g. steinbrück, university of hamburg, slhc workshop, perugia, 3-4 april 20061 epitaxial silicon...
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G. Steinbrück, University of Hamburg, SLHC Workshop, Perugia, 3-4 April 2006 1
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
Joint Project: Bucharest-Hamburg-Ljubljana
with ITME (EPI), CiS (diodes), CERN (PS-p)
work done in the RD 50 collaboration
presented by:
Georg Steinbrück
Hamburg University
Motivation
Material parameters
Results for proton and neutron irradiated devices
S-LHC scenario: simulation and experimental data
Outlook
G. Steinbrück, University of Hamburg, SLHC Workshop, Perugia, 3-4 April 2006 2
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
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
G. Steinbrück, University of Hamburg, SLHC Workshop, Perugia, 3-4 April 2006 3
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 m
50 m
u50
mu
SIMS 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)
epi
Cz-substrate
O concentration dep. on thickness
G. Steinbrück, University of Hamburg, SLHC Workshop, Perugia, 3-4 April 2006 4
Quasi-Stable Damage ComponentQuasi-Stable Damage Component
Neff(t0): Value taken at annealing time t0 at which Vfd maximal
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
23 GeV protons23 GeV protons
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
G. Steinbrück, University of Hamburg, SLHC Workshop, Perugia, 3-4 April 2006 5
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
23 GeV protons23 GeV protons
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
Strong correlation between [O]-[BD]-gC
generation of O (dimer?)-related BD reason for superior radiation tolerance of EPI Si detectors
G. Steinbrück, University of Hamburg, SLHC Workshop, Perugia, 3-4 April 2006 6
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
23 GeV protons23 GeV protons
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
Reactor neutronsReactor neutrons
Ta = 80oCTa = 80oC
Amplitude in Neff
G. Steinbrück, University of Hamburg, SLHC Workshop, Perugia, 3-4 April 2006 7
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
100 oC 80 oC 60 oC 40 oC 20 oC
Ea = 1.3 eVEa = 1.3 eV
Temperature Dependence of Temperature Dependence of Y1
23 GeV protons
Arrhenius relation: 1/ Y = k0exp(-Ea/kBT)
Y1 component: Ea = 1.3 eV, k0 = 1.5 1015 s-1
High resistivity FZ Si: M. Moll, PhD thesis
Rises linearly
reliable extrapolation to
operating
temperature/room
temperature!
LT annealing
No difference between FZ and
EPI wrt. LT annealing!
G. Steinbrück, University of Hamburg, SLHC Workshop, Perugia, 3-4 April 2006 8
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 Analyzed parameters agree reasonably well Projection from our 60°C, 80°C-results to RT annealing reliable
G. Steinbrück, University of Hamburg, SLHC Workshop, Perugia, 3-4 April 2006 9
Charge Collection EfficiencyCharge Collection Efficiency
Charge collection efficiency measured with 90Sr electrons(mip’s), shaping time 25 ns
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 !
No degradation of CCE at low temperatures !
G. Steinbrück, University of Hamburg, SLHC Workshop, Perugia, 3-4 April 2006 10
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
G. Steinbrück, University of Hamburg, SLHC Workshop, Perugia, 3-4 April 2006 11
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 265 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)
G. Steinbrück, University of Hamburg, SLHC Workshop, Perugia, 3-4 April 2006 12
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
1.E-01
1.E+00
1.E+01
1.E+02
1.E+03
0 10 20 30 40 50 60 70
w [m]
rho
[
cm] p-type epi
50 µm, 150 ΩcmITME CiS
1.E-03
1.E-02
1.E-01
1.E+00
1.E+01
1.E+02
1.E+03
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 …..
G. Steinbrück, University of Hamburg, SLHC Workshop, Perugia, 3-4 April 2006 13
BACKUP
G. Steinbrück, University of Hamburg, SLHC Workshop, Perugia, 3-4 April 2006 14
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
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
G. Steinbrück, University of Hamburg, SLHC Workshop, Perugia, 3-4 April 2006 15
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))
G. Steinbrück, University of Hamburg, SLHC Workshop, Perugia, 3-4 April 2006 16
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
Annealing time [min]
-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
23 GeV protons23 GeV protons
Ta=80oCTa=80oC
G. Steinbrück, University of Hamburg, SLHC Workshop, Perugia, 3-4 April 2006 17
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
Reactor neutronsReactor neutrons
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
23 GeV protons23 GeV protons
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
23 GeV protons23 GeV protons
G. Steinbrück, University of Hamburg, SLHC Workshop, Perugia, 3-4 April 2006 18
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)
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