G. Lindström (a) , E. Fretwurst (a) , F. Hönniger (a) , G. Kramberger (b) ,

Epitaxial Silicon Detectors for Particle Tracking Epitaxial Silicon Detectors for Particle Tracking Overview on Radiation Tolerance at Extreme Hadron FluenceOverview on Radiation Tolerance at Extreme Hadron Fluence

G. Lindström(a), E. Fretwurst(a), F. Hönniger(a), G. Kramberger(b),

M. Moll(c), E. Nossarzewska(d), I. Pintilie(e), R. Röder(e)

(a) Institute for Experimental Physics, University of Hamburg

(b) Jozef Stefan Institute, University of Ljubljana

(c) CERN

(d) ITME Institute of Electronic Materials Technology, Warsaw

(e) National Institute for Materials Physics, Bucharest

(f) CiS Institut für Mikrosensorik gGmbH, Erfurt

Joint Project: Bucharest-Hamburg-Ljubljanawith ITME (EPI), CiS (diodes), CERN (PS-p) Motivation

Material parameters

Results for proton and neutron irradiated devices

S-LHC scenario: simulation and experimental data

Summary

1 G. Lindström, University of Hamburg, 10th European Symposium on Semiconductor Detectors, Wildbad Kreuth,12-16 June 2005

MotivationMotivation

LHC upgrade to Super-LHCLuminostity LHC: L ~ 1034 cm-2s-1 S-LHC: L ~ 1035 cm-2s-1

Expected radiation at inner pixel layer (4 cm) under S-LHC conditions:

Fluence for fast hadrons: 1.61016 cm-2 Dose: 420 Mrad

Proposed Solution: thin EPI-SI for small size pixelsSi best candidate: low cost, large availability, proven technology

thickness doesn’t matter! CCE limited at 1016 cm-2 by e 20 m, h 10 m

small pixel size needed, allows thin devices with acceptable capacitance for S/N

high Neff,0 (low ρ) provides large donor reservoir, delays type inversion

Needed data for prediction of S-LHC operational scenario:

Reliable projection of damage data to S-LHC operation Full annealing cycles at elevated temperatures Charge collection efficiency at very high fluences


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]

(SIMS-measurements: A. Barcz/ITME, Simulations: L. Long/CiS)


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

(SR-measurements: E. Nossarzewska, ITME)

Typical Annealing CurvesTypical Annealing Curves

Comparison EPI- with FZ-device:

Vfd development:

short term: EPI increasing, FZ decreasing long term: EPI decreasing, FZ increasing

EPI not inverted, FZ inverted, already

immediately after irradiation

100 101 102 103 104 105

Annealing time [min]

0

20

40

60

80

100

120

140

Vfd

[V

]

50 m EPI, 9.7.1014 cm-250 m EPI, 9.7.1014 cm-2

50 m FZ, 1.1.1015 cm-250 m FZ, 1.1.1015 cm-2

23 GeV protons23 GeV protons

Ta=80oCTa=80oC

100 101 102 103 104 105


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


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 (t < 500d), 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


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 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 acceptors


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

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+?

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+?

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)

SIMS profiling of [O] Stable Damage after PS p-irradiation

Generation of positive space charge most pronounced in 25 µm diodes

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

Annealing Curves for 25 µm and 50 µmAnnealing Curves for 25 µm and 50 µm

Nearly identical time dependence, constant difference between both curves Shift due to higher introduction of shallow donors in 25 µm epi-Si Concentration of donors not affected by long term annealing

Radiation induced donors are stable at 80°C (verified by TSC)

100 101 102 103 104 105


-2.0.1014

-1.0.1014

0.0

1.0.1014

2.0.1014

3.0.1014

4.0.1014

Nef

f [cm

-3]

50 m50 m

25 m25 m


Ta=80oCTa=80oC


Examples of parameter evaluation from annealing:Examples of parameter evaluation from annealing:Fluence Dependence of NFluence Dependence of NY1Y1

Introduction rate for protons:

Independent of epi-layer thickness andannealing temperature gY1 = 3.110-2 cm-1

Introduction rate for neutrons:

Value for 25 µm slightly lower compared to 50 µm, average value:

gY1 = 1.710-2 cm-1

0 2.1015 4.1015 6.1015 8.1015 1016

eq [cm-2]

0.0

1.0.1014

2.0.1014

3.0.1014

NY

1 [c

m-3

]

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]

0.0

1.0.1014

2.0.1014

NY

1 [c

m-3

]

25 m25 m

50m50m


Ta = 80oCTa = 80oC


Reverse Annealing Time ConstantsReverse Annealing Time Constants

Protons:above 1015 cm-2 Y1 and Y2 constant

Ratio Y1(60°C)/ Y1(80°C) = 11

Ratio Y2(60°C)/ Y2(80°C) = 10

below 1015 cm-2 Y2 1/eq

Neutrons:above 21015 cm-2 Y1 and Y2 constantY1(50 µm) = 1.3102 min, Y1(25 µm) = 3.3102 min

Y2(50 µm) = 2.9103 min, Y2(25 µm) = 5.3103 min

0 2.1015 4.1015 6.1015 8.1015 1016

eq [cm-2]

101

102

103

104

105

Y [

min

]

25 m25 m

Y,1Y,1

25 m25 m50 m50 m50 m50 m

Y,2Y,2


Ta = 80oCTa = 80oC

0 2.1015 4.1015 6.1015 8.1015 1016

eq [cm-2]

101

102

103

104

Y,1

[m

in]

50 m50 m

60oC60oC

50 m50 m

80oC80oC

25 m25 m


1014 1015 1016

eq [cm-2]

103

104

105

106

Y,2

[m

in]

50 m, 60oC50 m, 60oC

60oC60oC

50 m, 80oC50 m, 80oC

80oC80oC

25 m, 80oC25 m, 80oC



Temperature Dependence of Temperature Dependence of Y1 and Y2

23 GeV protons

Arrhenius relation: 1/ Y = k0exp(-Ea/kBT)

Y1 component: Ea = 1.3 eV, k0 = 1.5 1015 s-1

Y2 component: Ea = 1.3 eV, k0 = 5.4 1013 s-1

2.6 2.8 3 3.2 3.41/T [10-3 K-1]

100

101

102

103

104

105

106

Y [

min

]

Y : FZ-Si Y : FZ-Si

Y1: EPI-Si Y1: EPI-Si

Y2: EPI-Si Y2: EPI-Si

100 oC 80 oC 60 oC 40 oC 20 oC

Ea = 1.3 eVEa = 1.3 eV

High resistivity FZ Si: M. Moll, PhD thesis


Reliability check: Annealing at 20Reliability check: Annealing at 20°C°C


0 50 100 150 200 250

annealing time at 20oC [days]

0

50

100

150

200

250

300

VF

D [V

]

experimental dataexperimental data

fit: Hamburg modelfit: Hamburg modelparameter 20°C data fit 80°C data fit

Stable dam. NC

-8.9·1013 cm-3 -8.6 ·1013 cm-3

Benef. Ann. Na

3 ·1013 cm-3 5 ·1013 cm-3

Rev. Ann. NY1

2.2 ·1014 cm-3 1.8 ·1014 cm-3

Example: EPI 50 µm, Φp = 1.01·1016 cm-2

20°C annealing results can be fitted with Hamburg model RT Analysis agrees reasonably well with results from 60°, 80°C Projection from high T annealing to behavior at RT reliable

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 %

Charge collection efficiency 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


Charge collection efficiency measured with 90Sr electrons(mip’s), shaping time 25 ns

CCE no degradation at low temperatures ! degradation linear with fluence if the devices

CCE measured after n- and p-irradiation

CCE(Φp=1016 cm-2) = 2400 e (mp-value)

Extracted trapping parameters coincide with those measured in FZ diodes for small Φ, forlarge Φ less trapping than expected !


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.

Proposal: 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 operational scenario simulation resultssimulation results


0 365 730 1095 1460 1825time [days]

0

100

200

300

400

500

600

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)

SummarySummary


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, space charge sign remains positive even during long time annealing

Annealing experiments at elevated temperatures reveal stable donor generation (in contrast to FZ), overcompensating the damage induced acceptor concentration

Elevated temperature annealing results verified at 20°C

Dedicated CERN scenario experiment shows benefits of RT storage in contrast to required cooling for FZ silicon, experimental results in excellent agreement with simulations using the Hamburg model parameters

Simulation of real SLHC operational scenario with RT annealing during beam off periods show that Vfd kept at <300V (50μm), <150V (25μm) for full 5 y SLHC

Donors identified: BD point defects (EC-0.23 eV) most likely related to O-dimers strong correlation found between [O](SIMS)-[BD](TSC)-NC(annealing exp.)

Trapping almost as expected from FZ, 2400 e measured for mips after 1016 cm-2

Current related damage rate 4·10-17 Acm-1 (as known for FZ)

G. Lindström (a) , E. Fretwurst (a) , F. Hönniger (a) , G. Kramberger (b) ,

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Transcript of G. Lindström (a) , E. Fretwurst (a) , F. Hönniger (a) , G. Kramberger (b) ,