Simulation results from double-sided and standard 3D detectors

Simulation results from double-sided and standard 3D detectors

David Pennicard, University of Glasgow

Celeste Fleta, Chris Parkes, Richard Bates – University of Glasgow

G. Pellegrini, M. Lozano - CNM, Barcelona

10th RD50 Workshop, June 2007, Vilnius, Lithuania

Overview

• Simulations of different 3D detectors in ISE-TCAD– Comparison of double-sided 3D and full-3D

detectors before irradiation– Radiation damage models– Preliminary results of radiation damage

modelling

Overview



modelling

Double-sided 3D detectors

• Proposed by CNM, also being produced by IRST

• Columns etched from opposite sides of the substrate

• Metal layer on back surface connects bias columns

– Backside biasing

• Medipix configuration (55m pitch) and 300m thickness

Oxide layer

n+ column250m length

10m diameter

p-stopInner radius 10mOuter radius 15m

Dose 1013cm-2

55m pitch

p- substrate300m thick,

doping 7*1011cm-3

Separate contact toeach n+ column

On back side:Oxide layer covered with metal

All p+ columns connected together

p+ column250m length

10m diameter p+ column

Double-sided 3D: Depletion behaviour

0.0x10+00

-1.0x10+11

-2.0x10+11

-3.0x10+11

-4.0x10+11

-5.0x10+11

-6.0x10+11

-7.0x10+11

0V

p+

Depletionaroundn+column

n+

Spacecharge(e/cm3)

1V

Mostlydepleted

Undepletedaround p+column andbase

n+ p+

10V

Fullydepleted

p+n+

Doping

p+n+

• ~2V lateral depletion (same as standard 3D)

• ~8V to deplete to back surface of device

Doping 0V 1V 10V

Double-sided 3D: Electric fieldDouble -sided 3D

Standard 3D

X (um)

Y(u

m)

0 10 200

5

10

15

20

25

80000700006000050000400003000020000100000

Electric field (V/cm) in cross-sectionof double-sided detector at 100V bias

n+

p+

Electricfield (V/cm)

Similar behaviour in overlap

region

Double-sided 3D: Electric field at front

D (um)

Z(u

m)

0 10 20 30 40

0

10

20

30

40

50

60

Detail of electric field (V/cm) around top ofdouble-sided 3D device (100V bias)

n+

p+

p-stop 2500

5000

3000

040

000

40

00

0

65

00

0

10000

20000

20000

D (um)

Z(u

m)

0 10 20 30 40

0

10

20

30

40

50

60

1300009000060000400003000020000100000

Detail of electric field (V/cm) around top ofdouble-sided 3D device (100V bias)

130000

n+

p+

Electricfield (V/cm)

Electric field matches full 3D where columns overlap

Low fields around front

High field at column tip

Double-sided 3D detectors: Collection time

2.5ns0.75ns250μmDouble-sided 3D

1.0ns0.40ns270μmDouble-sided 3D

300μm

290μm

Column length

0.5ns0.35nsStandard 3D

0.5ns0.35nsDouble-sided 3D

99% collection90% collectionDetector

0.0 0.5 1.0 1.5 2.0 2.50

2

4

6

8

10

12

14

16

18

20

22

24

MIP signals in double-sided and standard 3D at 100V

Ele

ctro

de c

urre

nt (

)

Time (ns)

Double-sided detector Standard 3D detector

Simulated particle track passing midway between n+ and p+ columnsVariation in charge collection time with depth

0.00

1.00

2.00

3.00

4.00

0 50 100 150 200 250 300

Depth (um)

Co

lle

cti

on

tim

e (

ns

)

0

1

2

3

4

5

0 50 100 150 200 250 300

50%

90%

Full

Time (ns) for given collection:

Variation in charge collection time with choice of device structure

Overview



modelling

University of Perugia trap models

0.92.5*10-152.5*10-14CiOiEc+0.36Donor

0.95.0*10-145.0*10-15VVVEc-0.46Acceptor

1.6132.0*10-142.0*10-15VVEc-0.42Acceptor

η (cm-1)σh (cm2)σe (cm2)Trap

Energy (eV)Type

Perugia P-type model (FZ)

IEEE Trans. Nucl. Sci., vol. 53, pp. 2971–2976, 2006 “Numerical Simulation of Radiation Damage Effects in p-Type and n-Type FZ Silicon Detectors”, M. Petasecca, F. Moscatelli, D. Passeri, and G. U. Pignatel

Ec

Ev

-- -

0

• 2 Acceptor levels: Close to midgap

– Leakage current, negative charge (Neff), trapping of free electrons

• Donor level: Further from midgap

– Trapping of free holes

• Experimental trapping times for p-type silicon (V. Cindro et al., IEEE NSS, Nov 2006) up to 1015neq/cm2

– βe= 4.0*10-7cm2s-1 βh= 4.4*10-7cm2s-1

• Calculated values from p-type trap model

– βe= 1.6*10-7cm2s-1 βh= 3.5*10-8cm2s-1

University of Perugia trap models• Aspects of model:

– Leakage current – reasonably close to α=4.0*10-17A/cm

– Depletion voltage – matched to experimental results (M. Lozano et al., IEEE Trans. Nucl. Sci., vol. 52, pp. 1468–1473, 2005)

– Carrier trapping –

• Model reproduces CCE tests of 300m pad detectors

• But trapping times don’t match experimental results

e

nt

n

ee

the v

eqee

th

ee

the

v

Nv

1

eqee

1

Link between model and experiment

VolI

Altering the trap models

• Priorities: Trapping time and depletion behaviour

– Leakage current should just be “sensible”: α = 2-10 *10-17A/cm

• Chose to alter cross-sections, while keeping σh/σe constant

hehe

thhe v ,,

, Carrier trapping:

Space charge:

Modified P-type model

0.93.23*10-143.23*10-13CiOiEc+0.36Donor

0.95.0*10-145.0*10-15VVVEc-0.46Acceptor

1.6139.5*10-149.5*10-15VVEc-0.42Acceptor


Energy (eV)Type

kT

Ev

v

n

nkT

ENfNn te

the

hthh

i

ttrapntrapTrape expexp,

Modified P-type model and experimental data

0.93.23*10-143.23*10-13CiOiEc+0.36Donor

0.95.0*10-145.0*10-15VVVEc-0.46Acceptor

1.6139.5*10-149.5*10-15VVEc-0.42Acceptor


Energy (eV)Type

P-type trap models: Depletion voltages

300

350

400

450

500

550

600

0 1E+14 2E+14 3E+14 4E+14 5E+14 6E+14 7E+14

Fluence (Neq/cm2)

Dep

leti

on

vo

ltag

e (V

)

Default p-type sim

Modified p-type sim

Experimental

“Comparison of Radiation Hardness of P-in-N, N-in-N, and N-in-P Silicon Pad Detectors”, M. Lozano et al., IEEE Trans. Nucl. Sci., vol. 52, pp. 1468–1473, 2005

P-type trap model: Leakage Current

0.00

0.04

0.08

0.12

0.16

0.20

0 1E+15 2E+15 3E+15 4E+15 5E+15 6E+15

Fluence (neq/cm^2)

Lea

kag

e cu

rren

t (A

/cm

^3)

α=3.75*10-17A/cm

Experimentally,α=3.99*10-17A/cm3 after 80 mins anneal at 60˚C (M. Moll thesis)

Perugia N-type model

• Works similarly to the p-type model

• Donor removal is modelled by altering the substrate doping directly

• Experimental trapping times for n-type silicon (G. Kramberger et al., NIMA, vol. 481, pp297-305, 2002)

– βe= 4.0*10-7cm2s-1 βh= 5.3*10-7cm2s-1

• Calculated values from n-type trap model

– βe= 5.3*10-7cm2s-1 βh= 4.5*10-8cm2s-1

1.12.5*10-152.0*10-18CiOiEc+0.36Donor

0.083.5*10-145.0*10-15VVOEc-0.50Acceptor

131.2*10-142.0*10-15VVEc-0.42Acceptor


Energy (eV)Type

Perugia N-type model (FZ) Donor removal

)exp(0 DDD cNN

constKcN CDD *0

KC=(2.2±0.2)*10-2cm-1

N-type trap model: Leakage Current

0.00

0.04

0.08

0.12

0.16

0 1E+15 2E+15 3E+15 4E+15 5E+15 6E+15

Fluence (neq/cm^2)

Lea

kag

e cu

rren

t (A

/cm

^3)

Modified N-type model

α=2.35*10-17A/cm

N-type trap models: Depletion voltages

0

100

200

300

400

500

0 2E+14 4E+14 6E+14 8E+14 1E+15 1.2E+15

Fluence (Neq/cm2)

Dep

leti

on

vo

ltag

e (V

)

Default n-type sim

Modified n-type sim

Experimental

“Characterization of n and p-type diodes processed on Fz and MCz silicon after irradiation with 24 GeV/c and 26 MeV protons and with reactor neutrons”, Donato Creanza et al., 6th RD50 Helsinki June 2-4 2005

1.13.1*10-152.5*10-17CiOiEc+0.36Donor

0.083.5*10-145.0*10-15VVOEc-0.5Acceptor

130.9*10-141.5*10-15VVEc-0.42Acceptor


Energy (eV)Type

Experimentally,α=3.99*10-17A/cm after 80 mins anneal at 60˚C (M. Moll thesis)

Bug in ISE-TCAD version 7

• Currently using Dessis, in ISE-TCAD v7 (2001)

• Non time-dependent simulations with trapping

are OK

• Error occurs in transient simulations with traps

– Carrier behaviour in depletion region is OK

– Displacement current is miscalculated

– This affects currents at the electrodes

• This bug is not present in the latest release of Synopsis TCAD (2007)

– Synopsis bought ISE TCAD, and renamed Dessis as “Sentaurus Device”

– Don’t know which specific release fixed the problem

0.... pndisptot JJJJCorrect behaviour:

Error: 73.1(~)*)(.. ,,, TraphTrapetoterrordisp RRqJJ

Test of charge trapping in Synopsis TCAD• Simulated a simple diode with carriers generated at its midpoint

No traps

“Double step” seen because electrons are collected before holes


• Acceptor and donor traps further from the midgap

– Produces charge trapping but little change in Neff

– Trap levels should give τe≈ τh ≈ 1ns

?!

ISE TCAD traps


• Acceptor and donor traps further from the midgap

– Produces charge trapping but little change in Neff

– Trap levels should give τe≈ τh ≈ 1ns

With traps, signal decays as exp (-t/1ns) as expected

Synopsis traps

Overview



modelling

Full 3D – Depletion voltage (p-type)• Depletion voltage is low, but strongly dependent on pitch• Double sided 3D shows the same lateral depletion voltage as full 3D

Depletion voltages and radiation damage

0

20

40

60

80

100

120

140

160

0 2E+15 4E+15 6E+15 8E+15 1E+16 1.2E+16

Fluence (Neq/cm^2)

Dep

leti

on

vo

lta

ge

(V)

Full 3D, ptype, Medipix (55um)

Full 3D, ptype, 3-column ATLAS

50m

133m

X

Y

0 20 40 60

0

10

20

30

40

50

55m

55000

55000

30000

30000

1000

0

1000

0

X (m)

Y(

m)

0 10 200

5

10

15

20

25

30

35

40100000800006000040000200000

Full 3D, p-type, 0neq/cm2

n+

p+

ElectricField (V/cm)

80000

30000

30000

10000

1000

0

X (m)Y

(m

)0 10 20

0

5

10

15

20

25

30

35

40100000800006000040000200000

Full 3D, p-type, 1e+16neq/cm2

n+

p+


X (m)

Y(

m)

0 10 200

5

10

15

20

25

30

35

40

Full 3D, p-type

n+

p+

Full 3D – electric field at 100V

No damage 1016 neq/cm2

Full depletion is achieved well under 100V, but electric field is altered

Double-sided 3D – front surface

30

00

0

300

00

10000

5000

2500

20000

D (m)

Z(

m)

0 25 50

0

10

20

30

40

50

60

70

19000017000015000013000011000090000700005000030000200001000050000

Double-sided 3D, p-type,1e+16neq/cm2, front surface

n+

p+


D (m)

Z(

m)

0 25 50

0

10

20

30

40

50

60

70

Double-sided 3D, p-type,front surface

n+

p+

30000

30

00

0

10000

5000

2500

20000

D (m)

Z(

m)

0 25 50

0

10

20

30

40

50

60

70

19000017000015000013000011000090000700005000030000200001000050000

Double-sided 3D, p-type,0neq/cm2, front surface

n+

p+



Once again, double-sided devices show different behaviour at front and back surfaces

70

00

0

25000

2500

0

10000

2500

D (m)

Z(

m)

0 25 50

230

240

250

260

270

280

290

300

19000017000015000013000011000090000700005000030000200001000050000

Double-sided 3D, p-type,1e+16neq/cm2, back surface

n+

p+


50

00

0

40

00

0

3000

015000

2500

7500

D (m)

Z(

m)

0 25 50

230

240

250

260

270

280

290

300

19000017000015000013000011000090000700005000030000200001000050000

Double-sided 3D, p-type,0neq/cm2, back surface

n+

p+


D (m)

Z(

m)

0 25 50

230

240

250

260

270

280

290

300

Double-sided 3D, p-type,back surface

n+

p+

Double-sided 3D – back surface

Undepleted

Region at back surface depletes more slowly – not fully depleted at 100V bias


Further work

• Simulate charge collection!

• Consider effects of different available pixel layouts

– CCE, depletion voltage, insensitive area, capacitance

X

Y

0 20 40 60

0

10

20

30

40

50

X

Y

0 20 40 60

0

10

20

30

40

50

133m

3

50m

8 50m

Conclusions

• Double-sided 3D detectors:

– Behaviour mostly similar to standard 3D

– Depletion to back surface requires a higher bias

– Front and back surfaces show slower charge collection

• Radiation damage model

– Trap behaviour is directly simulated in ISE-TCAD

– Trap models based on Perugia models, altered to match experimental trapping times

• Preliminary tests of damage model with 3D

– Relatively low depletion voltages, but electric field pattern is altered

– Double-sided 3D shows undepleted region at back surface at high fluences

Thank you for listening

Additional slides

3D detectors

• N+ and p+ columns pass through substrate

• Fast charge collection

• Low depletion voltage

• Low charge sharing

• Additional processing (DRIE for hole etching)

Planar

3D

e- h+

Particle

+ve

-ve

n-electrode

p-electrode

~300ume- h+

Particle

+ve

-ve

n-electrode

p-electrode

~300um

e- h+

Particle

+ve -ve

p-columnn-column

~30um

e- h+

Particle

+ve -ve

p-columnn-column

~30um

Breakdown in double-sided 3D

2000

80000

6000

0

1000

00

2000

00

D (um)

Z(u

m)

25 30 35

40

42

44

46

48

50

52

54

56

343000

Electric field (V/cm) aroundtip of p+ column at 215V

p+

• Breakdown occurs at column tips around 230V

– Dependent on shape, e.g. 185V for square columns

Breakdown in double-sided 3D

D (um)

Z(u

m)

0 10 20 30 40

0

10

20

30

40

50

60

n+

p+

• With 1012cm-2 charge, breakdown at 210V

D (um)

Z(u

m)

01020300

10

20

30

40

50

60

p+

n+

D (um)

Z(u

m)

01020300

10

20

30

40

50

60

300000250000200000150000100000500000

Electric field (V/cm) in double-sided 3Dat 175V with 1012 cm-2 oxide charge

p+

n+

Electric field(V/cm)

D (um)

Z(u

m)

0 10 20 30 40

0

10

20

30

40

50

60

300000250000200000150000100000500000

Electric field (V/cm) in double-sided 3Dat 175V with 1012 cm-2 oxide charge

n+

p+

Electric field(V/cm)

P-stop

P+ base

Column tips

Front Back

Example of ISE TCAD bug

N+P+

300μm

In simulation, charge deposited at the front

Current distribution after 0.06ns

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

0 50 100 150 200 250 300

Position (um)

Cu

rren

t d

ensi

ty (

A/c

m2)

Total Current

Current distribution after 1ns

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

0 50 100 150 200 250 300

Position (um)

Cu

rren

t d

ensi

ty (

A/c

m2)

Total Current


N+P+

300μm

Holes drift


Depletion voltages and radiation damage

0

20

40

60

80

100

120

140

160

0 2E+15 4E+15 6E+15 8E+15 1E+16 1.2E+16

Fluence (Neq/cm^2)

Dep

leti

on

vo

lta

ge

(V)

Full 3D, ptype, Medipix (55um)

Full 3D, ptype, 3-column ATLAS

3-column ATLAS test, pointwhere CCE maximised

Full 3D – Depletion voltage (p-type)• Depletion voltage is low, but strongly dependent on pitch• Double sided 3D shows the same lateral depletion voltage as full 3D

50m

133m

X

Y

0 20 40 60

0

10

20

30

40

50

55m

Weighting fields and electrode layouts

X

Y

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70

0

10

20

30

40

50

Abs(ElectricField)300002500020000150001000050000

Square layout, symmetrical layout of p+ and n+

Max field: 26500 V/cm

Symmetrical layout of n+ and p+

Weighting potential is the same for electrons and holes

X

Y

0 20 40 60

0

10

20

30

40

50

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.80.9

X

Y

0 10 20 30 40 50 60 70

0

10

20

30

40

50

10.90.80.70.60.50.40.30.20.10

Square layout, symmetrical layout of n+ and p+

Weightingpotential

Electric field, 100V bias Weighting potential

X

Y

0 20 40 60

0

10

20

30

40

50

X

Y

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75

0

10

20

30

40

50

Abs(ElectricField)300002500020000150001000050000

Square layout, 3 n+ bias columns per p+ readout column

Max field: 44700 V/cm

Weighting fields and electrode layouts

3 bias columns per readout column

Weighing potential favours electron collection

0.90.

70.5

0.30.

20.

1

X

Y

0 10 20 30 40 50 60 70

0

10

20

30

40

50

10.90.80.70.60.50.40.30.20.10

Square layout, 3 p+ bias columns per n+ readout column

WeightingPotential

Electric field, 100V bias Weighting potential

X

Y

0 20 40 60

0

10

20

30

40

50

• Choice of electrode layout:

– In general, two main layouts possible

– Second option doubles number of columns

– However, increasing no. of p+ columns means larger electron signal

X

Y

0 20 40 60

0

10

20

30

40

50

Future work – Design choices with 3D

Future work – Design choices with 3D

• ATLAS pixel (400m * 50m) allows a variety of layouts

– No of n+ electrodes per pixel could vary from ~3-8

– Have to consider Vdep, speed, total column area, capacitance

– FP420 / ATLAS run at Stanford already has different layouts

• CMS (100 m * 150m)

133m

50m

3

8

50m

Documents

Simulation results from double-sided and standard 3D detectors