Transcript Document

ADVANCES IN SEMICONDUCTOR DETECTORS FOR 1016
PARTICLE TRACKING IN EXTREME RADIATION
ENVIRONMENTS. Cinzia Da Via’, Brunel University, UK
OUTLINE
123-
INTRODUCTION
PRESENT STATUS OF RADIATION HARD
SILICON DETECTORS UP TO 1015 neq/cm2
STRATEGIES FOR SURVIVAL BEYOND 1015 neq/cm2:
a
b
c
DEVICE GEOMETRY : short collection distance -3D,thin
TEMPERATURE and FORWARD BIAS OPERATION
DEFECT ENGINEERING :O and O2
4-
CONCLUSIONS
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Cinzia Da Via' - Brunel University UK
INTRODUCTION
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LARGE HADRON COLLIDER
CERN - GENEVA
new physics expected!!
BUT NEED HIGH STATISTICS
s
14TeV
Luminosity
[cm-2s-1]
pp
Bunch
[collisions/s] Spacing [ns]
LHC
2007
1034
8x108
~25
SLHC
~2015
1035
1011
~12
~6000 tracks per bunch crossing!!
27 Km
2
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PHYSICS REQUIREMENTS
p
Most probable
Higgs channel
Was it there already??
b
p
H
b
PRECISE
MEASUREMENTS OF
•MOMENTUM RESOLUTION
•TRACK RECONSTRUCTION
•b-TAGGING EFFICIENCY
HIGHER STATISTICS NEEDED FOR
Aleph
GOOD
TRACKER
ESSENTIAL!
Cinzia Da Via' - Brunel University UK
•ACCURACY OF STANDARD MODEL PARAMETERS
•ACCURACY OF NEW PHYSICS PARAMETERS
•SUPERSYMMETRIC PARTICLES
•EXTRA DIMENSIONS
•RARE PROCESSES (TOP DECAYS, HIGGS PAIRS ETC)
~10 SMALLER PITCH SILICON
DETECTORS CAN DO IT!!! 3
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RADIATION ENVIRONMENT AT LHC AND
SLHC
B-LAYER ~4cm
1.6x1016
ATLAS
>85%
Ch hadrons
total
n
p
other
charged
hadrons
210 m2 of microstrips
silicon detectors
Multiple particle environment:
NIEL scaling 1 MeV n equivalent
Violation observed for oxygen
rich materials
~5x1015
~5x1014
Data from CERN-TH/2002-078
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SILICON DETECTORS "NORMALLY "
USED IN PARTICLE PHYSICS
Substrate normally:
300 mm
+V
oxide
W
+ +
+
+
+
+
- - - - -
Incident
particle
metallised
strips
p-type
junctions
•n-type
•4 k-cm FZ
•Doping of ~1012 cm-3
•[O] ~1015 cm-3
•[C] ~1015 cm-3
•300mm thick
•Orientation <111>
n-type substrate
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RADIATION INDUCED BULK DAMAGE in Si
Primary Knock on Atom
Displacement threshold in Si:
Frenkel pair E~25eV
Clusters
E~5keV
Vacancy
Interstitial
Van Lint 1980
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RADIATION INDUCED STABLE DEFECTS IN SILICON
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From Cern ROSE RD48
Neutron irradiated
DEFECT KINETICS ( 300K ):
V,I +
IMPURITIES
DOPANTS
CHARGED DEFECTS
==>NEFF, VBIAS
DEEP TRAPS, RECOMBINATION
CENTERS ==>CHARGE LOSS
DLTS
spectrum
Ec
Ei
GENERATION
CENTERS==>LEAKAGE CURRENT
V6
VOEc - 0.17eV
V2(=/-)+Vn Ec-0.22eV
V2(-/0)+Vn Ec-0.40eV
V2O
CIOI(0/+)
Ev
Cinzia Da Via' - Brunel University UK
EV+0.36eV
VO effective e and h trap
V2 and V2O deep acceptors
7
contribute to Neff
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PRESENT RESEARCH FOCUSES AT FLUENCES
UP TO 1x1015 n/cm2
STANDARD 300mm n-type SILICON at 1015 n/cm2
10 years of operation at L=1034 cm-2s-1 at R=4 cm
EFFECTIVE DRIFT LENGTH
Due to charge trapping
~150mm e-
~50mm h
SPACE CHARGE
TYPE INVERSION
-ve Neff (1013/cm3) ~ VFD (5000V)~ F
depletion from n-contact (e-field)
REVERSE ANNEALING
INCREASE OF -ve Neff temp. dep
LEACKAGE CURRENT
prop to F (I/V ~5x10-17 F)
Noise
Thermal
runaway
Signal formation
Charge sharing
Speed
Double junction
Charge diffusion
Time [y]
Maintenance
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MAIN DETECTOR STRATEGIES PROPOSED
FOR LIFE ABOVE 1015 n/cm2
OPTIMIZATION OF:
COLLECTION DISTANCE
CCE (trapping)
SPEED
SPACE CHARGE
REVERSE ANNEALLING
CCE (undepletion)
STRATEGIES:
DEVICE GEOMETRY
3D, THIN
DEFECT ENGINEERING
O, P-TYPE SUBSTRATE
MODE OF OPERATION
Temperature, Forward bias
CHARGE SHARING
LEAKAGE CURRENT
MORE TO GAIN BY COMBINING TECHNIQUES!
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EFFECTIVE DRIFT LENGTH
Leff = tt x Vdrift
-1
2500
( 1V/micron)
7
1.2 10
14
10 n cm
Vde
Vdh
-2
7
1 10
teffn
teffnh
25
6
8 10
20
6
6 10
6
4 10
6
2 10
10
50
Measured
values
100
150
200
250
300
350
Temperature (K)
Leff at 1016 proton/cm2
~ 20 mm electrons
~ 10 mm holes
Data avalable for neutron andprotons for effective trapping time 220K-300K from Kramberger et al
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-2
4
-1
E = 10 V cm
2000
Proton
Electrons
1500
1000
Neutron
Holes
Proton
500
100
150
3000
5
200
250
300
350
Temperature (K)
-1
14
-2
10 ncm
E = 10 Vcm
Effective Drift Length (microns)
15
14
FOR FLUENCE = 10 cm
Neutron
0
50
-1
Drift Velocity (cm s )
Effective Trapping Time (ns)
30
Effective Trapping Length ( microns)
4
E = 10 V cm
( mt )
2500
neutron
2000
protons
Electrons
1500
neutrons
Holes
1000
protons
500
50
100
150
200
250
300
Temperature (K)
Simulation by S. Watts/Brunel
Accepted for publication on NIM
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350
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SIGNAL FORMATION AFTER IRRADIATION
W. Shockley, Jour. Appl.Phys. 9,635 (1938)
S. Ramo, Proc. of I.R.E. 27, 584 (1939)
Gatti and coworkers
RAMO's THEOREM
Signal ~ q(Vxw-V0w) e-th/th + (Vcw-Vxw) e-te/te)
Depends on carriers drift length
0.16 A/x
h+
p+ 1
e
h
0.6
0.4
0.2
n+
COLLECTION ELECTRODE
WeightPot STRIP
-2
1E15 n cm 200K
Prob e STRIP
Prob h STRIP
Prob signal STRIP
0.8
p /p /Signal
e-
collecting
Trapping
Shaping time
0
0
0
0.005
0.01
0.015
0.02
Distance (cm)
0.025
x
0.03
0.035
c
HOLES DON' T CONTRIBUTE
Cinzia Da Via' - Brunel University UK
Simulation by S. Watts
Accepted for publication
On NIMA
Waiting potential is steeper if contact
small compared with detector thickness
moreover minimize charge sharing
with neighbours due to charge trapping
Planar device
Small contact area
Thin substrate
High e-field
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SHORT COLLECTION DISTANCE:
S. Parker, C. Kenney
3D DETECTOR
1995
n
n
p
SHORT COLLECTION PATHS
50 mm (300mm)
LOW DEPLETION VOLTAGES
<10V (60V)
RAPID CHARGE COLLECTION
1-2n (25 ns)
EDGELESS CAPABILITY
active edges
LARGE AREA COVERAGE
active edges
SUBSTRATE THICKNESS INDEPENDENT :
BIG SIGNALS
X-RAY DETECTION EFFICIENCY
for low Z materials
p
p+
n+
n+
Same
Generated
Charge!!!
+
300 mm
+
-
50 mm
depletion
Cinzia Da Via' - Brunel University UK
C=0.2pF
IEEE vol46 N4 Aug. 99
p+
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ETCHING TECHNIQUES
DEEP REACTIVE ION ETCHING
LASER ABLATION
ELECTROCHEMICAL
ETCHING
ELECTRODE
FILLED WITH
POLYSILICON
fs pulses is cleaner, any substrate
Fast, high aspect ratio
NIMA 487 (2002) 19
ASPECT RATIO = 11:1, 19:1
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20:1<13
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3D DETECTOR RESULTS before
irradiation
DETECTOR THICKNESS 121mm
282e noise PREAMP - SHAPING TIME 1 ms
200 mm PITCH mSTRIP TYPE DETECTOR
GAUSSIAN
RESPONSE
SPEED
1.5ns rise
AT 130K
3.5ns rise
AT 300K
350 e rms , fast electronic designed at CERNmicroelectronics group
200mm pitch detector TO BE PUBLISHED
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3D RADIATION RESULTS AT 300K
After irradiation
1x1015 p/cm2 (5x1014n/cm2)
NON OXYGENATED
100mm pitch detector
FULL DEPLETION BIAS =
105 V AFTER 2x1015 n/cm2
SPEED 3.5 ns rise time
40V bias, 300K
joined work Brunel, Cern, Hawaii
To be published
Cinzia Da Via' - Brunel University UK
IEEE Trans on Nucl Sci 48 (2001) 1629
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3D CHARGE COLLECTION EFFICINECY
After irradiation
More on 3D later this morning (P. Roy, 11:30)
Vbias Vsig Vbias= 40V
n
p
100 mm
n
CCE =61%
USING THE INTEGRATED 22-25 KeV XRAY PULSES FROM A 109Cd SOURCE
COLLECTION FROM p-ELECTRODE
Vbias Vsig Vbias
=40V
n
134 mm
p
n
100
mm
200mm
Non-Irradiated, 300 K
1 x 1015 p/cm2, 300 K
No Oxygen
Diffusion
Reverse
Annealed
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Brunel, CERN, Hawaii to be published
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MAIN DETECTOR STRATEGIES PROPOSED
FOR LIFE ABOVE 1015 n/cm2
OPTIMIZATION OF:
COLLECTION DISTANCE
CCE (trapping)
SPEED
SPACE CHARGE
REVERSE ANNEALLING
CCE (undepletion)
STRATEGIES:
DEVICE GEOMETRY
3D, THIN
DEFECT ENGINEERING
O2, P-TYPE SUBSTRATE
MODE OF OPERATION
Temperature, Forward bias
CHARGE SHARING
MORE TO GAIN BY COMBINING TECHNIQUES!
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SPACE CHARGE after
Irradiation – type inversion
1016
At 300K
Introduction of radiation induced
Deep acceptors
p+
Active volume
before
- - irradiation
- W- d
-Active volume
- after irradiation
High
field
n+
Type inversion
AFTER TYPE INVERSION
DEPLETION STARTS FROM
n+ CONTACT
Cinzia Da Via' - Brunel University UK
VFD 
(W )2  e  N eff
2ε 0ε Si
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THE OXYGEN MIRACLE : ROSE/RD48
REDUCED
VFD
3 times
Nucl. Instr. Meth. A 466 (2001) 308
Reduced
Reverse
Annealing
Saturation
(2 times)
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NEUTRON PROTON PUZZLE
COMPETING MECHANISM DUE TO COULOMB INTERACTION
MORE POINT DEFECTS WHEN CHARGED PARTICLE IRRADIATION
V+O = VO
DOES NOT CONTRINUTE TO NEFF
V2+0 = V2O
CONTRIBUTES TO NEFF
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CHARGE COLLECTION EFFICIENCY
AFTER IRRADIATION
p+
-W
p-type bulk
n on p
n+
- d
High field
Qcoll = q * d/W  Vbias
TRAPPING
Standard p on n
Oxygenated p on n
25ns electronics
3x1014 n/cm2
T=-170C
UNDEPLETED REGION
1 – 3 x 1014 n/cm2
0
100
200
300
400
500
OXYGEN ONLY DOES NOT HELP!
NIMA 487 (2002) 465-470
NIM A 412 (1998) 238
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Vbias
21
600
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ATLAS PIXELS AFTER 1015 n/cm2
Nucl Inst Meth A 456 (2001) 217-232
These data curtesy from L. Rossi, unpublished
CCE  97.7%
AT 600V
250mm
Time=10ns
n+ on n
oxygenated
250 mm
Multi guard - p-spray
COMBINED
STRATEGIES!!
13 mm
Spatial resolution
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EFFECT ON CHARGE SHARING
Diffusion due to low field region after type inversion
Double sided strips
p+
10
Electric Field (V/cm)
Resolution [mm]
3.1014 n/cm2
4
n+
1000
100
5V
10V
20V
50V
200V
10
LHCb
Vbias
180K
1
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
p side
Distance (cm)
p+
Vbias
NIM A 440 (2000) 17
n side
Efficiency
ATLAS
1-5 x 1014 n/cm2
Cinzia Da Via' - Brunel University UK
>1015 n/cm2
NIMA 426 (1999) 140
SIMULATION S WATTS UNPUBLISHED
Vbias
23
NIM A 450 (2000) 297
Vbias
SPACE CHARGE
Below 200 K
1016
NEFF DECREASE WITH T!!
energy level occupancy ~ e- E/kT
1.3 10
LAZARUS effect
12
1x1014 n/cm2 > type inverted : -ve SC
1.2 10
12
1.1 10
12
1.0 10
12
9.0 10
11
8.0 10
11
7.0 10
11
TRAPPING
NEFF
-3
Neff [cm ]
CCE INCREASES!
Low leakage current
No reverse annealing
High carriers mobility
Phosphorus doping level
6.0 10
11
5.0 10
11
+ve SC
80
100
120
140
T [K]
T [K]
Cinzia Da Via' - Brunel University UK
160
180
C Da Via
To be published
NIM..
Nucl Inst Meth A 413 (1998) 475
Nucl Inst Meth A 440 (2000) 5
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FORWARD BIAS OPERATION
AT LOW TEMPERATURE
d
Forward bias
Reverse bias
NIM A 440 (2000) 5
f = 1015 n/cm2
T=130K
0 min
CCE %
x
5 min
15 min
30 min
time
V bias
undepleted
td ~
eE/kT
T=249K (-24C)
f = 1015 n/cm2
NIM A 439 (2000) 293.
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Reverse bias,
700 V
Higher CCE
"polarization
effect"
Forward bias
90 V
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IF IRRADIATION AT 130K:
different kinetics!
1- formation of defects V, I, Vn, In, depending on particles
2-
V
+
and V-
observed already at 4.2K after
e-
0 Fluence
CCE(W) 5E14
6e14 n/cm2
CCE(W) 2E15
6E14n/cm2 after WU
CCE(W) 1E15
100
irradiation
3- V present in 5 charge states V2+, V+, V0, V-, V2-.
80
~70K in n-type low res
CCE%
~150K in p-type
~200K in high res. material
5- at 200K new spectra appears (V2, VO)
migrates!!
=> V
6- V migration also possible by ionisation = athermal
process
CCE %
4- the V spectra disappear at :
After annealing at 200K
better by 20%
60
40
Irradiated at 300K
For comparison
20
7- I mobile at 4.2K in p-type, ~140-175K in n-type
(G. Watkins .Mat. Sci. in Sem. Proc. 3 (2000) 227)
0
0
Systematic study needed!
50
100
150
200
voltage
VOLTAGE (V)
NIM A 476 (2002) 583
26
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250
1016
NEW DEFECT ENGINEERED MATERIAL:
O-DIMER TO CONTROL CHARGE TRAPPING
10
5 10
OXYGEN INTERSTITIAL
Si
0
Oi
Si OXYGEN DIMER Si
Oi
Concentration (cm
-3
)
Si
1.1 x1011 p/cm2
10
-5 10
11
-1 10
11
-1.5 10
11
-2 10
E(90)
E(225)
E(170)
Oi
Si
HIGH TEMPERATURE 60Co g IRRADIATION
AT T > 350 0C OXYGEN ATOMS BECOMES
MOBILE AND START TO CLUSTER
QUASI CHEMICAL REACTIONS:
V+Oi => VOi
VOi + Oi => VO2i
I + VO2i => O2i
Cinzia Da Via' - Brunel University UK
366p
309p
366Dp
309Dp
11
-2.5 10
NIM B 186 (2002) 111
100
150
200
250
300
Temperature (K) D= dimerized
p=proton irradiated
DLTS shows VO suppressed
Less trapping!
Theory predicts VO2 is NEUTRAL!
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SUMMARY
WE KNOW HOW TO:
1- HAVE A SHORT COLLECTION
DISTANCE + COLLECTING eoptimise signal formation
spatial resolution
speed
2- CONTROL THE SPACE CHARGE
power dissipation (noise)
CCE
spatial resolution
3- CONTROL CHARGE TRAPPING
CCE
spatial resolution
USING :
device structure
3D – THIN (small
pitch)
Defect engineering
operational mode
Temperature,
forward bias
Defect engineering
p-type
operational mode
MORE GAIN BY COMBINING TECHNIQUES!!!28
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CONCLUSIONS
THE COMBINATION OF:



ENGINEERED SILICON (oxygen enriched), p-type substrate
INNOVATIVE SHORT DRIFT LENGTH GEOMETRIES (3D, thin)
OPERATIONAL CONDITION (temperature, forward bias)
COULD PROVIDE THE RADIATION TOLERANCE OF SILICON NEEDED TO
GUARANTEE THE OPERATION OF PARTICLE TRACKERS AT 1016 n/cm2

ELECTRONICS PLAYING A KEY ROLE!!
•Recently formed CERN R&D (RD50) will explore several of the proposed
strategies
•Interest expressed by LHC elastic scattering, Luminosity monitor
collaborations to use existing technologies like 3Dand cryogenic silicon.
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ACKNOWLEDGEMENTS
Luca Casagrande/ Roma
GianLuigi Casse/Liverpool
Alex Chilingarov /Lancaster
Paula Collins/Cern
Leo Rossi /Atlas pixel
Mahfuzur Rahman/Glasgow
Angela Kok, Anna Karpenko,Gennaro Ruggiero/
Brunel
Erik Heijne/Cern
Sherwood Parker/Hawaii
Steve Watts /Brunel
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“The most important thing in science
is imagination”
A. Einstein
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