Design, simulation, production and initial characterisation of 3D silicon detectors

Design, simulation, production and initial characterisation of 3D silicon detectors

David Pennicard – University of Glasgow

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

G. Pellegrini, M. Lozano - CNM, Barcelona

D.Pennicard, University of Glasgow, INSTR08, Novosibirsk

• Array of electrode columns passing through substrate• Electrode spacing << wafer thickness (e.g. 30m:300m)• Benefits

– Vdepletion (Electrode spacing)2

– Collection time Electrode spacing– Reduced charge sharing

• More complicated fabrication - micromachining

3D Detector Structure

+ve+ve

holes

-ve

electrons

Lightly doped p-type

silicon

n-typeelectrode

p-typeelectrode

Particle

+ve+ve

holes

-ve

electrons

Lightly doped p-type

silicon

n-typeelectrode

p-typeelectrode

Particle

Planar 3D

Around30µm

+ve +ve-ve

holes

300µm

n-typeelectrode

p-type electrode

electrons

Particle Around30µm

+ve +ve-ve

holes

300µm

n-typeelectrode

p-type electrode

electrons

Particle

300µm300µm


Background

• Invented in 1997 - S. Parker, C. Kenney, J. Segal– First produced in 1999 - Stanford Nanofabrication facility

• Recent development: R&D towards experimental use– Improvements in micromachining make larger-scale, reliable production

more feasible– Application: radiation-hard detectors for Super-LHC

• 3D detector collaboration between Glasgow and CNM (Centro Nacional de Microelectronica, Spain)– Optimisation of 3D design through simulation– Fabrication of 3D detectors in CNM cleanroom– Initial characterisation

• Overview of other 3D detector projects


Super-LHC and Radiation Damage• RD50 collaboration – see G. Casse talk• Upgrade to LHC, planned for sometime after 2017

– 10x increase in luminosity • 10x increase in radiation damage

– Inner layer of ATLAS pixel tracker will receive 1016neq/cm2 damage over SLHC running time

Ian Dawson, University of SheffieldATLAS upgrade workshop, Valencia, December 2007


3D Detectors and Radiation Hardness

• Increase in effective p-type doping with damage– Increased depletion voltage– 300μm planar detectors cannot be fully

depleted far beyond 1015neq/cm2

– 3D detectors have short depletion distance, reducing Vdep

• Charge trapping– Free electrons and holes trapped by defects,

reducing CCE

– Dominant effect at very high fluences– 3D structure reduces collection time – less

trapping

• Increased leakage current– Need to cool detectors

See M. Moll thesis, Hamburg 1999

G. Kramberger, Aug. 23-24, 2006, Hamburg, Germany

eeff

nt

n

,


1014 1015 1016

eq [cm-2]

5000

10000

15000

20000

25000

sign

al [e

lect

rons

]

3D simulation

Double-sided 3D, 250 m, simulation! [1]n-in-p (FZ), 280 m [2,3]n-in-p (MCZ), 300m [4,5]p-in-np-in-n (MCZ), 300m [6]n-in-p (FZ), 140 m, 500V [7]p-in-n (EPI), 150 m [8,9]p-in-n (EPI), 75m [10]

75m n-EPI

150m n-EPI

n-in-p

140m p-FZ

M.Moll 2007

[1] 3D, double sided, 250m columns, 300m substrate [Pennicard 2007][2] p-FZ, 280m, (-30oC, 25ns), strip [Casse 2007][3] p-FZ, 280m, (-30oC, 25ns), strip [Casse 2004][4] p-MCZ, 300m, (-30OC, s), pad [Bruzzi 2006][5] p-MCZ, 300m, (<0OC, s), strip [Bernadini 2007][6] n-MCZ, 300m, (-30OC, 25ns), strip [Messineo 2007][7] p-FZ, 140m, (-30oC, 25ns), strip [Casse 2007][8] n-EPI, 150m, (-30OC, 25ns), strip [Messineo 2007][9] n-epi Si, 150m, (-30oC, 25ns), pad [Kramberger 2006][10] n-epi Si, 75m, (-30oC, 25ns), pad [Kramberger 2006]

See also: [M. Bruzzi et al. NIM A 579 (2007) 754-761] [H.Sadrozinski, IEEE NSS 2007, RD50 talk]

pixelsstrips

Simulation of 3D detectors after radiation damage• Simulations performed using Synopsys TCAD• Predict higher collection efficiency for 3D than for planar sensors

– Model uses pessimistic values for trapping rates

Plot compiled by M. Moll


Optimisation of ATLAS 3D structure

• ATLAS pixel is 400μm * 50μm – Different layouts available

– Trade-offs between Vdep, CCE, capacitance, column area…

0 20 40 60 80 1000

2

4

6

8

10

12

14

2

76

5

4

3

8

Cha

rge

colle

ctio

n (k

e-)

Electrode spacing (m)

ATLAS 3D CCE

0 20 40 60 80 1000

100

200

300

400

500

600

2

7

6

5

4

3

8

Cap

acita

nce

(fF

)


Total C per pixel Interpixel C

8 column

3 column

Charge collection with 1016neq/cm2 radiation damage

Smaller electrode spacing improves CCE

Capacitance at each pixel

Bars show variation in CCE with hit position


Double-sided 3D detectors at CNM• Alternative 3D structure proposed by IMB-CNM • N- and p-type columns etched from opposite sides of substrate

– Columns do not pass through full substrate thickness (in first production run)

– 250μm deep in 300μm substrate • Recently finished production with p+ column readout and n-type substrate

Passivation

p+ doped

55m pitch

50m

300m

n+ doped

10m

Oxide

n+ doped

Metal

Poly 3m

Oxide

Metal

50m

TEOS oxide 2m

UBM/bump

n-type Si

Passivation

p+ doped

55m pitch

50m

300m

n+ doped

10m

Oxide

n+ doped

Metal

Poly 3m

Oxide

Metal

50m

TEOS oxide 2m

UBM/bump

n-type Si


Si, n-type, 300 um

SiO2

Al/Cu

Si, n-type, 300 um

SiO2

Al/Cu

Double-sided 3D Detector production

• Column fabrication introduces extra steps

• Begin with columns on back side



• Deep Reactive Ion Etching– F plasma etches away base of hole

– CF2 coating protects sidewall – Limit on depth : diameter ratio– 250m depth, 10m diameter

Hole etching

Si, n-type, 300 um

SiO2

Al/Cu

Si, n-type, 300 um

SiO2

Al/Cu10μm

250μm



• Deposit 3μm poly-silicon• Phosphorus doping through poly

• Passivate inside of column with SiO2

Column filling and doping

2.9m

TEOS

PolyJunction

2.9m

TEOS

PolyJunction

n-Si

(p+) Si-n+

Poly-n+

SiO2

Si-n+

Poly-n+

SiO2



• P+ columns fabricated on front side• Contacts on front• Backside coated with metal for biasing

Finished detector

10μm

250μm

Poly-n+

Passivation

Si-p+

Si-n+

Al/Cu

Al/Cu

Poly-n+

Passivation

Si-p+

Si-n+

Al/Cu

Al/Cu


Finished 3D devices

3D guard ring

Collecting electrodes

Bias electrodes(back surface)

Bond pads

Typical device layout – Strip detector, 80μm pitch

80μm

Devices include: Pads, strips, pixels detectors, test structures


Finished 3D devices

m

SiO2

Polysilicon

Dry etching of the poly

SEM after polysilicon deposition and etching

Pixel on Medipix detector

Polysilicon and column (under passivation)

Passivation (SiO2 and SiN)

Bump-bond contact


Pad detector CV

0.0E+00

2.0E-10

4.0E-10

6.0E-10

8.0E-10

1.0E-09

1.2E-09

1.4E-09

1.6E-09

1.8E-09

2.0E-09

0.0 5.0 10.0 15.0 20.0

Bias (V)

Cap

acit

ance

(F

)

Initial tests - CV• Pad detector – 90 * 90 columns, 55μm pitch

P+

N+

Lateral depletion around column (~2V in sim.)

Depletion to back surface from tip of column (~8V in sim.)

2.3V lateral depletion


1/Capacitance, Pad detector

0.0E+00

5.0E+08

1.0E+09

1.5E+09

2.0E+09

2.5E+09

3.0E+09

3.5E+09

4.0E+09

4.5E+09

5.0E+09

0.0 5.0 10.0 15.0 20.0

Bias (V)

1/C

(F

-1)

Initial tests - CV

P+

N+

Lateral depletion around column (~2V in sim.)

Depletion to back surface from tip of column (~8V in sim.)

2.3V lateral depletion

~9V back surface depletion

• Pad detector – 90 * 90 columns, 55μm pitch


Initial tests – Strip detector IV• 128 strips, 50 holes/strip, pitch 80um, length 4mm

• Measured with 3 strips and guard ring at 0V, and backside biased

• Strip currents ~100pA (T=21˚C) in all 4 detectors

• Can reliably bias detectors to 50V (20 times lateral depletion voltage)

• Capacitance 5pF / strip

• Guard ring currents vary:

– Highest 20μA at 10V

– Lowest 0.03μA at 50V

strip detector 4

1.0E-11

1.0E-10

1.0E-09

1.0E-08

1.0E-07

1.0E-06

1.0E-05

1.0E-04

0.0 10.0 20.0 30.0 40.0 50.0V(V)

I(A

)

Strip

Neighbours

Guard ring


Future work• Tests on these detectors

– Charge collection test on strip detector with beta source and LHCb readout electronics

• Tests before and after irradiation– X-ray detection test, using Medipix pixel

readout (single-photon-counting)

• New production run at CNM– Columns pass through full substrate thickness– Both p+ readout with n-substrate, and n+

readout with p-substrate– Includes ATLAS pixel detectors

• Testbeams at CERN in summer– Collection performance vs position


Other 3D detector projects

• Stanford / Manchester / Sintef

• FBK-IRST (Trento, Italy)

• Glasgow / Diamond / IceMOS


Stanford / Manchester / Sintef• First 3D detectors produced at Stanford Nanofabrication Facility• University of Manchester and CERN testing detectors

– Have demonstrated good charge collection behaviour of ATLAS 3D pixels after SLHC radiation fluences

• Working with Sintef (independent research foundation in Norway) to reproduce Stanford fabrication process on a larger scale

Charge collection and signal/noise results

Thanks to Cinzia da Via (Manchester)


Stanford / Manchester / Sintef• “Active edge” electrode

– Usually, silicon sensors have >100μm insensitive area at edge (need to avoid current flow from saw-cut edges)

– Instead, plasma etch edge, and add a doped polysilicon layer– Edge acts as an electrode – dead area just 5μm

• Achieve good coverage with fewer overlapping layers

0

60

120

180

240

300

360

0918

27

36

45

54

microns

45-54

36-45

27-36

18-27

9-18

0-9

X-ray microbeam scan

Developments in Trento, Italy

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

0 20 40 60 80 100

Vrev [V]

Idio

de

[n

A]

stc2 stc3

dtc2 dtc3

3Ddtc1 - Wafer#861

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

0 1 2 3 4Vrev [V]

Cd

iod

e [

pF

]

stc100

dtc100

stc80

dtc80

CV-diode - W861

First prototypes (p-on-n) completed, and n-on-p available soon.

Double-side Double-Column 3D detectors

Good results from preliminary electrical tests (C-V and I-V)


Glasgow / Diamond / IceMOS• Project between Glasgow and Diamond synchrotron to develop 3D

detectors for X-ray crystallography– Single-photon-counting pixel sensors (Medipix, Pilatus) – Lower charge sharing in 3D detectors– Potential for thick 3D silicon detectors with good performance

• Detectors produced in fabrication company IceMOS (Belfast)– First 3D detectors produced entirely in industry– Prototype run finished

• Working test structures, but some problems with full devices– Starting second run with improved fabrication flow

Si-n+

poly-n+

Si-p+poly-p+

SiO2

SiO2

passivation

Si(n--)

Metal

Si-n+

poly-n+

Si-p+poly-p+

SiO2

SiO2

passivation

Si(n--)

Metal

n-electrode (bias)p-electrode (readout)


Conclusions

• 3D detectors– Fast collection, low depletion voltage– Radiation hard – candidate for SLHC inner pixel layers

• 3D production at CNM– First set of double-sided 3D detectors produced– Preliminary tests successful – continuing with charge collection tests– More production runs underway

• Other 3D projects– Different groups working towards 3D detectors for high-luminosity

colliders– Other applications possible, such as X-ray crystallography


Thank you for listening



First CNM 3D production run

• P+ readout, n-type substrate devices on 4” wafer

• 6 Medipix2 pixels Pitch 55μm, 256x256

– Single-photon counting sensor for medical X-ray detection (CERN)

• 1 Pilatus pixel Pitch 172μm, 97x60

– Single-photon-counting sensor for X-ray crystallography (PSI)

• 6 ATLAS pixels Pitch 50x400μm, 164x18

– Prototypes (wrong readout polarity)

• 4 short strip Pitch 80μm, 50x50

• 1 long strip Pitch 80μm, 50x180

• Pad detectors, test structures


Double-sided 3D detector – simulated behaviour

• Where columns overlap, same behaviour as standard 3D

• Weaker field near front and back surfaces – slower collection

• Greater device thickness for given column length

P+

N+

2500

5000

10000

20000

30000

30

00

0

40

00

0

40

00

0

D (um)

Z(u

m)

0 10 20 30 40 50

0

10

20

30

40

50

60

70

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

140000

Electric field, 100V bias

Variation in charge collection with depth

0.00

1.00

2.00

3.00

4.00

5.00

0 50 100 150 200 250 300

Depth (um)

Co

llec

tio

n t

ime

(ns)

50%90%Full

Time (ns) for given %collection:


Simulation of 3D detectors after radiation damage

• Simulations performed using Synopsys TCAD• Predict higher collection efficiency than planar sensors

– Model uses conservative values for trapping rates

0.0 2.0 4.0 6.0 8.0 10.0 12.00

5

10

15

20

25

C

harg

e co

llect

ion(

ke-)

Fluence (1015neq/cm2)

Simulated CNM 3D (55m pitch)

Experimental n-on-p results

Simulated n-on-p

N-on-p results: PP Allport et al., IEEE Trans. Nucl. Sci., vol 52, Oct 2005


Simulation methods

• See presentation from 10th RD50 meeting• Synopsis TCAD finite element simulation

• Damage model– Trap dynamics modelled directly– P-type FZ material– Based on work at Uni. Perugia – see M.

Petasecca et al., IEEE Trans. Nucl. Sci., vol. 53, pp. 2971–2976, 2006

– Modified to match experimental trap times (V. Cindro et al., IEEE NSS, Nov 2006)

Example of a simulated 3D structure

n+ contact

p+ contact

oxide

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

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

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

η (cm-1)σh (cm2)σe (cm2)Trap

Energy (eV)Type

βe= 4.0*10-7cm2s-1, βh= 4.4*10-7cm2s-1, eqee

1


0.0 2.0 4.0 6.0 8.0 10.00

5

10

15

20

25

C

harg

e co

llect

ion(

ke-)


Simulated strip Experimental results

N+ on p strip detector: CCE• At high fluence, simulated CCE is lower than experimental value

– Trapping rates were extrapolated from measurements below 1015neq/cm2

– In reality, trapping rate at high fluence probably lower than predicted

PP Allport et al., IEEE Trans. Nucl. Sci., vol 52, Oct 2005

900V bias, 280m thick

From β values used, expect 25μm drift distance, 2ke- signal


ATLAS 3D detector: CCE• Experiment used n+ readout, with 3 n+ columns per ATLAS pixel• Experiment used defocused IR laser pulse to flood the pixel with charge; the

simulation mimics this• Both experiment and simulation show improved CCE at high fluence

C. da Via et al., Liverpool ATLAS 3D meeting, Nov. 06

Detectors produced at Stanford

0.0 2.0 4.0 6.0 8.0 10.00

5

10

15

20

25

160V

100V

60V

60V

C

harg

e co

llect

ion

(ke-

)


Simulated ATLAS 3D Experimental results

At high fluences, simulated CCE ~2/3 of experimental value (like with planar detector)


Overview

• Radiation damage model and comparison with experiment

• Behaviour of different ATLAS pixel 3D layouts

• Comparison of double-sided & standard 3D


ATLAS 3D simulations

• ATLAS pixel (400m * 50m) allows layouts with different electrode spacing

– No of n+ columns per pixel could vary from ~2-8

• Stanford have produced devices with 2-4 n+ columns

• Previous ATLAS results shown used 3 columns

• Simulations use 230m-thick p-type substrate, n+ readout

– Columns have 5m radius, with dopant profile extending ~2m further

– P-spray is used to isolate the columns

50m cell length

8

133m cell length

3 50m

400m

Spacing

Note larger volume occupied by columns


0 20 40 60 800

50

100

150

200

250

Fit:V=0.07(X-13.5m)2-1.5

76

5

4

3

8

B

ias

(V)


Depletion voltage

ATLAS 3D – Depletion voltage at 1016neq/cm2

• Depletion voltage will depend on substrate material (this model matches p-type FZ, rather than oxygenated silicon)

• No. of n+ columns shown next to each data point

• Vdep proportional to depletion distance squared


0 20 40 60 800

50

100

150

200

250

76

5

4

3

8

B

ias

(V)


Depletion voltage High field voltage

ATLAS 3D – high-field voltage at 1016neq/cm2

• As an approximate judge of a “safe voltage”, found the bias at which the maximum field in each device reached 2.5*105V/cm

• Surprisingly, all the devices gave much the same results at 1016neq/cm2

150V safe level


Device structure and high-field regions • P-spray links p+ columns to n+• So, the p-spray is at the same potential as the p+, resulting in high field at

front surface where it meets the n+ columns• At higher bias the p-spray around the n+ column becomes depleted• These effects won’t be greatly affected by the electrode spacing itself

Y

X

Z

6.0E+18

8.8E+15

1.3E+13

-1.3E+13

-8.8E+15

-6.0E+18

5-column ATLAS 3D device1016neq/cm2, 150V bias

p-spray

n+ p+ Doping concentration(cm-3)

Y

X

Z

-10

-30

-50

-70

-90

-110

-130

-150


p-spray

n+ p+Electrostatic potential(V)

Doping conc. (cm-3)

5-column ATLAS 3D, 1016neq/cm2, 150V bias


Electrostatic potential (V)


Device structure and high-field regions • P-spray links p+ columns to n+• So, the p-spray is at the same potential as the p+, resulting in high field at

front surface where it meets the n+ columns• At higher bias the p-spray around the n+ column becomes depleted• These effects won’t be greatly affected by the electrode spacing itself

Y

X

Z

6.0E+18

8.8E+15

1.3E+13

-1.3E+13

-8.8E+15

-6.0E+18


p-spray

n+ p+ Doping concentration(cm-3)

Y

X

Z

1.0E+14

4.1E+13

1.7E+13

7.0E+12

2.8E+12

1.0E+12

0.0E+00


p-spray

n+ p+Hole concentration(cm-3)



Doping conc. (cm-3) Hole conc.

(cm-3)


05

1015

2025

0

5

10

15

20

25

024

6

8

10

12

14

10

12

6

9

11

p+

n+

02.04.06.08.0101214

05

1015

2025

30

0

5

10

15

20

25

0246

8

10

12

14

8

11

6

8

10

p+

n+

02.04.06.08.010.012.014.0

Charge collection vs position at 1016neq/cm2

• Simulated MIPs passing through detector at 25 positions, to roughly map the collection efficiency. Charge sharing not taken into account.

8 columns 6 columns


0

510

1520

2530

3540

4550

0

5

10

15

2025

02468101214

7

84

65

p+

n+02.04.06.08.010.012.014.0 0

5

1015

2025

3035

4045

5055

6065

05

1015

2025

02468101214

5

24

64

p+

n+

02.04.06.08.010.012.014.0

Charge collection vs position at 1016neq/cm2

• Simulated MIPs passing through detector at 25 positions, to roughly map the collection efficiency. Charge sharing not taken into account.

4 columns 3 columns


Average ATLAS CCE at 1016neq/cm2

• Average CCE found by flooding entire pixel with charge• Previous simulations used to find RMS variation from average, as a

measure of nonuniformity. Shown by “error bars”.• CCE improves as electrode spacing is reduced (faster collection)

0 20 40 60 80 1000

2

4

6

8

10

12

14

2

76

5

4

3

8

C

harg

e co

llect

ion

(ke-

)


ATLAS 3D CCE

Variation in collection with position larger relative to CCE


0 20 40 60 80 1000

100

200

300

400

500

600

2

7

6

5

4

3

8

C

apac

itanc

e (f

F)


Total C per pixel Interpixel C

Total capacitance seen at each ATLAS pixel• The total pixel capacitance was found with 1012cm-2 oxide charge (a typical

saturated value) but without radiation damage.• C increases rapidly with no. of columns – the column capacitances add in

parallel, and the capacitance per column gets larger as spacing decreases.

Unlike in planar detectors, interpixel C is only a small component of total


Signal to noise estimate at 1016neq/cm2

• Uses noise vs. capacitance data from unirradiated ATLAS sensors (won’t include high leakage current or damage to readout chip)– Assume 100fF from preamplifier input and bump bond– Also 70e- threshold dispersion

Noise≈60e-+39e-/100fF

“Progresses on the ATLAS pixel detector”, A. Andreazza, NIMA vol. 461, pp. 168-171, 2001

0 20 40 60 80 1000

5

10

15

20

25

30

35

40

2

76 5

4

3

8

Est

imat

ed s

igna

l-to

-noi

se r

atio


ATLAS 3D SNR

Increasing C noise counteracts improving CCE


Overview

• Radiation damage model and comparison with experiment

• Behaviour of different ATLAS pixel 3D layouts

• Comparison of double-sided & standard 3D


Comparison of double-sided & standard 3D

• Full 3D (Parker et al., Stanford, Sintef, ICEMOS) • Double-sided 3D (CNM, Trento)

– Readout columns etched from front surface – Bias columns etched from back surface – Columns don’t pass through full substrate thickness

• The maximum column depth that can be etched is about 250m (with a 5m radius) – Double-sided 3D simulation uses 250m columns in a

300m substrate– Full-3D device used for comparison is 250m thick

• Device structure used for comparison– N+ columns used for readout, p-type substrate– 55m* 55m pixel size (Medipix)– 100V bias

p+ bias

n+ readout


Double-sided 3D field and depletion• Where the columns overlap, (from 50m to 250m depth) the

field matches that in the full-3D detector• At front and back surfaces, fields are lower as shown below• Region at back is difficult to deplete at high fluence

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+

ElectricField (V/cm)

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+


A.

A.

B.

B.

Undepleted

100V 100V

1016neq/cm2, front surface 1016neq/cm2, back surface


Collection with double-sided 3D• Slightly higher collection at low damage • But at high fluence, results match standard 3D due to poorer collection from

front and back surfaces.

20% greater substrate thickness

0.0 2.0 4.0 6.0 8.0 10.00

5

10

15

20

25

Cha

rge

colle

ctio

n (k

e-)


Standard 3D, 250m substrate Double-sided 3D, 250m

columns, 300m substrate


High-field regions in full and double-sided 3D• Simulated full and double-sided 3D using p-spray isolation at 1016 neq/cm2

• Double-sided 3D is less prone to surface effects because columns are etched from opposite sides, but high-field regions develop at n+ column tip.

10000

200

00

70000

40000

600

00

30

000

D (m)

Z(

m)

0 10 20 30 40 50

0

20

40

60

19000017000015000013000011000090000700005000030000200001000050000

n+

p+


25

00

01000

00

50

00

0

30

000

60

00

0

25

00

0

D (m)

Z(

m)

0 10 20 30 40 50

0

10

20

30

40

19000017000015000013000011000090000700005000030000200001000050000

n+ p+


Full 3D Double-sided 3D

Field reaches 2.5*105V/cm at 170V

Field reaches 2.5*105V/cm at 130V


P-type FZ model – proton irradiation

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

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

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

η (cm-1)σh (cm2)σe (cm2)Trap

Energy (eV)Type

• See presentation from RD50 June 2007• Based on work at Uni. Perugia – see M. Petasecca et al., IEEE Trans. Nucl.

Sci., vol. 53, pp. 2971–2976, 2006

• Modified to give correct trapping times while maintaining depletion behaviour

• 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

• Assume these can be extrapolated to 1016neq/cm2

e

nt

n

e

ethe veqe

e

1


Comparison with experiment

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 α=3.75*10-17A/cm

• Compared with experimental results with proton irradiation

• Depletion voltage matches experiment

• Leakage current is higher than experiment, but not excessive

P-type trap model: Leakage Current

0.00

0.05

0.10

0.15

0.20

0.25

0.30

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)

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

α=5.13*10-17A/cm


Example of CCE with varying bias

Collection vs bias in 5-column ATLAS

0

2

4

6

8

10

12

14

16

0 20 40 60 80 100 120 140 160 180

Bias (V)

Ch

arg

e co

llect

ed (

ke-)

10^16neq/cm^2

5*10^15neq/cm^2

Vdep

Vdep

• CCE curves show a smaller gradient after depletion voltage is reached

CCE increases beyond Vdep, due to increasing carrier velocity


Electric field distribution – 8 columns per pixel

110000

50000

10000

70000

1000

0

4000

0

40000

X (m)

Y(

m)

0 5 10 15 20 25 300

5

10

15

20

25

19000017000015000013000011000090000700005000030000200001000050000

ATLAS 3D, p-type, 50m cell, 8 column1e+16neq/cm2, 150V bias

n+

p+

ElectricField(V/cm)

• The previous simulations showed an “average” CCE for the pixel, but the uniformity across the pixel is also important. The following slides show how the electric field distribution varies with the pixel layout

Documents

Design, simulation, production and initial characterisation of 3D silicon detectors