KIT – University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association
Institut für Experimentelle Kernphysik
www.kit.edu
Annealing study of a highly irradiated FZ CMS mini sensor with the ALiBaVa setup at KIT
Robert Eber, Tanja PfisterA. Nürnberg, T. Barvich, W. de Boer, A. Dierlamm, M. Frey, Th. Müller, P. Steck, A. Kornmayer
17th RD50 Workshop218.11.2010
Robert EberInstitut für Experimentelle Kernphysik, KIT
Overview
Alibava setup at Karlsruhe
Annealing study of a FZ CMS mini sensorReverse bias
Forward bias
Leakage current
Signal to noise ratio
Comparison of operating modes
Conclusion
17th RD50 Workshop318.11.2010
Robert EberInstitut für Experimentelle Kernphysik, KIT
ALiBaVa Station at Karlsruhe
Setup shielded inside a metal box
Daughterboard thermally isolated from sensor
Temperature rangeCooling to -30°C
Heating to +80°C for annealing studies inside the setup
Signal generation byLaser 1060nm90Sr beta source
XYZ-stage for position dependent studies
Fully automated software and temperature control for complete annealing study
17th RD50 Workshop418.11.2010
Robert EberInstitut für Experimentelle Kernphysik, KIT
ALiBaVa Station at Karlsruhe
XYZ stage
Collimator for source
IR laser mount
Sensor
Daughterboard
Peltier cooling
Primary cooling
Scintillator
Isolation and shielding
17th RD50 Workshop518.11.2010
Robert EberInstitut für Experimentelle Kernphysik, KIT
Sensors above expected LHC fluenceSensor
CMS mini: FZ p-in-n sensor, 295µm active thickness, 192 strips
Irradiation: 7.5E14 Neq/cm2, 25MeV protons (@KA)
Fluence is equivalent to around 10 years of LHC operation at radius 4 – 5cm (pixel region), 300fb-1
Outer barrel SLHC strip region
Annealing study
Signal and signal to noise ratio
Current
Reverse bias
Forward bias, CID
Time [h] 0.5 0.5 0.5 0.5 0.84 1.33
Temperature 60 60 60 70 70 70
Approx. time at RT [h] 130 130 130 400 700 1400
Sum approx time[h] 130 260 390 800 1500 2900
17th RD50 Workshop618.11.2010
Robert EberInstitut für Experimentelle Kernphysik, KIT
Reverse bias operation
Higher collected chargeHigher voltage
Lower temperature
As expected
Sensor at 500V is not fully depletedSignal and S/N drops with longer annealing times
1 ADC ~ 80e-
500V-30°C
No annealing
17th RD50 Workshop718.11.2010
Robert EberInstitut für Experimentelle Kernphysik, KIT
CID MeasurementsForward bias
Generation of electric field throughout whole sensor volume
Entire sensor depth is sensitive
Current fills trap levels permanently
Lower bias voltage necessary to collect charges
Landau-Gauss fits well
Signal
Signal to noise ratio
Fluence 7.5e14 Neq/cm2 and T= -30°C not optimal for CID mode
Investigate operability
-150V-30°C
No annealing
[5]
𝐸 (𝑥 )=32𝑉𝑑 √ 𝑥𝑑[4]
17th RD50 Workshop818.11.2010
Robert EberInstitut für Experimentelle Kernphysik, KIT
CID Measurements
Signal increases with voltage
S/N shows maximum at certain bias voltage:
Noise increase
Related to current
Overall annealing behaviour:
Slight drop in S/N with annealing
17th RD50 Workshop918.11.2010
Robert EberInstitut für Experimentelle Kernphysik, KIT
Current annealing
Leakage current shows known annealing behaviour with reverse bias applied
LC decreases
More impact at higher temperatures
Under forward bias condition, current increases drastically with annealing
Noise rises due to current
Operation at lower temperatures necessary to reduce current level
Powerful cooling required
Current annealing at first step only
Reverse bias Forward bias
17th RD50 Workshop1018.11.2010
Robert EberInstitut für Experimentelle Kernphysik, KIT
Comparison: CID – reverse bias (Signal)
Reverse bias
Signal level increases at lower voltages after short annealing
Signal decreases with longer annealing
Forward bias
Annealing has almost no influence on signal height
10d RT annealing
100d RT annealing
No annealing
17th RD50 Workshop1118.11.2010
Robert EberInstitut für Experimentelle Kernphysik, KIT
Comparison: CID – reverse bias (S/N)
Reverse biasSignal to Noise ratio improved due to beneficial annealing
Forward biasSlight decrease in S/N due to current increase
No beneficial annealing observed
No annealing 10d RT annealing
100d RT annealing
17th RD50 Workshop1218.11.2010
Robert EberInstitut für Experimentelle Kernphysik, KIT
Summary
Sensor in CID mode outperforms the sensor with reverse bias with no annealing at only -150V
It almost reaches the reverse bias 10d at RT annealing level
500V, no annealing, fits well into known data
500V, 10d annealing almost doubles the collected charge
1000V, 10d annealing even performs like the n-in-n pixels at 600V
No improvement during annealing in CID mode
References:[1] p/n-FZ, 300µm (-30°C,25ns), strip [Casse 2008][2] n/n-FZ, 285µm (-10°C,40ns), pixel [Rohe et al. 2005][3] p/n-FZ, 295µm (-30°C,25ns), strip [Pfister 2010]
17th RD50 Workshop1318.11.2010
Robert EberInstitut für Experimentelle Kernphysik, KIT
Conclusion
Sensor could be operated in CID mode with fluence of „only“ 7.5e14 Neq/cm2 and temperature -30°C
CID is possible readout mode…
Feasible S/N can be achieved at much lower voltages compared to reverse bias
But..
Applicable in detectors only when not annealed
Operation at low temperature and high forward current requires very powerful cooling
Lack of beneficial annealing rules out advantages of forward bias
With appropriate annealing the sensor can resist fluences above the expected ones at LHC (300fb-1)
Known FZ p-in-n material could be chosen for outer barrel strip regions at SLHC
17th RD50 Workshop1418.11.2010
Robert EberInstitut für Experimentelle Kernphysik, KIT
Thank you for your attention!
Diploma Thesis, Tanja Pfister, KIT 2010: IEKP-KA/2010-20
17th RD50 Workshop1518.11.2010
Robert EberInstitut für Experimentelle Kernphysik, KIT
References
[4] Beatti, L.J., et al. Forward-bias operating of Si detectors: a way to work in high-radiation environment. Nuclear Instruments and Methods in Physics Research, 439:293, 2000.
[5] Zheng, L. et col. Cryogenic Si detectors for ultra radiation hardness in SLHC environment. Nuclear Instruments and Methods in Physics Research, 579(A):775-781, 2007.
Prof. Max Mustermann - Title
17th RD50 Workshop1618.11.2010
Robert EberInstitut für Experimentelle Kernphysik, KIT
Landau-Gauss fits at 600V, -10°CSignal: No Annealing 10d Annealing at RT
S2N: No Annealing 10d Annealing at RT
17th RD50 Workshop1718.11.2010
Robert EberInstitut für Experimentelle Kernphysik, KIT
Landau-Gauss fits at -150V, -30°CSignal: No Annealing 10d Annealing at RT
S2N: No Annealing 10d Annealing at RT
17th RD50 Workshop1818.11.2010
Robert EberInstitut für Experimentelle Kernphysik, KIT
Current – Voltage at different T
17th RD50 Workshop1918.11.2010
Robert EberInstitut für Experimentelle Kernphysik, KIT
Current – Voltage at different annealing
17th RD50 Workshop2018.11.2010
Robert EberInstitut für Experimentelle Kernphysik, KIT
Clustersignal – Time Plots
Reverse Bias
Forward Bias
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