Gunnar Lindstroem – University of HamburgWODEAN workshop, Vilnius 02/03 June 071 Gunnar Lindstroem University of Hamburg The WODEAN Project present status

Gunnar Lindstroem – University of Hamburg WODEAN workshop, Vilnius 02/03 June 07 1

Gunnar LindstroemUniversity of Hamburg

The WODEAN Projectpresent status


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


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!


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


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 !


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


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:


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)


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


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.


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


ITME KC, ITME

Vilnius Vilnius


ITME KC, ITME

Vilnius Vilnius

1E15 Florence ITME KC, ITME

Vilnius Oslo Vilnius NIMPITME

3E15 ITME KC, ITME


1E16 ITME KC, ITME


3E16 ITME KC, ITME


150 samples n-MCz <100>1 kΩcm (OKMETIC, CiS): 84 diodes, 48 nude standard, 16 nude thick

1st WODEAN batch sample list


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


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

3E13 HH, NIMP


ITME KC, ITME

Vilnius Vilnius

3E14 HH, NIMP


Vilnius Oslo Vilnius

NIMPITME

3E15 ITME KC, ITME

Oslo NIMPITME


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


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


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.


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


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.


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.


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)

Documents

Gunnar Lindstroem – University of HamburgWODEAN workshop, Vilnius 02/03 June 071 Gunnar Lindstroem University of Hamburg The WODEAN Project present status