SCIPP Development of Radiation Hard Tracking Detectors · SCIPP Development of Radiation Hard Tracking Detectors Hartmut F.-W. Sadrozinski, SCIPP UC Santa Cruz, 1156 High Street,

1Hartmut F.-W. Sadrozinski, SLAC AIS Jan 9, 2008

SCIPPSCIPP

Development of Radiation Hard Tracking Detectors

Hartmut F.-W. Sadrozinski, SCIPP UC Santa Cruz, 1156 High Street, 95064 CA, USA

1) LHC Upgrade environment2) New tracker materials?3) Radiation damage in Si

a) Effectsb) Present microscopic interpretation

4) Bias Dependence of collected charge5) Thin sensors and Pixel sensors


SCIPPSCIPP

1/9/2008 2

LHC vs time: a wild guess …

L=1035

?


SCIPPSCIPP

1/9/2008 3

L=1035

Time to half Stat. Error

0

5

10

15

2008 2010 2012 2014 2016 2018 2020 2022Year

Year

s

LHCLHC + sLHC

Need to Upgrade

ID dies of radiation damage


SCIPPSCIPPFluence in Proposed sATLAS Tracker

sATLAS Fluences for 3000fb-1

1.E+12

1.E+13

1.E+14

1.E+15

1.E+16

1.E+17

0 20 40 60 80 100 120

Radius R [cm]

Flue

nce

neq/

cm2

All: RTF Formulan (5cm poly)pionproton

ATLAS Radiation Taskforce http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/RADIATION/RadiationTF_document.html

5 - 10 x LHC Fluence

Mix of n, p, πdepending on radius R

Pixels

Radial Distributionof Sensors determined by Occupancy < 2%

ShortStrips

LongStrips

Design fluences for sensors (includes 2x safety factor) :Innermost Pixel Layer: 1*1016 neq/cm2

Outert Pixel Layers: 3*1015 neq/cm2

Short strips: 1*1015 neq/cm2

Long strips: 4*1014 neq/cm2

Strips damage largely due to neutrons

Pixels Damage due to neutrons+pions


SCIPPSCIPP

42 European and Asian institutesBelarus (Minsk), Belgium (Louvain), Czech Republic (Prague

(3x)), Finland (Helsinki) , Laappeenranta), Germany (Dortmund, Erfurt, Freiburg, Hamburg, Karlsruhe, Munich), Israel (Tel Aviv),

Italy (Bari, Bologna, Florence, Padova, Perugia, Pisa, Torino, Trento), Lithuania (Vilnius), Netherlands (NIKHEF), 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)

8 North-American institutesCanada (Montreal), USA (BNL, Fermilab, New Mexico, Purdue,

Rochester, UC Santa Cruz, Syracuse)

Started in 2002, now 261 Members from 50 Institutes

Detailed member list, Progress Reports, Workshop papers etc. :

http://cern.ch/rd50

RD50 – CERN R&D Collaboration “Development of Radiation Hard Semiconductor

Devices for High Luminosity Colliders”


SCIPPSCIPP

RD50 started when the design of the LHC tracking detectors based on large-scale silicon strip and pixel sensor were frozen.

The performance of the LHC Si sensors (p-on-n FZ strips, n-on-noxigenated FZ DOFZ) was limited by radiation damage. The aim of RD50 is to develop Radiation-Hard Semiconductor Devices for High Luminosity Colliders -- like the LHC Upgrade, the Super-LHC (sLHC).

The program of RD50 was laid out and is progressing along these lines:

• Extend the radiation testing to the predicted sLHC fluences (1016, neutrons!)

• Search for alternative sensor materials to Si (more radiation-hard)

• Develop new experimental methods to help gaining insight into the radiation damage mechanism

• Understand on the microscopic level the observed radiation damage effects

• Optimize sensor geometry for radiation tolerance

• Start to transfer fabrication to commercial manufacturer in anticipation of large-scale production

RD50 : R&D Plan


SCIPPSCIPP

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 μe [cm2/Vs] 1800 1000 800 1450 μh [cm2/Vs] 1200 30 115 450 vsat [cm/s] 2.2·107 - 2·107 0.8·107 Z 6 31/7 14/6 14 εr 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 20 25 13-20

New Materials: Diamond, SiC, GaN

• Wide bandgap (3.3eV) ⇒ lower leakage current

than silicon

• Signal:Diamond 36 e/μmSiC 51 e/μmSi 89 e/μm

⇒ more charge than diamond

• Higher displacement threshold than silicon

⇒ radiation harder than silicon (?)

R&D on diamond detectors:RD42 – Collaboration

http://cern.ch/rd42/

1013 1014 1015 101610-11

1x10-9

1x10-7

1x10-5

1x10-3

Leak

age

Cur

rent

Den

sity

[A/c

m2 ]

Fluence [1MeV n/cm2]

Si 300μm; Vfd = 600V -30°C SiC 55μm +20°C pCVD diam 300μm +20°C

Partial depletion


SCIPPSCIPP

1014 1015 10160

5000

10000

15000

20000

25000

# el

ectro

ns

1 MeV n fluence [cm-2]

strips

pixels

p FZ Si 280μm; 25ns; -30°C [1] p-MCz Si 300μm;0.2-2.5μs; -30°C [2] n EPI Si 75μm; 25ns; -30°C [3] n EPI Si 150μm; 25ns; -30°C [3] sCVD Diam 770μm; 25ns; +20°C [4] pCVD Diam 300μm; 25ns; +20°C [4] n EPI SiC 55μm; 2.5μs; +20°C [5] 3D FZ Si 235μm [6]

[1] G. Casse et al. NIM A (2004)[2] M. Bruzzi et al. , STD6[3] G. Kramberger, RD50 Work. Prague 06[4] W: Adams et al. NIM A (2006)[5] F. Moscatelli RD50 Work.CERN 2005[6] C. Da Vià, STD6: Laser only

Not shown: GaN, other excotics

Plot (Sept. ‘06) outdated: much new Si data will be discussed

Comparison of measured collected charge on different radiation-hard materials and devices(M. Bruzzi, H. F.-W. Sadrozinski, A. Seiden, NIM A 579 (2007) 754–761)

New materials for Tracking Sensors?

Line to guide the eye for planar devices

At a fluence of ~1015 neq/cm2, all planar semiconductor sensors loose sensitivity:on-set of trapping!Solution for Pixels: 3-D sensors, which provide shorter drift distance

No “Wunder” material found, so investigate in depth best known and devloped material: Si.Erosion of collected charge @ Φ > ~1015 neq/cm2 : is S/N ok?


SCIPPSCIPP

Reverse Bias of junction: only thermal current generationScale : Band gap 1.12eV vs. kT = 1/40eV: huge Boltzmann factor

Cooling needed only in ultra-low noise applications.Wafer thickness 300um = 0.3%RL: 23k e-h pairs (small fluctuations)Depletion Voltage ~ thickness2 : < 100V Collection Time of e-h pairs: ~ 20nsPosition Resolution: 10-100umArea is given by wafer size: 4” & 6” => Ladders

Properties of Silicon Strip Detectors SSD

25-200 μm

300-400 μm

Alat ~ 100V

n+ implant

Al SiO2

p+ implantat ground

Depletion region. Charged particletraversing region produces ~80electron/hole pairs per micron.

Readout electronics(S/N typically > 20)

holes

Determine location of single particles on the micron scale


SCIPPSCIPPIf you still have Questions…

http://britneyspears.ac/lasers.htm

Visit your Favorite Web Site

http://britneyspears.ac/lasers.htm

SCIPPSCIPPRD50

SCIPPSCIPPRD50 Radiation Damage in Silicon Sensors

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

I. Change of effective doping concentration⇒ type inversion, higher depletion voltage, under-depletion

⇒ loss of active volume ⇒ decrease of signal, increase of noiseDifferent for neutron and proton irradiation

II. Increase of leakage current⇒ increase of shot noise, thermal runaway, power consumption…

⇒ need for cooling (Diamond has advantage, RD42)Universal if fluence is scaled according to NIEL

II. Increase of charge carrier trapping⇒ loss of charge

Different for electrons and holes

• Surface damage due to Ionizing Energy Loss (IEL- accumulation of +charges in oxide (SiO2) and the Si/SiO2 interface, saturates

⇒ interstrip capacitance, strip isolation, breakdown behavior, …

Influenced by impuritiesin Si – Defect Engineeringis possible!

~ Same for all tested Silicon materials!

• Important latent effects:Space charge sign inversion (SCSI)Annealing

Hartmut F.-W. Sadrozinski, SCIPP IEEE07


SCIPPSCIPP

particle Sis Vacancy + Interstitial

Point Defects (V-V, V-O .. ) clusters

EK > 25 eV EK > 5 keV

Frenkel pairV

I

[Mika Huhtinen NIMA 491(2002) 194]

10 MeV protons 24 GeV/c protons 1 MeV neutrons

Initial distribution of vacancies after 1014 particles/cm2

Mainly clustersMore point defects

Ec

Ev

Ei

V-O

Ci-Oi

V2-

V2-O

Clusters

SD/TD

Main radiation induced defects in Si

Point -Defects

Radiation Damage Induced Defects in Bandgap


SCIPPSCIPPRadiation Damage caused by Defects

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

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


SCIPPSCIPPRadiation Damage – Leakage Current

1011 1012 1013 1014 1015

Φeq [cm-2]10-6

10-5

10-4

10-3

10-2

10-1

ΔI /

V

[A/c

m3 ]

n-type FZ - 7 to 25 KΩcmn-type FZ - 7 KΩcmn-type FZ - 4 KΩcmn-type FZ - 3 KΩcm

n-type FZ - 780 Ωcmn-type FZ - 410 Ωcmn-type FZ - 130 Ωcmn-type FZ - 110 Ωcmn-type CZ - 140 Ωcm

p-type EPI - 2 and 4 KΩcm

p-type EPI - 380 Ωcm

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

• Damage parameter α (slope in figure)

Leakage currentper unit volume

and particle fluence

• α is constant over several orders of fluenceand independent of impurity concentration in Si

can be used for fluence measurement

eqVI

Φ⋅Δ

=α

80 min 60°C

• Leakage current decreasing in time (depending on temperature)

• Strong temperature dependence:

Consequence:Cool detectors during operation!

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

0

1

2

3

4

5

6

α(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 60°C

annealing

cmAxC 1710)03.099.3(min)80,60( −±=°α ⎟⎟

⎠

⎞⎜⎜⎝

⎛−

KTE

TTI gexp)( 2α


SCIPPSCIPPRadiation Damage – Effective Doping

Change of Depletion Voltage Vdep in high resistivity n-type FZ Si

Full depletion voltage too high to fully depletedetectors at very high fluences (>1000V @ 1015cm-2

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

10-1 100 101 102 103

Φeq [ 1012 cm-2 ]

1

510

50100

5001000

5000

Ude

p [V

] (d

= 3

00μm

)

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]

…. annealing

Short term: “Beneficial annealing”Long term: “Reverse annealing”3x stable component

- time constant depends on temperature:~ 500 years (-10°C)~ 500 days ( 20°C)~ 21 hours ( 60°C)

- Consequence: Detectors must be cooledeven when the experiment is not running!

NC

NC0

gC Φeq

NYNA

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

0

2

4

6

8

10

Δ N

eff [

1011

cm-3

]

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

2

2xNeffqV

ε= →2

2xNeffqV

ε= →


SCIPPSCIPP

Influence the defect kinetics by incorporation of impurities or defects: Oxygen

Initial idea: Incorporate Oxygen to getter radiation-induced vacancies⇒ prevent formation of Di-vacancy (V2) related deep acceptor levels

•Higher oxygen content ⇒ less negative space chargeOne possible mechanism: V2O is a deep acceptor

O VO (not harmful at RT)V

VO V2O (negative space charge)

V2O(?)

Ec

EV

VO

V2 in clusters

Defect Engineering of Silicon

0 1 2 3 4 5Φ24 GeV/c proton [1014 cm-2]

0

2

4

6

8

10

|Nef

f| [1

012cm

-3]

100

200

300

400

500

600

Vde

p [V

] (30

0 μm

)

Carbon-enriched (P503)Standard (P51)

O-diffusion 24 hours (P52)O-diffusion 48 hours (P54)O-diffusion 72 hours (P56)

Carbonated

Standard

Oxygenated

DOFZ (Diffusion Oxygenated Float Zone Silicon) RD48 NIM A465 (2001) 60 MCz (Magnetic Czochralski) has even higher O content NIM A568, 1, (2006), 83-88


SCIPPSCIPP

0,0 5,0x1014 1,0x1015 1,5x10150

200400600800

100012001400

Vfd = 7E-13 fn - 18,818

24 GeV p - n-MCz Si [1] Reactor n n-MCz Si [2]

Vfd [V

]

Fluence 1 MeV neq [cm2]0 50 100 150 200 250 300

0

1x104

2x104

3x104

24 GeV protons 2.1x1015 cm-2

Reactor neutrons 5x1014 cm-2

Ele

ctric

Fie

ld [V

/cm

]

x [μm]

“Double Junction” develops mostly from back in neutron irradiated silicon, probably due to a high generation of cluster, behaving as a source of quasi-midgap acceptors.

n-type MCz Si after 24GeV p and after reactor neutrons:

Oxygen not effective for neutrons

Electric field distribution by TCT (Ioffe-St Petesburg on SMART n-

MCz Si single pad diodes)

M. Bruzzi 6th International "Hiroshima" Symposiumk STD06, Carmel Sept. 06

Difference in p and n irradiation in n-type Si


SCIPPSCIPPCharge Trapping

Collected Charge is limited by:

Collected Charge: trapεε Q Q depo ⋅⋅=

depbiasdep VVWx /==ε

t

c

etrapττ

ε−

=

W: Detector thicknessx: Active thicknessτc : Collection timeτt : Trapping time

Partial depletion Trapping at deep levels

1/τe,h = βe,h·[Φeq/1016 cm-2]βe,h = 3

τt = 3 ns for Φ = 1015 cm-2 ,

τt = 0.3 ns for Φ = 1016 cm-2

Trapping is the ultimate limitation for the active region in all semiconductors (even for Diamond!)

Annealing favorable for electrons not favorably for holes

Bias dependence of charge collection:increase depleted region & speed up collection J. Weber, XI RD50 Workshop, CERN, Nov ‘07


SCIPPSCIPP

p-on-n silicon, under-depleted:

• Charge spread – degraded resolution

• Charge loss – reduced CCE

p+on-n

n-on-p silicon, under-depleted:

•Limited loss in CCE

•Less degradation with under-depletion

•Collect electrons (fast)

n+on-p

Be careful, this is a very schematic explanation,reality is more complex, e.g. DJ!

Device engineering: Collection at junctionp-on-n versus n-on-p (or n-on-n) SSD

n-type silicon after high fluences: p-type silicon after high fluences:


SCIPPSCIPPCharge collection efficiency CCE on p- and n-side after Inversion

Advantage of collecting on the n-side after inversion was established long time ago:

Double-sided n-type SSD

106 Ru telescope

(5.1013p/cm2)

This motivated the

n-on-n development for (ATLAS SCT), ATLAS & CMS Pixels, LHCb Velo

Paradigm Change for Upgrade Tracker:

Collect electrons, use n-on-p sensors (expect be much cheaper than n-on-n)


SCIPPSCIPPSSD Development for ATLAS Upgrade Tracker

Inst

itutio

n

P-ty

pe S

SD

Stri

p Is

olat

ion

HV

des

ign

Mod

ules

con

str.

Mec

h. S

truc

ture

s co

olin

g

Hyb

rids

,Rea

dout

Ele

ctr.

Cha

r.

Las

er C

CE

CC

E

Tra

ppin

g

Ope

r. P

aram

.

KEK x x x x x x x x x x Tsukuba x x x x x x Liverpool x x x x x x x x Lancaster x x x Glasgow x x x? x x? Sheffield x x x x Cambridge x x x QML x x Freiburg x x x x MPI x x x x Ljubljana x x x x Prague x x x Barcelona x x x x x x x Valencia x x x x x x Santa Cruz x x x BNL x x x PTI x x x x x


SCIPPSCIPP

Bias Voltage Dependence of Depletion after Neutron irradiation

The depleted sensor thickness x: can be measured two ways:

Capacitance-Voltage C-V measurement:

for un-irradiated sensor:

Collected Charge vs. Bias Q(CCE) – V measurements

for un-irradiated sensor

•All detectors studied are with n+ readout (n-on-p and n-on-n) – “electron collection”

Investigation of p-type SensorsLjubljana Univ., SCIPP - UC Santa Cruz, Univ. of Liverpool

x(V)AεC(V) = 2

2xNeffqV

ε= VC ~/1 2→

)(~)( VxVQ xVQ ~)(

– What collected charge can we expect at fixed bias 500 V for different materials?(ATLAS wants / needs to continue the use of present cables which are rated to 500V!)

– How much does charge collection depend on different readout (pads, strips, binary, analog)

– What is the most promising Si wafer material ?


SCIPPSCIPP

RD50 MICRON 6” project

MCz (n-p) MCz(n-n) Fz (n-p) Fz (n-n)WaferResitivity 1.5 Ωcm 2 kΩcm 14 kΩcm ~20 kΩcmOrientation <100> <100> <100> <100>

2552-7 2553-11 2551-7 2535-11

Neutron and Proton and Pion (Aug. ’07 ) irradiation of SSD and Diodes•Liverpool: CCE with SSD and diodes•UCSC: CCE with SSD, both p-type and n-type, C-V, i-V on SSD and Diodes•Ljubljana: CCE with Diodes, C-V, i-V on SSD and Diodes

•36 processed , 20 received•Fz (topsil) and MCz (Okmetic) wafers of p&n type material•n-on-n, n-on-p, p-on-n structures (pixels, strips, diodes)

Strips: ATLAS strips geometry 80 μm pitch (w/p~1/3)Pads: 2.5 x 2.5 mm2 , multiple guard rings

MCz wafers have very high oxygen content


SCIPPSCIPP

0

200

400

600

800

1000

1200

1400

0 2 4 6 8 10 12

Φ eq [1014 cm2]

Vfd

[V]

MCz n-n (2553-11)Fz n-n (2535-11)MCz n-p (2552-7)Fz n-p (2551-7)

C-V Measurements after Neutron Irradiation

•all detectors have negative space charge (decrease of Vfd during short term annealing)•Leakage current agrees with expectations (α~3.5-5.5∙10-17A/cm)

Defect Introduction Rate consistent with microscopic picture:•MCz (p and n type): 55 V/1014 cm-2 (gc~0.8 cm-2) – lower stable damage than seen before ?•Fz (p and n type): 125 V/1014 cm-2 (gc~1.8 cm-2) – in agreement with previous results

Charge collection (CCE) in all p-type wafers and n-type FZ should be similar at these fluences.Expect that n-type MCz should perform better – do we see this performance in CCE?Expect that MCz should be advantageous at very high fluences.

PADS

after 80 min @ 60oCG. KrambergerATLAS Tracker Upgrade Workshop, Valencia 12th-14th Dec. 2007


SCIPPSCIPP

A. Affolder ATLAS Tracker Upgrade Workshop, Valencia 12th-14th Dec. 2007

Charge Collection CCE for p-type Sensors

5x1014 n cm-2

0

5

10

15

20

25

0 200 400 600 800 1000 1200Bias Voltage (V)

Cha

rge

Col

lect

ed (k

e- )

Micron FZ (30 kohm-cm)Micron FZ (14 kohm-cm)HPK FZ (5 kohm-cm)HPK MCz (2.1 kohm-cm)Micron MCz (1.5 kohm-cm)

Φ= 5×1014 n cm-2

fluence motivated by long strip (10 cm) region of straw-man design

No effect on CCE seen for different resistivities or FZ/MCz (as expected)

13-14 ke- collected at 500V

0

5

10

15

20

25

0 200 400 600 800 1000 1200

Charge Collected (ke-)

Bias Voltage (V)

1x1015 n cm-2

Micron FZ (14 kohm-cm)HPK FZ (5 kohm-cm)HPK FZ2 (5 kohm-cm)HPK MCz (2.1 kohm-cm)Micron MCz (1.5 kohm-cm)

Φ= 1×1015 n cm-2

fluence motivated by short strip (2.5 cm) region of straw-man design

8.5-10 ke- collected at 500V


SCIPPSCIPPBias Dependence of Charge collection CCE

NN--onon--NN NN--onon--PP

Open – FZ, Solid - MCZ

•Vfd from CV (denoted by arrows) agrees well with the kink in CCE•The slope of charge increase with voltage is directly related toVfd:

•increase of Vfd can be measured by the change of slope and vice versa•Similar Vfd = similar slope -> same E field

•High resistive non-depleted bulk is well reflected in linear increase of charge – different from un-irr.•N-type FZ and all P-type show similar behavior, and N-type MCz has best depletion characteristics, as predicted from C-V

G. Kramberger

ATLAS Tracker Upgrade Workshop,

Valencia 12th-14th Dec. 2007


SCIPPSCIPP

1015cm-2

0.00E+00

2.00E+03

4.00E+03

6.00E+03

8.00E+03

1.00E+04

1.20E+04

1.40E+04

1.60E+04

1.80E+04

2.00E+04

0 200 400 600 800 1000 1200bias voltage [V]

Cha

rge

[e]

pad (peak)

strips (binary, mean, MCz n-n)

strips (binary, mean, FZ n-p)strips (analog, peak, Fz n-p)

pads (peak, Fz n-p)

Vfd~590 V measured by C-V

Big difference in the charge collection between MCz n-n and Fz n-p~14000 e vs. ~8000 e at 500V!

Fully depleted detector – one can see kink in Q-V plot

The difference in CCE is related to the difference in Vfd

Fz-p vs. MCz-n Difference due to Depletion Voltage

Vfd from CCE

80min@60oC

0

200

400

600

800

1000

1200

1400

0 2 4 6 8 10 12

Φ eq [1014 cm2]

Vfd

[V]

MCz n-n (2553-11)Fz n-n (2535-11)MCz n-p (2552-7)Fz n-p (2551-7)

G. Kramberger, ATLAS Tracker Upgrade Workshop, Valencia 12th-14th Dec. 2007


SCIPPSCIPP

Depletion Voltage from C-V vs. from Q(CCE)-VCorrelation of Vfd (CCE, CV)

0

200

400

600

800

1000

1200

0 200 400 600 800 1000 1200

Vfd (measured from CV)

Vfd

(mea

sure

d fro

m k

ink

in C

CE)

Pad detectorsstrips, binarystrips, analog

as irradiated (5e14)

5∙1014 cm-2

1∙1015 cm-2

1∙1014 cm-2

Vfd from CV underestimates the onset of saturation in CCE by max. 100-150 V!

•after Vfd the collected charge continues to increase due to shorter drift

•due to growth of depletion depth from electrode side the offset is smaller than in inverted p-on-n!

Advantage of charge collection on the junction0 100 200 300 400 500

0

100

200

300

400

500standard - oxygenated

Casse et al. Robinson et al. Buffini et al. Robinson et al. Casse et al. Lindstroem et al.

Vre

v 95%

Cha

rge

Col

l. [V

]

Vdep CV analysis [V]

Vfd from saturation in C-V and Q(CCE)-V curves( 80min @ 60oC –end of beneficial annealing )

The correlation holds for all investigated fluences in range of full depletion voltages up to 1000V!G. Kramberger

ATLAS Tracker Upgrade Workshop,

Valencia 12th-14th Dec. 2007

M. Bruzzi, H. F.-W. Sadrozinski

STD6 Carmel, Sept. 07


SCIPPSCIPP

Long term annealing of charge collection

The CCE for n-type MCz follows the annealing trend of the depletion Voltage Vfd:• initial rise (beneficial annealing) increase in collected charge by ~10% (@500V)•decrease by again 20-30% (@500V) during the reverse annealing 10000 min

Increases for p-type FZ-p by 30% and then slow decrease to the pre-anneal value

After depletion annealing of trapping visible

~30%

~10%

10000 min@60oC = 3 years RT

G. Kramberger, ATLAS Tracker Upgrade Workshop, Valencia 12th-14th Dec. 2007


SCIPPSCIPPAnnealing of p-type FZ and DOFZ sensors

(p irradiated)

• p-type strip detector (280μm) irradiated with 23 GeV p

(7.5 × 1015 p/cm2 )• expected from previous CV

measurement of Vdepon n FZ:- 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 500time at 80oC[min]

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

02468

101214161820

CCE

(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]


SCIPPSCIPP

A. Affolder ATLAS Tracker Upgrade Workshop, Valencia 12th-14th Dec. 2007

CCE vs. Annealing (n irradiated)

Stable plateau of increased signal between 20-100 days (30% for this piece)

(Current decreases by ~30% over same time period)

02468

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At sLHC fluences for p-type sensors, the entire annealing process is much less pronounced. than for n type FZ.It opens the possibility that sensors need to be cooled only during operations to control the leakage current, but not during beam-off time to prevent anti-annealing


SCIPPSCIPPMitigation of Radiation Damage in Si

• Increase depleted region at fixed bias: Wafer materials• Oxygen But neutrons• Epi But neutrons, protons• MCz But special wafer processing• -N type wafers: low resistivity , But SCSI, annealing• P-type wafers: high resistivity Need experience, good annealing

• Decrease drift distance to decrease trapping: Geometry• Thin But inferior at low / medium, no advantage at high fluences• 3-D But high capacitance, need experience

• Reduce trapping with beneficial annealing: Carrier• Collect at (main) junction n-on-p or n-on-n• Collect electrons less trapping, good trapping annealing


SCIPPSCIPP

NEG. SPACE CHARGE

POS. SPACE CHARGE

Wafer Scorecard• Materials: Neff = Neff0+g*Φeq

• For p-type: need Neff0 low: high resistivity• For n-type, need Neff0 high: low resistivity

FZ and Mcz data verified for neutron irradiation, some proton data puzzling. Will soon have proton and pion data to check the advantage of MCz.

-1.00

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FZ-p,n DOFZ-p,n MCz - n? MCz - p EpiSi-p,n

g c[1

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-1]

24 GeV Protons reactor neutrons


SCIPPSCIPP

Peak and Median Q @ 800V

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SCIPP n-on-p FZ 2551-7 n irr (prel

SCIPP n-on-p FZ n irr 1000 min ann (prel

Casse NIM A n-on-p FZ p irr

SCIPP n-on-n MCz 2553-11 n irr (prel

SCIPP n-on-n MCz n irr 1000min ann (prel

SCIPP p-on-n MCz 176-7 n irr (prel

SCIPP p-on-n MCz n irr 1000 min ann. (prel

.Casse IEEE07 n-on-p FZ n irr

SCIPP: Binary, Median, StripsCasse: Analog, Peak, Strips

N-on-p strip sensors are sufficiently radiation-hard for the sLHCNo obvious advantage for MCz over FZ. 7500 e after 1016 n/cm2!

Charge Collection in Irradiated SSD

p-on-n Mcz

Long StripsS/N > 10

Short StripsS/N > 10 n-on-p FZ


SCIPPSCIPP

N-on-p strip sensors are sufficiently radiation-hard for the sLHC ?

Charge Collection in Upgrade Strips ATLAS bias voltage is constraint to < 500V (cables!).

Peak and Median Q @ 500V

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SCIPP n-on-p FZ 2551-7 n irr (prel

SCIPP n-on-p FZ n irr annealed (prel

Casse n-on-p FZ n-irr. IEEE07

Ljubljana n-on-p FZ pad 2551-7 n irr (prel

Ljubljana n-on-p Mcz pad 2552-7 n irr(prel


SCIPP n-on-n MCz 2553-11 n irr (prel

SCIPP n-on-n MCz n irr ann. 80 min (prel

SCIPP n-on-n MCz n irr ann. 1000 min (prel

.Casse IEEE07 n-onp nirrLong StripsS/N = 10

Short StripsS/N = 10

SCIPP: Binary, Median, StripsCasse: Analog, Peak, StripsLjubljana: Analog, Peak, Pads


SCIPPSCIPP

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Efficiency Median Q Fluence

Long strips efficient at 1fC threshold

Efficiency vs. Collected Charge • For tracking sensors with

binary readout, the figure of merit is not the collected charge, but the efficiency.

• 100% efficiency is reached at a signal-to-noise ratio of S/N ≈ 10, S/Thr > 2.5

• For long strips (5e14 cm-2) with a signal of about 14ke, the usual threshold of 1fC = 6400 e can be used.


SCIPPSCIPP

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Short strips efficient if threshold can be lowered

Efficiency vs. Collected Charge

• For short strips (1e15 cm-

2) with a signal of about 8ke, the efficiency at 500V is only 70%.

• The threshold needs to be reduced to about 4500 e, i.e. electronics must be designed for a noise of ~700e.


SCIPPSCIPP

Thin and Pixel sensors


SCIPPSCIPPThin Sensors

300um + 200um 400V

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Simulations 2005:(M. Bruzzi, H. F.-W. Sadrozinski, A. Seiden, NIM A 579 (2007) 754–761)

Measurements 2007(G. Casse, Affolder, P.P. Allport, IEEE 07, N07-06)

Benefits of thin sensors:Can be fully depleted at high fluences (important for p-on-n sensors ?):Thin detectors allow very high effective doping densities in n-type detectors and thus “delay” of inversion to very high fluences. Vbias = q*Neff/(2ε)*x2

Less material (sensor only a fraction of the total material budget)Disadvantage of thin sensors:Signal lower for much of the operationThick sensor can be operated under-depleted (current is lower)


SCIPPSCIPP

• Planar electrodes replaced by columns through the wafer- diameter: 10mm, distance: 50 - 100mm

• De-couple deposit and charge collection

3D Detector - Concept n-columns p-columns wafer surface

P- or n-type substrateIntroduced by: S.I. Parker et al., NIMA 395 (1997) 328

p+

------

++++

++++

--

--

++

300

μm

n+

p+

50 μm

------

++ ++++++

----

++

3D PLANARp+

No proton irradiation

No radiation hardness with MIP (only laser)

• Lateral depletion assures Radiation Hardness– Low depletion voltage: Increase active thickness– Short drift distance and fast signal: Decrease

trapping


SCIPPSCIPP

growth

substrate

Grain size: ~100-150μm

• large band gap and strong atomic bonds promise fantastic radiation hardness

• low leakage current and low capacitance both give low noise• Ionization energy is high: MIP≈ 2x less signal for same X0 of SI

–Diamond: ∼13.9ke- in 361 μm (140 enc; bare threshold ~1500e)–SI: ∼22.5 ke- in 282 μm

• Grain-boundaries, dislocations, and defects can influence carrier lifetime, mobility, charge collection distance and position resolution

• Available Size ~2 x 6 cm2 (12cm diameter wafer; ~2mm thick)

pCVD Diamond

ATLAS pixel module

hitmap

H.Kagan

M. Mikuz ATLAS Tracker Upgrade Workshop, Valencia 12th-14th Dec. 2007


SCIPPSCIPPPixel Sensor Efficiency: Signal/Threshold

Threshold “bare” threshold is set as low as the system permitsBare Threshold ~ 1500e for Diamond

~ 2500e for Silicon(why does it not scale with noise?)

In order to fit the hit into the beam crossing of 20 ns, the signal has to exceed the threshold by the “overdrive”.In-time Threshold = bare threshold + overdrive

Sensor Threshold [e] Bare Overdrive In-time

Required Signal [e]

Si planar 2500 1300 3800 7600

Si 3D 2500 (?) 1800 4300 8600

Diamond 1500 800 2300 4600

Signal needs to be > 2x In-time Threshold:

Overdrive scales with noise

Signal is Landau (here Diamond):

Efficiency requires Signal/Threshold > 2

O. Roehne ATLAS Tracker Upgrade Workshop, Valencia 12th-14th Dec. 2007

C. daVia ATLAS B-Layer Workshop, CERN Sep. 28-30. 2007


SCIPPSCIPP

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.Casse IEEE07 n-on-p FZ n irr

Diamond

3D 2E

Pixel S/N -> Signal/Threshold

Need comparisons of CCE(V) with (m.i.p.) and S/N after 1016neq/cm2 of protonsPreliminary results show marginal performance for 3D.Need to optimize FEE?

Diamond4600e

Planar Si7600e

3D8600e

Planar n-on-p adequate for all but innermost Pixel Layer

Planar (protons!) and diamond are not adequate for innermost Pixel Layer


SCIPPSCIPP

RD50 provided the bases for understanding the use of tracking detectors at the LHC upgrade. No magic new semiconductor tracking material found.

Paradigm change in Si at fluence of about 1015 neq/cm2:At lower fluences depletion of sensors important. MCz seems to be favored, at least for neutronsStrong annealing in n-type FZ, little annealing in p-type and n-type MCz.Collect electrons in n-on-p (cheaper than n-on-n) because of high mobility.Collected charge almost independent of wafer type except n-type FZ.At higher fluences trapping dominatesbut high resistivity MCz p-type could have depletion advantage at very high fluences.

A straw-man tracker layout at the sLHC looks like this: Planar n-on-p sensors with long and short strips at large and medium radius and the outer pixels.At small radii, the pixel sensors might need to be made from 3D sensors, but we need more high fluence proton data with planar p-type MCz.

Conclusions


SCIPPSCIPP

Thanks to

the foundries and institutes who supplied sensors,

RD50 collaborators in Ljubljana, Liverpool, Louvain, CERN, Karlsruhe, PSI, UCSC for carrying out the irradiations, and analyzing the data.

the many students who spend their evenings and nights taking and analyzing the data.

Acknowledgments


SCIPPSCIPP

ATLAS Tracker Upgrade Workshop Valencia Dec 11-14 2007

http://indico.cern.ch/conferenceTimeTable.py?confId=21398

ATLAS Upgrade Website

http://indico.cern.ch/categoryDisplay.py?categId=350

RD50 Website

http://rd50.web.cern.ch/rd50/

LHC Machine Operations Website

http://lhc-operation.web.cern.ch/lhc-operation/

References

http://indico.cern.ch/conferenceTimeTable.py?confId=21398


SCIPPSCIPPTo keep ATLAS running more than 10 years the inner tracker will have to go ... (Current tracker designed to survive up to 730 fb-1 ≈ 10Mrad in strip detectors)For the luminosity-upgrade the new tracker will have to cope with:

• much higher occupancy levels 3000 fb-1 • much higher dose rates ~ 300Mrad• same performnace

To build a new tracker for 2015, major R&D program already needed.Steering group (lead Nigel Hessey) and several working groups. Formal proposal submittal structure.

Timescales:• R&D leading into a full tracker Technical Design Report (TDR) in 2010• Construction phase to start immediately TDR completed and approved.

The intermediate radius barrels are expected to consist of modules arranged in rows with common cooling, power, clocking and cooling.The TDR will require prototype super-modules/staves (complete module rows as an integrated structure) to be assembled and fully evaluatedAll components will need to demonstrate unprecedented radiation hardness

ATLAS Inner Detector Replacement


SCIPPSCIPP

1/9/2008 48

many strategies to follow up, new techniques, many unknown parameters …. needs first beam

25 ns vrs 50 ns …. 12ns,75ns gone!

LHC nominal and ultimate L strategy -> new large aperture triplet

Early separation scheme, magnets inside the detector … small crossing angle

Beam-beam effects : unclear can be tolerated, wait for LHC beam

Luminosity leveling : new …. more fill lifetime, less peak luminosity

Crab cavities,… : new magic technology, need substantial R&D

ATLAS message is always the same:

we prefer more constant luminosity, less we prefer more constant luminosity, less pile up at the start of the run, higher luminosity at the pile up at the start of the run, higher luminosity at the endend


SCIPPSCIPP

Pixels (50 μm × 400 μm): 3 barrels, 2×3 disks 5cm < r < 15cm• Pattern recognition in high occupancy region• Impact parameter resolution (in 3d)Radiation hard technology: n+-in-n Silicon technology, operated at -6°CStrips (80 μm × 12 cm) (small stereo angle): “SCT” 4 barrels, 2×9 disks• pattern recognition 30cm < r < 51cm• momentum resolutionp-strips in n-type silicon, operated at -7°CTRT 4mm diameter straw drift tubes: barrel + wheels 55cm < r < 105cm• Additional pattern recognition by having many hits (~36)• Standalone electron id. from transition radiation

Current Inner Tracker Layout

r=30cm

0.61%

Mean Occupancy in Innermost Layer of Current SCT

Pixels: 1.8 m2, ~80M channels

SCT: 61 m2, ~6.3M channels

TRT straws: ~400k channels

ID TDR


SCIPPSCIPP

Pixels:Short (2.4 cm) μ-strips (stereo layers):Long (9.6 cm) μ-strips (stereo layers):

r=5cm, 12cm, 18cm, 27cmr=38cm, 49cm, 60cmr=75cm, 95cm

z=±40cmz=±100cmz=±190cm

Strawman 4+3+2New SLHC Layout Implications

Including disks this leads to:Pixels: 5 m2, ~300,000,000 channelsShort strips: 60 m2, ~28,000,000 channelsLong strips: 100 m2, ~15,000,000 channels

layer radius40 50 60 70 80 90 100

mea

n o

ccu

pan

cy

0.006

0.008

0.01

0.012

0.014

0.016

mean occupancy per layer (Muon+pileup)

1.6%

1.2%

0.8%

Short and Long Strip Occupancy Only LO MC (Pythia) . May

need to include ×2 safety factor?

J. Tseng

J. Mechnich

Documents

SCIPP Development of Radiation Hard Tracking Detectors · SCIPP Development of Radiation Hard Tracking Detectors Hartmut F.-W. Sadrozinski, SCIPP UC Santa Cruz, 1156 High Street,