punch through protection and p-stop ion concentration in hpk strip mini-sensors

J.Bohm, 20th RD50 Workshop, Bari, Italy

Punch through protection and p-stop ion concentration in HPK strip mini-sensors

Jan Bohm, Institute of Physics ASCR, Prague

Peter Kodys, Pavel Novotny, Tomas Jindra, Zdenek Dolezal, Jan Scheirich, Charles University in Prague

Petr Masek, Michael Solar, Institute of Experimental and Applied Physics of Czech Technical University in Prague

5/30/2012

J.Bohm, 20th RD50 Workshop, Bari, Italy5/30/2012

The performance of the sample of 75 n-in-p 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.This report is a compilation of measured characteristics before irradiation. The second part of this study, i.e. after irradiation, will be available soon.

-Description of the sample of miniature sensors

-Bulk characteristics, IV and CV measurement

-Punch Through Protection and PT voltages

-Interstrip capacitance

-Interstrip resistance--------------------------------------------------------Thermal dependence of poly-silicon bias resistors of non-irradiated and of irradiated sensors up to 4E14neq/cm^2.

Survey


Sample of miniature sensors

5/30/2012

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.

The micro-strip silicon miniature sensors of 1cmx1cm (strip length 0.8cm) are ATLAS07 Series fabricated by Hamamatsu Photonics (HPK) using 6” (150 mm) process technology . The baseline is p-type float zone silicon with crystal orientation <100> and having thickness of 320 μ. Sensors are single-sided with AC coupled readout n-type strips which are biased through polysilicon resistors. One hundred readout strips with pitch 74.5 μ are electrically isolated by a common and floating p-implant (‘p-stop’ isolation)


IV characteristics-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.

5/30/2012


IV characteristics

5/30/2012

-4.0

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

ATLAS07 pre-series 3rdPstop (2E12) + Pspray (2E12)

BZ4A-D

W04 AW04 B W04 C W04 D W05 A W05 C W05 D W06 A W06 B W06 C W06 D W10 A W10 B W10 C W10 D

Bias [V]

Curr

ent [

nA]

All sensors with p-stop isolation and with different ion concentrations were successfully operating up to 1000V, no onset of micro-discharges was observed.On other side, sensors with P-stop + P-spray isolation behaves differently and an onset of breakdowns are above already Vbias=900V.


CV Characteristics

5/30/2012

-400-300-200-10000

0.0004

0.000800000000000001

0.0012

0.0016ATLAS07 pre-series 3 Pstop 2E12

BZ4D

W14 DW17 DW19 DW31 D

Bias [V]

!/C

2̂ [1

/pF̂

2]

-400-300-200-10000

0.0004

0.000800000000000001

0.0012

0.0016

ATLAS07 Series 3 Pstop 4E12BZ4D P22

W264 DW278 DW281 D

Bias [V]

!/C^

2 [1

/pF̂

2]

-400-300-200-10000

0.0004

0.000800000000000001

0.0012

0.0016ATLAS series 2nd STD Pstop 1E13

BZ4D


Bias [V]

1/C^

2 [1

/pF̂

2]

-400-300-200-10000

0.0004

0.000800000000000001

0.0012

0.0016

ATLAS07 series 2 HPKex Pstop 1E13 BZ4D


Bias [V]1/

C2̂

[1/p

F2̂]

Bulk capacitance has been measured on sensors BZ4D at each wafers.Sensors BZ4A-D from wafer W75 of Series 2 STD have higher full depletion voltage, Vfd=286V


CV Characteristics

5/30/2012

-400-20000

0.0004

0.000800000000000001

0.0012

0.0016ATLAS07 pre-Series 3

P stop 2E12 + P spray 2E12 BZ4D

W04 D

W05 D

W06 D

W10 D

Bias [V]

1/C^

2 [1

/Pf^

]̂

0.1 1 10 100 100018

23

28

ATLAS07 series 2nd HPKex Pstop 1E13 BZ4D

Vbias=-240V

W89 D

W91 D

W93 D

W97 D

Freq [kHz]

Capa

cita

nce

[pF]

Series Pre-Series3 Series 3 Series 2 STD Series2 HPK Pre-Series3

Concentration [ion/cm^2]

2E12 4E12 1E13 1E13 2E12 P stop2E12 P spray

V full depletion -183V -292V -186V*)

-252V -204V

*) Sensors BZ4A-D from wafer W75 of Series 2 STD have higher full depletion voltage, Vfd=286V

Bulk capacitance does not depend on testing frequency in range of 200Hz up to 20kHz


Punch Through Protection Structures

5/30/2012

A protection of AC coupling capacitors against the beam splashes should ensure special structures, Z4A,B,C and D 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 sensor Z4D without any other structure.


5/30/2012

Reff=dVtest/dItest, where Vtest is an applied voltage (Uappl) to DC pad and Itest is an current between DC pad and the bias ring. Rpt is supposed to be parallel to Rbias: 1/Reff=1/Rbias+1/Rpt.

BiasRing

Itest

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 for PT structures Z4A-D

R implant

DC pad NEAR END Vtest

DC pad FAR END

n+ implantPT structure Rpt

RbiasDC method S.Lindgren et.al NIM A636(2011)S111-S11&

-50 -30 -10 100

0.4

0.8

1.2

ATLAS07 Series 3 P-stop 4E12 ion/cm^2W264 BZ4B P10

FAR END

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

Vtest [V]

Reff

[MΩ

]

-70 -50 -30 -10 100

0.4

0.8

1.2

1.6

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

NEAR END

Vb -100V

Vb -300V

Vb -500V

Vb -700V

Vb -900V

Vtest [V]

Reff

[MΩ

]


Punch Through Protection Structures - Rpt

5/30/2012

-70 -50 -30 -100

0.4

0.8

1.2

1.6 ATLAS07 Series 2 P-stop 1E13 ion/cm^2W89 BZ4A-D NEAR END

BZ4ABZ4BBZ4DBZ4C

Vtest [V]

Reff

[MΩ

]

-800000 -600000 -400000 -200000 00.01

0.1

1

10 Rpt vs ItestW89 Series 2 P-stop 1E13 ion/cm^2

Vbias=-300V

BZ4DBZ4CBZ4BBZ4A

Itest [nA]

Rpt [

MΩ

]

-50 -30 -10 100

0.4

0.8

1.2ATLAS07 Series3 Pstop 4E12

W264 BZ4C P16 NEAR END

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

Vtest [V]

Reff

[MΩ

]

Calculated Rpt‘s as a function of Itest for the same structure, BZ4C, and different bias voltages are the same contrary to Rpt’s evaluated for different PT structures but the same bias voltagewhich show different dependences. Structure BZ4A is very effective at high current.

Vbias=-300V

-400000 -200000 00.01

0.1

1

10W264 Series3 BZ4C 4E12 ion/cm^2

Vb -100VVb -500VVb -900VW264 CVb -700V

Itest [nA]PT

resis

tanc

e Rp

t [m

Ω]


Punch Through Protection Structures - Rpt

5/30/2012

-600000 -400000 -200000 00.01

0.1

1

10 Rpt vs ItestPre-Series3 P-stop 2E12

ion/cm^2

W14 BZ4A

W14 BZ4B

W14 BZ4C

W14 BZ4D

Itest [nA]

Rpt [

MΩ

]

-800000 -600000 -400000 -200000 00.01

0.1

1

10 Rpt vs ItestW89 Series 2 P-stop 1E13 ion/cm^2

Vbias=-300V

BZ4DBZ4CBZ4BBZ4A

Itest [nA]

Rpt [

MΩ

]

-800000 -600000 -400000 -200000 00.01

0.1

1

10 Rpt vs ItestSeries3 P-stop 4E12 ion/cm^2

W281 A

W264 B

W281 D

W264 C

Itest [nA]

Rpt [

MΩ

]

Structure BZ4A it seems to be the most effective short at low currents : -7µA, -18µA and -26µA for P-stop ion concentration 2E12, 4E12 and 1E13 ion/cm^2 , respectively.


Punch Through Voltage

5/30/2012

-900-700-500-300-100

-60

-40

-20

0

W89-HPK Pstop 1E13; W14-Pstop 2E12;

W281&W264-Pstop 4E12W04-Pstop+Pspray 2E12

W89 Z4AW89 Z4BW89 Z4CW89 Z4DW14 Z4AW14 Z4BW14 Z4CW14 Z4DW281 Z4AW264 Z4BW264 Z4CW281 Z4D

Bias [V]

PT V

olta

ge [V

]

FAR END-900-700-500-300-100

-40

-20

0NEAR END

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

P-stop+P-spray 2E12 ion/cm^2

-Punch through voltage dominantly depends on P-stop ion concentration for all punch through structures.-PT voltage for P-stop+P-spray isolation is considerable higher than for P-stop isolation at same p-dose 2E12 ion/cm^2-Differences among PT voltages for each structure 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 voltage of the coupling capacitor which are typically tested to 100V.Punch through protection structures will be tested soon by laser technique.



5/30/2012

-900-700-500-300-100

-60

-50

-40

-30

-20

ATLAS07 Series2 HPK Pstop 1E13W89 BZ4A-D FAR & NEAR ENDS

A NEARA FARB FARC FARD FARB NEARC NEARD NEAR

Bias [V]

PT V

olta

ge [V

]

-900-700-500-300-100

-20

-16

-12

-8

-4

ATLAS07 pre-series 3 Pstop 2E12W14 BZ4A-D FAR & NEAR ENDS

A FARB FAR C F ARD FARA NEARB NEARC NEARD NEAR

Vbias [V]

Punc

h Th

roug

h Vo

ltage

[V]

-900-700-500-300-100

-25

-20

-15

-10

ATLAS07 Series3 Pstop 4E12BZ4A-D FAR&NEAR ENDS

W281 A FARW264 B FARW264 C FARW281 D FARW281 A NEARW264 B NEARW264 C NEARW281 D NEARBias [V]

PT V

olta

ge [V

]

-900-700-500-300-100-10

-5

0

5PT Voltage (FAR END) -- PT Voltage (NEAR END)

W89 AW89 BW89 CW89 DW14 AW14 BW14 CW14 DW281 AW264 BW264 CW281 D

Bias [V]

ΔPTV

olta

ge [V

]


Interstrip Capacitance - Method of measurement

5/30/2012

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]

Cint

[pF

]

2 probes

5 probes GND

3 probes5probes

2-probes3-probes

5-probes

LCR High

DC pad

LCR Low

Isolated 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

5/30/2012

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

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 [p

F]

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 probes.

C interstrip depends strongly on frequency.Capacitance is measured at 1MHz

For Vbias<Vfd the values of C interstrip depend on the P-stop & P-spray ion concentration .

There is narrow deep minimum of Cint at Vbias =-4V for P-stop+P-spray isolation.

J.Bohm, 20th RD50 Workshop, Bari, Italy5/30/2012

-600-400-20000.2

0.4

0.6

0.8

1

1.2Inter-strip Capacitance

ATLAS07 Series2, pre-Series3 & Series3W89 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

Reverse Bias [V]

Cint

er [p

F]


Interstrip Capacitance

5/30/2012

Wafer W14 W264 W78 W89 W04

Series Pre-Ser3 Series3 Series2 STD Series2 HPK Pstop Pspray

Ion/cm^2 2E12 4E12 1E13 1E13 2E12

Vfd [V] -183 -292 -186 -252 -186

Cint BZ4A pF 0.69 0.66 0.68 0.69 0.71

Cint BZ4B pF 0.68 0.67 0.68 0.68 0.71

Cint BZ4C pF 0.68 0.67 0.68 0.68 0.71

Cint BZ4D pF 0.71 0.66 0.68 0.69 0.70

Interstrip capacitance in this table was evaluated for Vbias=Vfd+10V

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 ±20fF.

Possible time dependence of Cint and an influence of relative humidity is in progress.


Interstrip Resistance

5/30/2012

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

200

400

600

800

BZ4A 300VBZ4B 300VBZ4C 300VBZ4D 300VBZ4A 100VBZ4B 100VBZ4C 100VBZ4D 100VBZ4A 50VBZ4B 50VBZ4C 50VBZ4D 50V

P-stop ion concentration/cm^2

Resis

tanc

e [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

Interstrip Resistance

5/30/2012 J.Bohm, 20th RD50 Workshop, Bari, Italy

50 100 300

100

300

500

700

W04 A PstSpr 2e12

W04 C PstSpr 2e12

W14 A Pst 2E12

W14 C Pst 2E12

Vbias [V]

Resis

tanc

e [G

Ω]

Interstrip resistance for case of P-stop + P-spray isolation is about two times higher than one for P-stop isolation for all punch through structures with exception of BZ4B.

W14 A 2E12

W17 B 2E12

W14 C 2E12

W17 D 2E12

W264 A 4E12

W264 B 4E12

W264 C 4E12

W264 D 4E12

W89 A 1E13

W89 B 1E13

W89 C 1E13

W89 D 1E13

0

100

200

300

400

500

600

700

800

50300

Interstrip resistance

50

100

300

Resis

tanc

e [G

Ω]

Vbias [V]

0.00E+00 5.00E+12 1.00E+13100

300

500

700

f(x) = 4.32307692307692E-11 x + 103.769230769231R² = 0.960845231313776

BZ4D 300V

Ion concentration/cm^2

Resis

tanc

e [G

Ω]

The interstrip resistance dependence on ion concentration can be estimated for Z4D structure : Rint=4E-11xIons/cm^2+103.8G

Presumably not only ion concentration is responsiblefor Rint value but also fabrication processes in various series.


Thermal Dependence of Polysilicon Bias Resistor

5/30/2012

-40 -20 0 20-0.2

0.2

0.6

1

1.4

1.8 PTP W05 BZ4A pre-Ser3 PstopSpray 2E12ion/cm^2 Φ=0

W05 4CW05 -10CW05 -20CW05 -30C

Uappl [V]

Reff

[MΩ

]

-40 -20 0 20 401.4

1.6

1.8

2

f(x) = − 0.006697351533061 x + 1.60249040670999R² = 0.998112955407818

W12 Series1 BZ6 P12 non-irrad dV/dI/Rbias

Temperature [°C]

Bias

Res

istor

[MΩ

]

-40 -35 -30 -25 -20 -15 -10 -5 0 5 101.4

1.5

1.6

1.7

f(x) = − 0.00669377786462906 x + 1.42456859025895R² = 0.994353281117485

W05 BZ4A pre-Ser3 PstopSpray 2E12 Φ=0PTP/Rbias

Temperature [°C]

Bias

Res

istor

[MΩ

]

PT voltage is slightly higher for low temperature (-30C) than for room temperature (24C).The difference is explained by lower bias resistance for room temperature than for -30C.

-80-60-40-2001.2

1.6

2 Bias Resistor dV/dIW12 Ser1 BZ6 P12 non-irrad

T=24.7C

T=-7.8C

T=-21C

T=-31.8

Bias [V]

Bias

Res

istor

[MΩ

]

Points in the figure are taken at -80V. Temperature was measured at each bias voltage.

Both methods used for the evaluationof Rbias dependence on temperaturegave the same slope of -0.0067 MΩ/1°C


Thermal Dependence of Poly silicon Bias Resistor

5/30/2012

-30 -20 -10 01.4

1.6

1.8

2Rbias vs Temperature

Trend lines

φ=0 PTP Ser3φ=0 Rb Ser3φ=1E14 PTPφ=1E14 RbΦ=0 Rb Ser1φ=4E14 RbΦ=0 Rb Ser1Linear (Φ=0 Rb Ser1)

Temperature [°C]

Bias

Res

istor

[MΩ

]

0 200000000000000 400000000000000

-12

-8

-4

Thermal dependency of polysilicon resistance

Fluency [neq/cm2]

Ther

mal

coe

ffici

ent [

kΩ/

centi

grad

e]

-50 -30 -10 100

0.5

1

1.5

2

PTP FAR END Vb=-100VATLAS07 Series 1 Pstop 1E12

W13 BZ3 P18 Φ=1E14neq/cm2

T=-10CT=-20CT=-30C

Uappl [V]

Reff

[MΩ

]

-35 -30 -25 -20 -15 -10 -51.7

1.8

1.9

2

f(x) = − 0.00906417 x + 1.63148R² = 0.98719992476755

Rbias from PTPW13 BZ3 P18

Φ=1E14neq/cm2

Temperature [°C]

Rbia

s [M

Ω]

The respective temperature coefficients are -6.7kΩ/1°C for non-irradiated sensors and -10.1kΩ/1°C for fluency 4e14neq/cm^2

An evidence that the thermal coefficient ofpoly-silicon bias resistor increases with fluency?


Summary

5/30/2012

All sensors ATLAS07 with p-stop isolation and with different ion concentrations were successfully operating up to 1000V, no onset of micro-discharges was observed.On other side, sensors with P-stop + P-spray isolation behave differently and an onset of breakdowns are above already Vbias=900V.

Full depletion voltages of tested sensors are in the range of 180V-290V

Punch through voltage dominantly depends on the P-stop ion concentration for all punch through structures. PT voltage for P-stop+P-spray isolation is considerable higher than one for P-stop isolation at same p-dose 2E12 ion/cm^2. PT voltage increases with applied bias.PT voltages are smaller than 50V, i.e. they are significantly below the hold-off voltage of the coupling capacitor which are typically tested to 100V.Study of Rpt dependence on the test current shows that the most effective short, i.e. protection against beam splashes , ensures the structure BZ4A for all tested P-stop ion concentrations.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 ±20fF.Interstrip resistance increases with P-stop ion concentration from 4E12 up to 1E13ion/cm^2The polysilicon bias resistance depends on temperature. The respective temperature coefficients are -6.7kΩ/1°C for non-irradiated sensors and -10.1kΩ/1°C for fluency 4e14neq/cm^2 .

punch through protection and p-stop ion concentration in hpk strip mini-sensors

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