1Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
Developement of Radiation Hard Silicon for Tracking Detektors
Student Seminar, 10. April 2006
Frank HönnigerUniversity of Hamburg,
Institut für Experimentalphysik
2Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
Outline
• Motivation
• Properties of Silicon Detectors
• Radiation Damage
• Experimental Methods
• Experimental Results
• Conclusion and Outlook
3Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
q q
pp
nn
nnp
ppp
p
n
nnp
pnpnp
Standard model of particle physics
Open questions: is there a universal force? (GUT?) what is the origin of mass (Higgs-
boson?) unknown types of matter (dark matter,
SUSY) HEP-Experiments towards higher energies
electromagnetic strong
weak gravitation
quarks: d, u, s, c, b, t --------- leptons: (e- e) (- ) (- )
4Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
LHC
LHCproperties
Proton-proton colliderEnergy: 2 x 7 TeVLuminosity: 1034cm-2 s-1
Bunch crossing: every 25 nsecRate: 40 MHzpp-collision event rate: 109/sec(23 interactions per bunch crossing)Annual operational period: 107 secExpected total op. period: 10 years
Experimental request Detector property
Reliable detection of mips S/N ≈ 10 reachable withemploying minimum minimum detector thicknessmaterial budget
High event rate excellent time- (~10 ns) and& high track accuracy position resolution (~10 µm)
Complex detector design low voltage operation in normal
ambients, (hybrid integration)
Intense radiation field Radiation tolerance up tothroughout operational 1015 1MeV eq. n/cm² period of 10 years low dissipation power moderate
cooling
Silicon pixel and microstrip detectors meetall requirements for LHC
How about future developments?
5Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
Radiation requirements for LHC-experiments
0 10 20 30 40 50 60R [cm]
1012
1013
1014
1015 e
q [c
m-2
] total eq
neutrons eq
pions eq
other chargedhadrons eq
SCT - barrelSCT - barrelPixelPixel
3x1014cm-23x1014cm-2
SCT - barrelSCT - barrel
PixelPixel
CERN-RD48http://cern.ch/rd48/
• radiation damage for ATLAS inner detector• annual hadron fluence (1 MeV n equiv.)
LHC: L=1e34 cm-2 s-1
technology for Si-detectors available, however serious radiation damage
S-LHC: factor 10: L=1e35 cm-2 s-1
5 years (R=4cm) ~ 1.6E16 cm-2
• no technology for Si-detectors at S-LHC available yet (thinner detectors?)• coordinated R&D needed • developement of radiation hard and cost-effctive detectors
CERN-RD50http://cern.h/rd50/
luminosity upgradevertex
6Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
Motivation for thinner detectors
• higher initial doping concentration (more n-type) • to maintain reasonable reverse bias during operation
Thickness: 300 m
Pixel: oxygen enriched silicon – DOFZSCT: standard silicon - StFZ
LHC: use of high resistivity FZ silicon
10-1 100 101 102 103
eq [ 1012 cm-2 ]
1
510
50100
5001000
5000
Ude
p [V
] (d
= 3
00m
)
10-1
100
101
102
103
| Nef
f | [
1011
cm
-3 ]
600 V 600 V
1014cm-21014cm-2
"p - type""p - type"
type inversiontype inversion
n - typen - type
[Data from R. Wunstorf 92]
S-LHC: to prevent type inversion
but all show „type inversion“ after 2*1013 p/cm2
„type inversion“
• shorter charge collection time faster signal response• less charge loss through trapping better signals• thin detectors reduction of e.g. pixel area higher position resolution
Si-detectors have to be thin
7Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
Motivation of radiation tests and annealing studies
• use pad detectors with simple and cheap structures• irradiate them with different particles and fluences• simulation of the irradiation of the whole operation time for
silicon detectors in short time• annealing studies at higher temperatures (60°C, 80°C)• acceleration of annealing (2 min@80°C 10 days@RT)
• extract particle, fluence and time dependencies of the detector
parameters• make predictions
Radiation damage and annealing (thermal treatment) have a big influence on detector performance
8Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
Use of silicon
9Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
Semiconductor detector - principle
• high energy- and position resolution• fast readout of the signals• large S/N-ratio (CCE=100%)• compact geometry possible• silicon: wide availibility, operation at
RT, in ambient atmospheres and under low voltages
a solid state ionisation chamber
• segmented detectors by planar process (Kemmer 1984)
microstrip-, pixel-detectors, CCD‘s
various application in HEP, space, atomic & material physics, and in medicine
p+nn+ - junction
fully depleted
10Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
4 Parameters of silicon detectors
+ –
+–
+
+
+
+
+
+
+
+–
–
–+
+–
+
+
–
–
–
p n
donor/acceptorconcentration
space chargedistribution
carrier distribution
electricfield
electricpotential
depletion region
• you can assume an abrupt p-n-junction under reverse bias
depletion voltage Vdep
ADeff NNN
dep20
0eff V
dq
2εεN
2V
|N|qεεAC(V) eff00
V>Vdep
capacitance C of depletion region
influence on S/N-ratio
most important: determines the bias supply
1
2q
AC
oend
11Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
Operational parameters of silicon detectors
leakage current
VI
volume generation current (caused by impurities and defects) +diffusion current + surface generation current
• important for the S/N-ratio • and the power consumption• prevention by cooling (ATLAS: -10°C)
charge collection efficiency CCE
CCE = Q/Q0
• ratio of measured charge to the induced charge• non-irradiated detector CCE = 1
3
4
12Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
Radiation Damage in silicon
mobile Interstitial I
mobile Vacancy V
CsCi
Point defects:• they can have discrete energy levels in the band gap• can have electrical influence on detectors:
• generation and recombination of e-h-pairs • carriers can be trapped• compensation of the initial doping
• primäry point defects are V and I• secondary complex defects: VP, VO, V2O, CO• influence of oxygen: Theory (thus DOFZ-Silicon) more O more VO (elect. not active at RT) less O more V2O (elect. active at RT)
Cluster: regions of dislocations• high energy PKA cascades of shifted atoms • can locally change the band structure
• generation and recombination of e-h-pairs • not really understood yet
impinging particle
impinging particle Cluster
classify into bulk damage (and surface damages)
dislocation of Si -atoms(PKA = Primäry knocked on atom)
13Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
Experimental findings
No influence on the macroscopic parametersInfluencing doping and currentInfluencing only dopingInfluencing only current
Defect states of the defect levels
VP-defect „donor removal“
Effective doping: donors acceptors
tteff npN
nt is large for a deep acceptor if p >> n
Reverse current: Traps
SCRtBGC VGqI 0
)cosh(2TkEE
cnNG
B
it
nitt Generation rate:
14Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
NIEL - Theory
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
How can I compare the irradiation effects of different particles and energies?
Simulation (M. Huhtinen): Initial distribution of vacancies in (1µm)3 after 1014 particles/cm²
10 MeV protons 24 GeV/c protons neutrons
• with PKA (>2keV), sort of irradiation defects become independent of particle and energy NIEL scales with radiation damage
D(E) NIEL
charged particle: coulomb scatteringneutrons: elastic scatteringboth, at higher energies: nuclear react.
one can convert the particle fluence to1 MeV n equivalent fluence
hardness factor
eq= 24 GeV/c protons: 0.62reactor neutrons: 0.9110 MeV protons: 3.99
Li-ions: 50.7
15Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
Damage induced changes of macroscopic properties
Degradation of charge collection efficiency
due to increase of charge carrier trapping 1/eff,e,h = e,h
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 to 25 Kcmn-type FZ - 7 Kcmn-type FZ - 7 Kcmn-type FZ - 4 Kcmn-type FZ - 4 Kcmn-type FZ - 3 Kcmn-type FZ - 3 Kcm
n-type FZ - 780 cmn-type FZ - 780 cmn-type FZ - 410 cmn-type FZ - 410 cmn-type FZ - 130 cmn-type FZ - 130 cmn-type FZ - 110 cmn-type FZ - 110 cmn-type CZ - 140 cmn-type CZ - 140 cm
p-type EPI - 2 and 4 Kcmp-type EPI - 2 and 4 Kcm
p-type EPI - 380 cmp-type EPI - 380 cm
10-1 100 101 102 103
eq [ 1012 cm-2 ]
1
510
50100
5001000
5000
Ude
p [V
] (d
= 3
00m
)10-1
100
101
102
103
| Nef
f | [
1011
cm
-3 ]
600 V 600 V
1014cm-21014cm-2
"p - type""p - type"
type inversiontype inversion
n - typen - type
[Data from R. Wunstorf 92]
Increase of leakage current
Introduction of defects/clusters with near to mid-gap levels as generation centers, increase of noise and power consumption, thermal run-away I/V =
Change effective doping concentration
change of voltage for total depletion VdepIntroduction of defects which are charged in the space charge region,(acceptor creation) e.g.: V + P = VP (donor removal)
„type inversion“
16Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
Silicon detectors – used test structures
StFZ - Standard Float-Zone Silicon
• produced at Wacker Siltronic, processed at CiS, standard oxidation (passivation)• 305 m thick, orientation <111>
• n-doped ([P] = 7e11 cm-3 ), [O] = 6e15 cm-3, [C] = 7.5e15 cm-3 , = 6.4 kcm
DOFZ – Diffusion Oxyge- nated Float-Zone Silicon
• produced at Wacker Siltronic, processed at CiS, add. oxidation (72h@1150°C)• 305 m thick, orientation <111>• n-doped ([P] = 7e11 cm-3 ), [O] = 2.34e17 cm-3, [C] = 11.7e15 cm-3 , = 6.4 kcm
CZ - Czochralski Silicon• produced at Sumitomo/Sitix, processed at CiS, 300 m thick, orientation <100>• n-doped ([P] = 3e12 cm-3 ), [O] = 7.3e17 cm-3, [C] = 4.1e15 cm-3 , = 1.2 kcm
EPI - Epitaxial Silicon
25, 50 and 75 μm
• 25, 50, 75 m n-doped EPI-layer [P] = 7e13 cm-3 on
320 m CZ-substrate n+ doped ([Sb] = 5.3e17 cm-3)• orientation <111>, produced at ITME/Warsaw, processed at CiS
EPI-diodestandard diode
CZ, FZ-processEpitaxy
25, 50, 75 μm
17Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
CV/IV- measurements
prober to pad
prober toguard ring
• easy determination of macroscopic properties (depletion voltage, leakage current)• allows a fast check of detector functionality
1 10 100
100
1000
0.1
1 C/V-KurveI(U
dep) = 0,92 A
Udep
= 122,51 V
C [
pF]
U [V]
I/V-Kurve
I [A
]
• measuring in dark box• bias supply to the bottom• guard ring is grounded
18Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
TCT- measurements (transient current technique)fro n t e lek trod e(-) back e lec tro de (+ )
la s e r p u ls
+
+-
-
0 d
gene ra ted ca rriers
x
ho le in jec tion e lectron in jec tion
H e izung
Tem peratu r-sensor
optische r Le iterfür F ron tbeleuch tung
optische r Le iterfür R ückbe leuchtung
H a lterung /F rontkon takt
Tisch / R ückkontakt
flüss iger Sticksto ff
A lum iniumG ehäuse
G lasgefäß
Kühlka m m e r
cooling possible with nitrogen
• measurements of current pulses with oscilloscope• induced from drift of free carriers• front and back illumination with 670 (3m) and 1060 nm (across) laser• penetration depth proportional to • also exposure with (23 m) or (across) (get absolute values)
10 15 20 25 30 35
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35DOFZ 300 mfront injection
I [re
l.Ein
heite
n]
t [ns]
U = 140V U = 120V U = 100V U = 80V U = 60V
investigation of • elect. field distribution• sign of the space charge• trapping probability, separated for e and h• depletion voltage• CCE
19Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
40 80 120 160 200 240 280T [K]
0
0.02
0.04
0.06
0.08
0.1
0.12
DL
TS
sign
al [
pF]
0
0.02
0.04
0.06
0.08
0.1
0.12
Ci(-/0)Ci(-/0)
VOi+CiCs(A)VOi+CiCs(A)
V2(=/-)V2(=/-)
ER(170)ER(170)
V2(-/0)V2(-/0)
DLTS and TSC
Trap concentration Nt is proportional to the peak height
DLTS-spectrum after proton irradiation
DLTS Method: • p/n junction is hold under reverse bias• Electrical or optical pulse fills traps inside the SCR with carriers• Traps release carriers by thermal emission• Emission is monitored as a capacitance signal
TSC-spectrum after neutron irradiation
TSC Method: Traps filled at low temperature by electrical or optical injection Diode heated under reverse bias Current during the heating is monitored
Trap concentration is proportional to the released charge
• • •
TS
C c
urre
nt [
A]
T [K]
20Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
DLTS principle
[1] A bias pulse towards a smaller voltage will reduce the SCR
[2] The junction capacitance is reduced because positive space charge is partially compensated by trapped electrons in the SCR
[3] The process of carrier emission can be followed as a capacitance transient
C h a rg e s ta te o f d e fe c t le v e ls
E le c tro n tra p -e le c tro n in je c tio n
H o le tra p -h ig h in je c tio n
VP
V R
0 VB ia sp u ls e
C a p a c ita n c etra n s ie n t
VP
V R
C RC R
0 V
1 Q uiescen t reve rse b ia s (V )R
3 T h erm a l em issio n o f c arrie rs (V )R
2 M ajority ca rr ie r pu lse (V )P
1 Q uiescen t reve rse b ia s (V )R
3 T h erm a l em issio n o f c arrie rs (V )R
2 In jec tion pu lse (V , f o rw ard b ia s)P
1 3
2
1 3
2
RD
P
RR
P
R
RDt C
CN
C
C
A
C
C
C
C
CNN 0
1
0
2
0 212
12
21Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
DLTS method
The emission time constant can be evaluated:
2
1
21max
ln
)(
tt
ttTe
capa
cita
nce
tran
sien
ts m
onit
ored
at v
ario
us te
mpe
ratu
res
tim e
tWtem p era tu re T
h ig h T
lo w T
C = C (t ) - C (t )1 ,2 1 2t 1 t 2
T m a x
22Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
CERN Scenario Experiment-Depletion Voltage
0 5 10 15 20 250
100
200
300
400
500
600
700
EPI <111> 50 cm, 50m (Jul.2003, 20 GeV/c)
CERN-Szenario, 24 GeV/c Protons
EPI <111> 50 cm, 50 m (Okt. 2002, 24 GeV/c)
CZ <100> 1,2 kcm, 300 m DOFZ <111> 1-6 kcm, 300 m StFZ <111> 1-6 kcm, 300 m
Ude
p [V
]
eq
[1014cm-2]
160 V120 V
• large improvement for EPI-detectors• small change in depletion voltage for EPI up to very high fluences• no type inversion for EPI• limitation for StFZ, DOFZ and CZ for very high luminosity colliders
CERN Scenario Experiment:• consecutive irradiation steps• in between annealing for 4 min@80°C• after annealing CV/IV-measurements• quasi „online“ monitoring• annealing corresponds to 20 days at 20 °C• closely related to stable damage
Why is EPI radiation harder: shifted donor removal, because of higher initial donor concentration radiation induced acceptor creation compensated by radiation induced donors
High energy protons max. biassupply
23Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
Material ParametersMaterial Parameters
Oxygen depth profiles
SIMS-measurements after diode processing
O diffusion from substrate into epi-layer interstial Oi + dimers O2i
[O] 25 µm > [O] 50 µm process simulation yields reliable [O]
Resistivity profiles
SR before diode process, C-V on diodes
SR coincides well with C-V method
Excellent homogeneity in epi-layers
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 m50
mu
50 m
uSIMS 75 mSIMS 75 m
75 m
u75
mu
simulation 25 msimulation 25 msimulation 50 msimulation 50 msimulation 75msimulation 75m
0 20 40 60 80 100Depth [m]
10-2
10-1
100
101
102
Res
istiv
ity [
cm]
25 m, C-V method25 m, C-V method
50 m, C-V method50 m, C-V method
50 m, spreading resistance 50 m, spreading resistance
75 mum, C-V method75 mum, C-V method
24Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
Typical Annealing CurvesTypical Annealing Curves
100 101 102 103 104 105
Annealing time [min]
10
100
1000
Vfd
[V
]
9.1015 cm-29.1015 cm-2
6.1015 cm-26.1015 cm-2
2.1015 cm-22.1015 cm-2
1.1015 cm-21.1015 cm-2
3.1014 cm-23.1014 cm-2
23 GeV protons23 GeV protons
Ta=80oCTa=80oC
Typical annealing behavior of EPI-devices:
Vfd development:
Inversion only(!) during annealing ()(100 min @ 80C ≈ 500 days @ RT)
EPI never inverted at RT, even for 1016
25Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
Parameterization of Annealing ResultsParameterization of Annealing Results
Annealing components:
Short term annealing NA(,t(T))
Stable damage NC()NC = NC0(1-exp(-cΦeq) + gCΦeq
gC negative for EPI (effective positive space charge generation!)
Long term (reverse) annealing:Two components: NY,1(,t(T)), first order process NY,2(,t(T)), second order process
NY1, NY2 ~ Φeq, NY1+NY2 similar to FZ
100 101 102 103 104 105
Annealing time [min]
0.0
1.0.1013
2.0.1013
3.0.1013
4.0.1013
5.0.1013
Nef
f [ c
m-3
]
NANA
NCNC
NY,1NY,1
NY,2NY,2
Ta=80oCTa=80oC
Change of effective “doping“ concentration: Neff = Neff,0 – Neff (,t(T))
Standard parameterization: Neff = NA(,t(T)) + NC() + NY(,t(T))
26Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
Stable Damage ComponentStable Damage Component
Neff(t0): Value taken at annealing time t0 at which Vfd maximum
0 2.1015 4.1015 6.1015 8.1015 1016
eq [cm-2]
0.0
1.0.1014
2.0.1014
3.0.1014
Nef
f(t0)
[cm
-3]
0
100
200
300
400
500
600
Vfd
(t0)
[V
] no
rmal
ized
to 5
0 m
25 m, 80oC25 m, 80oC
50 m, 80oC50 m, 80oC
50 m, 60oC50 m, 60oC
23 GeV protons23 GeV protons
0 2.1015 4.1015 6.1015 8.1015 1016
eq [cm-2]
0
5.1013
1014
Nef
f (t 0
) [cm
-3]
0
50
100
150
Vfd
(t 0
)[V
] no
rmal
ized
to 5
0 m
50 m50 m
25 m25 m
Reactor neutronsReactor neutrons
Ta = 80oCTa = 80oC
No space charge sign inversion after proton and neutron irradiationIntroduction of shallow donors overcompensates creation of deep acceptors
Protons: Stronger increase for 25 µm compared to 50 µm higher [O] and possibly [O2] in 25 µm (see SIMS profiles)
Neutrons: Similar effect but not nearly as pronounced most probably due to less generation of shallow donors and as strong influence of deep acceptors (clusters)
27Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
Shallow Donors, the real issue for EPIShallow Donors, the real issue for EPI-Comparison of 25, 50 and 75 -Comparison of 25, 50 and 75 µm Diodes-µm Diodes-
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 m50
mu
50 m
uSIMS 75 mSIMS 75 m
75 m
u75
mu
simulation 25 msimulation 25 msimulation 50 msimulation 50 msimulation 75msimulation 75m
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
SIMS profiling:
[O](25µm) > [O](50µm) > [O](75µm)
Stable Damage:
Neff(25µm) > Neff(50µm) > Neff(75µm)
TSC Defect Spectroscopy:
[BD](25µm) > [BD](50µm) >[BD](75µm)
Defect spectroscopy after PS p-irradiation
Generation of recently found shallow donors BD (Ec-0.23 eV) strongly related to [O] Possibly caused by O-dimers, outdiffused from Cz with larger diffusion constant dimers monitored by IO2 complex
Strong correlation between [O]-[BD]-gC
generation of O (dimer?)-related BD reason forsuperior radiation tolerance of EPI Si detectors
80 100 120 140 160 1800.0
0.2
0.4
0.6
0.8
1.0
1.2
Nor
mal
ised
TS
C s
igna
l (pA
/m
)
Temperature (K)
75 m 50 m 25 m
BD0/++
CiO
i
V2
-/0+?
80 100 120 140 160 1800.0
0.2
0.4
No
rma
lise
d T
SC
sig
na
l (p
A/
m)
Temperature (K)
75 m 50 m 25 m
BD0/++
CiO
i
V2
-/0+?
≈ 105 V (25 µm)
≈ 230 V (50 µm)
≈ 320V (75 µm)
28Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
DLTS (Deep Level Transient Spectroscopy)
Φ(25 μm epi) = 1.2 ·1012 p/cm2
25 μm epi: defect at 67K
TW = 200 ms, tp= 100 ms UR=-20V, UP=-0.1V
0 50 100 150 200 250 3000,00
0,05
0,10
0,15
0,20
0,25
0,30
0,35
0,40
35KV2(=/-)
176K
V2(-/0) + VP
IO2
VOi
b 1 [p
F]
T [K]
1,0E+16
1,0E+17
1,0E+18
0 5 10 15 20 25 30
Depth [μm]
con
cen
trat
ion
[O
] [1
/cm
3]
1,0E+10
1,0E+11
1,0E+12
con
cen
trat
ion
[IO
2]
[1/c
m3]
25 μm epi
29Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
Charge Collection EfficiencyCharge Collection Efficiency
CCE degradation linear with fluence if the devices are fully depletedCCE = 1 – , = 2.710-17 cm2
CCE(1016 cm-2) = 70 %
CCE measured with 244Cm -particles (5.8 MeV, R30 µm)Integration time window 20 ns
0 2.1015 4.1015 6.1015 8.1015 1016
eq [cm-2]
0.6
0.7
0.8
0.9
1.0
Cha
rge
colle
ctio
n ef
fici
ency
25 m, 80oC25 m, 80oC
50 m, 80oC50 m, 80oC
50 m, 60oC50 m, 60oC
23 GeV protons23 GeV protons
CCE measured with 90Sr electrons (mip’s), shaping time 25 ns
CCE no degradation at low temperatures !
CCE measured after n- and p-irradiation
CCE(Φp=1016 cm-2) = 2400 e (mp-value)
trapping parameters = thos for FZ diodes for small Φ, For large Φ less trapping than expected !
30Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
0 2.1015 4.1015 6.1015 8.1015 1016
eq [cm-2]
0
1000
2000
3000
4000
5000
Sign
al [
e]
simulationsimulation
reactor neutronsreactor neutrons
24 GeV/c protons24 GeV/c protons
90Sr source, 50 m epi-device 90Sr source, 50 m epi-device
peaking time 25 ns, T = -10 oC peaking time 25 ns, T = -10 oC
Charge Collection EfficiencyCharge Collection Efficiency
CCE(Φp=1016 cm-2) = 2400 e (mp-Wert)
CCE mit 90Sr Elektronen (mip’s), Integrationtime 25 ns
31Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
Current GenerationCurrent Generation
0 2.1015 4.1015 6.1015 8.1015 1016
eq [cm-2]
0.0
0.1
0.2
0.3
0.4
0.5
I/V
[Acm
-3] 50 m50 m
25 m25 m
I = x eq x VolI = x eq x Vol
Ta = 80oCTa = 80oC
ta = 8 min ta = 8 min
Result almost identical to FZ silicon:Current related damage rate α = 4.1·10-17 Acm-1
(Small deviations in short term annealing)
32Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
S-LHCS-LHC CERN scenario experimentCERN scenario experiment
Simulation:reproducing the experimental scenario
with damage parameters from analysis
Experimental parameter:Irradiation:
fluence steps 2.21015 cm-2 irradiation temperature 25°C
After each irradiation stepannealing at 80°C for 50 min,corresponding 265 days at 20°C
Excellent agreement between experimental data and simulated results
Simulation + parameters reliable!
0 2.1015 4.1015 6.1015 8.1015 1016
eq [cm-2]
0
50
100
150
200
250
Vfd
[V
]
50 m simulation50 m simulation
50 m after 50 min@80C annealing50 m after 50 min@80C annealing
25 m simulation25 m simulation
25 m after 50 min@80C annealing25 m after 50 min@80C annealing
Stable donor generation at high Φ would lead to larger Vfd, but acceptor generation during RT anneal could compensate this.
Proposed Benefit: Storage of EPI-detectors during beam off periods at RT (in contrast to required cold storage for FZ)
Check by dedicated experiment:
33Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
S-LHCS-LHC operational scenario simulation resultsoperational scenario simulation results
0 365 730 1095 1460 1825time [days]
0
100
200
300
400
500
600
Vfd
[V
]
50 m cold50 m cold
50 m warm50 m warm
25 m cold25 m cold
25 m warm25 m warm
S-LHC scenarioS-LHC scenario
RT storage during beam off periods extremely beneficial Damage during operation at -7°C compensated by 100 d RT annealing Effect more pronounced for 50 µm: less donor creation, same acceptor component Depletion voltage for full SLHC period less than 300 V
S-LHC: L=10S-LHC: L=103535cmcm-2-2ss-1-1
Most inner pixel layerMost inner pixel layer
operational period per year:operational period per year:100 d, -7100 d, -7°C, °C, ΦΦ = 3.48 = 3.48·10·101515cmcm-2-2
beam off period per yearbeam off period per year265 d, +20°C (lower curves)265 d, +20°C (lower curves) -7°C (upper curves) -7°C (upper curves)
34Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
Summary Summary
Thin low resistivity EPI diodes (grown on Cz) are extremely radiation tolerant
No type inversion observed up to Φeq = 1016 cm-2 for protons and neutrons
Radiation induced stable donor generation related most likely to O-dimers
Elevated temperature annealing results verified at 20°C
Dedicated CERN scenario experiment shows benefits of RT storage
Simulation of real SLHC operational scenario with RT storage demonstrated 50 µm EPI Detectors withstand 5y SLHC with Vop ≤ 300V (full depl.)
1.E-03
1.E-02
1.E-01
1.E+00
1.E+01
1.E+02
1.E+03
0 10 20 30 40 50 60 70
w [m]
rho
[
cm] p-type epi
50 µm, 150 ΩcmITME CiS
1.E-03
1.E-02
1.E-01
1.E+00
1.E+01
1.E+02
1.E+03
0 10 20 30 40 50 60 70 80 90 100
w [m]
rho
[
cm]
n-type epi70 µm, 150 ΩcmITME CiS
Future plans: p-type epi, thicker n-type epi, thin Cz …..Future plans: p-type epi, thicker n-type epi, thin Cz …..
35Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
To understand the nature of the universe !
DestinationDestination
36Frank Hönniger, Institute for Experimental Physics
Student Seminar, 10th April 2006
Experimental conditions at LHC
Detector requirements
• reliable detection of charged particles • material budget has to kept in mind, because of big detectors• high event rate & high track accuracy • complex detector design • intense radiation field in the whole operational
period of 10 years Radiation damage
negative influence on detector parameters
Silicon detector can handle with all
requirements for LHC
LHCproperties
Proton-proton colliderEnergy: 2 x 7 TeVLuminosity: 1034 cm-2 s-1
Bunch crossing: every 25 nsecRate: 40 MHzpp-collision event rate: 109/sec(23 interactions per bunch crossing)Annual operational period: 107 secExpected total op. period: 10 years