentalphysik



Outline

• Motivation

• Properties of Silicon Detectors

• Radiation Damage

• Experimental Methods

• Experimental Results

• Conclusion and Outlook



q q

pp

nn

nnp

ppp

p

n

nnp

pnpnp

Standard model of particle physics

Open questions: is there a universal force? (GUT?) what is the origin of mass (Higgs-

boson?) unknown types of matter (dark matter,

SUSY) HEP-Experiments towards higher energies

electromagnetic strong

weak gravitation

quarks: d, u, s, c, b, t --------- leptons: (e- e) (- ) (- )



LHC

LHCproperties

Proton-proton colliderEnergy: 2 x 7 TeVLuminosity: 1034cm-2 s-1

Bunch crossing: every 25 nsecRate: 40 MHzpp-collision event rate: 109/sec(23 interactions per bunch crossing)Annual operational period: 107 secExpected total op. period: 10 years

Experimental request Detector property

Reliable detection of mips S/N ≈ 10 reachable withemploying minimum minimum detector thicknessmaterial budget

High event rate excellent time- (~10 ns) and& high track accuracy position resolution (~10 µm)

Complex detector design low voltage operation in normal

ambients, (hybrid integration)

Intense radiation field Radiation tolerance up tothroughout operational 1015 1MeV eq. n/cm² period of 10 years low dissipation power moderate

cooling

Silicon pixel and microstrip detectors meetall requirements for LHC

How about future developments?



Radiation requirements for LHC-experiments

0 10 20 30 40 50 60R [cm]

1012

1013

1014

1015 e

q [c

m-2

] total eq

neutrons eq

pions eq

other chargedhadrons eq

SCT - barrelSCT - barrelPixelPixel

3x1014cm-23x1014cm-2

SCT - barrelSCT - barrel

PixelPixel

CERN-RD48http://cern.ch/rd48/

• radiation damage for ATLAS inner detector• annual hadron fluence (1 MeV n equiv.)

LHC: L=1e34 cm-2 s-1

technology for Si-detectors available, however serious radiation damage

S-LHC: factor 10: L=1e35 cm-2 s-1

5 years (R=4cm) ~ 1.6E16 cm-2

• no technology for Si-detectors at S-LHC available yet (thinner detectors?)• coordinated R&D needed • developement of radiation hard and cost-effctive detectors

CERN-RD50http://cern.h/rd50/

luminosity upgradevertex



Motivation for thinner detectors

• higher initial doping concentration (more n-type) • to maintain reasonable reverse bias during operation

Thickness: 300 m

Pixel: oxygen enriched silicon – DOFZSCT: standard silicon - StFZ

LHC: use of high resistivity FZ silicon

10-1 100 101 102 103

eq [ 1012 cm-2 ]

1

510

50100

5001000

5000

Ude

p [V

] (d

= 3

00m

)

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. Wunstorf 92]

S-LHC: to prevent type inversion

but all show „type inversion“ after 2*1013 p/cm2

„type inversion“

• shorter charge collection time faster signal response• less charge loss through trapping better signals• thin detectors reduction of e.g. pixel area higher position resolution

Si-detectors have to be thin



Motivation of radiation tests and annealing studies

• use pad detectors with simple and cheap structures• irradiate them with different particles and fluences• simulation of the irradiation of the whole operation time for

silicon detectors in short time• annealing studies at higher temperatures (60°C, 80°C)• acceleration of annealing (2 min@80°C 10 days@RT)

• extract particle, fluence and time dependencies of the detector

parameters• make predictions

Radiation damage and annealing (thermal treatment) have a big influence on detector performance



Use of silicon



Semiconductor detector - principle

• high energy- and position resolution• fast readout of the signals• large S/N-ratio (CCE=100%)• compact geometry possible• silicon: wide availibility, operation at

RT, in ambient atmospheres and under low voltages

a solid state ionisation chamber

• segmented detectors by planar process (Kemmer 1984)

microstrip-, pixel-detectors, CCD‘s

various application in HEP, space, atomic & material physics, and in medicine

p+nn+ - junction

fully depleted



4 Parameters of silicon detectors

+ –

+–

+

+

+

+

+

+

+

+–

–

–+

+–

+

+

–

–

–

p n

donor/acceptorconcentration

space chargedistribution

carrier distribution

electricfield

electricpotential

depletion region

• you can assume an abrupt p-n-junction under reverse bias

depletion voltage Vdep

ADeff NNN

dep20

0eff V

dq

2εεN

2V

|N|qεεAC(V) eff00

V>Vdep

capacitance C of depletion region

influence on S/N-ratio

most important: determines the bias supply

1

2q

AC

oend



Operational parameters of silicon detectors

leakage current

VI

volume generation current (caused by impurities and defects) +diffusion current + surface generation current

• important for the S/N-ratio • and the power consumption• prevention by cooling (ATLAS: -10°C)

charge collection efficiency CCE

CCE = Q/Q0

• ratio of measured charge to the induced charge• non-irradiated detector CCE = 1

3

4



Radiation Damage in silicon

mobile Interstitial I

mobile Vacancy V

CsCi

Point defects:• they can have discrete energy levels in the band gap• can have electrical influence on detectors:

• generation and recombination of e-h-pairs • carriers can be trapped• compensation of the initial doping

• primäry point defects are V and I• secondary complex defects: VP, VO, V2O, CO• influence of oxygen: Theory (thus DOFZ-Silicon) more O more VO (elect. not active at RT) less O more V2O (elect. active at RT)

Cluster: regions of dislocations• high energy PKA cascades of shifted atoms • can locally change the band structure

• generation and recombination of e-h-pairs • not really understood yet

impinging particle

impinging particle Cluster

classify into bulk damage (and surface damages)

dislocation of Si -atoms(PKA = Primäry knocked on atom)



Experimental findings

No influence on the macroscopic parametersInfluencing doping and currentInfluencing only dopingInfluencing only current

Defect states of the defect levels

VP-defect „donor removal“

Effective doping: donors acceptors

tteff npN

nt is large for a deep acceptor if p >> n

Reverse current: Traps

SCRtBGC VGqI 0

)cosh(2TkEE

cnNG

B

it

nitt Generation rate:



NIEL - Theory

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

How can I compare the irradiation effects of different particles and energies?

Simulation (M. Huhtinen): Initial distribution of vacancies in (1µm)3 after 1014 particles/cm²

10 MeV protons 24 GeV/c protons neutrons

• with PKA (>2keV), sort of irradiation defects become independent of particle and energy NIEL scales with radiation damage

D(E) NIEL

charged particle: coulomb scatteringneutrons: elastic scatteringboth, at higher energies: nuclear react.

one can convert the particle fluence to1 MeV n equivalent fluence

hardness factor

eq= 24 GeV/c protons: 0.62reactor neutrons: 0.9110 MeV protons: 3.99

Li-ions: 50.7



Damage induced changes of macroscopic properties

Degradation of charge collection efficiency

due to increase of charge carrier trapping 1/eff,e,h = e,h

1011 1012 1013 1014 1015

eq [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 Kcmn-type FZ - 7 to 25 Kcmn-type FZ - 7 Kcmn-type FZ - 7 Kcmn-type FZ - 4 Kcmn-type FZ - 4 Kcmn-type FZ - 3 Kcmn-type FZ - 3 Kcm

n-type FZ - 780 cmn-type FZ - 780 cmn-type FZ - 410 cmn-type FZ - 410 cmn-type FZ - 130 cmn-type FZ - 130 cmn-type FZ - 110 cmn-type FZ - 110 cmn-type CZ - 140 cmn-type CZ - 140 cm

p-type EPI - 2 and 4 Kcmp-type EPI - 2 and 4 Kcm

p-type EPI - 380 cmp-type EPI - 380 cm

10-1 100 101 102 103

eq [ 1012 cm-2 ]

1

510

50100

5001000

5000

Ude

p [V

] (d

= 3

00m

)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. Wunstorf 92]

Increase of leakage current

Introduction of defects/clusters with near to mid-gap levels as generation centers, increase of noise and power consumption, thermal run-away I/V =

Change effective doping concentration

change of voltage for total depletion VdepIntroduction of defects which are charged in the space charge region,(acceptor creation) e.g.: V + P = VP (donor removal)

„type inversion“



Silicon detectors – used test structures

StFZ - Standard Float-Zone Silicon

• produced at Wacker Siltronic, processed at CiS, standard oxidation (passivation)• 305 m thick, orientation <111>

• n-doped ([P] = 7e11 cm-3 ), [O] = 6e15 cm-3, [C] = 7.5e15 cm-3 , = 6.4 kcm

DOFZ – Diffusion Oxyge- nated Float-Zone Silicon

• produced at Wacker Siltronic, processed at CiS, add. oxidation (72h@1150°C)• 305 m thick, orientation <111>• n-doped ([P] = 7e11 cm-3 ), [O] = 2.34e17 cm-3, [C] = 11.7e15 cm-3 , = 6.4 kcm

CZ - Czochralski Silicon• produced at Sumitomo/Sitix, processed at CiS, 300 m thick, orientation <100>• n-doped ([P] = 3e12 cm-3 ), [O] = 7.3e17 cm-3, [C] = 4.1e15 cm-3 , = 1.2 kcm

EPI - Epitaxial Silicon

25, 50 and 75 μm

• 25, 50, 75 m n-doped EPI-layer [P] = 7e13 cm-3 on

320 m CZ-substrate n+ doped ([Sb] = 5.3e17 cm-3)• orientation <111>, produced at ITME/Warsaw, processed at CiS

EPI-diodestandard diode

CZ, FZ-processEpitaxy

25, 50, 75 μm



CV/IV- measurements

prober to pad

prober toguard ring

• easy determination of macroscopic properties (depletion voltage, leakage current)• allows a fast check of detector functionality

1 10 100

100

1000

0.1

1 C/V-KurveI(U

dep) = 0,92 A

Udep

= 122,51 V

C [

pF]

U [V]

I/V-Kurve

I [A

]

• measuring in dark box• bias supply to the bottom• guard ring is grounded



TCT- measurements (transient current technique)fro n t e lek trod e(-) back e lec tro de (+ )

la s e r p u ls

+

+-

-

0 d

gene ra ted ca rriers

x

ho le in jec tion e lectron in jec tion

H e izung

Tem peratu r-sensor

optische r Le iterfür F ron tbeleuch tung

optische r Le iterfür R ückbe leuchtung

H a lterung /F rontkon takt

Tisch / R ückkontakt

flüss iger Sticksto ff

A lum iniumG ehäuse

G lasgefäß

Kühlka m m e r

cooling possible with nitrogen

• measurements of current pulses with oscilloscope• induced from drift of free carriers• front and back illumination with 670 (3m) and 1060 nm (across) laser• penetration depth proportional to • also exposure with (23 m) or (across) (get absolute values)

10 15 20 25 30 35

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35DOFZ 300 mfront injection

I [re

l.Ein

heite

n]

t [ns]

U = 140V U = 120V U = 100V U = 80V U = 60V

investigation of • elect. field distribution• sign of the space charge• trapping probability, separated for e and h• depletion voltage• CCE



40 80 120 160 200 240 280T [K]

0

0.02

0.04

0.06

0.08

0.1

0.12

DL

TS

sign

al [

pF]

0

0.02

0.04

0.06

0.08

0.1

0.12

Ci(-/0)Ci(-/0)

VOi+CiCs(A)VOi+CiCs(A)

V2(=/-)V2(=/-)

ER(170)ER(170)

V2(-/0)V2(-/0)

DLTS and TSC

Trap concentration Nt is proportional to the peak height

DLTS-spectrum after proton irradiation

DLTS Method: • p/n junction is hold under reverse bias• Electrical or optical pulse fills traps inside the SCR with carriers• Traps release carriers by thermal emission• Emission is monitored as a capacitance signal

TSC-spectrum after neutron irradiation

TSC Method: Traps filled at low temperature by electrical or optical injection Diode heated under reverse bias Current during the heating is monitored

Trap concentration is proportional to the released charge

• • •

TS

C c

urre

nt [

A]

T [K]



DLTS principle

[1] A bias pulse towards a smaller voltage will reduce the SCR

[2] The junction capacitance is reduced because positive space charge is partially compensated by trapped electrons in the SCR

[3] The process of carrier emission can be followed as a capacitance transient

C h a rg e s ta te o f d e fe c t le v e ls

E le c tro n tra p -e le c tro n in je c tio n

H o le tra p -h ig h in je c tio n

VP

V R

0 VB ia sp u ls e

C a p a c ita n c etra n s ie n t

VP

V R

C RC R

0 V

1 Q uiescen t reve rse b ia s (V )R

3 T h erm a l em issio n o f c arrie rs (V )R

2 M ajority ca rr ie r pu lse (V )P

1 Q uiescen t reve rse b ia s (V )R

3 T h erm a l em issio n o f c arrie rs (V )R

2 In jec tion pu lse (V , f o rw ard b ia s)P

1 3

2

1 3

2

RD

P

RR

P

R

RDt C

CN

C

C

A

C

C

C

C

CNN 0

1

0

2

0 212

12



DLTS method

The emission time constant can be evaluated:

2

1

21max

ln

)(

tt

ttTe

capa

cita

nce

tran

sien

ts m

onit

ored

at v

ario

us te

mpe

ratu

res

tim e

tWtem p era tu re T

h ig h T

lo w T

C = C (t ) - C (t )1 ,2 1 2t 1 t 2

T m a x



CERN Scenario Experiment-Depletion Voltage

0 5 10 15 20 250

100

200

300

400

500

600

700

EPI <111> 50 cm, 50m (Jul.2003, 20 GeV/c)

CERN-Szenario, 24 GeV/c Protons

EPI <111> 50 cm, 50 m (Okt. 2002, 24 GeV/c)

CZ <100> 1,2 kcm, 300 m DOFZ <111> 1-6 kcm, 300 m StFZ <111> 1-6 kcm, 300 m

Ude

p [V

]

eq

[1014cm-2]

160 V120 V

• large improvement for EPI-detectors• small change in depletion voltage for EPI up to very high fluences• no type inversion for EPI• limitation for StFZ, DOFZ and CZ for very high luminosity colliders

CERN Scenario Experiment:• consecutive irradiation steps• in between annealing for 4 min@80°C• after annealing CV/IV-measurements• quasi „online“ monitoring• annealing corresponds to 20 days at 20 °C• closely related to stable damage

Why is EPI radiation harder: shifted donor removal, because of higher initial donor concentration radiation induced acceptor creation compensated by radiation induced donors

High energy protons max. biassupply



Material ParametersMaterial Parameters

Oxygen depth profiles

SIMS-measurements after diode processing

O diffusion from substrate into epi-layer interstial Oi + dimers O2i

[O] 25 µm > [O] 50 µm process simulation yields reliable [O]

Resistivity profiles

SR before diode process, C-V on diodes

SR coincides well with C-V method

Excellent homogeneity in epi-layers

0 10 20 30 40 50 60 70 80 90 100Depth [m]

51016

51017

51018

5

O-c

once

ntra

tion

[1/c

m3 ]

SIMS 25 m SIMS 25 m

25 m

u25

mu

SIMS 50 mSIMS 50 m50

mu

50 m

uSIMS 75 mSIMS 75 m

75 m

u75

mu

simulation 25 msimulation 25 msimulation 50 msimulation 50 msimulation 75msimulation 75m

0 20 40 60 80 100Depth [m]

10-2

10-1

100

101

102

Res

istiv

ity [

cm]

25 m, C-V method25 m, C-V method

50 m, C-V method50 m, C-V method

50 m, spreading resistance 50 m, spreading resistance

75 mum, C-V method75 mum, C-V method



Typical Annealing CurvesTypical Annealing Curves

100 101 102 103 104 105

Annealing time [min]

10

100

1000

Vfd

[V

]

9.1015 cm-29.1015 cm-2

6.1015 cm-26.1015 cm-2

2.1015 cm-22.1015 cm-2

1.1015 cm-21.1015 cm-2

3.1014 cm-23.1014 cm-2

23 GeV protons23 GeV protons

Ta=80oCTa=80oC

Typical annealing behavior of EPI-devices:

Vfd development:

Inversion only(!) during annealing ()(100 min @ 80C ≈ 500 days @ RT)

EPI never inverted at RT, even for 1016



Parameterization of Annealing ResultsParameterization of Annealing Results

Annealing components:

Short term annealing NA(,t(T))

Stable damage NC()NC = NC0(1-exp(-cΦeq) + gCΦeq

gC negative for EPI (effective positive space charge generation!)

Long term (reverse) annealing:Two components: NY,1(,t(T)), first order process NY,2(,t(T)), second order process

NY1, NY2 ~ Φeq, NY1+NY2 similar to FZ

100 101 102 103 104 105

Annealing time [min]

0.0

1.0.1013

2.0.1013

3.0.1013

4.0.1013

5.0.1013

Nef

f [ c

m-3

]

NANA

NCNC

NY,1NY,1

NY,2NY,2

Ta=80oCTa=80oC

Change of effective “doping“ concentration: Neff = Neff,0 – Neff (,t(T))

Standard parameterization: Neff = NA(,t(T)) + NC() + NY(,t(T))



Stable Damage ComponentStable Damage Component

Neff(t0): Value taken at annealing time t0 at which Vfd maximum

0 2.1015 4.1015 6.1015 8.1015 1016

eq [cm-2]

0.0

1.0.1014

2.0.1014

3.0.1014

Nef

f(t0)

[cm

-3]

0

100

200

300

400

500

600

Vfd

(t0)

[V

] no

rmal

ized

to 5

0 m

25 m, 80oC25 m, 80oC

50 m, 80oC50 m, 80oC

50 m, 60oC50 m, 60oC


0 2.1015 4.1015 6.1015 8.1015 1016

eq [cm-2]

0

5.1013

1014

Nef

f (t 0

) [cm

-3]

0

50

100

150

Vfd

(t 0

)[V

] no

rmal

ized

to 5

0 m

50 m50 m

25 m25 m

Reactor neutronsReactor neutrons

Ta = 80oCTa = 80oC

No space charge sign inversion after proton and neutron irradiationIntroduction of shallow donors overcompensates creation of deep acceptors

Protons: Stronger increase for 25 µm compared to 50 µm higher [O] and possibly [O2] in 25 µm (see SIMS profiles)

Neutrons: Similar effect but not nearly as pronounced most probably due to less generation of shallow donors and as strong influence of deep acceptors (clusters)



Shallow Donors, the real issue for EPIShallow Donors, the real issue for EPI-Comparison of 25, 50 and 75 -Comparison of 25, 50 and 75 µm Diodes-µm Diodes-

0 10 20 30 40 50 60 70 80 90 100Depth [m]

51016

51017

51018

5

O-c

once

ntra

tion

[1/c

m3 ]

SIMS 25 m SIMS 25 m

25 m

u25

mu

SIMS 50 mSIMS 50 m50

mu

50 m

uSIMS 75 mSIMS 75 m

75 m

u75

mu

simulation 25 msimulation 25 msimulation 50 msimulation 50 msimulation 75msimulation 75m

0 2.1015 4.1015 6.1015 8.1015 1016

eq [cm-2]

0

1014

2.1014

Nef

f(t0)

[cm

-3]

25 m, 80 oC25 m, 80 oC

50 m, 80 oC50 m, 80 oC

75 m, 80 oC75 m, 80 oC


SIMS profiling:

[O](25µm) > [O](50µm) > [O](75µm)

Stable Damage:

Neff(25µm) > Neff(50µm) > Neff(75µm)

TSC Defect Spectroscopy:

[BD](25µm) > [BD](50µm) >[BD](75µm)

Defect spectroscopy after PS p-irradiation

Generation of recently found shallow donors BD (Ec-0.23 eV) strongly related to [O] Possibly caused by O-dimers, outdiffused from Cz with larger diffusion constant dimers monitored by IO2 complex

Strong correlation between [O]-[BD]-gC

generation of O (dimer?)-related BD reason forsuperior radiation tolerance of EPI Si detectors

80 100 120 140 160 1800.0

0.2

0.4

0.6

0.8

1.0

1.2

Nor

mal

ised

TS

C s

igna

l (pA

/m

)

Temperature (K)

75 m 50 m 25 m

BD0/++

CiO

i

V2

-/0+?

80 100 120 140 160 1800.0

0.2

0.4

No

rma

lise

d T

SC

sig

na

l (p

A/

m)

Temperature (K)

75 m 50 m 25 m

BD0/++

CiO

i

V2

-/0+?

≈ 105 V (25 µm)

≈ 230 V (50 µm)

≈ 320V (75 µm)



DLTS (Deep Level Transient Spectroscopy)

Φ(25 μm epi) = 1.2 ·1012 p/cm2

25 μm epi: defect at 67K

TW = 200 ms, tp= 100 ms UR=-20V, UP=-0.1V

0 50 100 150 200 250 3000,00

0,05

0,10

0,15

0,20

0,25

0,30

0,35

0,40

35KV2(=/-)

176K

V2(-/0) + VP

IO2

VOi

b 1 [p

F]

T [K]

1,0E+16

1,0E+17

1,0E+18

0 5 10 15 20 25 30

Depth [μm]

con

cen

trat

ion

[O

] [1

/cm

3]

1,0E+10

1,0E+11

1,0E+12

con

cen

trat

ion

[IO

2]

[1/c

m3]

25 μm epi



Charge Collection EfficiencyCharge Collection Efficiency

CCE degradation linear with fluence if the devices are fully depletedCCE = 1 – , = 2.710-17 cm2

CCE(1016 cm-2) = 70 %

CCE measured with 244Cm -particles (5.8 MeV, R30 µm)Integration time window 20 ns

0 2.1015 4.1015 6.1015 8.1015 1016

eq [cm-2]

0.6

0.7

0.8

0.9

1.0

Cha

rge

colle

ctio

n ef

fici

ency

25 m, 80oC25 m, 80oC

50 m, 80oC50 m, 80oC

50 m, 60oC50 m, 60oC


CCE measured with 90Sr electrons (mip’s), shaping time 25 ns

CCE no degradation at low temperatures !

CCE measured after n- and p-irradiation

CCE(Φp=1016 cm-2) = 2400 e (mp-value)

trapping parameters = thos for FZ diodes for small Φ, For large Φ less trapping than expected !



0 2.1015 4.1015 6.1015 8.1015 1016

eq [cm-2]

0

1000

2000

3000

4000

5000

Sign

al [

e]

simulationsimulation

reactor neutronsreactor neutrons

24 GeV/c protons24 GeV/c protons

90Sr source, 50 m epi-device 90Sr source, 50 m epi-device

peaking time 25 ns, T = -10 oC peaking time 25 ns, T = -10 oC

Charge Collection EfficiencyCharge Collection Efficiency

CCE(Φp=1016 cm-2) = 2400 e (mp-Wert)

CCE mit 90Sr Elektronen (mip’s), Integrationtime 25 ns



Current GenerationCurrent Generation

0 2.1015 4.1015 6.1015 8.1015 1016

eq [cm-2]

0.0

0.1

0.2

0.3

0.4

0.5

I/V

[Acm

-3] 50 m50 m

25 m25 m

I = x eq x VolI = x eq x Vol

Ta = 80oCTa = 80oC

ta = 8 min ta = 8 min

Result almost identical to FZ silicon:Current related damage rate α = 4.1·10-17 Acm-1

(Small deviations in short term annealing)



S-LHCS-LHC CERN scenario experimentCERN scenario experiment

Simulation:reproducing the experimental scenario

with damage parameters from analysis

Experimental parameter:Irradiation:

fluence steps 2.21015 cm-2 irradiation temperature 25°C

After each irradiation stepannealing at 80°C for 50 min,corresponding 265 days at 20°C

Excellent agreement between experimental data and simulated results

Simulation + parameters reliable!

0 2.1015 4.1015 6.1015 8.1015 1016

eq [cm-2]

0

50

100

150

200

250

Vfd

[V

]

50 m simulation50 m simulation

50 m after 50 min@80C annealing50 m after 50 min@80C annealing

25 m simulation25 m simulation

25 m after 50 min@80C annealing25 m after 50 min@80C annealing

Stable donor generation at high Φ would lead to larger Vfd, but acceptor generation during RT anneal could compensate this.

Proposed Benefit: Storage of EPI-detectors during beam off periods at RT (in contrast to required cold storage for FZ)

Check by dedicated experiment:



S-LHCS-LHC operational scenario simulation resultsoperational scenario simulation results

0 365 730 1095 1460 1825time [days]

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Vfd

[V

]

50 m cold50 m cold

50 m warm50 m warm

25 m cold25 m cold

25 m warm25 m warm

S-LHC scenarioS-LHC scenario

RT storage during beam off periods extremely beneficial Damage during operation at -7°C compensated by 100 d RT annealing Effect more pronounced for 50 µm: less donor creation, same acceptor component Depletion voltage for full SLHC period less than 300 V

S-LHC: L=10S-LHC: L=103535cmcm-2-2ss-1-1

Most inner pixel layerMost inner pixel layer

operational period per year:operational period per year:100 d, -7100 d, -7°C, °C, ΦΦ = 3.48 = 3.48·10·101515cmcm-2-2

beam off period per yearbeam off period per year265 d, +20°C (lower curves)265 d, +20°C (lower curves) -7°C (upper curves) -7°C (upper curves)



Summary Summary

Thin low resistivity EPI diodes (grown on Cz) are extremely radiation tolerant

No type inversion observed up to Φeq = 1016 cm-2 for protons and neutrons

Radiation induced stable donor generation related most likely to O-dimers

Elevated temperature annealing results verified at 20°C

Dedicated CERN scenario experiment shows benefits of RT storage

Simulation of real SLHC operational scenario with RT storage demonstrated 50 µm EPI Detectors withstand 5y SLHC with Vop ≤ 300V (full depl.)

1.E-03

1.E-02

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1.E+00

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rho

[

cm] p-type epi

50 µm, 150 ΩcmITME CiS

1.E-03

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1.E+00

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0 10 20 30 40 50 60 70 80 90 100

w [m]

rho

[

cm]

n-type epi70 µm, 150 ΩcmITME CiS

Future plans: p-type epi, thicker n-type epi, thin Cz …..Future plans: p-type epi, thicker n-type epi, thin Cz …..



To understand the nature of the universe !

DestinationDestination



Experimental conditions at LHC

Detector requirements

• reliable detection of charged particles • material budget has to kept in mind, because of big detectors• high event rate & high track accuracy • complex detector design • intense radiation field in the whole operational

period of 10 years Radiation damage

negative influence on detector parameters

Silicon detector can handle with all

requirements for LHC

LHCproperties

Proton-proton colliderEnergy: 2 x 7 TeVLuminosity: 1034 cm-2 s-1

Bunch crossing: every 25 nsecRate: 40 MHzpp-collision event rate: 109/sec(23 interactions per bunch crossing)Annual operational period: 107 secExpected total op. period: 10 years

Documents

Frank Hönniger, Institute for Experimental Physics Student Seminar, 10th April 2006 1 Developement of Radiation Hard Silicon for Tracking Detektors Student