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Radiation Tolerant Sensors for Solid State Tracking Detectors
Michael MollMichael Moll
CERN - Geneva - SwitzerlandCERN - Geneva - Switzerland
EPFL – LPHE, Lausanne, January 29, 2007
- CERN-RD50 project –
http://www.cern.ch/rd50http://www.cern.ch/rd50
Michael Moll – Lausanne, 29. January 2007 -2-
RD50 Outline
Introduction: LHC and LHC experiment
Motivation to develop radiation harder detectors
Introduction to the RD50 collaboration
Part I: Radiation Damage in Silicon Detectors (A very brief review) Microscopic defects (changes in bulk material) Macroscopic damage (changes in detector properties)
Part II: RD50 - Approaches to obtain radiation hard sensors Material Engineering Device Engineering
Summary and preliminary conclusion
Michael Moll – Lausanne, 29. January 2007 -3-
RD50 LHC - Large Hadron Collider
Start : 2007
• Installation in existing LEP tunnel
• 27 Km ring
• 1232 dipoles B=8.3T
• 4000 MCHF (machine+experiments)
• pp s = 14 TeV Ldesign = 1034 cm-2 s-1
• Heavy ions (e.g. Pb-Pb at s ~ 1000 TeV)LHC experiments located at 4 interaction points
p p
Michael Moll – Lausanne, 29. January 2007 -6-
RD50 LHC example: CMS inner tracker
5.4 m
2.4
m
Inner TrackerOuter Barrel
(TOB)Inner Barrel (TIB) End Cap
(TEC)Inner Disks(TID)
CMS – “Currently the Most Silicon” Micro Strip: ~ 214 m2 of silicon strip sensors, 11.4 million strips
Pixel: Inner 3 layers: silicon pixels (~ 1m2) 66 million pixels (100x150m) Precision: σ(rφ) ~ σ(z) ~ 15m Most challenging operating environments (LHC)
CMS
Pixel
93 cm
30 cm
Pixel Detector
Total weight 12500 t
Diameter 15m
Length 21.6m
Magnetic field 4 T
Michael Moll – Lausanne, 29. January 2007 -7-
RD50 Status December 2006
LHC Silicon Trackers close to or under commissioning
CMS Tracker Outer Barrel
ATLAS Silicon Tracker (08/2006)August 2006 – installed in ATLAS
CMS Tracker (12/2006)(foreseen: June 2007 into the pit)
Michael Moll – Lausanne, 29. January 2007 -8-
RD50 Motivation 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.
5 years
2500 fb-1
10 years
500 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]
Michael Moll – Lausanne, 29. January 2007 -9-
RD50 The CERN RD50 Collaboration http://www.cern.ch/rd50
Collaboration formed in November 2001 Experiment approved as RD50 by CERN in June 2002 Main objective:
Presently 264 members from 52 institutes
Development of ultra-radiation hard semiconductor detectors for the luminosity upgrade of the LHC to 1035 cm-2s-1 (“Super-LHC”).
Challenges: - Radiation hardness up to 1016 cm-2 required - Fast signal collection (Going from 25ns to 10 ns bunch crossing ?)
- Low mass (reducing multiple scattering close to interaction point)- Cost effectiveness (big surfaces have to be covered with detectors!)
RD50: Development of Radiation Hard Semiconductor Devices for High Luminosity Colliders
Belarus (Minsk), Belgium (Louvain), Canada (Montreal), Czech Republic (Prague (3x)), Finland (Helsinki, Lappeenranta), Germany (Berlin, Dortmund, Erfurt, Freiburg, Hamburg, Karlsruhe),
Israel (Tel Aviv), Italy (Bari, Bologna, Florence, Padova, Perugia, Pisa, Trento, Turin), Lithuania (Vilnius), The Netherlands (Amsterdam), Norway (Oslo (2x)), Poland (Warsaw (2x)), Romania (Bucharest (2x)), Russia
(Moscow), St.Petersburg), Slovenia (Ljubljana), Spain (Barcelona, Valencia), Switzerland (CERN, PSI), Ukraine (Kiev), United Kingdom (Diamond, Exeter, Glasgow, Lancaster, Liverpool, Sheffield),
USA (Fermilab, Purdue University, Rochester University, SCIPP Santa Cruz, Syracuse University, BNL, University of New Mexico)
Michael Moll – Lausanne, 29. January 2007 -10-
RD50 Outline
Motivation to develop radiation harder detectors
Introduction to the RD50 collaboration
Part I: Radiation Damage in Silicon Detectors (A very brief review) Microscopic defects (changes in bulk material) Macroscopic damage (changes in detector properties)
Part II: RD50 - Approaches to obtain radiation hard sensors Material Engineering Device Engineering
Summary and preliminary conclusion
Michael Moll – Lausanne, 29. January 2007 -11-
RD50 Radiation Damage – Microscopic Effects
particle SiS Vacancy + Interstitial
point defects (V-O, C-O, .. )
point defects and clusters of defects
EK>25 eV
EK > 5 keV
V
I
I
I
V
V
Spatial distribution of vacancies created by a 50 keV Si-ion in silicon. (typical recoil energy for 1 MeV neutrons)
van Lint 1980
M.Huhtinen 2001
Michael Moll – Lausanne, 29. January 2007 -12-
RD50 Radiation Damage – Microscopic Effects
particle SiS Vacancy + Interstitial
point defects (V-O, C-O, .. )
point defects and clusters of defects
EK>25 eV
EK > 5 keV
V
I
Neutrons (elastic scattering) En > 185 eV for displacement En > 35 keV for cluster
60Co-gammasCompton Electrons with max. E 1 MeV (no cluster production)
ElectronsEe > 255 keV for displacementEe > 8 MeV for cluster
Only point defects point defects & clusters Mainly clusters
10 MeV protons 24 GeV/c protons 1 MeV neutronsSimulation:
Initial distribution of vacancies in (1m)3
after 1014 particles/cm2
[Mika Huhtinen NIMA 491(2002) 194]
Michael Moll – Lausanne, 29. January 2007 -13-
RD50 Primary Damage and secondary defect formation
Two basic defects
I - Silicon Interstitial V - Vacancy
Primary defect generation I, I2 higher order I (?) I -CLUSTER (?) V, V2, higher order V (?) V -CLUSTER (?)
Secondary defect generation
Main impurities in silicon: Carbon (Cs) Oxygen (O i)I+Cs Ci Ci+Cs CiCS
Ci+Oi CiOi
Ci+Ps CiPS
V+V V2 V+V2 V3
V+Oi VOi V+VOi V2Oi
V+Ps VPs
I+V2 V I+VOi Oi .......................
I
I
V
V
Damage?! (“V2O-model”)
Damage?!
Michael Moll – Lausanne, 29. January 2007 -14-
RD50 Example of defect spectroscopyExample of defect spectroscopy- neutron irradiated -- neutron irradiated -
50 100 150 200 250Temperature [ K ]
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
DL
TS-
sign
al (
b 1)
[pF]
60 min 60 min170 days170 days
CiCs(-/0)CiCs(-/0)
VOi(-/0)VOi(-/0)
VV(--/-)VV(--/-)
Ci(-/0)Ci(-/0)
CiOi(+/0)CiOi(+/0)
H(220K)H(220K)
Ci(+/0)Ci(+/0)
E(40K)E(40K)E(45K)E(45K)
E(35K)E(35K)
? + VV(-/0) + ?? + VV(-/0) + ? Introduction RatesNt/eq:
Ci :1.55 cm-1
CiCs : CiOi : 0.40 cm-1 1.10 cm-1
Introduction rates of main defects 1 cm-1
Introduction rate of negative space charge 0.05 cm-1
example : eq = 11014 cm-2
defects 11014 cm-3
space charge 51012cm-3
Deep Level Transient Spectroscopy
Michael Moll – Lausanne, 29. January 2007 -15-
RD50 Impact of Defects on Detector properties
Shockley-Read-Hall statistics Shockley-Read-Hall statistics (standard theory) (standard theory)
Impact on detector properties can be calculated if all defect parameters are known:Impact on detector properties can be calculated if all defect parameters are known:n,pn,p : cross sections : cross sections E : ionization energy NE : ionization energy Ntt : concentration : concentration
Trapping (e and h) CCE
shallow defects do not contribute at room
temperature due to fast detrapping
charged defects
Neff , Vdep
e.g. donors in upper and acceptors in lower half of band
gap
generation leakage current
Levels close to midgap
most effective
enhanced generation leakage current space charge
Inter-center chargeInter-center charge transfer model transfer model
(inside clusters only)(inside clusters only)
Michael Moll – Lausanne, 29. January 2007 -16-
RD50
d ep le ted zo n e
n eu tra l b u lk(n o e lec tric f ie ld )
Poisson’s equation
Reverse biased abrupt pReverse biased abrupt p++-n junction-n junction
Electrical Electrical charge densitycharge density
Electrical Electrical field strengthfield strength
Electron Electron potential energypotential energy
effNq
xdx
d
0
02
2
2
0
0 dNq
V effdep
effective space charge density
depletion voltage
Full charge collection only for VB>Vdep !
Positive space charge, Neff =[P](ionized Phosphorus atoms)
p a rtic le (m ip )
+ V < VB d ep + V > VB d ep
Michael Moll – Lausanne, 29. January 2007 -17-
RD50 Macroscopic Effects – I. Depletion Voltage
Change of Depletion Voltage Vdep (Neff)
…. with particle fluence:
before inversion
after inversion
n+ p+ n+
• “Type inversion”: Neff changes from positive to
negative (Space Charge Sign Inversion)
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]
• 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: Detectors must be cooled even when the experiment is not running!
…. 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]
p+
Michael Moll – Lausanne, 29. January 2007 -18-
RD50 Radiation Damage – II. 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
eqV
I
α
80 min 60C
Change of Leakage Current (after hadron irradiation)
…. with particle fluence:
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
Michael Moll – Lausanne, 29. January 2007 -19-
RD50
Deterioration of Charge Collection Efficiency (CCE) by trapping
tQtQ
heeffhehe
,,0,
1exp)(
0 2.1014 4.1014 6.1014 8.1014 1015
particle fluence - eq [cm-2]
0
0.1
0.2
0.3
0.4
0.5
Inve
rse
trap
ping
tim
e 1
/ [n
s-1]
data for electronsdata for electronsdata for holesdata for holes
24 GeV/c proton irradiation24 GeV/c proton irradiation
[M.Moll; Data: O.Krasel, PhD thesis 2004, Uni Dortmund][M.Moll; Data: O.Krasel, PhD thesis 2004, Uni Dortmund]
Increase of inverse trapping time (1/) with fluence
Trapping is characterized by an effective trapping time eff for electrons and holes:
….. and change with time (annealing):
5 101 5 102 5 103
annealing time at 60oC [min]
0.1
0.15
0.2
0.25
Inve
rse
trap
ping
tim
e 1
/ [n
s-1]
data for holesdata for holesdata for electronsdata for electrons
24 GeV/c proton irradiation24 GeV/c proton irradiationeq = 4.5.1014 cm-2 eq = 4.5.1014 cm-2
[M.Moll; Data: O.Krasel, PhD thesis 2004, Uni Dortmund][M.Moll; Data: O.Krasel, PhD thesis 2004, Uni Dortmund]
where defectsheeff
N,
1
Radiation Damage – III. CCE (Trapping)
Michael Moll – Lausanne, 29. January 2007 -20-
RD50 Summary: Radiation Damage in Silicon Sensors
Two general types of radiation damage to the detector materials:
Bulk (Crystal) damage due to Non Ionizing Energy Loss (NIEL) - displacement damage, built up of crystal defects –
I. Change of effective doping concentration (higher depletion voltage, under- depletion)
II. Increase of leakage current (increase of shot noise, thermal runaway)
III. Increase of charge carrier trapping (loss of charge)
Surface damage due to Ionizing Energy Loss (IEL) - accumulation of positive in the oxide (SiO2) and the Si/SiO2 interface – affects: interstrip capacitance (noise factor), breakdown behavior, …
Impact on detector performance and Charge Collection Efficiency (depending on detector type and geometry and readout electronics!)
Signal/noise ratio is the quantity to watch Sensors can fail from radiation damage !
Same for all tested Silicon
materials!
Influenced by impurities
in Si – Defect Engineeringis possible!
Can be optimized!
Michael Moll – Lausanne, 29. January 2007 -21-
RD50 Outline
Motivation to develop radiation harder detectors
Introduction to the RD50 collaboration
Part I: Radiation Damage in Silicon Detectors (A very brief review) Microscopic defects (changes in bulk material) Macroscopic damage (changes in detector properties)
Part II: RD50 - Approaches to obtain radiation hard sensors Material Engineering Device Engineering
Summary and preliminary conclusion
Michael Moll – Lausanne, 29. January 2007 -22-
RD50 Approaches of RD50 to develop radiation harder tracking detectors
Defect Engineering of Silicon Understanding radiation damage
• Macroscopic effects and Microscopic defects• Simulation of defect properties and defect kinetics• Irradiation with different particles at different
energies Oxygen rich silicon
• DOFZ, Cz, MCZ, EPI Oxygen dimer enriched silicon Hydrogen enriched silicon Pre-irradiated silicon Influence of processing technology
New Materials Silicon Carbide (SiC), Gallium Nitride (GaN) Diamond: CERN RD42 Collaboration
Device Engineering (New Detector Designs) p-type silicon detectors (n-in-p) Thin detectors 3D and Semi 3D detectors Cost effective detectors Simulation of highly irradiated detectors
Scientific strategies:
I. Material engineering
II. Device engineering
III. Variation of detectoroperational conditions
CERN-RD39“Cryogenic Tracking Detectors”
Michael Moll – Lausanne, 29. January 2007 -23-
RD50
Influence the defect kinetics by incorporation of impurities or defects
Best example: Oxygen
Initial idea: Incorporate Oxygen to getter radiation-induced vacancies prevent formation of Di-vacancy (V2) related deep acceptor levels Observation: Higher oxygen content less negative space charge (less charged acceptors)
One possible mechanism: V2O is a deep acceptor O VO (not harmful at room temperature) V VO V2O (negative space charge)
Defect Engineering of Silicon
V2O(?)
Ec
EV
VO
V2 in clusters
Michael Moll – Lausanne, 29. January 2007 -24-
RD50 Spectacular Improvement of -irradiation tolerance
No type inversion for oxygen enriched silicon! Slight increase of positive space charge
(due to Thermal Donor generation?)
[E.Fretwurst et al. 1st RD50 Workshop] See also:- Z.Li et al. [NIMA461(2001)126]- Z.Li et al. [1st RD50 Workshop]
0 200 400 600 800 1000dose [Mrad]
0
50
100
150
200
250
Vde
p [V
]
0
10
20
30
40
Nef
f [10
11 c
m-3
]
CA: <111> STFZ CA: <111> STFZ CB: <111> DOFZ 24 hCB: <111> DOFZ 24 hCC: <111>DOFZ 48 hCC: <111>DOFZ 48 hCD: <111> DOFZ 72 hCD: <111> DOFZ 72 hCE: <100> STFZCE: <100> STFZCF: <100> DOFZ 24hCF: <100> DOFZ 24hCG: <100> DOFZ 48hCG: <100> DOFZ 48hCH: <100> DOFZ 72hCH: <100> DOFZ 72h
(a)(a)
Depletion Voltage
0 200 400 600 800 1000dose [Mrad]
0
500
1000
1500
I rev
[nA
]
CA: <111> STFZCA: <111> STFZCB: <111> DOFZ 24hCB: <111> DOFZ 24hCC: <111> DOFZ 48hCC: <111> DOFZ 48hCD: <111> DOFZ 78hCD: <111> DOFZ 78h
(b)(b)
CE: <100> STFZ CE: <100> STFZ CF: <100> DOFZ 24hCF: <100> DOFZ 24hCG: <100> DOFZ 48hCG: <100> DOFZ 48hCH: <100> DOFZ 72hCH: <100> DOFZ 72h
(b)
Leakage increase not linear and depending on oxygen concentration
Leakage Current
Michael Moll – Lausanne, 29. January 2007 -25-
RD50 Characterization of microscopic defects - and proton irradiated silicon detectors -
2003: Major breakthrough on -irradiated samples For the first time macroscopic changes of the depletion voltage and leakage current
can be explained by electrical properties of measured defects !
since 2004: Big steps in understanding the improved radiation tolerance of oxygen enriched and epitaxial silicon after proton irradiation
[APL, 82, 2169, March 2003]
Almost independent of oxygen content: Donor removal “Cluster damage” negative charge
Influenced by initial oxygen content: I–defect: deep acceptor level at EC-0.54eV (good candidate for the V2O defect) negative charge
Influenced by initial oxygen dimer content (?): BD-defect: bistable shallow thermal donor (formed via oxygen dimers O2i) positive charge
Levels responsible for depletion voltage changes after proton irradiation:
D-defectI-defect
[I.Pintilie, RESMDD, Oct.2004]
Michael Moll – Lausanne, 29. January 2007 -26-
RD50 Oxygen enriched silicon – DOFZ- proton irradiation -
• DOFZ (Diffusion Oxygenated Float Zone Silicon) 1982 First oxygen diffusion tests on FZ [Brotherton et al. J.Appl.Phys.,Vol.53,
No.8.,5720]
1995 First tests on detector grade silicon [Z.Li et al. IEEE TNS Vol.42,No.4,219]
1999 Introduced to the HEP community by RD48 (ROSE)
0 1 2 3 4 524 GeV/c proton [1014 cm-2]
0
2
4
6
8
10
|Nef
f| [
1012
cm-3
]
100
200
300
400
500
600
Vde
p [V
] (3
00 m
)
Carbon-enriched (P503)Standard (P51)
O-diffusion 24 hours (P52)O-diffusion 48 hours (P54)O-diffusion 72 hours (P56)
Carbonated
Standard
Oxygenated
[RD48-NIMA 465(2001) 60]
http://cern.ch/rd48
ROSERD48
First tests in 1999 show clear advantage of oxygenation
Later systematic tests reveal strong variations with no clear dependence
on oxygen content
0 2 4 6 8 1024GeV/c proton [1014 cm-2]
0123456789
10
|Nef
f| [10
12cm
-3]
100
200
300
400
500
600
700
Vde
p [V
] (3
00 m
)
SGS-30h-1200C ; Wacker <111>: SGS W316-T-A3-02 (7/99)
oxy - 2Kcm <111> W316-07 oxy - 2Kcm <111> W309-07oxy - 2Kcm <100> W319-08oxy - 2Kcm <100> W320-05oxy - 1Kcm <111> W301-3oxy - 2.2Kcm <100> W311-2oxy - 2.4Kcm <100> W320-2oxy - 2Kcm <111> W309-5oxy - 15 Kcm <111> W324-2
15 Kcm <111> - oxygenated
oxy - 15 Kcm <111> W317-3oxy - 1Kcm <111> W306-2oxy - 1Kcm <100> W305-2oxy - 2.2Kcm <111> W316-2 oxy - 2Kcm <100> W319-3
std - 1Kcm <100> W330-A2std - 1Kcm <111> W333 -B6std - 2Kcm <100> W335-C4std - 2 Kcm <111> W336-B6std - 15Kcm <111> W339-B4
15 Kcm <111> - standard
Standard material
Oxygenated material
[M.Moll - NIMA 511 (2003) 97]
However, only non-oxygenated diodes show a “bad” behavior.
Michael Moll – Lausanne, 29. January 2007 -27-
RD50 Silicon Growth Processes
Single crystal silicon
Poly silicon
RF Heating coil
Float Zone Growth
Floating Zone Silicon (FZ) Czochralski Silicon (CZ)
Czochralski Growth
Basically all silicon detectors made out of high resistivety FZ silicon
Epitaxial Silicon (EPI)
The growth method used by the IC industry.
Difficult to producevery high resistivity
Chemical-Vapor Deposition (CVD) of Si up to 150 m thick layers produced growth rate about 1m/min
Michael Moll – Lausanne, 29. January 2007 -28-
RD50
0 10 20 30 40 50 60 70 80 90 100Depth [m]
51016
51017
51018
5
O-c
once
ntra
tion
[1/c
m3 ]
SIMS 25 m SIMS 25 m
25 m
u25
mu
SIMS 50 mSIMS 50 m
50 m
u50
mu
SIMS 75 mSIMS 75 m
75 m
u75
mu
simulation 25 msimulation 25 msimulation 50 msimulation 50 msimulation 75msimulation 75m
Oxygen concentration in FZ, CZ and EPI
DOFZ and CZ silicon Epitaxial silicon
EPI: Oi and O2i (?) diffusion from substrate into epi-layer during production
EPI: in-homogeneous oxygen distribution
[G.Lindström et al.,10th European Symposium on Semiconductor Detectors, 12-16 June 2005]
DOFZ: inhomogeneous oxygen distribution DOFZ: oxygen content increasing with time
at high temperature
EPIlayer CZ substrate
0 50 100 150 200 250depth [m]
5
1016
5
1017
5
1018
O-c
once
ntra
tion
[cm
-3]
51016
51017
51018
5
DOFZ 72h/1150oCDOFZ 48h/1150oCDOFZ 24h/1150oC
Data: G.Lindstroem et al.
[M.Moll]
CZ: high Oi (oxygen) and O2i (oxygen dimer) concentration (homogeneous)
CZ: formation of Thermal Donors possible !
0 50 100 150 200 250depth [m]
5
1016
5
1017
5
1018
O-c
once
ntra
tion
[cm
-3]
51016
51017
51018
5
Cz as grown
DOFZ 72h/1150oCDOFZ 48h/1150oCDOFZ 24h/1150oC
Data: G.Lindstroem et al.
[M.Moll]
Michael Moll – Lausanne, 29. January 2007 -29-
RD50 Silicon Materials under Investigation by RD50
Material Symbol (cm) [Oi] (cm-3)
Standard FZ (n- and p-type) FZ 1–710 3 < 51016
Diffusion oxygenated FZ (n- and p-type) DOFZ 1–710 3 ~ 1–21017
Magnetic Czochralski Si, Okmetic, Finland (n- and p-type)
MCz ~ 110 3 ~ 51017
Czochralski Si, Sumitomo, Japan (n-type) Cz ~ 110 3 ~ 8-91017
Epitaxial layers on Cz-substrates, ITME, Poland (n- and p-type, 25, 50, 75, 150 m thick)
EPI 50 – 400 < 11017
Diffusion oxygenated Epitaxial layers on CZ EPI–DO 50 – 100 ~ 71017
DOFZ silicon - Enriched with oxygen on wafer level, inhomogeneous distribution of oxygen CZ/MCZ silicon - high Oi (oxygen) and O2i (oxygen dimer) concentration (homogeneous)
- formation of shallow Thermal Donors possible Epi silicon - high Oi , O2i content due to out-diffusion from the CZ substrate (inhomogeneous)
- thin layers: high doping possible (low starting resistivity) Epi-Do silicon - as EPI, however additional Oi diffused reaching homogeneous Oi content
standardfor
particledetectors
used for LHC Pixel
detectors
“new”material
Michael Moll – Lausanne, 29. January 2007 -30-
RD50 Standard FZ, DOFZ, Cz and MCz Silicon
24 GeV/c proton irradiation
Standard FZ silicon• type inversion at ~ 21013 p/cm2
• strong Neff increase at high fluence
Oxygenated FZ (DOFZ)• type inversion at ~ 21013 p/cm2
• reduced Neff increase at high fluence
CZ silicon and MCZ silicon no type inversion in the overall fluence range (verified by TCT measurements)
(verified for CZ silicon by TCT measurements, preliminary result for MCZ silicon) donor generation overcompensates acceptor generation in high fluence range
Common to all materials (after hadron irradiation): reverse current increase increase of trapping (electrons and holes) within ~ 20%
0 2 4 6 8 10proton fluence [1014 cm-2]
0
200
400
600
800
Vde
p (3
00m
) [V
]0
2
4
6
8
10
12
|Nef
f| [1
012 c
m-3
]
FZ <111>FZ <111>DOFZ <111> (72 h 11500C)DOFZ <111> (72 h 11500C)MCZ <100>MCZ <100> CZ <100> (TD killed) CZ <100> (TD killed)
Michael Moll – Lausanne, 29. January 2007 -31-
RD50 Epitaxial silicon
Layer thickness: 25, 50, 75 m (resistivity: ~ 50 cm); 150 m (resistivity: ~ 400 cm) Oxygen: [O] 91016cm-3; Oxygen dimers (detected via IO2-defect formation)
EPI Devices – Irradiation experiments
Only little change in depletion voltage
No type inversion up to ~ 1016 p/cm2 and ~ 1016 n/cm2
high electric field will stay at front electrode!reverse annealing will decreases depletion voltage!
Explanation: introduction of shallow donors is bigger than generation of deep acceptors
G.Lindström et al.,10th European Symposium on Semiconductor Detectors, 12-16 June 2005 G.Kramberger et al., Hamburg RD50 Workshop, August 2006
0 2.1015 4.1015 6.1015 8.1015 1016
eq [cm-2]
0
1014
2.1014
Nef
f(t0)
[cm
-3]
25 m, 80 oC25 m, 80 oC
50 m, 80 oC50 m, 80 oC
75 m, 80 oC75 m, 80 oC
23 GeV protons23 GeV protons
320V (75m)
105V (25m)
230V (50m)
CCE (Sr90 source, 25ns shaping): 6400 e (150 m; 2x1015 n/cm-2) 3300 e (75m; 8x1015 n/cm-2) 2300 e (50m; 8x1015 n/cm-2)
0 20 40 60 80 100eq [1014 cm-2]
0
2000
4000
6000
8000
10000
12000
Sign
al [
e]
150 m - neutron irradiated 75 m - proton irradiated 75 m - neutron irradiated 50 m - neutron irradiated 50 m - proton irradiated
[M.Moll]
[Data: G.Kramberger et al., Hamburg RD50 Workshop, August 2006]
Michael Moll – Lausanne, 29. January 2007 -32-
RD50 Advantage of non-inverting materialp-in-n detectors (schematic figures!)
Fully depleted detector(non – irradiated):
Michael Moll – Lausanne, 29. January 2007 -33-
RD50
inverted to “p-type”, under-depleted:
• Charge spread – degraded resolution
• Charge loss – reduced CCE
Advantage of non-inverting materialp-in-n detectors (schematic figures!)
Fully depleted detector(non – irradiated):
heavy irradiation
inverted
non-inverted, under-depleted:
•Limited loss in CCE
•Less degradation with under-depletion
non inverted
Be careful, this is a very schematic explanation, reality is more complex !
Michael Moll – Lausanne, 29. January 2007 -34-
RD50 Epitaxial silicon - Annealing
50 m thick silicon detectors:- Epitaxial silicon (50cm on CZ substrate, ITME & CiS) - Thin FZ silicon (4Kcm, MPI Munich, wafer bonding technique)
Thin FZ silicon: Type inverted, increase of depletion voltage with time Epitaxial silicon: No type inversion, decrease of depletion voltage with time
No need for low temperature during maintenance of SLHC detectors!
[E.Fretwurst et al.,RESMDD - October 2004]
100 101 102 103 104 105
annealing time [min]
0
50
100
150
Vfd
[V
]
EPI (ITME), 9.6.1014 p/cm2EPI (ITME), 9.6.1014 p/cm2
FZ (MPI), 1.7.1015 p/cm2FZ (MPI), 1.7.1015 p/cm2
Ta=80oCTa=80oC
[E.Fretwurst et al., Hamburg][E.Fretwurst et al., Hamburg]
0 20 40 60 80 100proton fluence [1014 cm-2]
0
50
100
150
200
250
Vde
p [V
]
0.20.40.60.81.01.21.4
|Nef
f| [1
014 c
m-3
]
EPI (ITME), 50mEPI (ITME), 50mFZ (MPI), 50mFZ (MPI), 50m
Ta=80oCTa=80oC
ta=8 minta=8 min
Michael Moll – Lausanne, 29. January 2007 -35-
RD50
Property Diamond GaN 4H SiC Si Eg [eV] 5.5 3.39 3.3 1.12 Ebreakdown [V/cm] 107 4·106 2.2·106 3·105 e [cm2/Vs] 1800 1000 800 1450 h [cm2/Vs] 1200 30 115 450 vsat [cm/s] 2.2·107 - 2·107 0.8·107 Z 6 31/7 14/6 14 r 5.7 9.6 9.7 11.9 e-h energy [eV] 13 8.9 7.6-8.4 3.6 Density [g/cm3] 3.515 6.15 3.22 2.33 Displacem. [eV] 43 15 25 13-20
New Materials: Epitaxial SiC “A material between Silicon and Diamond”
Wide bandgap (3.3eV) lower leakage current
than silicon
Signal:Diamond 36 e/mSiC 51 e/mSi 89 e/m
more charge than diamond
Higher displacement threshold than silicon
radiation harder than silicon (?)
R&D on diamond detectors:RD42 – Collaboration
http://cern.ch/rd42/
Michael Moll – Lausanne, 29. January 2007 -36-
RD50 SiC: CCE after neutron irradiation
CCE before irradiation 100 % with particles and MIPS
CCE after irradiation (example) material produced by CREE 55 m thick layer neutron irradiated samples tested with particles
Conclusion: SiC is less radiation tolerant than
expected
Consequence: RD50 will stop working on this topic
[F.Moscatelli, Bologna, December 2006]
0.1 1E14 1E15 1E160
1000
2000
3000
Before irradiation
Co
llect
ed
Ch
arg
e (
e- )
Fluence ((1MeV) n/cm2)
@ 950 V
Michael Moll – Lausanne, 29. January 2007 -37-
RD50 Outline
Motivation to develop radiation harder detectors
Introduction to the RD50 collaboration
Part I: Radiation Damage in Silicon Detectors (A very brief review) Microscopic defects (changes in bulk material) Macroscopic damage (changes in detector properties)
Part II: RD50 - Approaches to obtain radiation hard sensors Material Engineering Device Engineering
Summary and preliminary conclusion
Michael Moll – Lausanne, 29. January 2007 -38-
RD50
p-on-n silicon, under-depleted:
• Charge spread – degraded resolution
• Charge loss – reduced CCE
p+on-n
Device engineeringp-in-n versus n-in-p detectors
n-on-p silicon, under-depleted:
•Limited loss in CCE
•Less degradation with under-depletion
•Collect electrons (fast)
n+on-p
n-type silicon after high fluences: p-type silicon after high fluences:
Be careful, this is a very schematic explanation,reality is more complex !
Michael Moll – Lausanne, 29. January 2007 -39-
RD50
0 2 4 6 8 10fluence [1015cm-2]
0
5
10
15
20
25
CC
E (
103 e
lect
rons
)
24 GeV/c p irradiation24 GeV/c p irradiation
[M.Moll][M.Moll]
[Data: G.Casse et al., NIMA535(2004) 362][Data: G.Casse et al., NIMA535(2004) 362]
n-in-p microstrip detectors
n-in-p microstrip detectors (280m) on p-type FZ silicon Detectors read-out with 40MHz
CCE ~ 6500 e (30%) after 7.5 1015 p cm-2 at
900V
n-in-p: - no type inversion, high electric field stays on structured side - collection of electrons
no reverse annealing visible in the CCE measurement ! e.g. for 7.5 1015 p/cm2 increase of Vdep from
Vdep~ 2800V to Vdep > 12000V is expected !
0 100 200 300 400 500time at 80oC[min]
0 500 1000 1500 2000 2500time [days at 20oC]
02468
101214161820
CC
E (
103 e
lect
rons
)
800 V800 V
1.1 x 1015cm-2 1.1 x 1015cm-2 500 V500 V
3.5 x 1015cm-2 (500 V)3.5 x 1015cm-2 (500 V)
7.5 x 1015cm-2 (700 V)7.5 x 1015cm-2 (700 V)
M.MollM.Moll
[Data: G.Casse et al., to be published in NIMA][Data: G.Casse et al., to be published in NIMA]
Michael Moll – Lausanne, 29. January 2007 -40-
RD50 “3D” electrodes: - narrow columns along detector thickness,
- diameter: 10m, distance: 50 - 100m Lateral depletion: - lower depletion voltage needed
- thicker detectors possible- fast signal- radiation hard
3D detector - concepts
n-columns p-columnswafer surface
n-type substrate
Introduced by: S.I. Parker et al., NIMA 395 (1997) 328
p+
------
++++
++++
--
--
++
30
0
m
n+
p+
50 m
------
++ ++++++
----
++
3D PLANARp+
Michael Moll – Lausanne, 29. January 2007 -41-
RD50 “3D” electrodes: - narrow columns along detector thickness,
- diameter: 10m, distance: 50 - 100m Lateral depletion: - lower depletion voltage needed
- thicker detectors possible- fast signal- radiation hard
3D detector - concepts
n-columns p-columns wafer surface
n-type substrate
Simplified 3D architecture n+ columns in p-type substrate, p+ backplane operation similar to standard 3D detector
Simplified process hole etching and doping only done once no wafer bonding technology needed
Simulations performed Fabrication:
IRST(Italy), CNM Barcelona
[C. Piemonte et al., NIM A541 (2005) 441]
hole
hole metal strip
C.Piemonte et al., STD06, September 2006
Hole depth 120-150mHole diameter ~10m
First CCE tests under way
Michael Moll – Lausanne, 29. January 2007 -42-
RD50 Comparison of measured collected charge on different radiation-hard materials and devices
In the following: Comparison of collected charge as published in literature
Be careful: Values obtained partly under different conditions irradiation temperature of measurement electronics used (shaping time, noise) type of device – strip detectors or pad detectors
This comparison gives only an indication of which material/technology could be used, to be more specific, the exact application should be looked at!
Remember: The obtained signal has still to be compared to the noise
Acknowledgements:
Recent data collections: Mara Bruzzi (Hiroschima conference 2006)
Cinzia Da Via (Vertex conference 2006)
Michael Moll – Lausanne, 29. January 2007 -43-
RD50 Comparison of measured collected charge on different radiation-hard materials and devices
0 20 40 60 80 100 120eq [1014 cm-2]
0
1000
2000
3000
4000
sign
al [e
lect
rons
]
SiC, n-type, 55 m, (RT, 2.5s) [Moscatelli et al. 2006]
[M.Moll 2007]
4H-SiC layer, 55m, pad detector24 GeV/c protonsSr-90 source, 2.5 s shaping, room temperature mean values presented
sample:irradiation:
measurement:analysis:
Michael Moll – Lausanne, 29. January 2007 -44-
RD50 Comparison of measured collected charge on different radiation-hard materials and devices
0 20 40 60 80 100 120eq [1014 cm-2]
0
1000
2000
3000
4000
5000
6000
sign
al [e
lect
rons
]
pCVD-Diamond, 500m, (RT, s) [RD42 2002]SiC, n-type, 55 m, (RT, 2.5s) [Moscatelli et al. 2006]
[M.Moll 2007]
polycrystal, 500m thick, strip24 GeV/c protonstestbeam, s shapingmost probable values
sample:irradiation:
measurement:analysis:
Michael Moll – Lausanne, 29. January 2007 -45-
RD50 Comparison of measured collected charge on different radiation-hard materials and devices
0 20 40 60 80 100 120eq [1014 cm-2]
0
1000
2000
3000
4000
5000
6000
7000
sign
al [e
lect
rons
]
pCVD-Diamond, 500m, (RT, s) [RD42 2005]pCVD-Diamond, 500m, (RT, s) [RD42 2002]SiC, n-type, 55 m, (RT, 2.5s) [Moscatelli et al. 2006]
[M.Moll 2007]
polycrystal, 500m thick, strip24 GeV/c protonstestbeam, s shapingmost probable values
sample:irradiation:
measurement:analysis:
Michael Moll – Lausanne, 29. January 2007 -46-
RD50
0 20 40 60 80 100 120eq [1014 cm-2]
0
2000
4000
6000
8000
10000
sign
al [e
lect
rons
]
pCVD-Diamond, 500m, (RT, s) [RD42 2006]pCVD-Diamond, 500m, (RT, s) [RD42 2005]pCVD-Diamond, 500m, (RT, s) [RD42 2002]SiC, n-type, 55 m, (RT, 2.5s) [Moscatelli et al. 2006]
[M.Moll 2007]
polycrystal, 500m thick, strip24 GeV/c protonstestbeam, s shapingmost probable values
sample:irradiation:
measurement:analysis:
Comparison of measured collected charge on different radiation-hard materials and devices
Diamond quality increasing [2000-2006]
Michael Moll – Lausanne, 29. January 2007 -47-
RD50 Comparison of measured collected charge on different radiation-hard materials and devices
0 20 40 60 80 100 120eq [1014 cm-2]
0
2000
4000
6000
8000
10000
sign
al [e
lect
rons
]
pCVD-Diamond, 500m, (RT, s) [RD42 2002-2006] (scaled)SiC, n-type, 55 m, (RT, 2.5s) [Moscatelli et al. 2006]
[M.Moll 2007]
polycrystal, 500m thick, strip24 GeV/c protonstestbeam, s shapingmost probable values
sample:irradiation:
measurement:analysis:
Michael Moll – Lausanne, 29. January 2007 -48-
RD50 Comparison of measured collected charge on different radiation-hard materials and devices
0 20 40 60 80 100 120eq [1014 cm-2]
0
2000
4000
6000
8000
10000
12000
sign
al [e
lect
rons
] pCVD-Diamond, 500m, (RT, s), strip, [RD42 2002-2006] (scaled)n-epi Si, 150 m, (-30oC, 25ns), pad [Kramberger 2006]n-epi Si, 75 m, (-30oC, 25ns), pad [Kramberger 2006]SiC, n-type, 55 m, (RT, 2.5s), pad [Moscatelli et al. 2006]
[M.Moll 2007]
Michael Moll – Lausanne, 29. January 2007 -49-
RD50 Comparison of measured collected charge on different radiation-hard materials and devices
0 20 40 60 80 100 120eq [1014 cm-2]
0
5000
10000
15000
20000
25000
sign
al [e
lect
rons
]
p-FZ Si, 280 m, (-30oC, 25ns), strip [Casse 2004]p-MCZ Si, 300 m, (-30oC, s), pad [Bruzzi 2006]n-epi Si, 150 m, (-30oC, 25ns), pad [Kramberger 2006]n-epi Si, 75 m, (-30oC, 25ns), pad [Kramberger 2006]pCVD-Diamond, 500m, (RT, s), strip, [RD42 2002-2006] (scaled)SiC, n-type, 55 m, (RT, 2.5s), pad [Moscatelli et al. 2006]
[M.Moll 2007]
Michael Moll – Lausanne, 29. January 2007 -50-
RD50 Comparison of measured collected charge on different radiation-hard materials and devices
0 20 40 60 80 100 120eq [1014 cm-2]
0
5000
10000
15000
20000
25000
sign
al [e
lect
rons
]
3D FZ Si, 235 m, (laser injection, scaled!), pad [Da Via 2006]p-FZ Si, 280 m, (-30oC, 25ns), strip [Casse 2004]p-MCZ Si, 300 m, (-30oC, s), pad [Bruzzi 2006]n-epi Si, 150 m, (-30oC, 25ns), pad [Kramberger 2006]n-epi Si, 75 m, (-30oC, 25ns), pad [Kramberger 2006]pCVD-Diamond, 500m, (RT, s), strip, [RD42 2002-2006] (scaled)SiC, n-type, 55 m, (RT, 2.5s), pad [Moscatelli et al. 2006]
[M.Moll 2007]
Michael Moll – Lausanne, 29. January 2007 -51-
RD50 Comparison of measured collected charge on different radiation-hard materials and devices
0 20 40 60 80 100 120eq [1014 cm-2]
0
5000
10000
15000
20000
25000
sign
al [e
lect
rons
]
3D FZ Si, 235 m, (laser injection, scaled!), pad [Da Via 2006]p-FZ Si, 280 m, (-30oC, 25ns), strip [Casse 2004]p-MCZ Si, 300 m, (-30oC, s), pad [Bruzzi 2006]n-epi Si, 150 m, (-30oC, 25ns), pad [Kramberger 2006]n-epi Si, 75 m, (-30oC, 25ns), pad [Kramberger 2006]sCVD-Diamond, 770m, (RT, s), [RD42 2006] (preliminary data, scaled)pCVD-Diamond, 500m, (RT, s), strip, [RD42 2002-2006] (scaled)SiC, n-type, 55 m, (RT, 2.5s), pad [Moscatelli et al. 2006]
[M.Moll 2007]
Michael Moll – Lausanne, 29. January 2007 -52-
RD50 Signal Charge / Threshold Do not forget: The signal has still to be compared to the noise (the threshold)
Michael Moll – Lausanne, 29. January 2007 -53-
RD50 Summary – Radiation Damage
Radiation Damage in Silicon Detectors Change of Depletion Voltage (type inversion, reverse annealing, …)
(can be influenced by defect engineering!) Increase of Leakage Current (same for all silicon materials) Increase of Charge Trapping (same for all silicon materials)
Signal to Noise ratio is quantity to watch (material + geometry + electronics)
Microscopic defects Good understanding of damage after -irradiation (point defects) Damage after hadron damage still to be better understood (cluster defects)
CERN-RD50 collaboration working on: Material Engineering (Silicon: DOFZ, CZ, EPI, other impurities,. ) (Diamond) Device Engineering (3D and thin detectors, n-in-p, n-in-n, …)
To obtain ultra radiation hard sensors a combination of material and device engineering approaches depending on radiation environment, application and available readout electronics will be best solution
Michael Moll – Lausanne, 29. January 2007 -54-
RD50 Summary – Detectors for SLHC At fluences up to 1015cm-2 (Outer layers of SLHC detector) the change of the depletion
voltage and the large area to be covered by detectors are major problems.
CZ silicon detectors could be a cost-effective radiation hard solution no type inversion (to be confirmed), use cost effective p-in-n technology
oxygenated p-type silicon microstrip detectors show very encouraging results: CCE 6500 e; eq
= 41015 cm-2, 300m
At the fluence of 1016cm-2 (Innermost layers of SLHC detector) the active thickness of any silicon material is significantly reduced due to trapping.
The two most promising options besides regular replacement of sensors are: Thin/EPI detectors : drawback: radiation hard electronics for low signals needed (e.g. 2300e at eq 8x1015cm-2, 50m EPI)
3D detectors : looks very promising, drawback: technology has to be optimized
SiC and GaN have been characterized and abandoned by RD50.
Further information: http://cern.ch/rd50/
Michael Moll – Lausanne, 29. January 2007 -55-
RD50
1014 1015 10160
5000
10000
15000
20000
25000
# el
ectr
ons
1 MeV n fluence [cm-2]
strips
pixels
1014 1015 10160
5000
10000
15000
20000
25000
# el
ectr
ons
Fluence [cm-2]
p FZ Si 280m; 25ns; -30°C [1] p-MCz Si 300m;0.2-2.5s; -30°C [2] n EPI Si 75m; 25ns; -30°C [3] n EPI Si 150m; 25ns; -30°C [3] sCVD Diam 770m; 25ns; +20°C [4] pCVD Diam 300m; 25ns; +20°C [4] n EPI SiC 55m; 2.5s; +20°C [5] 3D FZ Si 235m [6]
[1] G. Casse et al. NIM A (2004)[2] M. Bruzzi et al. STD06, September 2006 [3] G. Kramberger, RD50 Work. Prague 06[4] W: Adam et al. NIM A (2006)[5] F. Moscatelli RD50 Work.CERN 2005[6] C. Da Vià, "Hiroshima" STD06 (charge induced by laser)
Comparison of measured collected charge on different radiation-hard materials and devices
Line to guide the eye for planar devices
160V
M. Bruzzi, Presented at STD6 Hiroshima Conference, Carmel, CA, September 2006
Thick (300m) p-type planar detectors can operate in partial depletion, collected charge higher than 12000e up to 2x1015cm-2.
Most charge at highest fluences collected with 3D detectors
Silicon comparable or even better than diamond in terms of collected charge(BUT: higher leakage current – cooling needed!)
Recommended