radiation tolerant semiconductor sensors for tracking detectors michael moll cern- ph-dt2 - geneva -...

Radiation Tolerant Semiconductor Sensorsfor Tracking Detectors

Michael MollMichael Moll

CERN- PH-DT2 - Geneva - SwitzerlandCERN- PH-DT2 - Geneva - Switzerland

TIME05 – Workshop on Tracking In high Multiplicity Environments

October 3-7, Zürich, Switzerland

on behalf of the

- CERN-RD50 project –

http://www.cern.ch/rd50http://www.cern.ch/rd50

Michael Moll – TIME05, October 7, 2005 -2-

RD50 Outline

Motivation to develop radiation harder detectors: Super-LHC

Introduction to the RD50 collaboration

Radiation Damage in Silicon Detectors (A review in 5 slides) Macroscopic damage (changes in detector properties)

Approaches to obtain radiation hard sensors Material Engineering Device Engineering

Summary


RD50 Main motivations for R&D on Radiation Tolerant Detectors: Super - LHC

• LHC upgrade LHC (2007), L = 1034cm-2s-1

(r=4cm) ~ 3·1015cm-2

Super-LHC (2015 ?), L = 1035cm-2s-1

(r=4cm) ~ 1.6·1016cm-2

• LHC (Replacement of components) e.g. - LHCb Velo detectors (~2010) - ATLAS Pixel B-layer (~2012)

• Linear collider experiments (generic R&D)Deep understanding of radiation damage will be fruitful for linear collider experiments where high doses of e, will play a significant role.

5 years

2500 fb-1

10 years

500 fb-1

5

0 10 20 30 40 50 60

r [cm]

1013

5

1014

5

1015

5

1016

eq

[cm

-2]

total fluence eqtotal fluence eq

neutrons eq

pions eq

other charged

SUPER - LHC (5 years, 2500 fb-1)

hadrons eqATLAS SCT - barrelATLAS Pixel

Pixel (?) Ministrip (?)

Macropixel (?)

(microstrip detectors)

[M.Moll, simplified, scaled from ATLAS TDR]


RD50 The CERN RD50 Collaboration http://www.cern.ch/rd50

Collaboration formed in November 2001 Experiment approved as RD50 by CERN in June 2002 Main objective:

Presently 251 members from 51 institutes

Development of ultra-radiation hard semiconductor detectors for the luminosity upgrade of the LHC to 1035 cm-2s-1 (“Super-LHC”).

Challenges: - Radiation hardness up to 1016 cm-2 required - Fast signal collection (Going from 25ns to 10 ns bunch crossing ?)

- Low mass (reducing multiple scattering close to interaction point)- Cost effectiveness (big surfaces have to be covered with detectors!)

RD50: Development of Radiation Hard Semiconductor Devices for High Luminosity Colliders

Belarus (Minsk), Belgium (Louvain), Canada (Montreal), Czech Republic (Prague (3x)), Finland (Helsinki, Lappeenranta), Germany (Berlin, Dortmund, Erfurt, Freiburg, Hamburg, Karlsruhe), Israel (Tel Aviv), Italy

(Bari, Bologna, Florence, Padova, Perugia, Pisa, Trento, Turin), Lithuania (Vilnius), Norway (Oslo (2x)), Poland (Warsaw(2x)), Romania (Bucharest (2x)), Russia (Moscow), St.Petersburg), Slovenia (Ljubljana), Spain

(Barcelona, Valencia), Switzerland (CERN, PSI), Ukraine (Kiev), United Kingdom (Exeter, Glasgow, Lancaster, Liverpool, Sheffield, University of Surrey), USA (Fermilab, Purdue University,

Rochester University, SCIPP Santa Cruz, Syracuse University, BNL, University of New Mexico)


RD50 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 !

A reviewin 5 slides


RD50Radiation Damage – I. Effective doping concentration

Change of Depletion Voltage Vdep (Neff)

…. with particle fluence:

before inversion

after inversion

n+ p+ n+

• “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 =

300

m)

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]

p+

Review(2/5)

(simplified, see talk of Gianluigi and Vincenzo)


RD50 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

eqV

I

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

-17 A

/cm

]

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

EI

B

g

2exp

Review(3/5)


RD50

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

trap

ping

tim

e 1

/ [n

s-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

trap

ping

tim

e 1

/ [n

s-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. Trapping Review(4/5)


RD50 Impact on Detector: Decrease of CCE - Loss of signal and increase of noise -

Two basic mechanisms reduce collectable charge: trapping of electrons and holes (depending on drift and shaping time !) under-depletion (depending on detector design and geometry !)

Example: ATLAS microstrip detectors + fast electronics (25ns)

n-in-n versus p-in-n - same material, ~ same fluence- over-depletion needed

0 100 200 300 400 500 600

bias [volts]

0.20

0.40

0.60

0.80

1.00

CC

E (

arb.

uni

ts)

n-in-n (7.1014 23 GeV p/cm2)

n-in-n

p-in-n (6.1014 23 GeV p/cm2)

p-in-n

Laser (1064nm) measurements

[M.Moll: Data: P.Allport et al. NIMA 513 (2003) 84]

p-in-n : oxygenated versus standard FZ- beta source- 20% charge loss after 5x1014 p/cm2 (23 GeV)

0 1 2 3 4 5p [1014 cm-2]

0

20

40

60

80

100

Q/Q

0 [%

]

oxygenatedstandard

max collected charge (overdepletion)

collected at depletion voltage

M.Moll [Data: P.Allport et all, NIMA 501 (2003) 146]

Review(5/5)


RD50 Approaches to develop radiation harder tracking detectors

Defect Engineering of Silicon Understanding radiation damage

• Macroscopic effects and Microscopic defects• Simulation of defect properties & kinetics• Irradiation with different particles & energies

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 3D and Semi 3D detectors Stripixels Cost effective detectors Simulation of highly irradiated detectors Monolithic devices

Scientific strategies:

I. Material engineering

II. Device engineering

III. Change of detectoroperational conditions

CERN-RD39“Cryogenic Tracking Detectors”

Talks this WorkshopGianluigi Casse

Vincenzo Chiochia


RD50 Outline




Approaches to obtain radiation hard sensors

Material Engineering Device Engineering

Summary


RD50

Property Diamond GaN 4H SiC Si Eg [eV] 5.5 3.39 3.26 1.12 Ebreakdown [V/cm] 107 4·106 2.2·106 3·105 e [cm2/Vs] 1800 1000 800 1450 h [cm2/Vs] 1200 30 115 450 vsat [cm/s] 2.2·107 - 2·107 0.8·107 Z 6 31/7 14/6 14 r 5.7 9.6 9.7 11.9 e-h energy [eV] 13 8.9 7.6-8.4 3.6 Density [g/cm3] 3.515 6.15 3.22 2.33 Displacem. [eV] 43 15 25 13-20

Sensor Materials: SiC and GaN

Wide bandgap (3.3eV) lower leakage current

than silicon

Signal:Diamond 36 e/mSiC 51 e/mSi 89 e/m

more charge than diamond

Higher displacement threshold than silicon

radiation harder than silicon (?)

R&D on diamond detectors:RD42 – Collaboration

http://cern.ch/rd42/

Recent review: P.J.Sellin and J.Vaitkus on behalf of RD50 “New materials for radiation hard semiconductor detectors”, submitted to NIMA


RD50 SiC: CCE after irradiation

CCE before irradiation 100 % with particles and MIPS tested on various samples 20-40m

CCE after irradiation with particles neutron irradiated samples material produced by CREE 25 m thick layer

[S.Sciortino et al., presented on the RESMDD 04 conference, in press with NIMA ]

20% CCE (α) after 7x1015 n/cm2!

35% CCE() (CCD ~6m ; ~ 300 e) after 1.4x1016 p/cm2

much less than in silicon (see later)


RD50 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


RD50 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 (~2 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 1m/min excellent homogeneity of resistivity up to 150 m thick layers produced price depending on thickness of epi-layer but not

extending ~ 3 x price of FZ wafer


RD50 Oxygen concentration in FZ, CZ and EPI

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

51016

51017

51018

5

O-c

once

ntra

tion

[1/c

m3 ]

SIMS 25 m SIMS 25 m

25 m

u25

mu

SIMS 50 mSIMS 50 m

50 m

u50

mu

SIMS 75 mSIMS 75 m

75 m

u75

mu

simulation 25 msimulation 25 msimulation 50 msimulation 50 msimulation 75msimulation 75m

Cz and DOFZ silicon Epitaxial silicon

EPI: Oi and O2i (?) diffusion from substrate into epi-layer during production EPI: in-homogeneous oxygen distribution

CZ: high Oi (oxygen) and O2i (oxygen dimer) concentration (homogeneous) CZ: formation of Thermal Donors possible !

0 50 100 150 200 250depth [m]

51016

51017

51018

5

O-c

once

ntra

tion

[cm

-3]

51016

51017

51018

5

Cz as grown

DOFZ 72h/1150oCDOFZ 48h/1150oCDOFZ 24h/1150oC [G.Lindstroem et al.]

[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


RD50 Standard FZ, DOFZ, Cz and MCz Silicon

24 GeV/c proton irradiation

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

0

200

400

600

800

Vde

p [V

]0

2

4

6

8

10

12

Nef

f [10

12 c

m-3

]

CZ <100>, TD killedCZ <100>, TD killedMCZ <100>, HelsinkiMCZ <100>, HelsinkiSTFZ <111>STFZ <111>DOFZ <111>, 72 h 11500CDOFZ <111>, 72 h 11500C 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 (verified by TCT measurements)

(verified for CZ silicon by TCT measurements, preliminary result for MCZ silicon) donor generation overcompensates acceptor generation in high fluence range

Common to all materials (after hadron irradiation): reverse current increase increase of trapping (electrons and holes) within ~ 20%


RD50

0 2.1015 4.1015 6.1015 8.1015 1016

eq [cm-2]

0

5.1013

1014

Nef

f (t 0

) [c

m-3

]

0

50

100

150

Vfd

(t 0

)[V

] no

rmal

ized

to 5

0 m

50 m50 m25 m25 m

Reactor neutronsReactor neutrons

Ta = 80oCTa = 80oC

Epitaxial silicon grown by ITME Layer thickness: 25, 50, 75 m; resistivity: ~ 50 cm Oxygen: [O] 91016cm-3; Oxygen dimers (detected via IO2-defect formation)

EPI Devices – Irradiation experiments

No type inversion in the full range up to ~ 1016 p/cm2 and ~ 1016 n/cm2 (type inversion only observed during long term annealing)

Proposed explanation: introduction of shallow donors bigger than generation of deep acceptors

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

0 2.1015 4.1015 6.1015 8.1015 1016

eq [cm-2]

0

1014

2.1014

Nef

f(t0)

[cm

-3]

25 m, 80 oC25 m, 80 oC

50 m, 80 oC50 m, 80 oC

75 m, 80 oC75 m, 80 oC

23 GeV protons23 GeV protons

320V (75m)

105V (25m)

230V (50m)


RD50 Epitaxial silicon - Annealing

50 m thick silicon detectors:- Epitaxial silicon (50cm on CZ substrate, ITME & CiS) - Thin FZ silicon (4Kcm, MPI Munich, wafer bonding technique)

Thin FZ silicon: Type inverted, increase of depletion voltage with time Epitaxial silicon: No type inversion, decrease of depletion voltage with time

No need for low temperature during maintenance of SLHC detectors!

[E.Fretwurst et al.,RESMDD - October 2004]

100 101 102 103 104 105

annealing time [min]

0

50

100

150

Vfd

[V

]

EPI (ITME), 9.6.1014 p/cm2EPI (ITME), 9.6.1014 p/cm2

FZ (MPI), 1.7.1015 p/cm2FZ (MPI), 1.7.1015 p/cm2

Ta=80oCTa=80oC

[E.Fretwurst et al., Hamburg][E.Fretwurst et al., Hamburg]

0 20 40 60 80 100proton fluence [1014 cm-2]

0

50

100

150

200

250

Vde

p [V

]

0.20.40.60.81.01.21.4

|Nef

f| [1

014 c

m-3

]

EPI (ITME), 50mEPI (ITME), 50mFZ (MPI), 50mFZ (MPI), 50m

Ta=80oCTa=80oC

ta=8 minta=8 min


RD50 Damage Projection – SLHC - 50 m EPI silicon: a solution for pixels ?-

Radiation level (4cm): eqeq(year) = 3.5 (year) = 3.5 10 101515 cm cm-2 -2

SLHC-scenario: 1 year = 1 year = 100 days beam (-7100 days beam (-7C)C) 30 days maintenance (20 30 days maintenance (20C)C)

235 days no beam (-7235 days no beam (-7C or 20C or 20C)C)

G.Lindström et al.,10th European Symposium on Semiconductor Detectors, 12-16 June 2005 (Damage projection: M.Moll)

Detector withcooling when not

operated

0 365 730 1095 1460 1825time [days]

0

100

200

300

400

500

600

Vfd

[V

]

50 m cold50 m cold

50 m warm50 m warm

25 m cold25 m cold

25 m warm25 m warm

S-LHC scenarioS-LHC scenario

Detector withoutcooling when not

operated


RD50 Signal from irradiated EPI

Epitaxial silicon: CCE measured with beta particles (90Sr) 25ns shaping time proton and neutron irradiations of 50 m and 75 m epi layers

CCE (50 m) eq= 8x1015 n/cm-2,

2300 electrons

CCE (50 m): 1x1016cm-2 (24GeV/c protons) 2400 electrons

CCE (75 m) = 2x1015 n/cm-2,4500 electrons

[G.Kramberger et al.,RESMDD - October 2004]


RD50 Microscopic defects

I

I

V

V

Distribution of vacancies created by a 50 keV Si-ion

in silicon (typical recoil energy for 1 MeV neutrons):

Schematic[Van Lint 1980]

Simulation[M.Huhtinen 2001]

Defects can be electrically active (levels in the band gap) - capture and release electrons and holes from conduction and valence band

can be charged - can be generation/recombination centers - can be trapping centers

Vacancy + Interstitial

“point defects”, mobile in silicon,can react with impurities (O,C,..)

V

I

point defects and clusters of defects

particle SiS EK>25 eV

EK > 5 keV

Damage to the silicon crystal: Displacement of lattice atoms

80 nm


RD50 Impact of Defects on Detector properties

Shockley-Read-Hall statistics Shockley-Read-Hall statistics (standard theory) (standard theory)

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

Trapping (e and h) CCE

shallow defects do not contribute at room

temperature due to fast detrapping

charged defects

Neff , Vdep

e.g. donors in upper and acceptors in lower half of band

gap

generation leakage current

Levels close to midgap

most effective

enhanced generation leakage current space charge

Inter-center chargeInter-center charge transfer model transfer model

(inside clusters only)(inside clusters only)


RD50 Microscopic defects Macroscopic properties - Co60 -irradiated silicon detectors -

Comparison for effective doping concentration (left) and leakage current (right)

for two different materials

- as predicted by the microscopic measurements (open symbols)

- as deduced from CV/IV characteristics (filled symbols)

[I.Pintilie et al.,Applied Physics Letters,82, 2169, March 2003]


RD50 Characterization of microscopic defects - and proton irradiated silicon detectors -

2003: Major breakthrough on -irradiated samples For the first time macroscopic changes of the depletion voltage and leakage current

can be explained by electrical properties of measured defects !

since 2004: Big step in understanding the improved radiation tolerance of oxygen enriched and epitaxial silicon after proton irradiation

[APL, 82, 2169, March 2003]

Almost independent of oxygen content: Donor removal “Cluster damage” negative charge

Influenced by initial oxygen content: I–defect: deep acceptor level at EC-0.54eV (good candidate for the V2O defect) negative charge

Influenced by initial oxygen dimer content (?): BD-defect: bistable shallow thermal donor (formed via oxygen dimers O2i) positive charge

Levels responsible for depletion voltage changes after proton irradiation:

D-defectI-defect

[I.Pintilie, RESMDD, Oct.2004]


RD50 Outline




Approaches to obtain radiation hard sensors Material Engineering

Device Engineering

Summary


RD50

p-on-n silicon, under-depleted:

• Charge spread – degraded resolution

• Charge loss – reduced CCE

p+on-n

Device engineeringp-in-n versus n-in-n detectors

n-on-n silicon, under-depleted:

•Limited loss in CCE

•Less degradation with under-depletion

•Collect electrons (fast)

n+on-n

n-type silicon after type inversion:

(simplified, see talk of Gianluigi and Vincenzo for more details)


RD50 n-in-p microstrip detectors

Miniature n-in-p microstrip detectors (280m) Detectors read-out with LHC speed (40MHz) chip (SCT128A) Material: standard p-type and oxygenated (DOFZ) p-type Irradiation:

At the highest fluence Q~6500e at Vbias=900V

G. Casse et al., NIMA535(2004) 362

CCE ~ 60% after 3 1015 p cm-2 at 900V( standard p-type)

0 2.1015 4.1015 6.1015 8.1015 1016

fluence [cm-2]

0

5

10

15

20

25

CC

E (

103 e

lect

rons

)

24 GeV/c proton irradiation24 GeV/c proton irradiation

[Data: G.Casse et al., Liverpool, February 2004][Data: G.Casse et al., Liverpool, February 2004]

CCE ~ 30% after 7.5 1015 p cm-2 900V (oxygenated p-type)

n-in-p: - no type inversion, high electric field stays on structured side - collection of electrons


RD50 Annealing of p-type sensors

p-type strip detector (280m) irradiated with 23 GeV p (7.5 1015 p/cm2 )

expected from previous CV measurement of Vdep:- before reverse annealing:

Vdep~ 2800V

- after reverse annealing

Vdep > 12000V

no reverse annealing visible in the CCE measurement !

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

0 100 200 300 400 500

time at 80oC[min]

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

02468

101214161820

CC

E (

103 e

lect

rons

)

800 V800 V

1.1 x 1015cm-2 1.1 x 1015cm-2 500 V500 V

3.5 x 1015cm-2 (500 V)3.5 x 1015cm-2 (500 V)

7.5 x 1015cm-2 (700 V)7.5 x 1015cm-2 (700 V)

M.MollM.Moll

[Data: G.Casse et al., to be published in NIMA][Data: G.Casse et al., to be published in NIMA]


RD50 Electrodes:

narrow columns along detector thickness-“3D” diameter: 10m distance: 50 - 100m

Lateral depletion: lower depletion voltage needed thicker detectors possible fast signal

Hole processing : Dry etching, Laser drilling, Photo Electro Chemical Present aspect ratio (RD50) 30:1

Device Engineering: 3D detectors

n

n

pp

n

n n

n

(Introduced by S.I. Parker et al., NIMA 395 (1997) 328)

Production of 3D sensor matched to ATLAS Pixel readout chip under way

(S.Parker, Pixel 2005)


RD50 Electrodes:

narrow columns along detector thickness-“3D” diameter: 10m distance: 50 - 100m

Lateral depletion: lower depletion voltage needed thicker detectors possible fast signal

Hole processing : Dry etching, Laser drilling, Photo Electro Chemical Present aspect ratio (RD50) 30:1

Device Engineering: 3D detectors

n

n

pp

n

n n

n

3D detector developments within RD50:

1) Glasgow University – pn junction & Schottky contacts Irradiation tests up to 5x1014 p/cm2 and 5x1014 /cm2: Vfd = 19V (inverted); CCE drop by 25% (-particles) 2) IRST-Trento and CNM Barcelona (since 2003) CNM: Hole etching (DRIE); IRST: all further processing diffused contacts or doped polysilicon deposition ~200 micron

hole

dia

mete

r 15

m

(Introduced by S.I. Parker et al., NIMA 395 (1997) 328)


RD50 3D Detectors: New Architecture

Simplified 3D architecture n+ columns in p-type substrate, p+ backplane operation similar to standard 3D detector

Simplified process hole etching and doping only done once

no wafer bonding technology needed

Fabrication planned for end 2005

INFN/Trento funded project: collaboration between IRST, Trento and CNM Barcelona

Simulation

CCE within < 10 ns worst case shown

(hit in middle of cell)

10ns

[C. Piemonte et al., NIM A541 (2005) 441]


RD50 Example for new structures - Stripixel

1000 m

80 m

X-cell(1st metal)

Y-cell

(1st metal)

2nd MetalY-strip

2nd MetalX-strip

FWHM

for charge

diffusion

Bonding

Pad for

Y-strip

Go to

BondingPad for

X-strip

Z. Li, D. Lissauer, D. Lynn, P. O’Connor, V. Radeka

New structures: There is a multitude of concepts for new (planar and mixed planar & 3D) detector structures aiming for improved radiation tolerance or less costly detectors (see e.g. Z.Li - 6th RD50 workshop)

Example: Stripixel concept:


RD50 Summary At fluences up to 1015cm-2 (Outer layers of a SLHC detector) the change of depletion

voltage and the large area to be covered by detectors is the major problem. CZ silicon detectors could be a cost-effective radiation hard solution

(no type inversion, use p-in-n technology) p-type silicon microstrip detectors show very encouraging results:

CCE 6500 e; eq=

41015 cm-2, 300m, collection of electrons, no reverse annealing observed in CCE measurement!

At the fluence of 1016cm-2 (Innermost layer of a SLHC detector) the active thickness of any silicon material is significantly reduced due to trapping. The promising new options are: Thin/EPI detectors : drawback: radiation hard electronics for low signals needed e.g. 2300e at eq 8x1015cm-2, 50m EPI, …. thicker layers will be tested in 2005/2006 3D detectors : drawback: technology has to be optimized ….. steady progress within RD50

New Materials like SiC and GaN (not shown) have been characterized . CCE tests show that these materials are not radiation harder than silicon Info: http://cern.ch/rd50 ; 7th RD50 Workshop at CERN: 14-16 November


RD50 Spares

Spare slides


RD50 Thin/EPI detectors: Why use them ?

Simulation: T.Lari – RD50 Workshop Nov 2003

radiation tolerant semiconductor sensors for tracking detectors michael moll cern- ph-dt2 - geneva -...

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