Transcript Folie 1

The WODEAN Project
present status
Gunnar Lindstroem
University of Hamburg
Gunnar Lindstroem – University of Hamburg
WODEAN workshop, Vilnius 02/03 June 07
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Silicon Detectors: Favorite Choice for Particle Tracking
Example: Large Hadron Collider LHC, start 2007
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 sec
Expected total op. period: 10 years
LHC
properties
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
Intense radiation field
during 10 years
low voltage operation in
normal ambients
Radiation tolerance up to
1015 hadrons/cm²
Feasibility, e.g.
200 m² for CMS
large scale availability
known technology, low cost
! Silicon Detectors meet all Requirements !
Gunnar Lindstroem – University of Hamburg
WODEAN workshop, Vilnius 02/03 June 07
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LHC ATLAS Detector – a Future HEP Experiment
Overall length: 46m, diameter: 22m,
total weight: 7000t, magnetic field: 2T
ATLAS collaboration: 1500 members
principle of a silicon detector:
solid state ionization chamber
micro-strip detector
for particle tracking
2nd general purpose experiment:
CMS, with all silicon tracker!
Gunnar Lindstroem – University of Hamburg
For innermost layers: pixel detectors
WODEAN workshop, Vilnius 02/03 June 07
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Main motivations for R&D on
Radiation Tolerant Detectors: Super - LHC
• LHC upgrade
LHC (2007), L =
500
fb-1
Pixel (?)
f(r=4cm) ~
3·1015cm-2
CERN-RD48
10
2500
fb-1
f(r=4cm) ~ 1.6·1016cm-2
CERN-RD50
• LHC (Replacement of components)
e.g. - LHCb Velo detectors (~2010)
- ATLAS Pixel B-layer (~2012)
Macropixel (?)
5
5
Super-LHC (2015 ?), L = 1035cm-2s-1
5 years
Ministrip (?)
16
total fluence eq
eq [cm-2]
10 years
SUPER - LHC (5 years, 2500 fb-1)
1034cm-2s-1
1015
5
neutrons eq
pions eq
1014
5
ATLAS SCT - barrel
(microstrip detectors)
ATLAS Pixel
13
10
0
10
other charged
hadrons eq
20
30
40
50
60
[M.Moll, simplified, scaled from ATLAS TDR]
r [cm]
• Linear collider experiments (generic R&D)
Deep understanding of radiation damage will be fruitful for linear collider experiments where
high doses of e, g will play a significant role.
Gunnar Lindstroem – University of Hamburg
WODEAN workshop, Vilnius 02/03 June 07
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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
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Deterioration of Detector Properties
by displacement damage NIEL
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
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Radiation Damage – Leakage current
Increase of Leakage Current
…. with particle fluence:
6
-2
10
10-3
n-type FZ - 780 cm
n-type FZ - 410 cm
n-type FZ - 130 cm
n-type FZ - 110 cm
n-type CZ - 140 cm
p-type EPI - 380 cm
10-4
10-5
10-6 11
10

n-type FZ - 7 to 25 Kcm
n-type FZ - 7 Kcm
n-type FZ - 4 Kcm
n-type FZ - 3 Kcm
p-type EPI - 2 and 4 Kcm
1012
1013
eq [cm-2]
1015
[M.Moll PhD Thesis]
Damage parameter  (slope in figure)
I
α
V   eq

1014
Leakage current
per unit volume
and particle fluence
 is constant over several orders of fluence
and independent of impurity concentration in Si
 can be used for fluence measurement
Gunnar Lindstroem – University of Hamburg
(t) [10-17 A/cm]
I / V [A/cm3]
10-1
with time (annealing):
6
80 min
60C
5
4
5
4
3
3
2
2
.
1
0
1
17
-3
oxygen enriched silicon [O] = 2 10 cm
parameterisation for standard silicon
1
[M.Moll PhD Thesis]
10
100
1000
10000
annealing time at 60oC [minutes]
 Leakage current decreasing in time
(depending on temperature)
 Strong temperature dependence:
 E

I  exp  g

2
k
T
B


Consequence:
Cool detectors during operation!
Example: I(-10°C) ~1/16 I(20°C)
WODEAN workshop, Vilnius 02/03 June 07
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Radiation Damage – Effective doping concentration
Change of Depletion Voltage Vdep (Neff)
…. with time (annealing):
10
1000
500
102
 600 V
type inversion
100
50
10
5
101
1014cm-2
1
10-1
10
"p-type"
n-type
[M.Moll: Data: R. Wunstorf, PhD thesis 1992, Uni Hamburg]
10
0
10
1
10
2
eq [ 1012 cm-2 ]
10
3
10
0
 Neff [1011cm-3]
103
5000
| Neff | [ 1011 cm-3 ]
Udep [V] (d = 300m)
…. with particle fluence:
p+
n+
p+
n+
NY
NA
4
NC
gC eq
2
NC0
0
1
-1
after inversion
6
„Hamburg model“
[M.Moll, PhD thesis 1999, Uni Hamburg]
“Type inversion”: Neff changes from positive to
negative (Space Charge Sign Inversion)
before inversion
8
10
100
1000 10000
annealing time at 60oC [min]
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)
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
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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
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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, trecomb, 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
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1st WODEAN batch sample list
 (1MeV n)
C-DLTS
3E11
HH,Oslo,
Minsk
6E11
HH,Oslo,
Minsk
I-DLTS
TSC
PITS
PL
trecomb
ITME
KC,
ITME
Vilnius
Vilnius
HH, NIMP
ITME
KC,
ITME
Vilnius
Vilnius
HH, NIMP
ITME
KC,
ITME
Vilnius
Vilnius
1E12
1E13
Florence
3E13
FTIR PC
EPR
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
NIMP
ITME
3E15
ITME
KC,
ITME
Vilnius
Oslo
Vilnius
NIMP
ITME
1E16
ITME
KC,
ITME
Vilnius
Oslo
Vilnius
NIMP
ITME
3E16
ITME
KC,
ITME
Vilnius
Oslo
Vilnius
NIMP
ITME
150 samples n-MCz <100>1 kΩcm (OKMETIC, CiS): 84 diodes, 48 nude standard, 16 nude thick
Gunnar Lindstroem – University of Hamburg
WODEAN workshop, Vilnius 02/03 June 07
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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/cm²s
Temperature increase during irradiation
3E+15: t ≈ 25 min, temp. rising to 70-80°C
within 15 min (then saturating)
1E+16: t ≈ 80 min, temp. 70-80°C
3E+16: t ≈ 4h, 10min, severe self anneal expected
Gunnar Lindstroem – University of Hamburg
WODEAN workshop, Vilnius 02/03 June 07
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2nd WODEAN batch sample list
 (1MeV n)
C-DLTS
3E11
HH,Oslo,
Minsk
6E11
HH,Oslo,
Minsk
I-DLTS
TSC
PITS
PL
trecomb
FTIR
PC
Florence
HH, NIMP
ITME
KC,
ITME
Vilnius
Vilnius
ITME
KC,
ITME
Vilnius
Vilnius
ITME
KC,
ITME
Vilnius
ITME
KC,
ITME
ITME
KC,
ITME
ITME
KC,
ITME
EPR
1E12
1E13
3E13
1E14
HH, NIMP
Florence
3E14
1E15
HH, NIMP
Florence
3E15
1E16
HH, NIMP
Florence
3E16
Oslo
Vilnius
Oslo
Vilnius
Oslo
NIMP
ITME
NIMP
ITME
Vilnius
Oslo
NIMP
ITME
NIMP
ITME
90 samples n-FZ <111>, 2 kΩcm (Wacker, STM): 67 diodes, 24 nude thick samples;
Gunnar Lindstroem – University of Hamburg
WODEAN workshop, Vilnius 02/03 June 07
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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/cm²s
Temperature increase during irradiation
3E+15: t ≈ 25 min, temp. rising to 70-80°C
within 15 min (then saturating)
1E+16: t ≈ 80 min, temp. 70-80°C
3E+16: t ≈ 4h, 10min, severe self anneal expected
Gunnar Lindstroem – University of Hamburg
WODEAN workshop, Vilnius 02/03 June 07
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Hamburg, 08-May-2007
WORKSHOP ON DEFECT ANALYSIS WODEAN
-RD50 internal projectI. Project Object
The 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
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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-type
As 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 Ljubljana
Maximum (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, Minsk
I-DLTS: Univ. Florence
TSC: Univ. Hamburg, NIMP Bucharest
PITS: ITME Warsaw
PL: Kings College London, ITME Warsaw
Lifetime: Univ. Vilnius
FTIR: Univ. Oslo
PC: Univ. Vilnius
EPR: NIMP Bucharest, ITME Warsaw
Detecor characteris. (C/V, I/V, TCT): CERN-PH, Univ HH, JSI Ljubljana
Gunnar Lindstroem – University of Hamburg
WODEAN workshop, Vilnius 02/03 June 07
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Memberlist with affiliation:
NIMP Bucharest: Sergiu Nistor, Ioana Pintilie (also guest in Hamburg Univ.)
CERN-PH: Michael Moll
Hamburg University: Eckhart Fretwurst, Gunnar Lindstroem, Ioana Pintilie (from NIMP)
Florence University: Mara Bruzzi, David Menichelli
JSI Ljubljana: Gregor Kramberger
Kings College London: Gordon Davies
Minsk University: Leonid Makarenko
Oslo University: Bengt Gunnar Svensson, Leonid Murin (guest from Minsk)
Vilnius University: Eugenius Gaubas, Juozas Vaitkus
ITME Warsaw: Pawel Kaminski, Roman Kozlowski, Mariusz Pawlowski, Barbara Surma
Needs to be updated!, Sergiu Nistor resigned, new members: Anfrey Aleev (ITEP)?
III. Present Status
A 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
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IV. Project Budget Proposal
Total budget breakdown:
Material-, processing, masks, special preparations:
Subcontracted analysis:
Total budget:
Requested support from RD50 common fund:
MCz- and FZ material:
Processing 15.000,- CHF
Analysis (SIMS, spreading resistance,…)
Total requested support from RD50:
Contributions from WODEAN members:
CERN-EP: 2.000,- CHF
Florence University:
Hamburg University:
Oslo University:
All other Institutes: contributions in kind:
Total contribution from WODEAN members:
35.000,- CHF
10.000,- CHF
45.000,- CHF
5.000,- CHF
10.000,- CHF
30.000,- CHF
2.000,- CHF
8.000,- CHF
3.000,- CHF
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
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Finally
Last changes to the application as internal project: accepted as is
what did we learn: this meeting
discussion about overview report for RD50
modifications for working program
what 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) included
I-DLTS: D. Menichelli (Florence): observer (manpower problems)
EPR: Sergiu Nistor (NIMP): observer (future participation possible)
Gunnar Lindstroem – University of Hamburg
WODEAN workshop, Vilnius 02/03 June 07
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