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Irradiation Study of n-on-P Strip Sensors
K. Hara, K. Inoue, A. Mochizuki (Univ. of Tsukuba)Y. Unno, S. Terada, T. Kohriki, Y. Ikegami (KEK)
K. Yamamura, K. Sato (HPK)
Proton irradiation: ~1x1014 to 5x1015 1MeV neq/cm2
1x1 cm2 miniature strip sensors
p-Bulk: FZ <111> and MCz <100> Effect of p -stop concentration and p-spray Various p-stop structures
S. Terada; KEK26 Feb. 2007, ID week @CERN
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High resistivity 4” wafers available to HPK• p-FZ (5~10 kΩcm, <111>)• p-MCz (0.6~1 kΩcm, <100>)
Strip isolation implant concentration (/cm2):
p-stop only: 5x1012, 2x1013
p-stop (2x1012) + p-splay (2x1012)
1x1 cm2 miniature sensors (of all above combinations) with 6 types of isolation structures (see next):
2 x 3 x 6 = 36 varieties
Proton fluence (6 points):
1, 2, 5, 10, 20, 50x1014 1MeV neq/cm2
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Proton Irradiation at Cyclotron and Radioisotope Center (CYRIC), Tohoku University Irradiation setup
– Proton beamline 31-2• Energy: 70 MeV• Current: 10 - 500 nA• Beam spot: 4.5 mm FWHM
– Samples• 3 sensors/board (10 boards stack in one run)• scanned over 20x44 mm2 for uniform irradiation• Took about 8 hours for 5x1015neq/cm2 with 350nA
– fluence• dosimetry: Al activation 27Al(p,x)24Na• 1x1014 ~ 5x1015 1 MeV-neq/cm2
Beam line
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I-V : isolation structures / p-implant concentrations
Pre- irrad: MD more often for MCz Leakage level depends on concentration/structure but less for MCzPost- irrad: Very uniform, little dependence on concentration/structure damage constant ~ 4 x10-17 A/cm (consistent with existing data)
Pstop+Pspray Pstop 5E12 Pstop 2E13
5E152E155E14@ - 20oC
FZ
MCz
Pre-irrad@20oC
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FDV (C-V and CCE) Summary
CV and CCE agree more or less with each other(Difficult to evaluate 5E15)
FZ reaches 600V at about 3E14, while MCz at 1E15MCz higher than 600V at low fluence, below 5E13
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CCE Summary
CCE: MCz better around 0.5 - 1x10E15Comparable to RD50 data
not fully depletedVB=1kV
p-MCz: H. Hoedlmoser,RD50 workshop 06p-DOFZ: G. Casse et al., NIMA535(2004) 362
1013 1014 1015 1016
0.0
5.0x103
1.0x104
1.5x104
2.0x104
2.5x104
nu
mb
er
of e
lect
ron
s (m
ea
n la
nd
au
)
fluence [cm-2]
p-spray high 100 V p-spray high 300 V p-spray low 100 V p-spray low 300 V G. Casse et al. 2004 @ 900 V
with 24 GeV/c protons
10161013
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Conclusions and discussions
Fabricated n-on-p microstrip sensors p-FZ and p-MCz wafers, with 6 types of n-strip isolation structures. p-stop implantation concentration: three values and the lowest with p-splay
1x1cm2 miniature sensors irradiated to 70-MeV protons up to 5x1015 1MeV neq/cm2
Still have micro-discharge(MD) particularly to MCz before irradiation, however, MD goes away once irradiated
FDV evaluated from C-V and laser CCE measurements p-MCz: starts at ~1kV, ~400V minimum around 2x1014/cm2, then increases to 600
V at ~1x1015/cm2 p-FZ: starts at ~150V, increases rapidly and reaches to 600V at ~3x1014/cm2
Partial DV operation may be inevitable particularly to MCz at the start, unless we get higher resistivity wafer
Noise studies have been under way
Sensor under fabrication: 6” wafer p-FZ <100>, p-MCz <100>
Next irradiation scheduled at the end of April, (then August, November and March)
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0
300
600
900
1200
1500
1800
0 10 20 30 40 50 60
fluence x10 14/ cm2
full
depl
etio
n vo
ltage
(V
)
FZMCZ
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Measurements of sensor characteristics
N+ N+
P-bulk
P-stop
SiO2
Al
LCR meter
A A
1.5MΩ 1.5MΩ
5VVbias
CV measurement
IV measurement
Isolation measurement
I-V ・・・ micro discharge ?C-V/ CCE (Charge Collection Efficiency ) ・・・ evaluate full depletion voltageIsolation ・・・ evaluate electrical isolation between readout strips
AlRead out
CCE measurement
Infrared laser
~1.5 uA if isolated,Larger if not
2200pF
2200pF
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Fluence evaluation by Al activation
P + Al → 24Na + X
efft EN
tmes
)exp(
Al (6x6cm2)
Al (1x1cm2) on sensor
Nmes : # of γ per second
λ : 24Na→γ decay rate⊿t : time from beam off to measurement Nt : # of Al atomΓ : 24Na→γ Branching ratioσ : cross sectionEeff : SSD efficiency
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Laser CCE setupQ-switched Nd:YAG(1064nm) laser
headIntensity control (Glan polarizer+ND filters)
Peltier cooling block with cold N2 gas outlets (-20oC)
Reference sample
Amplifier boxCurrent amp (PT=20ns)
Focusing lens
Laser position monitor
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