gunnar lindstroem – university of hamburgwodean workshop, vilnius 02/03 june 071 gunnar lindstroem...
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Gunnar Lindstroem – University of Hamburg WODEAN workshop, Vilnius 02/03 June 07 1
Gunnar LindstroemUniversity of Hamburg
The WODEAN Projectpresent status
Gunnar Lindstroem – University of Hamburg WODEAN workshop, Vilnius 02/03 June 07 2
LHCproperties
Proton-proton collider, 2 x 7 TeV Luminosity: 1034
Bunch crossing: every 25 nsec, Rate: 40 MHz event rate: 109/sec (23 interactions per bunch crossing)Annual operational period: 107 secExpected total op. period: 10 years
Experimental requests Detector properties
Reliable detection of mips S/N ≈ 10
High event rate time + position resolution:
high track accuracy ~10 ns and ~10 µm
Complex detector design low voltage operation in normal ambients
Intense radiation field Radiation tolerance up to during 10 years 1015 hadrons/cm²
Feasibility, e.g. large scale availability200 m² for CMS known technology, low cost
Silicon Detectors: Favorite Choice for Particle Tracking
! Silicon Detectors meet all Requirements !
Example: Large Hadron Collider LHC, start 2007
Gunnar Lindstroem – University of Hamburg WODEAN workshop, Vilnius 02/03 June 07 3
LHC ATLAS Detector – a Future HEP Experiment
Overall length: 46m, diameter: 22m, total weight: 7000t, magnetic field: 2TATLAS collaboration: 1500 members
micro-strip detectorfor particle tracking
principle of a silicon detector: solid state ionization chamber
For innermost layers: pixel detectors 2nd general purpose experiment:
CMS, with all silicon tracker!
Gunnar Lindstroem – University of Hamburg WODEAN workshop, Vilnius 02/03 June 07 4
Main motivations for R&D on Radiation Tolerant Detectors: Super - LHC
• LHC upgrade LHC (2007), L = 1034cm-2s-1
(r=4cm) ~ 3·1015cm-2
Super-LHC (2015 ?), L = 1035cm-2s-1
(r=4cm) ~ 1.6·1016cm-2
• LHC (Replacement of components) e.g. - LHCb Velo detectors (~2010) - ATLAS Pixel B-layer (~2012)
• Linear collider experiments (generic R&D)Deep understanding of radiation damage will be fruitful for linear collider experiments where high doses of e, will play a significant role.
10 years
500 fb-1
5 years
2500 fb-1
5
0 10 20 30 40 50 60
r [cm]
1013
5
1014
5
1015
5
1016
eq
[cm
-2]
total fluence eqtotal fluence eq
neutrons eq
pions eq
other charged
SUPER - LHC (5 years, 2500 fb-1)
hadrons eqATLAS SCT - barrelATLAS Pixel
Pixel (?) Ministrip (?)
Macropixel (?)
(microstrip detectors)
[M.Moll, simplified, scaled from ATLAS TDR]
CERN-RD48
CERN-RD50
Gunnar Lindstroem – University of Hamburg WODEAN workshop, Vilnius 02/03 June 07 5
Radiation Damage in Silicon Sensors
Two types of radiation damage in detector materials: Bulk (Crystal) damage due to Non Ionizing Energy Loss (NIEL
- displacement damage, built up of crystal defects –
I. Increase of leakage current (increase of shot noise, thermal runaway)
II. Change of effective doping concentration (higher depletion voltage, under- depletion)
III. Increase of charge carrier trapping (loss of charge)
Surface damage due to Ionizing Energy Loss (IEL)
- accumulation of charge in the oxide (SiO2) and Si/SiO2 interface – affects: interstrip capacitance (noise factor), breakdown behavior, …
! Signal/noise ratio = most important quantity !
Gunnar Lindstroem – University of Hamburg WODEAN workshop, Vilnius 02/03 June 07 6
Deterioration of Detector Properties by displacement damage NIEL
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
Point defects + clusters
Dominated by clusters
Damage effects generally ~ NIEL, however differences between proton & neutron damage important for defect generation in silicon bulk
Gunnar Lindstroem – University of Hamburg WODEAN workshop, Vilnius 02/03 June 07 7
Radiation Damage – Leakage current
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 Kcmn-type FZ - 4 Kcmn-type FZ - 3 Kcm
n-type FZ - 780 cmn-type FZ - 410 cmn-type FZ - 130 cmn-type FZ - 110 cmn-type CZ - 140 cm
p-type EPI - 2 and 4 Kcm
p-type EPI - 380 cm
[M.Moll PhD Thesis][M.Moll PhD Thesis]
Damage parameter (slope in figure)
Leakage current per unit volume and particle fluence
is constant over several orders of fluenceand independent of impurity concentration in Si can be used for fluence measurement
Increase of Leakage Current
eqV
I
α
Leakage current decreasing in time (depending on temperature) Strong temperature dependence:
Consequence: Cool detectors during operation! Example: I(-10°C) ~1/16 I(20°C)
1 10 100 1000 10000annealing time at 60oC [minutes]
0
1
2
3
4
5
6
(t)
[10
-17 A
/cm
]
1
2
3
4
5
6
oxygen enriched silicon [O] = 2.1017 cm-3
parameterisation for standard silicon [M.Moll PhD Thesis]
80 min 60C
with time (annealing):
Tk
EI
B
g
2exp
…. with particle fluence:
Gunnar Lindstroem – University of Hamburg WODEAN workshop, Vilnius 02/03 June 07 8
Radiation Damage – Effective doping concentration
n+ p+ n+
10-1 100 101 102 103
eq [ 1012 cm-2 ]
1
510
50100
5001000
5000
Ude
p [V
] (
d =
300
m)
10-1
100
101
102
103
| Nef
f | [
1011
cm
-3 ]
600 V
1014cm-2
type inversion
n-type "p-type"
[M.Moll: Data: R. Wunstorf, PhD thesis 1992, Uni Hamburg]
p+
Change of Depletion Voltage Vdep (Neff)
“Type inversion”: Neff changes from positive to
negative (Space Charge Sign Inversion)
Short term: “Beneficial annealing” Long term: “Reverse annealing” - time constant depends on temperature: ~ 500 years (-10°C) ~ 500 days ( 20°C) ~ 21 hours ( 60°C)
…. with time (annealing):
NC
NC0
gC eq
NYNA
1 10 100 1000 10000annealing time at 60oC [min]
0
2
4
6
8
10
N
eff [
1011
cm-3
]
[M.Moll, PhD thesis 1999, Uni Hamburg]
before inversion after inversion
„Hamburg model“
…. with particle fluence:
Consequence: Cool Detectors even during beam off (250 d/y)alternative: acceptor/donor compensation by defect enginrg.,e.g. see developm. with epi-devices (Hamburg group)
Gunnar Lindstroem – University of Hamburg WODEAN workshop, Vilnius 02/03 June 07 9
Summary
Silicon Detectors in the inner tracking area of future colliding beam experiments have to tolerate a hadronic fluence of up to eq = 1016/cm²
Deterioration of the detector performance is largely due to bulk damage caused by non ionizing energy loss of the particles
Reverse current increase (originating likely from both point defects and clusters) can be effectively reduced by cooling. Defect engineering so far not successful
Change of depletion voltage severe, also affected by type inversion and annealing effects. Modification by defect engineering possible, for standard devices continuous cooling essential (freezing of annealing)
Charge trapping is the ultimate limitation for detector application, responsible trapping centers widely unknown, cooling and annealing have little effects
Gunnar Lindstroem – University of Hamburg WODEAN workshop, Vilnius 02/03 June 07 10
Outline for a correlated project
• Main issue: charge trapping, the ultimate limitation for detector applications in future HEP experiments source for trapping so far unknown! Maximum to be tolerated: 1.5E+16 n/cm².
• Charge trapping: independent of material type (FZ, CZ, epi) and properties (std, DO, resistivity, doping type). not depending on type of irradiating particles and energy (23 GeV protons, reactor neutrons), if normalised to 1 MeV neutron equivalent values (NIEL). In contrast to IFD and Neff there are almost no annealing effects (in isothermal annealing studies up to 80C).
• Correlated project: use all available methods: DLTS, TSC, PITS, PL, recomb, FTIR, PC, EPR concentrate on single material (MCz chosen with possibility of std. FZ for checking of unexpected results. Use only one type of irradiation, most readily available (TRIGA reactor at Ljubljana) and do limited number of steps between 1E+12 and 3E+16 n/cm².
Gunnar Lindstroem – University of Hamburg WODEAN workshop, Vilnius 02/03 June 07 11
1MeV n) C-DLTS
I-DLTS
TSC PITS PL recomb FTIR
PC EPR
3E11 HH,Oslo, Minsk
6E11 HH,Oslo, Minsk
1E12 ITME KC, ITME
Vilnius Vilnius
1E13 Florence HH, NIMP
ITME KC, ITME
Vilnius Vilnius
3E13 HH, NIMP
ITME KC, ITME
Vilnius Vilnius
1E14 Florence HH, NIMP
ITME KC, ITME
Vilnius Vilnius
3E14 Florence HH, NIMP
ITME KC, ITME
Vilnius Vilnius
1E15 Florence ITME KC, ITME
Vilnius Oslo Vilnius NIMPITME
3E15 ITME KC, ITME
Vilnius Oslo Vilnius NIMPITME
1E16 ITME KC, ITME
Vilnius Oslo Vilnius NIMPITME
3E16 ITME KC, ITME
Vilnius Oslo Vilnius NIMPITME
150 samples n-MCz <100>1 kΩcm (OKMETIC, CiS): 84 diodes, 48 nude standard, 16 nude thick
1st WODEAN batch sample list
Gunnar Lindstroem – University of Hamburg WODEAN workshop, Vilnius 02/03 June 07 12
Irradiations
Date: November 2006
Delivery to Hamburg: 8 January 2007
Distribution to WODEAN members: 9 February 2007
Important Info about irradiations:
≤ 1E+15 n/cm²: T ≈ 20°C, duration ≤ 10 min
≥ 2E+15 n/cm²: high flux: d/dt = 2E12 n/cm²sTemperature increase during irradiation3E+15: t ≈ 25 min, temp. rising to 70-80°Cwithin 15 min (then saturating)1E+16: t ≈ 80 min, temp. 70-80°C3E+16: t ≈ 4h, 10min, severe self anneal expected
Gunnar Lindstroem – University of Hamburg WODEAN workshop, Vilnius 02/03 June 07 13
1MeV n) C-DLTS I-DLTS TSC PITS PL recomb FTIR PC EPR
3E11 HH,Oslo, Minsk
6E11 HH,Oslo, Minsk
1E12
1E13 Florence HH, NIMP
ITME KC, ITME
Vilnius Vilnius
3E13 HH, NIMP
1E14 Florence HH, NIMP
ITME KC, ITME
Vilnius Vilnius
3E14 HH, NIMP
1E15 Florence ITME KC, ITME
Vilnius Oslo Vilnius
NIMPITME
3E15 ITME KC, ITME
Oslo NIMPITME
1E16 Florence ITME KC, ITME
Vilnius Oslo Vilnius
NIMPITME
3E16 ITME KC, ITME
Oslo NIMPITME
90 samples n-FZ <111>, 2 kΩcm (Wacker, STM): 67 diodes, 24 nude thick samples;
2nd WODEAN batch sample list
Gunnar Lindstroem – University of Hamburg WODEAN workshop, Vilnius 02/03 June 07 14
Irradiations
Date: EarlyApril 2007
Delivery to Hamburg: foreseen 11 June 2007
Distribution to WODEAN members: foreseen end June 2007
Important Info about irradiations (as for 1st batch):
≤ 1E+15 n/cm²: T ≈ 20°C, duration ≤ 10 min
≥ 2E+15 n/cm²: high flux: d/dt = 2E12 n/cm²sTemperature increase during irradiation3E+15: t ≈ 25 min, temp. rising to 70-80°Cwithin 15 min (then saturating)1E+16: t ≈ 80 min, temp. 70-80°C3E+16: t ≈ 4h, 10min, severe self anneal expected
Gunnar Lindstroem – University of Hamburg WODEAN workshop, Vilnius 02/03 June 07 15
Hamburg, 08-May-2007WORKSHOP ON DEFECT ANALYSIS WODEAN
-RD50 internal project-I. Project ObjectThe project is based on discussions during the first WODEAN meeting, which was proposed during the RD50 workshop at CERN, November 2005 and finally held in Hamburg, 24/25 August, 2006. The main object was to address the problem of defect generation in detector grade silicon using a variety of available techniques. By doing this in a correlated project it is hoped to get more insight in defect creation and a better understanding of their implications for the operability in extremely harsh radiation environments. Thus the main focus is set by the application of silicon detectors in the innermost tracking area of the future SLHC experiments, where accumulated hadron fluences of up to 1.5·1016 cm-2 (1 MeV neutron equivalent) have to be tolerated. Surveying the main effects of radiation damage for detector properties (reverse current increase, change of depletion voltage and reduction of the charge collection for traversing minmum ionizing particles), the latter effect was screened out to be most challenging. Indeed charge carrier trapping would ultimately limit the applicability of silicon detectors.
Gunnar Lindstroem – University of Hamburg WODEAN workshop, Vilnius 02/03 June 07 16
II Project Outline Guide lines:Restrictions for the main objects such that results can be obtained within a reasonable time of 1 year with possible extension for a 2nd year.Common correlated project making optimum use of all available methods, intercomparability of obtained results (same material, identical irradiation, identical annealing steps etc.)As charge trapping is largely independent of the detector material, the project is restricted to MCz (magnetic Czochralski) and in a 2nd step to StFZ (standard float zone), both n-typeAs charge trapping after hadron irradiation is largely independent of particle type and energy (if fluence is NIEL normalised to 1 MeV neutrons), irradiations to be performed at the TRIGA reactor LjubljanaMaximum (1MeV neutron equivalent) hadron fluence expected in SLHC is 1.5·1016 cm-2. Irradiations should therefore cover a range from values usable for the most sensitive methods (DLTS) up to well above 1·1016 cm-2 in manageable steps.
Methods for investigations:C-DLTS: Univ. Hamburg, Oslo, MinskI-DLTS: Univ. FlorenceTSC: Univ. Hamburg, NIMP BucharestPITS: ITME WarsawPL: Kings College London, ITME WarsawLifetime: Univ. VilniusFTIR: Univ. OsloPC: Univ. VilniusEPR: NIMP Bucharest, ITME WarsawDetecor characteris. (C/V, I/V, TCT): CERN-PH, Univ HH, JSI Ljubljana
Gunnar Lindstroem – University of Hamburg WODEAN workshop, Vilnius 02/03 June 07 17
Memberlist with affiliation:NIMP Bucharest: Sergiu Nistor, Ioana Pintilie (also guest in Hamburg Univ.)CERN-PH: Michael MollHamburg University: Eckhart Fretwurst, Gunnar Lindstroem, Ioana Pintilie (from NIMP)Florence University: Mara Bruzzi, David MenichelliJSI Ljubljana: Gregor KrambergerKings College London: Gordon DaviesMinsk University: Leonid MakarenkoOslo University: Bengt Gunnar Svensson, Leonid Murin (guest from Minsk)Vilnius University: Eugenius Gaubas, Juozas VaitkusITME Warsaw: Pawel Kaminski, Roman Kozlowski, Mariusz Pawlowski, Barbara Surma
Needs to be updated!, Sergiu Nistor resigned, new members: Anfrey Aleev (ITEP)?
III. Present StatusA first batch of 120 different MCz samples (material from Okmetic; diodes and nude samples processed by CiS, 3 mm thick samples for FTIR and EPR from CERN) had been irradiated at the TRIGA reactor in November 2006 and distributed to the different collaborators. 11 irradiation fluences were chosen between 3·1011 and 3·1016 cm-2 with the smallest values for DLTS and the largest ones for EPR. A 2nd batch of FZ samples had been sent to Ljubljana and will be irradiated soon. First results on the measurements as well as an upgrade of the project program will be discussed in the 2nd WODEAN workshop scheduled on 2nd and 3rd June 2007 in Vilnius. A summary will then be presented on the following RD50 workshop.
Gunnar Lindstroem – University of Hamburg WODEAN workshop, Vilnius 02/03 June 07 18
IV. Project Budget Proposal Total budget breakdown:Material-, processing, masks, special preparations: 35.000,- CHFSubcontracted analysis: 10.000,- CHFTotal budget: 45.000,- CHF
Requested support from RD50 common fund:MCz- and FZ material: 5.000,- CHFProcessing 15.000,- CHFAnalysis (SIMS, spreading resistance,…) 10.000,- CHFTotal requested support from RD50: 30.000,- CHF
Contributions from WODEAN members:CERN-EP: 2.000,- CHFFlorence University: 2.000,- CHFHamburg University: 8.000,- CHFOslo University: 3.000,- CHFAll other Institutes: contributions in kind: Total contribution from WODEAN members: 15.000,- CHF
It is proposed that the finacial management for the RD50 support will be handled by the detector group, Institute for Experimental Physics, Hamburg University.
Gunnar Lindstroem – University of Hamburg WODEAN workshop, Vilnius 02/03 June 07 19
Finally
Last changes to the application as internal project: accepted as is what did we learn: this meeting
discussion about overview report for RD50modifications for working programwhat else should be done with existing MCz samples, isochronal anneal!interchanging results inbetween workshops continuously
next workshop date: end 2007
Changes to WODEAN member list:Diode characterisation: M. Moll (CERN-PH) includedI-DLTS: D. Menichelli (Florence): observer (manpower problems) EPR: Sergiu Nistor (NIMP): observer (future participation possible)