michael moll (cern/ph)

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Michael Moll (CERN/PH) 3 rd MC-PAD Network Training Event, Jožef Stefan Institute, Ljubljana, Slovenia - 29 September 2010 - iation Hardness of Semiconductor Detect - Radiation Effects and Detector Operation - … including an introduction to ongoing radiation tolerant sensors developments -1- Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010

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3 rd MC-PAD Network Training Event, Jožef Stefan Institute, Ljubljana, Slovenia - 29 September 2010 -. Radiation Hardness of Semiconductor Detectors - Radiation Effects and Detector Operation - . … including an introduction to ongoing radiation tolerant sensors developments. - PowerPoint PPT Presentation

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Page 1: Michael Moll  (CERN/PH)

Michael Moll (CERN/PH)

3rd MC-PAD Network Training Event, Jožef Stefan Institute, Ljubljana, Slovenia

- 29 September 2010 -

Radiation Hardness of Semiconductor Detectors- Radiation Effects and Detector Operation -

… including an introduction to ongoing radiation tolerant sensors developments

-1-Michael Moll – MC-PAD Network Training,

Ljubljana, 27.9.2010

Page 2: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -2-

Outline

· Motivation to develop radiation harder detectors · LHC upgrade and expected radiation levels· Radiation induced degradation of detector performance

· Radiation Damage in Silicon Detectors· Microscopic damage (crystal damage), NIEL

· Macroscopic damage (changes in detector properties)

· Approaches to obtain radiation tolerant sensors· Material Engineering

• New silicon materials – FZ, MCZ, DOFZ, EPI• Other semiconductors: Diamond, SiC, GaN, ….

· Device Engineering• p-in-n, n-in-n and n-in-p sensors, 3D sensors and thin devices

· Silicon Sensors for the LHC upgrade ….. open questions and ongoing developments

· Summary

For details on LHC detectors

see lecture ofPhil Allport

For details on sensor production

see lecture ofManolo Lozano

For surface effectssee lecture of

G.-F. Dalla Betta

For details on radiation induced defects

see lecture ofIoana Pintilie

Page 3: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -3-

LHC example: CMS inner tracker

5.4 m

2.4

m

Inner Tracker Outer Barrel (TOB)Inner Barrel

(TIB) End Cap (TEC)Inner Disks

(TID)

CMS – “Currently the Most Silicon”· Micro Strip:· ~ 214 m2 of silicon strip sensors, 11.4 million strips· Pixel:· Inner 3 layers: silicon pixels (~ 1m2) · 66 million pixels (100x150mm)· Precision: σ(rφ) ~ σ(z) ~ 15mm· Most challenging operating environments (LHC)

CMS

Pixel

93 cm

30 cm

Pixel Detector

Total weight 12500 t

Diameter 15m

Length 21.6m

Magnetic field 4 T

Page 4: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -4-

B-layer (R=3.7 cm): 2.5×1016 neq/cm2 = 1140 Mrad2nd Inner Pixel Layer (R=7 cm): 7.8×1015 neq/cm2 = 420 Mrad1st Outer Pixel Layer (R=11 cm): 3.6×1015 neq/cm2 = 207 MradShort strips (R=38 cm): 6.8×1014 neq/cm2 = 30 MradLong strips (R=85 cm): 3.2×1014 neq/cm2 = 8.4 Mrad

Radiation levels after 3000 fb-1

• Radiation hardness requirements (including safety factor of 2)• 2 × 1016 neq/cm2 for the innermost pixel layers• 7 × 1014 neq/cm2 for the innermost strip layers

Dominated bypion damage

Dominated byneutron damage

Page 5: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -5-

1013 5 1014 5 1015 5 1016

eq [cm-2]

5000

10000

15000

20000

25000

sign

al [e

lect

rons

]

n-in-n (FZ), 285mm, 600V, 23 GeV p p-in-n (FZ), 300mm, 500V, 23GeV pp-in-n (FZ), 300mm, 500V, neutrons

p-in-n-FZ (500V)n-in-n FZ (600V)

M.Moll - 08/2008

References:

[1] p/n-FZ, 300mm, (-30oC, 25ns), strip [Casse 2008][2] n/n-FZ, 285mm, (-10oC, 40ns), pixel [Rohe et al. 2005]

FZ Silicon Strip and Pixel Sensors

strip sensorspixel sensors

Signal degradation for LHC Silicon SensorsNote: Measured partly

under different conditions! Lines to guide the eye

(no modeling)!

Strip sensors: max. cumulated fluence for LHC

Pixel sensors: max. cumulated fluence for LHC

Situation in 2005

Page 6: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -6-

1013 5 1014 5 1015 5 1016

eq [cm-2]

5000

10000

15000

20000

25000

sign

al [e

lect

rons

]

n-in-n (FZ), 285mm, 600V, 23 GeV p p-in-n (FZ), 300mm, 500V, 23GeV pp-in-n (FZ), 300mm, 500V, neutrons

p-in-n-FZ (500V)n-in-n FZ (600V)

M.Moll - 08/2008

References:

[1] p/n-FZ, 300mm, (-30oC, 25ns), strip [Casse 2008][2] n/n-FZ, 285mm, (-10oC, 40ns), pixel [Rohe et al. 2005]

FZ Silicon Strip and Pixel Sensors

strip sensorspixel sensors

Signal degradation for LHC Silicon SensorsNote: Measured partly

under different conditions! Lines to guide the eye

(no modeling)!

Strip sensors: max. cumulated fluence for LHC and LHC upgrade

Pixel sensors: max. cumulated fluence for LHC and LHC upgrade

LHC upgrade will need more radiation tolerant tracking detector concepts!Boundary conditions & other challenges:

Granularity, Powering, Cooling, Connectivity,Triggering, Low mass, Low cost!

Page 7: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -7-

Outline

· Motivation to develop radiation harder detectors · LHC upgrade and expected radiation levels· Radiation induced degradation of detector performance

· Radiation Damage in Silicon Detectors· Microscopic damage (crystal damage), NIEL

· Macroscopic damage (changes in detector properties)

· Approaches to obtain radiation tolerant sensors· Material Engineering

• New silicon materials – FZ, MCZ, DOFZ, EPI• Other semiconductors: Diamond, SiC, GaN, ….

· Device Engineering• p-in-n, n-in-n and n-in-p sensors, 3D sensors and thin devices

· Silicon Sensors for the LHC upgrade ….. open questions and ongoing developments

· Summary

Page 8: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010

Radiation Damage – Microscopic Effects

particle

SiS Vacancy + Interstitial

point defects (V-O, C-O, .. )

point defects and clusters of defects

EK>25 eV

EK > 5 keV

V

I

I

I

V

V

¨ Spatial distribution of vacancies created by a 50 keV Si-ion in silicon. (typical recoil energy for 1 MeV neutrons)

van Lint 1980

M.Huhtinen 2001

-8-

Page 9: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010

Radiation Damage – Microscopic Effects

particle

SiS Vacancy + Interstitial

point defects (V-O, C-O, .. )

point defects and clusters of defects

EK>25 eV

EK > 5 keV

V

I

·Neutrons (elastic scattering)· En > 185 eV for displacement· En > 35 keV for cluster

·60Co-gammas· Compton Electrons

with max. E 1 MeV (no cluster production)

·Electrons·Ee > 255 keV for displacement·Ee > 8 MeV for cluster

Only point defects point defects & clusters Mainly clusters

10 MeV protons 24 GeV/c protons 1 MeV neutronsSimulation:

Initial distribution of vacancies in (1mm)3

after 1014 particles/cm2

[Mika Huhtinen NIMA 491(2002) 194]

-9-

Page 10: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010

10-10 10-9 10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 100 101 102 103 104

particle energy [MeV]

10-5

10-4

10-3

10-2

10-1

100

101

102

103

104

D(E

) / (9

5 M

eV m

b)

neutronsneutrons

pionspions

protonsprotons

electronselectrons

100 101 102 103 104

0.4

0.60.8

1

2

4

neutronsneutrons

pionspions

protonsprotons

NIEL - Displacement damage functions

· NIEL - Non Ionizing Energy Loss

· NIEL - Hypothesis: Damage parameters scale with the NIEL· Be careful, does not hold for all particles & damage parameters (see later)

1MeV

1 1 MeV neutron

equivalent damage

-11-

Page 11: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -12-

Impact of Defects on Detector Properties

Shockley-Read-Hall statistics

  

Impact on detector properties can be calculated if all defect parameters are known:n,p : cross sections E : ionization energy Nt : concentration

Trapping (e and h) CCE

shallow defects do not contribute at room

temperature due to fast detrapping

charged defects

Neff , Vdepe.g. donors in upper

and acceptors in lower half of band

gap

generation leakage current

Levels close to midgap

most effective

Details in next lecture by

Ioana Pintilie on defects.

Page 12: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -13-

Outline

· Motivation to develop radiation harder detectors · LHC upgrade and expected radiation levels· Radiation induced degradation of detector performance

· Radiation Damage in Silicon Detectors· Microscopic damage (crystal damage), NIEL

· Macroscopic damage (changes in detector properties)

· Approaches to obtain radiation tolerant sensors· Material Engineering

• New silicon materials – FZ, MCZ, DOFZ, EPI• Other semiconductors: Diamond, SiC, GaN, ….

· Device Engineering• p-in-n, n-in-n and n-in-p sensors, 3D sensors and thin devices

· Silicon Sensors for the LHC upgrade ….. open questions and ongoing developments

· Summary

Page 13: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -14-

Impact of Defects on Detector Properties

  

• Detectors are basically p+- n diodes made on high resistivity silicon• Standard detector grade silicon:• Float Zone silicon (FZ)• n-type: 220 Kcm • [P] = 2021011 cm-3 (very low concentration !! below 1ppba = 51013cm-3)• [O] several 1015cm-3

• [C] some 1015cm-3 , usually [C] < [O]

• crystal orientation: <111> or <100>

p+

n

n+

Page 14: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -15-

d ep le ted zo ne

n eu tra l b u lk(n o e lec tric f ie ld )

Poisson’s equation

Reminder: Reverse biased abrupt p+-n junction

Electrical charge density

Electrical field strength

Electron potential energy

effNqxdxd

0

02

2

2

0

0 dNqV effdep

effective space charge density

depletion voltage

Full charge collection only for VB>Vdep !

Positive space charge, Neff =[P](ionized Phosphorus atoms)

p artic le (m ip )

+ V < VB d ep + V > VB d ep

Page 15: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -16-

Macroscopic Effects – I. Depletion Voltage

Change of Depletion Voltage Vdep (Neff)

…. with particle fluence:

• “Type inversion”: Neff changes from positive to negative (Space Charge Sign Inversion)

10-1 100 101 102 103

eq [ 1012 cm-2 ]

1

510

50100

5001000

5000

Ude

p [V

] (d

= 3

00mm

)

10-1

100

101

102

103

| Nef

f | [

1011

cm

-3 ]

600 V

1014cm-2

type inversion

n-type "p-type"

[M.Moll: Data: R. Wunstorf, PhD thesis 1992, Uni Hamburg]

• Short term: “Beneficial annealing” • Long term: “Reverse annealing” - time constant depends on temperature: ~ 500 years (-10°C) ~ 500 days ( 20°C) ~ 21 hours ( 60°C) - Consequence: Detectors must be cooled even when the experiment is not running!

…. with time (annealing):

NC

NC0

gC eq

NYNA

1 10 100 1000 10000annealing time at 60oC [min]

0

2

4

6

8

10

N

eff [

1011

cm-3

]

[M.Moll, PhD thesis 1999, Uni Hamburg]

after inversion

before inversion n+ p+ n+p+

Page 16: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -17-

Radiation Damage – II. Leakage Current

1011 1012 1013 1014 1015

eq [cm-2]10-6

10-5

10-4

10-3

10-2

10-1

I /

V

[A/c

m3 ]

n-type FZ - 7 to 25 Kcmn-type FZ - 7 Kcmn-type FZ - 4 Kcmn-type FZ - 3 Kcm

n-type FZ - 780 cmn-type FZ - 410 cmn-type FZ - 130 cmn-type FZ - 110 cmn-type CZ - 140 cm

p-type EPI - 2 and 4 Kcm

p-type EPI - 380 cm

[M.Moll PhD Thesis][M.Moll PhD Thesis]

· Damage parameter (slope in figure)

Leakage current per unit volume and particle fluence

· is constant over several orders of fluenceand independent of impurity concentration in Si can be used for fluence measurement

eqVI

α

80 min 60C

Change of Leakage Current (after hadron irradiation) …. with particle fluence:

· Leakage current decreasing in time (depending on temperature)

· Strong temperature dependence

Consequence: Cool detectors during operation! Example: I(-10°C) ~1/16 I(20°C)

1 10 100 1000 10000annealing time at 60oC [minutes]

0

1

2

3

4

5

6

(t)

[10-1

7 A/c

m]

1

2

3

4

5

6

oxygen enriched silicon [O] = 2.1017 cm-3

parameterisation for standard silicon [M.Moll PhD Thesis]

80 min 60C

…. with time (annealing):

Tk

EIB

g2exp

Page 17: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -18-

Deterioration of Charge Collection Efficiency (CCE) by trapping

tQtQ

heeffhehe

,,0,

1exp)(

0 2.1014 4.1014 6.1014 8.1014 1015

particle fluence - eq [cm-2]

0

0.1

0.2

0.3

0.4

0.5

Inve

rse

trapp

ing

time

1/

[ns-1

]

data for electronsdata for electronsdata for holesdata for holes

24 GeV/c proton irradiation24 GeV/c proton irradiation

[M.Moll; Data: O.Krasel, PhD thesis 2004, Uni Dortmund][M.Moll; Data: O.Krasel, PhD thesis 2004, Uni Dortmund]

Increase of inverse trapping time (1/) with fluence

Trapping is characterized by an effective trapping time eff for electrons and holes:

….. and change with time (annealing):

5 101 5 102 5 103

annealing time at 60oC [min]

0.1

0.15

0.2

0.25

Inve

rse

trapp

ing

time

1/

[ns-1

]

data for holesdata for holesdata for electronsdata for electrons

24 GeV/c proton irradiation24 GeV/c proton irradiationeq = 4.5.1014 cm-2 eq = 4.5.1014 cm-2

[M.Moll; Data: O.Krasel, PhD thesis 2004, Uni Dortmund][M.Moll; Data: O.Krasel, PhD thesis 2004, Uni Dortmund]

where defectsheeff

N,

1

Radiation Damage – III. CCE (Trapping)

Page 18: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -19-

Summary: Radiation Damage in Silicon Sensors

Two general types of radiation damage to the detector materials:

· Bulk (Crystal) damage due to Non Ionizing Energy Loss (NIEL) - displacement damage, built up of crystal defects –

I. Change of effective doping concentration (higher depletion voltage, under- depletion)

II. Increase of leakage current (increase of shot noise, thermal runaway)

III. Increase of charge carrier trapping (loss of charge)

· Surface damage due to Ionizing Energy Loss (IEL) - accumulation of positive in the oxide (SiO2) and the Si/SiO2 interface – affects: interstrip capacitance (noise factor), breakdown behavior, …

Impact on detector performance and Charge Collection Efficiency (depending on detector type and geometry and readout electronics!)

Signal/noise ratio is the quantity to watch Sensors can fail from radiation damage !

Same for all tested Silicon

materials!

Influenced by impurities

in Si – Defect Engineeringis possible!

Can be optimized!

Page 19: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010

0 10 20 30 40 50 60 70 80Signal [1000 electrons]

0

100

200

300

400

500

600

Cou

nts

[M.Moll][M.Moll]

The charge signal

Collected Charge for a Minimum Ionizing Particle (MIP)

· Mean energy loss dE/dx (Si) = 3.88 MeV/cm 116 keV for 300mm thickness

· Most probable energy loss ≈ 0.7 mean 81 keV

· 3.6 eV to create an e-h pair 72 e-h / mm (mean) 108 e-h / mm (most probable)

· Most probable charge (300 mm)

≈ 22500 e ≈ 3.6 fC

Mean charge

Most probable charge ≈ 0.7 mean

noiseCut (threshold)

-20-

Page 20: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010

Signal to Noise ratio

Good hits selected by requiring NADC > noise tail If cut too high efficiency loss If cut too low noise occupancy

Figure of Merit: Signal-to-Noise Ratio S/N

Typical values >10-15, people get nervous below 10. Radiation damage severely degrades the S/N.

Landau distribution has a low energy tail - becomes even lower by noise broadening

Noise sources: (ENC = Equivalent Noise Charge) - Capacitance - Leakage Current

- Thermal Noise (bias resistor)

dCENC

IENC

RTkENC B

-21-

0 10 20 30 40 50 60 70 80Signal [1000 electrons]

0

200

400

600

800

1000

1200

Cou

nts

non irradiatednon irradiated

p-type MCZ silicon p-type MCZ silicon 5x5 mm2 pad5x5 mm2 pad90Sr - source90Sr - source

[M.Moll][M.Moll]

Page 21: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010

Signal to Noise ratio

Good hits selected by requiring NADC > noise tail If cut too high efficiency loss If cut too low noise occupancy

Figure of Merit: Signal-to-Noise Ratio S/N

Typical values >10-15, people get nervous below 10. Radiation damage severely degrades the S/N.

Landau distribution has a low energy tail - becomes even lower by noise broadening

Noise sources: (ENC = Equivalent Noise Charge) - Capacitance - Leakage Current

- Thermal Noise (bias resistor)

dCENC

IENC

RTkENC B

-22-

0 10 20 30 40 50 60 70 80Signal [1000 electrons]

0

200

400

600

800

1000

1200

Cou

nts

non irradiatednon irradiated

1.1 x 1015 p/cm21.1 x 1015 p/cm2

p-type MCZ silicon p-type MCZ silicon 5x5 mm2 pad5x5 mm2 pad90Sr - source90Sr - source

[M.Moll][M.Moll]

Page 22: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010

0 10 20 30 40 50 60 70 80Signal [1000 electrons]

0

200

400

600

800

1000

1200

Cou

nts

non irradiatednon irradiated

1.1 x 1015 p/cm21.1 x 1015 p/cm2

9.3 x 1015 p/cm29.3 x 1015 p/cm2

p-type MCZ silicon p-type MCZ silicon 5x5 mm2 pad5x5 mm2 pad90Sr - source90Sr - source

[M.Moll][M.Moll]

Signal to Noise ratio

Good hits selected by requiring NADC > noise tail If cut too high efficiency loss If cut too low noise occupancy

Figure of Merit: Signal-to-Noise Ratio S/N

Typical values >10-15, people get nervous below 10. Radiation damage severely degrades the S/N.

Landau distribution has a low energy tail - becomes even lower by noise broadening

Noise sources: (ENC = Equivalent Noise Charge) - Capacitance - Leakage Current

- Thermal Noise (bias resistor)

dCENC

IENC

RTkENC B

less signal

more noise

What is signal and what is noise?

-23-

Page 23: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -24-

Outline

· Motivation to develop radiation harder detectors · LHC upgrade and expected radiation levels· Radiation induced degradation of detector performance

· Radiation Damage in Silicon Detectors· Microscopic damage (crystal damage), NIEL

· Macroscopic damage (changes in detector properties)

· Approaches to obtain radiation tolerant sensors· Material Engineering

• New silicon materials – FZ, MCZ, DOFZ, EPI• Other semiconductors: Diamond, SiC, GaN, ….

· Device Engineering• p-in-n, n-in-n and n-in-p sensors, 3D sensors and thin devices

· Silicon Sensors for the LHC upgrade ….. open questions and ongoing developments

· Summary

Page 24: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010

Approaches to develop radiation harder solid state tracking detectors

· Defect Engineering of SiliconDeliberate incorporation of impurities or defects into the silicon bulk to improve radiation tolerance of detectors· Needs: Profound understanding of radiation damage

• microscopic defects, macroscopic parameters• dependence on particle type and energy• defect formation kinetics and annealing

· Examples:• Oxygen rich Silicon (DOFZ, Cz, MCZ, EPI)• Oxygen dimer & hydrogen enriched Si• Pre-irradiated Si• Influence of processing technology

· New Materials· Silicon Carbide (SiC), Gallium Nitride (GaN)· Diamond (CERN RD42 Collaboration)· Amorphous silicon

· Device Engineering (New Detector Designs)· p-type silicon detectors (n-in-p)· thin detectors, epitaxial detectors· 3D detectors and Semi 3D detectors, Stripixels· Cost effective detectors· Monolithic devices

Scientific strategies:

I. Material engineering

II. Device engineering

III. Change of detectoroperational conditions

CERN-RD39“Cryogenic Tracking Detectors”operation at 100-200K to reduce charge loss

-26-

Page 25: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010

Material: Float Zone Silicon (FZ)

· Using a single Si crystal seed, meltthe vertically oriented rod onto the seed using RF power and “pull” themonocrystalline ingot

Wafer production· Slicing, lapping, etching, polishing

Mono-crystalline Ingot

Single crystal silicon

Poly silicon rod

RF Heating coil

Float Zone process

Oxygen enrichment (DOFZ)· Oxidation of wafer at high temperatures

-28-

Page 26: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010

Czochralski silicon (Cz) & Epitaxial silicon (EPI)

· Pull Si-crystal from a Si-melt contained in a silica crucible while rotating.

· Silica crucible is dissolving oxygen into the melt high concentration of O in CZ

· Material used by IC industry (cheap) · Recent developments (~5 years) made CZ

available in sufficiently high purity (resistivity) to allow for use as particle detector.

Czochralski Growth

Czochralski silicon

Epitaxial silicon· Chemical-Vapor Deposition (CVD) of Silicon· CZ silicon substrate used in-diffusion of oxygen· growth rate about 1mm/min· excellent homogeneity of resistivity· up to 150 mm thick layers produced (thicker is possible)· price depending on thickness of epi-layer but not

extending ~ 3 x price of FZ wafer

-29-

Page 27: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010

0 10 20 30 40 50 60 70 80 90 100Depth [mm]

51016

51017

51018

5

O-co

ncen

tratio

n [1

/cm3 ]

SIMS 25 mm SIMS 25 mm

25 m

u25

mu

SIMS 50 mmSIMS 50 mm

50 m

u50

mu

SIMS 75 mmSIMS 75 mm

75 m

u75

mu

simulation 25 mmsimulation 25 mmsimulation 50 mmsimulation 50 mmsimulation 75mmsimulation 75mm

Oxygen concentration in FZ, CZ and EPI

DOFZ and CZ silicon Epitaxial silicon

· EPI: Oi and O2i (?) diffusion from substrate into epi-layer during production

· EPI: in-homogeneous oxygen distribution

[G.Lindström et al.,10th European Symposium on Semiconductor Detectors, 12-16 June 2005]

· DOFZ: inhomogeneous oxygen distribution· DOFZ: oxygen content increasing with time

at high temperature

EPIlayer CZ substrate

0 50 100 150 200 250depth [mm]

51016

51017

51018

O-c

once

ntra

tion

[cm

-3]

51016

51017

51018

5

DOFZ 72h/1150oCDOFZ 48h/1150oCDOFZ 24h/1150oC

Data: G.Lindstroem et al.

[M.Moll]

· CZ: high Oi (oxygen) and O2i (oxygen dimer) concentration (homogeneous)

· CZ: formation of Thermal Donors possible !

0 50 100 150 200 250depth [mm]

51016

51017

51018

O-c

once

ntra

tion

[cm

-3]

51016

51017

51018

5

Cz as grown

DOFZ 72h/1150oCDOFZ 48h/1150oCDOFZ 24h/1150oC

Data: G.Lindstroem et al.

[M.Moll]

-30-

Page 28: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010

Standard FZ, DOFZ, MCz and Cz silicon

24 GeV/c proton irradiation

· Standard FZ silicon• type inversion at ~ 21013 p/cm2

• strong Neff increase at high fluence

-31-

0 2 4 6 8 10proton fluence [1014 cm-2]

0

200

400

600

800

Vde

p (30

0mm

) [V

]0

2

4

6

8

10

12

|Nef

f| [1

012 c

m-3

]

FZ <111>FZ <111>

Page 29: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010

Standard FZ, DOFZ, MCz and Cz silicon

24 GeV/c proton irradiation

· Standard FZ silicon• type inversion at ~ 21013 p/cm2

• strong Neff increase at high fluence

· Oxygenated FZ (DOFZ)• type inversion at ~ 21013 p/cm2

• reduced Neff increase at high fluence

-32-

0 2 4 6 8 10proton fluence [1014 cm-2]

0

200

400

600

800

Vde

p (30

0mm

) [V

]0

2

4

6

8

10

12

|Nef

f| [1

012 c

m-3

]

FZ <111>FZ <111>DOFZ <111> (72 h 11500C)DOFZ <111> (72 h 11500C)

Page 30: Michael Moll  (CERN/PH)

0 2 4 6 8 10proton fluence [1014 cm-2]

0

200

400

600

800

Vde

p (30

0mm

) [V

]0

2

4

6

8

10

12

|Nef

f| [1

012 c

m-3

]

FZ <111>FZ <111>DOFZ <111> (72 h 11500C)DOFZ <111> (72 h 11500C)MCZ <100>MCZ <100> CZ <100> (TD killed) CZ <100> (TD killed)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010

Standard FZ, DOFZ, MCz and Cz silicon

24 GeV/c proton irradiation

· Standard FZ silicon• type inversion at ~ 21013 p/cm2

• strong Neff increase at high fluence

· Oxygenated FZ (DOFZ)• type inversion at ~ 21013 p/cm2

• reduced Neff increase at high fluence

· CZ silicon and MCZ silicon “no type inversion“ in the overall fluence range

(for experts: there is no “real” type inversion, a more clear understanding of the observed effects is obtained by investigating directly the internal electric field; look for: TCT, MCZ, double junction)

· Common to all materials (after hadron irradiation, not after irradiation): reverse current increase increase of trapping (electrons and holes) within ~ 20%

-33-

Page 31: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -34-

Proton vs. Neutron irradiation of oxygen rich silicon

· Epitaxial silicon (EPI-DO, 72mm, 170cm, diodes) irradiated with 23 GeV protons or reactor neutrons

0 20 40 60 80 1001 MeV neutron equivalent fluence eq [1014 cm-2]

0

100

200

300

400

500

Vde

p (30

0mm

) [V

]

23 GeV protons23 GeV protonsreactor neutronsreactor neutrons

Particle:Particle:

[Data: I.Pintilie et al., NIMA 611 (2009) 52]

[M.Moll][M.Moll]

0 20 40 60 80 1001 MeV neutron equivalent fluence eq [1014 cm-2]

-50

0

50

100

Nef

f [10

12 c

m-3

] 23 GeV protons23 GeV protonsreactor neutronsreactor neutrons

Particle:Particle:

[Data: I.Pintilie et al., NIMA 611 (2009) 52]

[M.Moll][M.Moll]

positive space chargepositive space charge

negative space chargenegative space charge

2

0

0 dNqV effdep

absolute effective space charge densitydepletion voltage

Page 32: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -35-

Why is proton and neutron damage different?

particle

SiS Vacancy + Interstitial

point defects (V-O, C-O, .. )

point defects and clusters of defects

EK>25 eV

EK > 5 keV

V

I

10 MeV protons 24 GeV/c protons 1 MeV neutronsSimulation:

Initial distribution of vacancies in (1mm)3

after 1014 particles/cm2

[Mika Huhtinen NIMA 491(2002) 194]

· A ‘simplified’ explanation for the ‘compensation effects’· Defect clusters produce predominantly negative space charge· Point defects produce predominantly positive space charge (in ‘oxygen rich’ silicon)

negative

positive

For the experts: Note the NIEL violation

Page 33: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -36-

Mixed irradiations – Change of Neff

· Exposure of FZ & MCZ silicon sensors to ‘mixed’ irradiations· First step: Irradiation with protons or pions · Second step: Irradiation with neutrons

FZ: Accumulation of damage MCZ: Compensation of damage

[G.Kramberger et al., “Performance of silicon pad detectors after mixed irradiations with neutrons and fast charged hadrons”, NIMA 609 (2009) 142-148]

Page 34: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -37-

Advantage of non-inverting materialp-in-n detectors (schematic figures!)

Fully depleted detector(non – irradiated):

Page 35: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -38-

inverted to “p-type”, under-depleted:• Charge spread – degraded resolution• Charge loss – reduced CCE

Advantage of non-inverting materialp-in-n detectors (schematic figures!)

Fully depleted detector(non – irradiated):

heavy irradiation

inverted

non-inverted, under-depleted:• Limited loss in CCE• Less degradation with under-depletion

non inverted

Be careful, this is a very schematic explanation, reality is more complex !

Page 36: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -39-

p-on-n silicon, under-depleted:• Charge spread – degraded resolution• Charge loss – reduced CCE

p+on-n

Device engineeringp-in-n versus n-in-p (or n-in-n) detectors

n-on-p silicon, under-depleted:• Limited loss in CCE• Less degradation with under-depletion• Collect electrons (3 x faster than holes)

n+on-p

n-type silicon after high fluences:(type inverted)

p-type silicon after high fluences:(still p-type)

Comments:- Instead of n-on-p also n-on-n devices could be used

Page 37: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -40-

· Dominant junction close to n+ readout strip for FZ n-in-p· For MCZ p-in-n even more complex fields have been reported:

· no “type inversion”(SCSI) = dominant field remains at p implant· “equal double junctions” with almost symmetrical fields on both sides

Reality is more complex: Double junctions

n+on-p

p-type silicon after high fluences:(still “p-type”)

Page 38: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -41-

FZ n-in-p microstrip detectors (n, p, p - irrad)

· n-in-p microstrip p-type FZ detectors (Micron, 280 or 300mm thick, 80mm pitch, 18mm implant )· Detectors read-out with 40MHz (SCT 128A)

· CCE: ~7300e (~30%) after ~ 11016cm-2 800V

· n-in-p sensors are strongly considered for ATLAS upgrade (previously p-in-n used)

Sign

al(1

03 ele

ctro

ns) [A.Affolder, Liverpool, RD50 Workshop, June 2009]

Fluence(1014 neq/cm2)

500V

800V

Page 39: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -42-

FZ n-in-p microstrip detectors (n, p, p irrad)

· n-in-p microstrip p-type FZ detectors (Micron, 280 or 300mm thick, 80mm pitch, 18mm implant )· Detectors read-out with 40MHz (SCT 128A)

· CCE: ~7300e (~30%) after ~ 11016cm-2 800V

· n-in-p sensors are strongly considered for ATLAS upgrade (previously p-in-n used)

Sign

al(1

03 ele

ctro

ns) [A.Affolder, Liverpool, RD50 Workshop, June 2009]

Fluence(1014 neq/cm2)0 100 200 300 400 500

time at 80oC[min]

0 500 1000 1500 2000 2500time [days at 20oC]

02468

101214161820

CC

E (1

03 ele

ctro

ns)

6.8 x 1014cm-2 (proton - 800V)6.8 x 1014cm-2 (proton - 800V)

2.2 x 1015cm-2 (proton - 500 V)2.2 x 1015cm-2 (proton - 500 V)

4.7 x 1015cm-2 (proton - 700 V)4.7 x 1015cm-2 (proton - 700 V)

1.6 x 1015cm-2 (neutron - 600V)1.6 x 1015cm-2 (neutron - 600V)

M.MollM.Moll

[Data: G.Casse et al., NIMA 568 (2006) 46 and RD50 Workshops][Data: G.Casse et al., NIMA 568 (2006) 46 and RD50 Workshops]

· no reverse annealing in CCE measurementsfor neutron and proton irradiated detectors

Page 40: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -43-

1014 5 1015 5 1016

eq [cm-2]

5

10

15

20

25

Colle

cted

Cha

rge

[103 e

lect

rons

]

n-in-p (FZ), 300mm, 500V, 23GeV p [1]n-in-p (FZ), 300mm, 500V, neutrons [1,2]n-in-p (FZ), 300mm, 500V, 26MeV p [1]n-in-p (FZ), 300mm, 800V, 23GeV p [1]n-in-p (FZ), 300mm, 800V, neutrons [1,2]n-in-p (FZ), 300mm, 800V, 26MeV p [1]

n-in-p-Fz (500V)

n-in-p-Fz (800V)

n-in-p-Fz (1700V)

n-in-p (FZ), 300mm, 1700V, neutrons [2]p-in-n (FZ), 300mm, 500V, 23GeV p [1]p-in-n (FZ), 300mm, 500V, neutrons [1]

p-in-n-FZ (500V)

M.Moll - 09/2009

References:

[1] G.Casse, VERTEX 2008 (p/n-FZ, 300mm, (-30oC, 25ns)

[2] I.Mandic et al., NIMA 603 (2009) 263 (p-FZ, 300mm, -20oC to -40oC, 25ns)

[3] n/n-FZ, 285mm, (-10oC, 40ns), pixel [Rohe et al. 2005][1] 3D, double sided, 250mm columns, 300mm substrate [Pennicard 2007][2] Diamond [RD42 Collaboration][3] p/n-FZ, 300mm, (-30oC, 25ns), strip [Casse 2008]

FZ Silicon Strip Sensors

Good performance of planar sensors at high fluence

· Why do planar silicon sensors with n-strip readout give such high signals after high levels (>1015 cm-2 p/cm2) of irradiation?

· Extrapolation of charge trapping parameters obtained at lower fluences would predict much lower signal!

· Assumption: ‘Charge multiplication effects’ as even CCE > 1 was observed

500V

800V

1700V

· Which voltage can be applied?

Page 41: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -44-

· “3D” electrodes: - narrow columns along detector thickness,

- diameter: 10mm, distance: 50 - 100mm· Lateral depletion: - lower depletion voltage needed

- thicker detectors possible- fast signal- radiation hard

3D detector - concept

n-columns p-columnswafer surface

n-type substrate

p+

-- -++

++

-

-

+

300 mm

n+

p+

50 mm

---

+ +++

-- +

3D PLANARp+

Page 42: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -45-

Passivation

p+ doped

55mm pitch

50mm

300mm

n+ doped

10mm

Oxide

n+ doped

Metal

Poly 3mm

OxideMetal

50mmTEOS oxide 2mm

UBM/bump

n-type Si

Passivation

p+ doped

55mm pitch

50mm

300mm

n+ doped

10mm

Oxide

n+ doped

Metal

Poly 3mm

OxideMetal

50mmTEOS oxide 2mm

UBM/bump

n-type Si

Example: Testbeam of 3D-DDTC· DDTC – Double sided double type column

[G.F

leta

, RD

50 W

orks

hop,

Jun

e 20

07]

· Testbeam data – Example: efficiency map[M.Koehler, Freiburg Uni, RD50 Workshop June 09]

· Processing of 3D sensors is challenging,but many good devices with reasonableproduction yield produced.

· Competing e.g. for ATLAS IBL pixel sensors40V applied

~98% efficiency

back column

front column

see lecture by Manuel Lozano

Page 43: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -46-

Property Diamond GaN 4H SiC Si Eg [eV] 5.5 3.39 3.3 1.12 Ebreakdown [V/cm] 107 4·106 2.2·106 3·105 me [cm2/Vs] 1800 1000 800 1450 mh [cm2/Vs] 1200 30 115 450 vsat [cm/s] 2.2·107 - 2·107 0.8·107 e-h energy [eV] 13 8.9 7.6-8.4 3.6 e-h pairs/X0 4.4 ~2-3 4.5 10.1

Use of other semiconductor materials?

· Diamond: wider bandgap

lower leakage current less cooling needed less noise

· Signal produced by m.i.p: Diamond 36 e/mm Si 89 e/mm Si gives more charge than diamond · GaAs, SiC and GaN strong radiation damage observed

no potential material for LHC upgrade detectors (judging on the investigated material)

· Diamond (RD42) good radiation tolerance (see later) already used in LHC beam condition monitoring systems considered as potential detector material for sLHC pixel sensors

poly-CVD Diamond –16 chip ATLAS

pixel module

single crystal CVD Diamond of few cm2

Diamond sensors are heavily used in LHC Experiments for Beam Monitoring

Page 44: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -47-

Are diamond sensors radiation hard?

[V.Ryjov, CERN ESE Seminar 9.11.2009]

[RD42, LHCC Status Report, Feb. 2010] [RD42, LHCC Status Report, Feb. 2010]

· Most published results on 23 GeV protons

· 70 MeV protons 3 times more damaging than 23 GeV protons

· 25 MeV protons seem to be even more damaging (Preliminary: RD42 about to cross check the data shown to the left)

· In line with NIEL calc. for Diamond [W. de Boer et al. Phys.Status Solidi 204:3009,2007]

23 GeV p 70 MeV p

23 GeV p

70 MeV p

26 MeV p

Page 45: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -56-

Summary – Radiation Damage· Radiation Damage in Silicon Detectors

· Change of Depletion Voltage (internal electric field modifications, “type inversion”, reverse annealing, loss of active volume, …) (can be influenced by defect engineering!)

· Increase of Leakage Current (same for all silicon materials)· Increase of Charge Trapping (same for all silicon materials)

Signal to Noise ratio is quantity to watch (material + geometry + electronics)

· Microscopic defects & Damage scaling factors· Microscopic crystal defects are the origin to detector degradation.· NIEL – Hypothesis used to scale damage of different particles with different energy· Different particles produce different types of defects! (NIEL – violation!)· There has been an enormous progress

in the last 5 years in understanding defects.

· Approaches to obtain radiation tolerant devices:· Material Engineering: - explore and develop new silicon materials

(oxygenated Si)- use of other semiconductors (Diamond)

· Device Engineering: - look for other sensor geometries - 3D, thin sensors, n-in-p, n-in-n, …

Details in next lecture by Ioana Pintilie on defects.

Page 46: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -57-

Detectors for the LHC upgrade· At fluences up to 1015cm-2 (outer layers – ministrip sensors):

The change of the depletion voltage and the large area to be covered by detectors are major problems.· n-MCZ silicon detectors show good performance in mixed fields due to compensation of

charged hadron damage and neutron damage (Neff compensation) (more work needed)· p-type silicon microstrip detectors show very encouraging results

CCE 6500 e; eq=

41015 cm-2, 300mm, immunity against reverse annealing! This is presently the “most considered option” for the ATLAS SCT upgrade

· At fluences > 1015cm-2 (Innermost tracking layers – pixel sensors)The active thickness of any silicon material is significantly reduced due to trapping. Collection of electrons at electrodes essential: Use n-in-p or n-in-n detectors!· Recent results show that planar silicon sensors might still give sufficient signal,

(still some interest in epitaxial silicon and thin sensor options)· 3D detectors : looks promising, drawback: technology has to be optimized!

Many collaborations and sensor producers working on this.· Diamond has become an interesting option (Higher damage due to low energy protons?)

· Questions to be answered: · a) Can we profit from avalanche effects and control them?· b) Can we profit from compensation effects in mixed fields?· c) Can we understand detector performance on the basis of simulations

using defect parameters as input?

? ? ?

Details in lecture by

Phil Allport

Page 47: Michael Moll  (CERN/PH)

Michael Moll – MC-PAD Network Training, Ljubljana, 27.9.2010 -58-

Acknowledgements & References· Many thanks to the MC-PAD Network for the invitation to give this lecture

· Most references to particular works given on the slides

· Some additional material taken from the following presentations:· RD50 presentations: http://www.cern.ch/rd50/· Anthony Affolder: Presentations on the RD50 Workshop in June 2009 (sATLAS fluence levels)· Frank Hartmann: Presentation at the VCI conference in February 2010 (Diamond results)

· Books containing chapters about radiation damage in silicon sensors· Helmuth Spieler, “Semiconductor Detector Systems”, Oxford University Press 2005· Frank Hartmann, “Evolution of silicon sensor technology in particle physics”, Springer 2009· L.Rossi, P.Fischer, T.Rohe, N.Wermes “Pixel Detectors”, Springer, 2006· Gerhard Lutz, “Semiconductor radiation detectors”, Springer 1999

· Research collaborations and web sites· The RD50 collaboration (http://www.cern.ch/rd50 ) - Radiation Tolerant Silicon Sensors· The RD39 collaboration – Cryogenic operation of Silicon Sensors· The RD42 collaboration – Diamond detectors· ATLAS IBL, ATLAS and CMS upgrade groups