June ‘09 RD50 Meeting Freiburg Hartmut Sadrozinski, SCIPP, UC Santa Cruz1
SCIPPSCIPP
Charge Collection in irradiated Si Sensors
C. Betancourt, B. Colby, N. Dawson, V. Fadeyev M. Gerling, F. Hurley, S. Lindgren, P. Maddock, H. F.-W. Sadrozinski, S. Sattari, J. v. Wilpert, J. Wright
SCIPP, UC Santa Cruz
• Monitoring the health of the Charge Collection System• New Parameter: Efficiency Voltage• Correlation between efficiency and cluster size
June ‘09 RD50 Meeting Freiburg Hartmut Sadrozinski, SCIPP, UC Santa Cruz2
SCIPPSCIPP
Charge Collection and C-V Measurementsin irradiated Si Sensors
C. Betancourt, B. Colby, N. Dawson, V. Fadeyev M. Gerling, F. Hurley, S. Lindgren, P. Maddock, H. F.-W. Sadrozinski, S. Sattari, J. v. Wilpert, J. Wright
SCIPP, UC Santa Cruz
• Monitoring the health of the Charge Collection System• New Parameter: Efficiency Voltage• Correlation between efficiency and cluster size• Admittance Measurement
June ‘09 RD50 Meeting Freiburg Hartmut Sadrozinski, SCIPP, UC Santa Cruz3
SCIPPSCIPPFluence in the sATLAS Tracker “du jour”
ATLAS Radiation Taskforce http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/RADIATION/RadiationTF_document.html
5 - 10 x LHC Fluence
Mix of n, p, depending on radius R
sATLAS Fluences for 3000fb-1
1.E+12
1.E+13
1.E+14
1.E+15
1.E+16
1.E+17
0 20 40 60 80 100 120
Radius R [cm]
Flu
en
ce
ne
q/c
m2
All: RTF Formulan (5cm poly)pionproton
Pixels
Radial Distributionof Sensors determined by Occupancy < 2%, still emerging
ShortStrips
LongStrips
Design fluences for sensors (includes 2x safety factor) :B layer (r=3.7 cm) 2.5*1016 neq/cm2 1140 MRad Innermost Pixel Layer (r=5cm): 1.4*1016 neq/cm2 712 MRad 2nd Pixel Layer (r=7cm): 7.8*1015 neq/cm2 420 MRad Outer Pixel Layers (r=11cm): 3.6*1015 neq/cm2 207 MRad Short strips (r=38cm): 6.8*1014 neq/cm2 30 MRad Long strips (r=85cm): 3.2*1014 neq/cm2 8.4 MRad
Strips damage largely due to neutrons
Pixels Damage due to neutrons+pions
June ‘09 RD50 Meeting Freiburg Hartmut Sadrozinski, SCIPP, UC Santa Cruz4
SCIPPSCIPP
<100><100><100><100>Orientation
3.3 kcm13 kcm1.4 kcm1.9 kcmResitivity
V(FD) [V] 9575220520
Fz (n-n), (p-n)Fz (n-p)MCz(n-n), (p-n)MCz (n-p)
<100><100><100><100>Orientation
3.3 kcm13 kcm1.4 kcm1.9 kcmResitivity
V(FD) [V] 9575220520
Fz (n-n), (p-n)Fz (n-p)MCz(n-n), (p-n)MCz (n-p)
4” : IRST(SMART)
Towards Commercialization of P-type
6” : Micron (RD50) HPK: (ATLAS07)
n-on-n, p-on-n, n-on-pFZ and Mcz
Testing: UC Santa Cruz, Liverpool U. , Ljubljana
n-on-p, FZn-on-n, p-on-n, n-on-pFZ and Mcz
June ‘09 RD50 Meeting Freiburg Hartmut Sadrozinski, SCIPP, UC Santa Cruz5
SCIPPSCIPP
5
Charge Collection System
CCE System is beta source (90Sr) with trigger from single thick scintillation counter. Measurements carried out in freezer at low temperature (-30 oC)
Accelerated Annealing at elevated temperature (60oC): about 440 times faster than at RT: 1000 min @ 60oC = 305 days at RTActivation energy E = 1.28 eV (Ziock et al. 1994)Annealing important for thermal management.
Binary readout with 100 ns shaping timePositive and negative charge readout
Measurement of collected charge with min. ion. particles (MIPs) combines all effects of radiation damage: depletion voltage increase, inversion, trapping…
June ‘09 RD50 Meeting Freiburg Hartmut Sadrozinski, SCIPP, UC Santa Cruz6
SCIPPSCIPP
6
Collected Charge: CCE
2. event-by-event: analogTime-over-Threshold ToT -> peak of distribution -> ToT Q
Good agreement between MedQ and ToTAccuracy: ~10% sample-to-samplefew % within one sample during anneal.
N.B. Complicated bias dependence!!
Charge Collection Efficiency vs Threshold (600V Bias )
0
0.5
1
0 50 100 150 200 250 300 350 400
Threshold [mV]
Eff
icie
ncy
2552-6-11-2 n-on-p MCz proton 1.3e1580min anneal ntcorr bias=600V
2552-6-11-2 n-on-p MCz proton 1.3e15 1000min anneal ntcorr bias=600V
W27-BZ3-P3 Proton-KEK proton 1.3e1580min anneal bias=600V
W27-BZ3-P3 Proton-KEK proton 1.3e151000min anneal bias=600V
Determination of collected charge
1. statistical: binaryThreshold curves -> Efficiency
-> Median Q (50% efficiency point)
0
0.5
1
1.5
2
2.5
3
3.5
4
0 200 400 600 800 1000 1200Bias (V)
Med
ian
Q (
e-)
0
1
2
3
4
5
6
7
8
9
10
To
T [
sec
]
Med Q 2535-9-3-3 p-on-n FZMed Q n-on-p MCz 2552-6-3-1TOT 2535-9-3-3 p-on-n FZTOT 2552-6-3-1 n-on-p MCz
Comparison after 6.1e14 pion: Medium Q / Time over Threshold ToT
June ‘09 RD50 Meeting Freiburg Hartmut Sadrozinski, SCIPP, UC Santa Cruz7
SCIPPSCIPPCollected Charge and Single Rate
Sensor single rate is crucial for health of apparatus.Single rate can foretell problems in charge collection measurement, which can’t be detected
efficiency or collected charge orleakage current
0
1
2
3
4
5
0 200 400 600 800 1000Bias (V)
Med
ium
Q [
fC]
0.000
0.005
0.010
0.015
Rat
e [a
.u.]
Med Q
Single Rate
P-on-N FZ 3e14 neq PROTON2535-8 3-1
June ‘09 RD50 Meeting Freiburg Hartmut Sadrozinski, SCIPP, UC Santa Cruz8
SCIPPSCIPPCollected Charge, Single Rates and Efficiency
Collected Charge, Single Rate and Efficiency
0
5000
10000
15000
20000
25000
0 200 400 600 800 1000 1200Bias [V]
Cou
nt R
ate
(kH
z)
0
0.5
1
1.5
2
2.5
Eff
icie
ncy
@ 1
fC T
hres
hold
Med Q [e-]
Single rate @ 1fC
Efficiency @ 1fC Threshold
HPK ATLAS07W27-BZ3-P3 1.3e15 neq/cm2 Proton
Sensor single rate at 1 fC threshold is tracking the median collected charge well.Efficiency at 1fC threshold saturates at much lower voltage and reaches 100% if
signal/threshold S / T > 2,2 Signal/Noise > 9 in the experiment
Determine the required voltage for 98.5% efficiency: “Efficiency Voltage” (e.g. 1 fC threshold)
Depletion VoltageEfficiency Voltage
June ‘09 RD50 Meeting Freiburg Hartmut Sadrozinski, SCIPP, UC Santa Cruz9
SCIPPSCIPPCollected Charge and Efficiency
Complete universal correlation between collected charge and efficiency
Eff. Voltage vs. Med QAll Sensors, Fluences, Anneal Times
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
0 5000 10000 15000 20000 25000
Med Q (e-)
Eff
icie
ncy
Micron 2552-6-11-2 n-on-p Proton MCz 1.3e15 neqMicron 2535-8-3-1 P-on-N FZ 3e14 neq ProtonMicron 2552-6-9-1 N-on-P MCz 1.3e14 protonHPK-ATLAS07 W27-BZ3-P3 n-on-p FZ no spray 1.3e15 protons2535-9 3-3 p-on-n FZ 6.1e14 pion 2552-6 3-1 n-on-p MCz 6.1e14 pion Micron 2552-7-11 n-on-p MCz 1e15 neutronMicron 2552-7-9 N-on-P MCz 5e14 neutronMicron 2553-11-11 n-on-n MCz 1e15 neutronMicron 2552-6-11-2 n-on-p Proton MCz 1.3e15 neqMicron 2535-8-3-1 P-on-N FZ 3e14 neq ProtonMicron 2552-6-9-1 N-on-P MCz 1.3e14 protonHPK-ATLAS07 W27-BZ3-P3 n-on-p FZ no spray 1.3e15 protons2552-6 3-1 n-on-p MCz 6.1e14 pion Micron 2552-7-11 n-on-p MCz 1e15 neutronMicron 2552-7-9 N-on-P MCz 5e14 neutronMicron 2553-11-11 n-on-n MCz 1e15 neutronMicron 2552-6-11-2 n-on-p Proton MCz 1.3e15 neqMicron 2535-8-3-1 P-on-N FZ 3e14 neq ProtonMicron 2552-6-9-1 N-on-P MCz 1.3e14 protonHPK-ATLAS07 W27-BZ3-P3 n-on-p FZ no spray 1.3e15 protons2535-9 3-3 p-on-n FZ 6.1e14 pion 2552-6 3-1 n-on-p MCz 6.1e14 pion Micron 2552-7-9 N-on-P MCz 5e14 neutronMicron 2553-11-11 n-on-n MCz 1e15 neutronMicron 2552-6-11-2 n-on-p Proton MCz 1.3e15 neqMicron 2535-8-3-1 P-on-N FZ 3e14 neq ProtonMicron 2552-6-9-1 N-on-P MCz 1.3e14 protonHPK-ATLAS07 W27-BZ3-P3 n-on-p FZ no spray 1.3e15 protons2552-6 3-1 n-on-p MCz 6.1e14 pion Micron 2552-7-11 n-on-p MCz 1e15 neutronMicron 2552-7-9 N-on-P MCz 5e14 neutronMicron 2553-11-11 n-on-n MCz 1e15 neutronMicron 2552-6-11-2 n-on-p Proton MCz 1.3e15 neqMicron 2535-8-3-1 P-on-N FZ 3e14 neq ProtonMicron 2552-6-9-1 N-on-P MCz 1.3e14 protonHPK-ATLAS07 W27-BZ3-P3 n-on-p FZ no spray 1.3e15 protons2535-9 3-3 p-on-n FZ 6.1e14 pion 2552-6 3-1 n-on-p MCz 6.1e14 pion Micron 2552-7-11 n-on-p MCz 1e15 neutronMicron 2552-7-9 N-on-P MCz 5e14 neutronMicron 2553-11-11 n-on-n MCz 1e15 neutron
June ‘09 RD50 Meeting Freiburg Hartmut Sadrozinski, SCIPP, UC Santa Cruz10
SCIPPSCIPPEfficiency Voltage (Threshold Dependence)
Efficiency Voltage is threshold dependent.
Threshold 1 fC -> 0.7 fC:
gives reduction of Efficiency Voltage of 100-200 V.
For stable operation:Breakdown Voltage >> Efficiency Voltage
Efficiency Voltage vs Anneal Time
0
200
400
600
800
1000
1 10 100 1000Anneal Time (min@60C)
Eff
icie
ncy
Vo
ltag
e [V
] HPK-ATLAS07 W27-BZ3-P3 n-on-p FZ no spray 1.3e15 protons
Saturation Voltage at70mV Threshold
Saturation Voltage at97mV Threshold
Breakdown Voltage vs Anneal Time
0
200
400
600
800
1000
1200
1400
1 10 100 1000Anneal Time (min@60C)
Bre
ak
do
wn
Vo
lta
ge
[V
]
HPK-ATLAS07 W27-BZ3-P3 n-on-p FZ no spray 1.3e15 protons
Breakdown Voltage at70mV ThresholdBreakdown Voltage at97mV Threshold
June ‘09 RD50 Meeting Freiburg Hartmut Sadrozinski, SCIPP, UC Santa Cruz11
SCIPPSCIPPAnnealing of Efficiency Voltage (@ 1fC)
Annealing benign for all but p-on-n FZ
0
500
1000
1500
2000
1 10 100 1000 10000Anneal Time @ 60° C (min)
Eff
icie
ncy
Vo
ltag
e (V
)
n-on-p MCz p+ 1.3e15 neq
p-on-n FZ p+ 3e14 neq
n-on-p MCz p+ 1.3e14 neq
n-on-p FZ p+ 1.3e15 neq
p-on-n FZ pi 6.1e14 neq
n-on-p MCz pi 3.8e14 neq
n-on-p MCz n 5e14
n-on-n MCz n 1e15
June ‘09 RD50 Meeting Freiburg Hartmut Sadrozinski, SCIPP, UC Santa Cruz12
SCIPPSCIPPAnnealing of Efficiency Voltage (@ 1fC)
No big difference between proton/pion and neutron irradiationN-on-n MCz shows “typical n-type” annealing, but on a small scale.
0
500
1000
1 10 100 1000 10000
Anneal Time @ 60° C (min)
Eff
icie
ncy
Vo
ltag
e (V
)n-on-p MCz p+ 1.3e15 neq
n-on-p MCz p+ 1.3e14 neq
n-on-p FZ p+ 1.3e15 neq
n-on-p MCz pi 3.8e14 neq
n-on-p MCz n 5e14
n-on-n MCz n 1e15
June ‘09 RD50 Meeting Freiburg Hartmut Sadrozinski, SCIPP, UC Santa Cruz13
SCIPPSCIPP
If one adjust the Efficiency voltage with difference in fluence, the Eff Voltage vs. Anneal curve will be above the Vfd curve, indicating that n-on-p MCz inverts with pion (also proton) irradiation. This is also seen in the Vfd as a function of fluence curve.
n-onp MCz Pions: Eff Voltage & Vfd vs Anneal time
0
200
400
600
800
1 10 100 1000 10000 100000
Anneal time @ 60° C (min)
Vo
ltag
e (V
)
Eff Voltage n-on-p MCz pi 3.8e14
2552-6-1-2 n-on-p MCz pi 5.6e14
Vfd vs Fluence (pions)
0
100
200
300
400
500
600
0 2E+14 4E+14 6E+14 8E+14 1E+15
Fluence (neq)
Vfd
(vo
lts) n-on-p FZ
n-on-p MCz
Comparison Efficiency Voltage - Vfd
June ‘09 RD50 Meeting Freiburg Hartmut Sadrozinski, SCIPP, UC Santa Cruz14
SCIPPSCIPP
Once the Efficiency voltage is scaled with the fluence, it would clearly be much larger than the Vfd for either Vfd fluence, indicating strong inversion of p-on-n FZ after proton irradiation
For n-on-p FZ, it can be seen that at a given fluence, the efficiency voltage will be lower than Vfd, indicating no inversion after prtoton irradiation. This is consistent with the p-on-n FZ being inverted (bulk becomes more p-type)
n-on-p FZ p+
0
100
200
300
400
500
600
700
800
900
1000
1 10 100 1000 10000
Anneal time @ 60deg C (min)
Vo
ltag
e (V
)
n-on-p FZ Eff Voltage 1.3e15 neq UCSC
n-on-p FZ Vfd 1.1e15 neq UNM
n-on-p FZ Vfd 1.5e14 neq UNM
p-on-n FZ p+
0
200
400
600
800
1000
1200
1400
1600
1800
2000
1 10 100 1000 10000
Anneal time @ 60deg C (min)
Vo
ltag
e (V
)
p-on-n FZ Eff Voltage 3e14 neq UCSC
p-on-n FZ Vfd 1.5e14 neq UNM
p-on-n FZ Vfd 1.1e15 neq UNM
Comparison Efficiency Voltage - Vfd
June ‘09 RD50 Meeting Freiburg Hartmut Sadrozinski, SCIPP, UC Santa Cruz15
SCIPPSCIPPWhat to do with C-V Measurements?
“C-V” means here “ learn something about the depletion of the sensor, to be used to predict CCE or learn something about the state of the sensor when compared to CCE”
At least 4 diferent approaches:
1. Measure C-V at 10 kHz and low temperature: wrong2. Measure C-V at R.T and 10 kHzless less wrong, good convention
(Gregor showed is ~ ok for diodes: Vdep(CEE) =Vdep(CV) within 200V)
3. Measure C-V at lower temperature, adjust frequency C-V(f,T) better4. Measure Admittance, extract the width of the space charge region best ?
June ‘09 RD50 Meeting Freiburg Hartmut Sadrozinski, SCIPP, UC Santa Cruz16
SCIPPSCIPPC-V(f,T)
3. Measure C-V at lower temperature, adjust frequency
Measure C-V at lower temperature, adjust frequency to match according to the emission coefficicnt C-V(f,T). (usual current temperature dependence)
M.K. Petterson, et al., RRESMDD06, Nucl. Inst. Meth. A 583, 189(2007)
June ‘09 RD50 Meeting Freiburg Hartmut Sadrozinski, SCIPP, UC Santa Cruz17
SCIPPSCIPPAdmittance
4. Measure Admittance, extract the width of the space charge region
Introduce Debye length to characterize non-abrupt junction(s)Since trapping and de-trapping is important, measure both Capacitance C and Conductance G as a function of temperature T and frequency
Frequency dependence of conductance reveals dynamics of trapping C, Betancourt , et al.,
RRESMDD08, IEEE 2009, Senior Thesis
Measured and simulated C and G/ω as a function of frequency for a pion irradiated n-type FZ detector taken at 100V and 22 degrees C
June ‘09 RD50 Meeting Freiburg Hartmut Sadrozinski, SCIPP, UC Santa Cruz18
SCIPPSCIPPResults of Admittance Measurement
Extracted depth of the space charge region from CCE andAdmittance
p-on-n FZ pion irradiated sensor and diode
n-on-p MCz neutron irradiated Sensor and diode
June ‘09 RD50 Meeting Freiburg Hartmut Sadrozinski, SCIPP, UC Santa Cruz19
SCIPPSCIPPResults of Admittance Measurement
Depleted depth of the space chare region for various pion detectors Extracted from Admittance measurements
June ‘09 RD50 Meeting Freiburg Hartmut Sadrozinski, SCIPP, UC Santa Cruz20
SCIPPSCIPPClustersize and Efficiency
Cluster size is given by the “Cluster Ratio” = # of clusters with multiple strips / # of clusters with one strips
Good Correlation, p-on-n FZ inverted.
Efficiency vs Cluster Ratio (1000min-Anneal)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
0 0.1 0.2 0.3 0.4 0.5
Cluster Ratio
Eff
icie
ncy
Micron 2552-6-11-2 n-on-p MCz1.3e15 neq Proton
Micron 2535-8-3-1 p-on-n FZ 3e14 neqProton
Micron 2552-6-9-1 n-on-p MCz 1.3e14Proton
ATLAS07 W27-BZ3-P3 n-on-p FZ nospray 1.3e15 neq Proton
2535-9 3-3 p-on-n FZ 6.1e14 Pion
2552-6 3-1 n-on-p MCz 6.1e14 Pion
Micron 2552-7-11 n-on-p MCz 1e15Neutron
Micron 2552-7-9 n-on-p MCz 5e14Neutron
Micron 2553-11-11 n-on-n MCz 1e15Neutron
June ‘09 RD50 Meeting Freiburg Hartmut Sadrozinski, SCIPP, UC Santa Cruz21
SCIPPSCIPPClustersize and Efficiency
Cluster size changes during annealing for n-type FZ
Efficiency vs Cluster RatioMicron 2535-8-3-1 p-on-n FZ 3e14 neq Proton
0
0.2
0.4
0.6
0.8
1
1.2
0 0.05 0.1 0.15 0.2
Cluster Ratio
Eff
icie
ncy
Pre-Anneal 10min
80min 1000min
10000min
Efficiency vs Cluster Ratio2535-9 3-3 p-on-n FZ 6.1e14 Pion
0
0.2
0.4
0.6
0.8
1
1.2
0 0.05 0.1 0.15 0.2
Cluster Ratio
Eff
icie
ncy
Pre-Anneal 10min
1000min
June ‘09 RD50 Meeting Freiburg Hartmut Sadrozinski, SCIPP, UC Santa Cruz22
SCIPPSCIPPClustersize and Efficiency
All p-type ~ same ?
Efficiency vs Cluster RatioMicron 2552-6-9-1 n-on-p MCz 1.3e14 Proton
0
0.2
0.4
0.6
0.8
1
1.2
0 0.05 0.1 0.15 0.2
Cluster Ratio
Eff
icie
ncy
Pre-Anneal 10min
80min 1000min
10000min
Efficiency vs Cluster Ratio2552-6 3-1 n-on-p MCz 6.1e14 Pion
0
0.2
0.4
0.6
0.8
1
1.2
0 0.05 0.1 0.15 0.2
Cluster Ratio
Eff
icie
ncy
Pre-Anneal 10min
80min 1360min
10000min
Efficiency vs Cluster RatioMicron 2552-6-11-2 n-on-p MCz 1.3e15 neq Proton
0
0.2
0.4
0.6
0.8
1
1.2
0 0.05 0.1 0.15 0.2
Cluster Ratio
Eff
icie
ncy
Pre-Anneal 10min
80min 1000min
10000min
Efficiency vs Cluster RatioATLAS07 W27-BZ3-P3 n-on-p FZ no spray 1.3e15 neq Proton
0
0.2
0.4
0.6
0.8
1
1.2
0 0.05 0.1 0.15 0.2
Cluster Ratio
Eff
icie
ncy
Pre-Anneal 10min
80min 1000min
10000min
June ‘09 RD50 Meeting Freiburg Hartmut Sadrozinski, SCIPP, UC Santa Cruz23
SCIPPSCIPP
For charge collection studies, the health of the system can be determined by monitoring the singles rate. It signals breakdown and thus unphysical behavior even before the leakage current or the collected charge do it.
In order to quantify the performance, we introduce the “efficiency voltage” as the bias voltage at which the efficiency reaches 100%. Very little annealing is observed, with the exception in p-on-n FZ.
The efficiency voltage for p-type material is about the same for FZ and MCz in this fluence range.
Comparison between efficiency voltage for SSD and full depletion voltage Vfd of diodes permits insight into the fact of “inversion”.
The correlation of the efficiency with the clustersize is uniform across many different sensor types, particle species during irradiation, and anneal steps (with the exception of the p-on-n FZ sensors,)
Admittance allows extraction the depth of the depleted region of irradiated sensors
Conclusions
June ‘09 RD50 Meeting Freiburg Hartmut Sadrozinski, SCIPP, UC Santa Cruz24
SCIPPSCIPP
Thanks to
the foundries and institutes who supplied sensors in a collaborative manner
staff in Ljubljana, Louvain, CERN, Karlsruhe, PSI, BNL, LANL, UCSC for carrying out the irradiations.
RD50 and ATLAS07 collaborators and the many students who spend their evenings and nights taking and analyzing the data.
Acknowledgments
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