outline : introduction ise simulation of non-irradiated and irradiated devices
DESCRIPTION
Study of charge collection properties of silicon microstrip detectors with different read out geometries after high doses of proton irradiation. G. Casse, P.P. Allport, S. F. Biagi, T.J.V. Bowcock, A. Greenall, A. Smith, P. Turner. Outline : Introduction - PowerPoint PPT PresentationTRANSCRIPT
VERTEX 2002 – Hawaii, 3-7 Nov. 2002
Department of Physics
Outline:
•Introduction
•ISE simulation of non-irradiated and irradiated devices
•Non-homogeneous irradiation of large area microstrip detectors
•Study of the non-homogenously irradiated detector - CCE(V) and charge sharing -
•Signal/noise as a function of the irradiation
•Conclusions
Study of charge collection properties of silicon microstrip detectors with different read out geometries
after high doses of proton irradiation
G. Casse, P.P. Allport, S. F. Biagi, T.J.V. Bowcock, A. Greenall, A. Smith, P. Turner
VERTEX 2002 – Hawaii, 3-7 Nov. 2002
Department of Physics
0
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1
1.2
0 100 200 300 400 500 600
Bias [V]
Q/Q
M
Q (10 ns) Q (25 ns)
Q (40 ns) Q (80ns)
0
0.2
0.4
0.6
0.8
1
1.2
0 200 400 600 800Bias [V]
Q/Q
M
Q (10 ns) Q (25 ns)
Q (40 ns) Q (80 ns)
(a) (b)
Vfd
CCE in silicon diodes before and after irradiation (4 1014 cm-2)
The radiation damage introduces charge trapping and changes in VFD, electric field profile, dielectric properties of non-depleted bulk
VERTEX 2002 – Hawaii, 3-7 Nov. 2002
Department of Physics
We use ISE-TCAD to simulate non-irradiated and irradiated silicon detectors.
The radiation effects have been introduced by electron and hole traps in the silicon band-gap. The trap density below corresponds to a fluence of 1x1015 1MeV neutron equivalent cm-2.
Trap typeTrap
density[cm-3]
Energy from mid
band gap [V]
El. capture cross section [cm-2]
Hole capture cross section [cm-2]
*Electron 1.50 1015 0.39 1.00 10-14 5.50 10-13
*Electron2.20 1015 0.13 2.00 10-15 1.20 10-14
Electron 3.60 1014 0.035 1.20 10-15 1.20 10-14
Hole 3.24 1014 -0.045 1.20 10-14 1.20 10-15
*Hole 1.50 1015 -0.20 1.50 10-14 2.00 10-15
* Hallen et al. J. Appl. Phys. 79(1996) 3906
VERTEX 2002 – Hawaii, 3-7 Nov. 2002
Department of Physics
ISE simulation of the electric field profile in a n-bulk silicon diode before and after irradiation (4 1014 p cm-2)
Note the presence of an electric field in the ‘non-depleted’ bulk at low biases and the ‘double-junction’
p+-implantn+-implant
VERTEX 2002 – Hawaii, 3-7 Nov. 2002
Department of Physics
ISE simulation of the majority carrier concentration in a silicon diode before and after irradiation (4 1014 p cm-2)
p+-implant n+-implant
VERTEX 2002 – Hawaii, 3-7 Nov. 2002
Department of Physics
1
2
34 5
6
7
8
Strip #128
Strip #256
Strip #384
Strip #512 Strip
#640
Strip #768
Strip #896
Inner radius 8mm
Outer radius42mm
1 2 3 4 5 6 7 6 5 4 3 2 1
Fluence contours x1014 p/cm2
Non-homogenous irradiation of large area LHCb VELO phi-type prototype detectors
VERTEX 2002 – Hawaii, 3-7 Nov. 2002
Department of Physics
Beam profile
0
10
20
30
40
50
60
70
80
20 30 40 50 60 70 80
Position from Ref [mm]
Mea
sure
d flu
ence
[E13
p c
m-2
]
Back AlFront Al
Irradiated devices : 200 m n-in-n 200 m p-in-n 300 m p-in-n
Irradiated together, maximum fluence ~ 7 1014 p cm-2
Maximum fluence ~ 4.6 1014 p cm-2
VERTEX 2002 – Hawaii, 3-7 Nov. 2002
Department of Physics
Tools for studying the non-homogeneously irradiated detector: comparison between CCE with infrared (1060 nm) laser and 106Ru ß–source. All measurements with SCT128-VG (LHC speed electronics)
CCE(V) for irradiated, 200m thick, detector with laser data (normalised to value at 400V) superimposed
VERTEX 2002 – Hawaii, 3-7 Nov. 2002
Department of Physics
From fits to the CCE(V), the depletion voltages for the different regions of the detector can be extracted.The Vfd (Neff) profile corresponds to the irradiation profile and allows to study the properties of the detector with a steep gradient of Vfd(Neff).
0
20
40
60
80
100
120
140
100 300 500 700 900
Strip Number
V fd [
cm-3
]
0.0E+00
5.0E+11
1.0E+12
1.5E+12
2.0E+12
2.5E+12
3.0E+12
3.5E+12
4.0E+12
4.5E+12
Nef
f [cm
-3]
h
ee
h
Gradient of Neff can introduces a ‘transverse’ component of the electric field and a distortion in the reconstructed cluster position. Distortions are expected to have opposite sign for opposite sign of the gradient of Neff.
VERTEX 2002 – Hawaii, 3-7 Nov. 2002
Department of Physics
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0 10 20 30 40 50 60 70 80 90 100Local position [µm]
Rig
ht c
harg
e/To
tal c
harg
e
25 volt
70 volt
200 volt
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1
1.2
0 10 20 30 40 50 60 70 80 90 100Local position [µm]
Righ
t cha
rge/
Tota
l cha
rge 30 volt
50 volt
150 volt
300 volt
Strip 517-518 Vfd=29 V
Strip 534-535 Vfd=34 V
= QR/(QR+QL)
N-in-n 200 m detector
VERTEX 2002 – Hawaii, 3-7 Nov. 2002
Department of Physics
0
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1
1.2
0 10 20 30 40 50 60 70 80 90 100Local position [µm]
Righ
t cha
rge/
Tota
l cha
rge 40 volt
200 volt
0
0.2
0.4
0.6
0.8
1
1.2
0 10 20 30 40 50 60 70 80 90 100Local position [µm]
Righ
t cha
rge/
Tota
l cha
rge
50 volt
150 volt
300 volt
0
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0.4
0.6
0.8
1
1.2
0 10 20 30 40 50 60 70 80 90 100Local position [µm]
Rig
ht c
harg
e/To
tal
char
ge
50 volt150 volt300 volt
0
0.2
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0.6
0.8
1
1.2
0 10 20 30 40 50 60 70 80 90 100
Local position [µm]
Rig
ht c
harg
e/To
tal c
harg
e
30 V
200 V
Strip 582-583 Vfd=90V
Strip 612-613 Vfd=105V
Strp 632-633 Vfd=110V
Strip 670-671 Vfd=95 V
= QR/(QR+QL)N-in-n 200 m detector
VERTEX 2002 – Hawaii, 3-7 Nov. 2002
Department of Physics
= QR/(QR+QL)P-in-n 300 m detector
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1
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0 10 20 30 40 50 60 70 80 90 100 110
Local position [µm]
Rig
ht c
harg
e/To
tal c
harg
e
20 Volt
50 Volt
200 Volt
Low radiation region Vfd=75V
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0.6
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1
1.2
0 20 40 60 80 100
Local position [µm]
Rig
ht c
harg
e/To
tal c
harg
e
150 Volt200 Volt400 Volt
Irradiated region with positive gradient of |Neff| as a function of the strip number (Vfd 230 V)
Irradiated region with negative gradient of |Neff| as a function of the strip number (Vfd 230 V)
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1
1.2
0 10 20 30 40 50 60 70 80 90 100 110
Local position [µm]
Rig
ht c
harg
e/To
tal c
harg
e
150 Volt
200 Volt
400 Volt
VERTEX 2002 – Hawaii, 3-7 Nov. 2002
Department of Physics
No evidence of distortion (spread observed () is approximately 2µm) in the reconstructed cluster position due to the high gradient of Neff in the detector. The experimental results are also supported by ISE simulations
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0.8
1
1.2
0 20 40 60 80 100
Local position [µm]
Righ
t cha
rge/
Tota
l cha
rge
#244 -245 (@ 200 Volt)
#634 - 635 (@ 400 Volt)
#760 - 761 (@ 400 Volt)
VERTEX 2002 – Hawaii, 3-7 Nov. 2002
Department of Physics
Signal (106Ru ß–source) degradation as a function of fluence in the non-homogeneous irradiated detector (n-in-n).
VERTEX 2002 – Hawaii, 3-7 Nov. 2002
Department of Physics
Noise as a function of the applied bias: dose varying from 2. 1014 to 7. 1014 p cm-2
The noise doesn’t change with irradiation and bias (when the total reverse current is kept low, below 1mA)
0
2
4
6
8
10
12
14
0.E+00 2.E+14 4.E+14 6.E+14 8.E+14
Fluence (p cm-2)
Nois
e (A
DC c
ount
s)
80 V
100 V
200 V
300 V
VERTEX 2002 – Hawaii, 3-7 Nov. 2002
Department of Physics
The signal/noise measured with this 200 m thick detector with about 7.5 pF input capacitance is about 16 and 12.5 in the non-irradiated and in the most irradiated areas respectively, as measured with the SCT128-VG analogue electronics
Signal of fast electrons from 106Ru source (non-irr. area)
Cluster significance (non-irr. area)
Cluster significance (irr. area)
VERTEX 2002 – Hawaii, 3-7 Nov. 2002
Department of Physics
Laser (1060 nm) CCE(V) in the highest irradiated areas for a n-in-n (7. 1014 p cm-2) and p-in-n (6. 1014 p cm-2) 200 m thick microstrip detectors
For simple one dimensional structures eg large area diodes little difference is expected between the signals seen on the n-side or the p-side.
Direct comparisons of n-side and p-side detectors with the same masks fabricated on the same material confirm the superiority of n-side read-out after irradiation.
VERTEX 2002 – Hawaii, 3-7 Nov. 2002
Department of PhysicsConclusions:
• ISE simulations describe well the device properties also after irradiation and successfully predict charge collection properties and are being used for updating designs.
• The effect of non-uniform irradiations (with resulting high gradient - 2.6 1012 cm-4 - of Neff across the detector and perpendicular to the strip) has been studied and small limit to the distortion of the reconstructed cluster position have been placed.
• The charge collected at a given voltage is reduced both by the trapping and by the changes to the effective doping concentration.
• The former is addressed by n-side read-out while the latter can be helped by using an oxygen enhanced substrate.
• Combining the techniques of n-side read-out (to reduce the influence of trapping) and enhanced interstitial oxygen should yield tracking detectors good to 1015p/cm2 at least.