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PTP and the inter-strip capacitance and resistance for irradiated - - PowerPoint PPT Presentation

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PTP and the inter-strip capacitance and resistance for irradiated ATLAS07 mini-sensors . Jan Bohm, Institute of Physics ASCR, Prague Peter Kodys, Zdenek Dolezal, Jan Scheirich, Charles University in Prague Petr Masek, Michael Solar, Institute

slide-1
SLIDE 1

PTP and the inter-strip capacitance and resistance for irradiated ATLAS07 mini-sensors.

Jan Bohm, Institute of Physics ASCR, Prague Peter Kodys, Zdenek Dolezal, Jan Scheirich, Charles University in Prague Petr Masek, Michael Solar, Institute of Experimental and Applied Physics

  • f Czech Technical University in Prague

18/02/2013 J.Bohm, 8th Trento Workshop, Trento, Italy 1

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SLIDE 2

18/02/2013 J.Bohm, 8th Trento Workshop, Trento, Italy 2

  • 1. Introduction
  • 2. IV characteristics of heavily irradiated sensors
  • 3. Interstrip capacitance and bias dependence
  • 4. Time evolution of interstrip and bulk capacitances
  • 5. Interstrip resistance
  • 6. Characteristics of punch through structures
  • 7. Summary and conclusions

The performance of the sample of 75 n-in-p ATLAS07 HPK miniature 1cm*1cm sensors developed by ATLAS Collaboration for LHC upgrade [Y. Unno, et.al., Nucl.

  • Inst. Meth. A636 (2011) S24-30] with different punch through structures, BZ4A-D,

and with three different ion concentrations of 2E12, 4E12 and 1E13 ion/cm^2 of the P-stop and P-stop + P-spray separation is studied before and after irradiation with the aim to select the P-stop ion concentration and punch through structure as the most effective protection against beam splashes

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SLIDE 3

Sample of HPK miniature sensors

18/02/2013 J.Bohm, 8th Trento Workshop, Trento, Italy

From Hamburg we received next 12 sensors BZ4A-D of Series 3 (wafers 264,278 and 281) with P-stop ion concentration 4E12 ion/cm^2. Many thanks to colleagues from DESY.

Wafer Isolation Ion/cm^2 Fluency neq/cm^2 Particles Where Annealing W06 Pspr+Pstp 2E+12 4E+14 neutrons Ljubljana 80min/60degC W10 Pspr+Pstp 2E+12 2E+15 neutrons Ljubljana 80minn/60degC W17 Pstop 2E+12 4E+14 neutrons Ljubljana 80min/60degC W19 Pstop 2E+12 2E+15 neutrons Ljubljana 80min/60degC W278 Pstop 4E+12 4E+14 neutrons Ljubljana 80min/60degC W281 Pstop 4E+12 2E+15 neutrons Ljubljana 80min/60degC W31 Pstop 2E+12 4E+14 p 23GeV/c CERN 80min/60degC W91 Pstop 1E+13 4E+14 neutrons Rez Prague 80min/60degC W93 Pstop 1E+13 2E+15 neutrons Rez Prague 80min/60degC W97 Pstop 1E+13 1E+16 neutrons Rez Prague 80min/60degC

Irradiation of sensors BZ4A, B, C and D for each wafer

3

Many thanks to Vlado Cindro , Morris Glaser and Jan Kucera for irradiation

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SLIDE 4

Punch Through Protection Structures for ATLAS07

18/02/2013 J.Bohm, 8th Trento Workshop, Trento, Italy

A protection of AC coupling capacitors against the beam splashes should ensure special structures, BZ4A,B,C on the HPK ATLAS07 mini-sensors. A beam splash generates a spike of voltage across the AC coupling insulator. When the distance between the bias rail and the n-strip implants is appropriate, this voltage between the bias rail and the n-strip implant ends can be limited. This distance is 20 µ and is used in all special structures BZ4A,B,C and sensor BZ4D Sensor BZ4D has no special structure and it is used for comparison with structures BZ4A, B and C.

4

BZ4A BZ4B BZ4C BZ4D

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SLIDE 5

IV characteristics of non-irradiated ATLAS07 sensors

J.Bohm, 8th Trento Workshop, Trento, Italy

  • 4
  • 3.5
  • 3
  • 2.5
  • 2
  • 1.5
  • 1
  • 0.5
  • 200
  • 400
  • 600
  • 800
  • 1,000

Current [nA] Bias [V]

ATLAS07 pre-series3 P-stop 2E12 BZ4A-D

W14 A W14 B W14 C W14 D W17 A W17 B W17 C W17 D W19 A W19 B W19 C W19 D W31 A W31 B W31 C W31 D

  • 4
  • 3.5
  • 3
  • 2.5
  • 2
  • 1.5
  • 1
  • 0.5
  • 1000
  • 800
  • 600
  • 400
  • 200

Current [nA] Bias [V]

ATLAS07 Series3 P-stop 4E12 BZ4A-D

W264 A W264 B W264 C W264 D W278 A W278 B W278 C W278 D W281 A W281 B W281 C W281 D

  • 4
  • 3.5
  • 3
  • 2.5
  • 2
  • 1.5
  • 1
  • 0.5
  • 200
  • 400
  • 600
  • 800
  • 1000

Current [nA] Bias [V]

ATLAS07 series 2nd STD P-stop 1E13

BZ4A-D

W75 A W75 B W75 C W75 D W78 A W78 B W78 C W78 D W80 A W80 B W80 C W80 D W81 A W81 B W81 C W81 D

  • 4
  • 3.5
  • 3
  • 2.5
  • 2
  • 1.5
  • 1
  • 0.5
  • 200
  • 400
  • 600
  • 800
  • 1000

Current [nA] Bias [V]

ATLAS07 series 2nd HPK P-stop 1E13 BZ4A-D

W89 A W89 B W89 C W89 D W91 A W91 B W91 C W91 D W93 A W93 B W93 C W93 D W97 A W97 B W97 C W97 D

Measured sensors were placed on the table without vacuum chuck jig to avoid possible strong stresses which could cause breakdowns.

18/02/2013 5

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SLIDE 6

1 10 100 1000

  • 1000
  • 800
  • 600
  • 400
  • 200

Leakage Current [µΩ] Bias [V]

W91 A 4E14 W91 B 4E14 W91 C 4E14 W91 D 4E14 W93 A 2E15 W93 B 2E15 W93 C 2E15 W93 D 2E15 W278A 4E14 W278B 4E14 W278C 4E14 W278D 4E14 W281A 2E15 W281B 2E15 W281C 2E15 W281D 2E15 W19A 2E15 W19B 2E15 W19D 2E15 W17B 4E14 W97 A 1E16 W97 B 1E16 W97 C 1E16 W97 D 1E16 W31 A p 4E14 W31 B p 4E14 W31 C p 4E14 W31 D p 4E14

2E15n/cm2 Proton irradiation at CERN

18/02/2013 J.Bohm, 8th Trento Workshop, Trento, Italy 6

IV Characteristics of irradiated ATLAS07 sensors

The heavily irradiated sensors (≥ 2E15n/cm2) with p-stop isolation of different ion concentrations were successfully operating up to 1000V with the exception of fluency 4E14n/cm2 where an onset of micro-discharges was observed above ~700V

1E16n/cm2 4E14n/cm2

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SLIDE 7

Interstrip Capacitance - Method of measurement

18/02/2013 J.Bohm, 8th Trento Workshop, Trento, Italy

0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 100 200 300 400 500 600

Cint [pF] Vbias [-V] V]

Cinter CpRp 100kHz

Sensor W37

2 probes 5 probes GND 3 probes 5probes –outer strips to LCR Low

2-probes 3-probes 5-probes LCR High DC pad LCR Low Outer strips to GND Cint(5-pr)/Cint(3-pr)=0.939 and 0.913 for 100kHz and 1MHz, respect. Cint(2-pr)/Cint(5-pr)=0.57 AC pad

J.Bohm, M.Mikestikova et.al, NIM A636 (2011)S104-S110

7

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SLIDE 8

Interstrip Capacitance – non-irradiated

18/02/2013 J.Bohm, 8th Trento Workshop, Trento, Italy

0.2 0.4 0.6 0.8 0.1 1 10 100 1000

Cinter [pF] Frequency [kHz]

Cinterstrip vs Frequency

W78-STD Pstop 1E13; W89-HPK Pstop 1E13; W14-Pstop 2E12; W04-PstopSpray 2E12 W264-Pstop 4E12 W78 B W89 B W14 B W04 B W264 B

0.5 0.6 0.7 0.8

  • 600
  • 400
  • 200

Cinterstrip [pF] Bias [V]

Interstrip Capacitance p-stop 1E13 ion/cm^2, Series 2 STD & HPK

W78 A W78 B W78 C W78 D W89 A W89 B W89 C W89 D

Vfd

0.2 0.4 0.6 0.8 1 1.2

  • 600
  • 400
  • 200

Cinter [pF] Bias [V]

Interstrip Capacitance

ATLAS07 pre-Series3 p-stop&spray 2E12ion/cm^2

W14 A W14 B W14 C W14 D W04 A W04 B W04 C W04 D

Vfd

Interstrip capacitance is measured by 3 probes at 1 MHz and CpRp C interstrip for frequency above 100kHz is slowly increasing up to 1MHz. For Vbias<Vfd the values of C interstrip depend

  • n the P-stop & P-spray ion concentration but

above Vfd the Cinter is constant and the same for all p-stop doses. There is narrow deep minimum of Cint at Vbias =-4V for P-stop+P-spray isolation.

8

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SLIDE 9

0.2 0.4 0.6 0.8 0.1 1 10 100 1000

Cinter [pF] Frequency [kHz]

Irradiated ATLAS07 sensors

1.E+13 W97 D 1E16 1.E+13 W97 A 1E16 4.E+12 W281A 2E15 4.E+12 W281B 2E15 2.E+12 W19 A 2E15 2.E+12 W10 A 2E15 PstSpr 2.E+12 W10 B 2E15 PstSpr 2.E+12 W19 B 2E15 1.E+13 W91 A 4E14 1.E+13 W91 C 4E14

0.2 0.4 0.6 0.8 0.1 1 10 100 1000

Cinter [pF] Frequency [kHz]

Non-irradiated ATLAS07 sensors

W78-STD Pstop 1E13; W89-HPK Pstop 1E13; W14-Pstop 2E12; W04-PstopSpray 2E12 W78 B W89 B W14 B W04 B W264 B 18/02/2013 J.Bohm, 8th Trento Workshop, Trento, Italy 9

Interstrip Capacitance Dependence on Frequency

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SLIDE 10

18/02/2013 J.Bohm, 8th Trento Workshop, Trento, Italy 0.2 0.4 0.6 0.8 1 1.2

  • 600
  • 400
  • 200

Cinter [pF] Reverse Bias [V]

Inter-strip Capacitance

ATLAS07 Series2, pre-Series3 & Series3

W89 A W89 B W89 C W89 D W14 A W14 B W14 C W14 D W04 A W04 B W04 C W04 D W264 A W264 B W264 C W264 D W78 A W78 B W78 C W78 D

10

The inter-strip capacitance, Cint, is constant for bias voltages higher than respective full depletion voltages and Cint does not depend in this region on an ion concentration and the punch through protection structures within measuring error of ±0.02pF.

Interstrip Capacitance – non-irradiated

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SLIDE 11

0.58 0.62 0.66 0.7 0.74

  • 500
  • 400
  • 300
  • 200
  • 100

Cinter [pF] Bias [V]

ATLAS07 Pstop 1E13 ion/cm2

W91 A 4E14 W91 B 4E14 W91 C 4E14 W91D 4E14 W93 A 2E15 W93 B 2E15 W93 C 2E15 W93 D 2E15 W97 A 1E16 W97 B 1E16 W97C 1E16 W97 D 1E16 W89 A nonirrad W89 B nonirrad W89 C nonirrad W89 D nonirrad

0.04pF

18/02/2013 J.Bohm, 8th Trento Workshop, Trento, Italy 11

Interstrip Capacitance of Heavily Irradiated Sensors

Cinter before irradiation for p-stop dose 1E13ion/cm2 is also shown. Cinter is not changed by irradiation up to 1E16n/cm2. A slow decrease is observed with growing bias voltage which is more pronounced for fluency 4E14n/cm2 than for higher doses.

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SLIDE 12

0.6 0.64 0.68 0.72 0.76

  • 500
  • 400
  • 300
  • 200
  • 100

Cinter [pF] Bias [V]

2.E+12 W10 A 2E15 PstSpr 2.E+12 W10 B 2E15 PstSpr 2.E+12 W10 C 2E15 PstSpr 2.E+12 W19A 2E15 2.E+12 W19 B 2E15 2.E+12 W19 C 2E15 4.E+12 W281A 2E15 4.E+12 W281B 2E15 4.E+12 W281C 2E15 1.E+13 W93 A 2E15 1.E+13 W93 B 2E15 1.E+13 W93 C 2E15

18/02/2013 J.Bohm, 8th Trento Workshop, Trento, Italy 12

Interstrip Capacity and p-stop ion concentration

Interstrip capacitance does not depend on ion concentration of p-stop implant within measuring error of ~0.02pF. A decrease of Cinter with bias voltage is the same for all p-stop and p-stop+p-spray implant doses. It is supposed that this decrease of Cinter is due to small contribution of Cg, capacitance between strip and the backplane. Cg is decreasing function of bias voltage. Fluency 2E15n/cm2

slide-13
SLIDE 13

18/02/2013 J.Bohm, 8th Trento Workshop, Trento, Italy 13

0.64 0.68 0.72 0.76 0.8 20 40 60 80

Cinter [pF] Time [min]

Time Evolution of Interstrip Capacity

W91 A 4E14 Vb-300V W97 A 1E16 Vb-300V

Time Evolution of Interstrip and Bulk Capacitances

40 80 120 160

  • 500
  • 300
  • 100

Bulk Capacitance [pF] Revers Bias [V]

C-V Characteristics

p-stop 1E13ion/cm2 T=-32C

W91 D 4E14 W93 D 2E15 W97 B 1E16 40 45 50 55

50 100 150 200

Cbulk [pF] Time [min]

Evolution of Bulk Capacitance

W97 C 1E16 Vb-300V

Total strip capacitance Cint=Cg + 2Cs in the first approximation. Here Cs is capacitance between 2 strips and Cg between the strip and backplane, Cs>>Cg. Cg one can estimate as Cbulk/n strips. Ruther long time is needed to rearrange charge carriers in the un-depleted region so as to bring the electric field back to zero.

Vb -300V

A decrease of Cinter with time at constant bias voltage could be due to decrease of Cbulk with time.

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SLIDE 14

18/02/2013 J.Bohm, 8th Trento Workshop, Trento, Italy 14

0.64 0.68 0.72 0.76 0.8

  • 500
  • 300
  • 100

Cinterstrip [pF] Bias [V]

Comparison of two Cinter measurements

W91 A W91 A stable 0.66 0.68 0.7 0.72 200 400

Cinterstrip [pF] Bias [V]

Interstrip Capacitance after Stabilization

W91 A 4E14 W97 A 1E16 W93 A 2E15

0.64 0.68 0.72 0.76 10 20 30 40 50 60

Cinterstrip [pF] Time [min]

ATLAS07 fluency 4E14neq/cm2

W91 A Vb-5V W91 A Vb-10V W91 A Vb-40V W91 A Vb-100V W91 A Vb-300V W91 A Vb-500V

Time evolution at constant Vbias

Time Evolution of Interstrip Capacitance

Measurement of Cinter must be done with appropriate time delay between consecutive steps. Cinter data taken after stabilization period agree well with Cinter results measured by the program

slide-15
SLIDE 15

Interstrip Resistance - non-irradiated

18/02/2013 J.Bohm, 8th Trento Workshop, Trento, Italy

200 400 600 800 0.E+00 2.E+12 4.E+12 6.E+12 8.E+12 1.E+13

Resistance [GΩ] P-stop ion concentration/cm^2

BZ4A 300V BZ4B 300V BZ4C 300V BZ4D 300V BZ4A 100V BZ4B 100V BZ4C 100V BZ4D 100V BZ4A 50V BZ4B 50V BZ4C 50V BZ4D 50V

Rbias Bias ring AC pad DC pad V V I Rint = 2*dV/dI measured at Vbias=-50V, -100V and -300V Interstrip resistance increases with P-stop ion concentration from 4E12ion/cm^2 up to 1E13 ion/cm^2 PT structures

15

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SLIDE 16

50 100 150 200 1.E+10 1.E+12 1.E+14 1.E+16 Rint [GΩ] Fluency [neq/cm2]

ATLAS07 Pstop 1E13ion/cm2

18/02/2013 J.Bohm, 8th Trento Workshop, Trento, Italy 16

Interstrip resistance is decreasing with increasing fluency K.Hara et al: Nucl.Instrum.Meth. A636

(2011) S83-S89

Interstrip Resistance – heavily irradiated

Resistance before irradiation Rint=587 GΩ

Resistance for fluency 1E16n/cm2 is about 0.7 GΩ which is many times higher than bias resistor ~1.5MΩ.

slide-17
SLIDE 17

18/02/2013 J.Bohm, 8th Trento Workshop, Trento, Italy 17

Punch Through Protection Structures for ATLAS07

The punch-through (PT) develops via 20µm gap between the strip implant edge and the bias rail . The gap is the same for all three structures and also for case of no structure. Characteristics of punch through structures are studied by DC method: Negative Vtest is an applied voltage to DC pad and Itest is current between DC pad and the bias ring. The effective resistance Reff=dVtest/dItest which is constant and equal to bias resistor Rbias for low values of Vtest and is rapidly decreasing when PT is developed. Then Rpt is supposed to be parallel to Rbias: 1/Reff=1/Rbias+1/Rpt. DC method S.Lindgren et.al NIM A636(2011)S111-S11& Punch-Through Voltage is the Test Voltage for Rbias=Rpt, i.e. for Reff=Rbias/2. PT voltage is evaluated at bias voltages -100, -300, -500, -700 and -900V .

0.4 0.8 1.2

  • 50
  • 30
  • 10

10

Reff [MΩ] Vtest [V]

ATLAS07 Series 3 P-stop 4E12 ion/cm^2

W264 BZ4B P10

Vb -100V Vb -300V Vb -500V Vb -700V Vb -900V

PT voltage

0.01 0.1 1 10

  • 800000
  • 600000
  • 400000
  • 200000

Rpt [MΩ] Itest [nA]

Rpt vs Itest

W89 Series 2 P-stop 1E13 ion/cm^2 Vbias=-300V

BZ4D BZ4C BZ4B BZ4A

Rbias/2 Laser method: C.Betancourt at al. IEEE Vol. 59, No3, June 2012

slide-18
SLIDE 18

Punch Through Voltage non-irradiated

18/02/2013 J.Bohm, 8th Trento Workshop, Trento, Italy

  • 50
  • 30
  • 10
  • 900
  • 700
  • 500
  • 300
  • 100

PT Voltage [V] Bias [V]

W89 C W89 A W89 B W89 D W14 A W14 B W14 C W14 D W281 A W264 B W264 C W281 D

1e13 ion/cm^2 4E12 ion/cm^2 2E12 ion/cm^2

  • Punch through voltage dominantly depends on P-stop ion concentration for all punch through structures.
  • Differences among PT voltages for structures BZ4A-D are small for all concentrations, several volts only
  • PT voltage increases with applied bias, for concentration 1E13 ion/cm^2 is observed nearly saturation for

Vb>500V.

  • PT voltages are smaller than 50V, i.e. they are significantly below the hold-off voltages of the coupling

capacitor which are typically tested to 100V.

18

0.4 0.8 1.2 1.6

  • 70
  • 50
  • 30
  • 10

10

Reff [MΩ] Vtest [V]

ATLAS07 Series 2HPK P-stop 1E13 ion/cm^2

W89 BZ4A P04

Vb -100V Vb -300V Vb -500V Vb -700V Vb -900V

slide-19
SLIDE 19

18/02/2013 J.Bohm, 8th Trento Workshop, Trento, Italy 19

  • 70
  • 50
  • 30
  • 10
  • 1000
  • 500

PT Voltage [V] Bias [V]

Punch-Through Voltage

ATLAS07 Pstop 4E12 ion/cm^2

W281 A 2E15 W281 B 2E15 W281 C 2E15 W281 D 2E15 W278 A 4E14 W278 B 4E14 W278 C 4E14 W278 D 4E14 W281A nonirr W264B nonirr W264C nonirr W281D nonirr

  • 70
  • 50
  • 30
  • 10
  • 1000
  • 800
  • 600
  • 400
  • 200

PT Voltage [V] Bias [V]

Punch-Through Voltage

ATLAS07 Pstop 2E12 ion/cm^2

W19A 2E15 W19B 2E15 W19C 2E15 W19D 2E15 W17A 4E14 W17B 4E14 W17C 4E14 W17D 4E14 W14A nonirr W14B nonirr W14C nonirr W14D nonirr

  • PT voltage increases predominantly with fluency

and very slowly with ion concentration

  • At fluency 2E15 n/cm^2 and for all tested ion

concentrations the PT voltage for structure BZ4A reaches minimum value and BZ4D without any special structure –the maximum. The same behaviour of structure BZ4A is observed also for p-stop doses 4E12 and 2E12 ion/cm2.

Punch Through Voltage

irradiated

  • 70
  • 60
  • 50
  • 40
  • 30
  • 20
  • 1000
  • 500

PT Voltage [V] Reverse Bias [V]

Fluency 2E15n/cm2

W93 A Pst 1E13 W93 D Pst 1E13 W281A Pst 4E12 W281D Pst 4E12 W19 A Pst 2E12 W19 D Pst 2E12

slide-20
SLIDE 20
  • 70
  • 50
  • 30
  • 1000
  • 800
  • 600
  • 400
  • 200

PT Voltage [V] Bias [V]

Punch-Through Voltage

ATLAS07 Pstop 1E13 ion/cm^2

W93 A 2E15 W93 B 2E15 W93 C 2E15 W93 D 2E15 W91 A 4E14 W91 B 4E14 W91 C 4E14 W91 D 4E14 W89 A nonirr W89 B nonirr W89 C nonirr W89 D nonirr W97 A 1E16 W97 B 1E16 W97 C 1E16 W97 D 1E16

18/02/2013 J.Bohm, 8th Trento Workshop, Trento, Italy 20

Punch Through Protection Structures for ATLAS07

  • 80
  • 60
  • 40
  • 20

1.E+12 1.E+13 1.E+14 1.E+15 1.E+16

PT Voltage [V] Fluence [neq/cm2]

PT Voltage

ATLAS07 Pstop 1e13ion/cm2 W89, W91, W93 and W97

A 300V B300V C 300V D 300V A 700V B 700V C 700V D 700V

  • PT voltages for P-stop ion concentration 1E13 ion/cm^2 and fluency 1E16n/cm2 are

surprisingly below the PTV for lower fluency and even smaller than safety level of 50V and do not depend on the bias voltage (saturation)

slide-21
SLIDE 21

18/02/2013 J.Bohm, 8th Trento Workshop, Trento, Italy 21 1 2

  • 80
  • 60
  • 40
  • 20

Reff [MΩ] Vtest [V] W97 BZ4A P-stop 1E13ion/cm2 Fluency 1E16n/cm2 T-32C

W97 A 100V W97 A 300V W97 A 500V W97 A 700V

Punch Through Voltage

irradiated Saturation

slide-22
SLIDE 22

18/02/2013 J.Bohm, 8th Trento Workshop, Trento, Italy 22

100000 200000 20 40 60 80 100

Strip Current [-nA] Test voltage [-V]

PT structure BZ4A

W91 A 4E14 W93 A 2E15 W97 A 1E16 W89 A nonirrad

Punch-Through Current for ATLAS07

100000 200000 20 40 60 80 100

Strip Current [-nA] Test Voltage [-V]

No structure BZ4D

W91 D 4E14 W93 D 2E15 W97 D 1E16 W89 D nonirrad

PT current

At low volts the current flows to BR

  • nly through the bias resistor and

grows linearly with voltage. At higher volts the PT current appears as a component additional to the linear rise. Typically the PT current grows very steeply with voltage above the onset value thus preventing the sensor. A.Chilingarov: Report on 21st RD50 Workshop, 15.11.2012, CERN 100µA

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SLIDE 23

18/02/2013 J.Bohm, 8th Trento Workshop, Trento, Italy 23 100000 200000 20 40 60 80

  • Itest [nA]
  • Vtest [V]

P-stop 1E13ion/cm2 Fluency 1E16n/cm2

W97 A 1E16 W97 B 1E16 W97 C 1E16 W97 D 1E16

100000 200000 20 40 60 80

  • Itest [nA]
  • Vtest [V]

P-stop 4E12ion/cm2 Fluency 2E15n/cm2

W281 A 2E15 W281 B 2E15 W281 C 2E15 W281 D 2E15

Comparison of PT structures

Punch-through current grows rapidly for structure BZ4A only . A difference among structures BZ4B, BZ4C and no-structure BZ4D is negligible. The better performance of zone BZ4A would be due to the gate effect since larger portion of the channel length is covered by the bias resistor (conformation of previous results). Radiation damage reduces the effectiveness of PTP structures. It is the question to what extent the effectiveness depends on p-stop implant dose. It will be tested with new irradiated In Ljubljana sensors up to 1E16n/cm2 and with several p-implant doses.

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SLIDE 24

18/02/2013 J.Bohm, 8th Trento Workshop, Trento, Italy 24

Summary and Conclusions

1 The heavily irradiated sensors (≥ 2E15n/cm2) with p-stop isolation of different ion concentrations were successfully operating up to 1000V but not for fluency 4E14n/cm2 where an onset of micro-discharges was observed above 700V. 2 Interstrip capacitance is the same within measuring error of ~0.02pF for irradiated (4E14, 2E15 and 1E16n/cm2) and non-irradiated sensors as well as for all tested p-stop ion concentrations (2E12, 4E12 and 1E13ion/cm2). 3 An observed decrease of interstrip capacitance after irradiation with growing bias voltage could be qualitatively explained by the contribution of the bulk capacitance. 4 Time evolution measurement has shown a slow decrease of the bulk and interstrip capacitances of irradiated sensors before the plateau is reached. 5 Interstrip resistance is decreasing with increasing fluency ; Resistance for fluency of 1E16n/cm2 is still ~0.7 GΩ which is significantly higher than Rbias ~ 1.5MΩ. 6 Punch-through protection was characterized by parameters of DC method: Effective resistance, PT voltage and PT resistance as a function of bias voltage. 7 An investigation of punch-through current allowed to estimate PT structure BZ4A as the most effective protection against beam splashes 8 Next 16 sensors were already irradiated in Ljubljana as the last step of investigation.

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SLIDE 25

18/02/2013 J.Bohm, 8th Trento Workshop, Trento, Italy 25

Thank you for your attention