ptp and the inter-strip capacitance and resistance for irradiated atlas07 mini-sensors

J.Bohm, 8th Trento Workshop, Trento, Italy 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 of Czech Technical University in Prague

18/02/2013

J.Bohm, 8th Trento Workshop, Trento, Italy 218/02/2013

1. Introduction2. IV characteristics of heavily irradiated sensors3. Interstrip capacitance and bias dependence4. Time evolution of interstrip and bulk capacitances5. Interstrip resistance6. Characteristics of punch through structures7. 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


Sample of HPK miniature sensors

18/02/2013

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 AnnealingW06 Pspr+Pstp 2E+12 4E+14 neutrons Ljubljana 80min/60degCW10 Pspr+Pstp 2E+12 2E+15 neutrons Ljubljana 80minn/60degCW17 Pstop 2E+12 4E+14 neutrons Ljubljana 80min/60degCW19 Pstop 2E+12 2E+15 neutrons Ljubljana 80min/60degC

W278 Pstop 4E+12 4E+14 neutrons Ljubljana 80min/60degCW281 Pstop 4E+12 2E+15 neutrons Ljubljana 80min/60degCW31 Pstop 2E+12 4E+14 p 23GeV/c CERN 80min/60degCW91 Pstop 1E+13 4E+14 neutrons Rez Prague 80min/60degCW93 Pstop 1E+13 2E+15 neutrons Rez Prague 80min/60degCW97 Pstop 1E+13 1E+16 neutrons Rez Prague 80min/60degC

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

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


Punch Through Protection Structures for ATLAS07

18/02/2013

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.

BZ4A BZ4B

BZ4C BZ4D


IV characteristics of non-irradiated ATLAS07 sensors

-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

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

Bias [V]

Curr

ent [

nA]

-1000-800-600-400-2000

-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

ATLAS07 Series3 P-stop 4E12BZ4A-D

W264 AW264 BW264 CW264 DW278 AW278 BW278 CW278 DW281 A W281 BW281 CW281 D

Bias [V]

Curr

ent [

nA]

-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

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

W75 A W75 B W75 C W75 D W78 A W78 B W78 C W78 DW80 A W80 B W80 C W80 D W81 A W81 B W81 C W81 D

Bias [V]

Curr

ent [

nA]

0 -60-120

-180-240

-300-360

-420-480

-540-600

-660-720

-780-840

-900-960

-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

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 DBias [V]

Curr

ent [

nA]

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

18/02/2013


-1000-800-600-400-20001

10

100

1000 W91 A 4E14W91 B 4E14W91 C 4E14W91 D 4E14W93 A 2E15 W93 B 2E15 W93 C 2E15 W93 D 2E15W278A 4E14W278B 4E14W278C 4E14W278D 4E14W281A 2E15W281B 2E15W281C 2E15W281D 2E15W19A 2E15W19B 2E15W19D 2E15W17B 4E14W97 A 1E16W97 B 1E16W97 C 1E16W97 D 1E16W31 A p 4E14W31 B p 4E14W31 C p 4E14W31 D p 4E14

Bias [V]

Leak

age

Curr

ent

[µΩ

]

2E15n/cm2

Proton irradiation at CERN

18/02/2013

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 fluency4E14n/cm2 where an onset of micro-discharges was observed above ~700V

1E16n/cm2

4E14n/cm2


Interstrip Capacitance - Method of measurement

18/02/2013

0 100 200 300 400 500 6000.600000000000001

0.800000000000001

1

1.2

1.4

1.6

1.8

2

2.2

Cinter CpRp 100kHz Sensor W37

Vbias [-V]

Cin

t [p

F]

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


Interstrip Capacitance – non-irradiated

18/02/2013

0.1 1 10 100 10000

0.2

0.4

0.6

0.8Cinterstrip 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

Frequency [kHz]

Cint

er [p

F]

-600-400-20000.5

0.6

0.7

0.8Interstrip 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

Bias [V]

Cint

erst

rip

[pF]

Vfd

-600-400-20000.2

0.4

0.6

0.8

1

1.2 Interstrip CapacitanceATLAS07 pre-Series3 p-stop&spray

2E12ion/cm^2W14 A

W14 B

W14 C

W14 D

W04 A

W04 B

W04 C

W04 D

Bias [V]

Cint

er [p

F]

Vfd

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


0.1 1 10 100 10000

0.2

0.4

0.6

0.8

Irradiated ATLAS07 sensors

1.E+13 W97 D 1E161.E+13 W97 A 1E164.E+12 W281A 2E154.E+12 W281B 2E152.E+12 W19 A 2E152.E+12 W10 A 2E15 PstSpr2.E+12 W10 B 2E15 PstSpr2.E+12 W19 B 2E151.E+13 W91 A 4E141.E+13 W91 C 4E14

Frequency [kHz]

Cint

er [p

F]

0.1 1 10 100 10000

0.2

0.4

0.6

0.8 Non-irradiated ATLAS07 sensorsW78-STD Pstop 1E13; W89-HPK Pstop 1E13;

W14-Pstop 2E12; W04-PstopSpray 2E12

W78 B

W89 B

W14 B

W04 B

W264 B

Frequency [kHz]

Cint

er [p

F]

18/02/2013

Interstrip Capacitance Dependence on Frequency


-600-400-20000.2

0.4

0.6

0.8

1

1.2Inter-strip Capacitance

ATLAS07 Series2, pre-Series3 & Series3W89 AW89 BW89 CW89 DW14 AW14 BW14 CW14 DW04 AW04 BW04 CW04 DW264 AW264 BW264 CW264 DW78 AW78 BW78 CW78 DReverse Bias [V]

Cint

er [p

F]

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 andthe punch through protection structures within measuring error of ±0.02pF.

Interstrip Capacitance – non-irradiated


-500-450-400-350-300-250-200-150-100-5000.58

0.62

0.66

0.7

0.74ATLAS07 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

Bias [V]

Cint

er [p

F] 0.04pF

18/02/2013

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 pronouncedfor fluency 4E14n/cm2 than for higher doses.


-500-400-300-200-10000.6

0.640000000000001

0.680000000000001

0.720000000000001

0.760000000000001

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

Bias [V]

Cint

er [p

F]

18/02/2013

Interstrip Capacity and p-stop ion concentration

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

Fluency 2E15n/cm2


0 10 20 30 40 50 60 70 800.640000000000001

0.680000000000001

0.720000000000001

0.760000000000001

0.800000000000001Time Evolution of Interstrip Capacity

W91 A 4E14 Vb-300V

W97 A 1E16 Vb-300V

Time [min]

Cint

er [p

F]

Time Evolution of Interstrip and Bulk Capacitances

-400-20000

40

80

120

160C-V Characteristics

p-stop 1E13ion/cm2 T=-32CW91 D 4E14

W93 D 2E15

W97 B 1E16

Revers Bias [V]

Bulk

Cap

acita

nce

[pF]

0 20 40 60 80 100 120 140 160 18040

45

50

55 Evolution of Bulk Capacitance

W97 C 1E16 Vb-300V

Time [min]

Cbul

k [p

F]

Total strip capacitanceCint=Cg + 2Cs in the first approximation.Here Cs is capacitance between 2 stripsand Cg between the strip and backplane,Cs>>Cg.Cg one can estimate as Cbulk/n strips.

Ruther long time is needed to rearrangecharge carriers in the un-depleted regionso as to bring the electric field back to zero.

Vb -300V

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


-400-20000.56

0.6

0.64

0.68

0.72

0.760000000000001

0.8

0.84

Comparison of two Cinter measurements

W91 A

W91 A stable

Bias [V]

Cint

erst

rip [p

F]

0 200 4000.660000000000002

0.680000000000002

0.700000000000002

0.720000000000002Interstrip Capacitance after Stabiliza-

tion

W91 A 4E14

W97 A 1E16

W93 A 2E15

Bias [V]Ci

nter

strip

[pF]

0 10 20 30 40 50 600.600000000000001

0.640000000000002

0.680000000000002

0.720000000000002

0.760000000000002

ATLAS07 fluency 4E14neq/cm2

W91 A Vb-5VW91 A Vb-10VW91 A Vb-40VW91 A Vb-100VW91 A Vb-300VW91 A Vb-500V

Time [min]

Cint

erstr

ip [p

F]Time evolution at constant Vbias

Time Evolution of Interstrip Capacitance

Measurement of Cinter must be donewith appropriate time delay betweenconsecutive steps.

Cinter data taken after stabilization period agree well with Cinter results measured by the program


Interstrip Resistance - non-irradiated

18/02/2013

0E+00 2E+12 4E+12 6E+12 8E+12 1E+130

200

400

600

800BZ4A 300V

BZ4B 300V

BZ4C 300V

BZ4D 300V

BZ4A 100V

BZ4B 100V

BZ4C 100V

BZ4D 100V

BZ4A 50V

BZ4B 50V

BZ4C 50V

BZ4D 50V

P-stop ion concentration/cm^2

Resi

stan

ce [G

Ω]

Rbias

Bias ring

AC pad

DC pad

VV

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


1E+10 1E+12 1E+14 1E+160

50

100

150

200

ATLAS07 Pstop 1E13ion/cm2

Fluency [neq/cm2]

Rint

[GΩ

]

18/02/2013

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/cm2is about 0.7 GΩ which is many times higher than bias resistor ~1.5MΩ.



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 .

-50 -30 -10 100

0.4

0.8

1.2

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

W264 BZ4B P10

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

Vtest [V]

Reff

[MΩ

]

PT voltage

-800000 -600000 -400000 -200000 00.01

0.1

1

10 Rpt vs ItestW89 Series 2 P-stop 1E13

ion/cm^2Vbias=-300V

BZ4DBZ4CBZ4BBZ4A

Itest [nA]

Rpt [

MΩ

]Rbias/2

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


Punch Through Voltagenon-irradiated

18/02/2013

-900-700-500-300-100

-40

-20

0

W89 C

W89 A

W89 B

W89 D

W14 A

W14 B

W14 C

W14 D

W281 A

W264 B

W264 C

W281 D

Bias [V]

PT V

olta

ge [V

]

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.

-70 -50 -30 -10 100

0.4

0.8

1.2

1.6

ATLAS07 Series 2HPK P-stop 1E13 ion/cm^2W89 BZ4A P04

Vb -100V

Vb -300V

Vb -500V

Vb -700V

Vb -900V

Vtest [V]

Reff

[MΩ

]


-1000-800-600-400-2000

-60

-40

-20

0

Punch-Through VoltageATLAS07 Pstop 4E12 ion/cm^2 W281 A 2E15

W281 B 2E15W281 C 2E15W281 D 2E15W278 A 4E14W278 B 4E14W278 C 4E14W278 D 4E14W281A nonirrW264B nonirrW264C nonirrW281D nonirr

Bias [V]

PT V

olta

ge [V

]

-1000-800-600-400-2000

-60

-40

-20

0

Punch-Through VoltageATLAS07 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

Bias [V]

PT V

olta

ge [V

]

-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

-1000-800-600-400-2000

-70

-60

-50

-40

-30

-20

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

Reverse Bias [V]

PT V

olta

ge [V

]


-1000-800-600-400-2000

-60

-40

-20

Punch-Through VoltageATLAS07 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 1E16Bias [V]

PT V

olta

ge [V

]

18/02/2013


1E+12 1E+14 1E+16

-80

-60

-40

-20

PT VoltageATLAS07 Pstop 1e13ion/cm2W89, W91, W93 and W97 A 300V

B300V

C 300V

D 300V

A 700V

B 700V

C 700V

D 700V

Fluence [neq/cm2]PT

Vol

tage

[V]

-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)


-80 -60 -40 -20 00

1

2

W97 BZ4A P-stop 1E13ion/cm2 Fluency 1E16n/cm2 T-32C

W97 A 100VW97 A 300VW97 A 500VW97 A 700V

Vtest [V]

Reff

[MΩ

]Punch Through Voltage

irradiated

Saturation

J.Bohm, 8th Trento Workshop, Trento, Italy 2218/02/20130 20 40 60 80 100

0

100000

200000

PT structure BZ4A

W91 A 4E14

W93 A 2E15

W97 A 1E16

W89 A nonirrad

Test voltage [-V]

Stri

p Cu

rren

t [-n

A]

Punch-Through Current for ATLAS07

0 20 40 60 80 1000

100000

200000No structure BZ4D W91 D 4E14

W93 D 2E15

W97 D 1E16

W89 D nonirrad

Test Voltage [-V]

Stri

p Cu

rren

t [-n

A]

PT current

At low volts the current flows to BR only 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 preventingthe sensor.

A.Chilingarov: Report on 21st RD50 Workshop, 15.11.2012, CERN

100µA


0 10 20 30 40 50 60 70 800

100000

200000 P-stop 1E13ion/cm2 Fluency 1E16n/cm2

W97 A 1E16

W97 B 1E16

W97 C 1E16

W97 D 1E16

-Vtest [V]

-Ites

t [nA

]

0 10 20 30 40 50 60 70 800

100000

200000 P-stop 4E12ion/cm2 Fluency 2E15n/cm2

W281 A 2E15

W281 B 2E15

W281 C 2E15

W281 D 2E15

-Vtest [V]

-Ites

t [nA

]Comparison of PT structures

Punch-through current grows rapidlyfor structure BZ4A only .

A difference among structures BZ4B, BZ4C and no-structure BZ4D is negligible.

The better performance of zone BZ4Awould be due to the gate effect sincelarger portion of the channel length iscovered by the bias resistor (conformation of previous results).

Radiation damage reduces theeffectiveness of PTP structures. It is thequestion to what extent the effectivenessdepends 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.


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 splashes8 Next 16 sensors were already irradiated in Ljubljana as the last step of investigation.


Thank you for your attention

ptp and the inter-strip capacitance and resistance for irradiated atlas07 mini-sensors

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