Tracking Detector Material Issues for the sLHC

Hartmut F.-W. Sadrozinski

SCIPP, UC Santa Cruz, CA 95064

Hartmut F.-W. Sadrozinski, US ATLAS Upgrade Meeting Nov 10, 2005 1

Outline of the talk

- Motivation for R&D in new Detector Materials - Radiation Damage - Initial Results with p-type Detectors - Expected Performance - R&D Plan - Much of the data from RD50 http://rd50.web.cern.ch/rd50/ - In collaboration with Mara Bruzzi and Abe Seiden - Presumably this is relevant for both strips and pixels - Will not discuss 3-D detectors here

Announcement: 2nd Trento Workshop on Advanced Detector Design (focus on 3-D and p-type SSD) Feb 15. –16. 2006

Hartmut F.-W. Sadrozinski, US ATLAS Upgrade Meeting Nov 10, 2005 2

Motivation for R&D in New Detector Materials

- The search for a substitute for silicon detectors (SSD) has come up empty. - Radiation damage in SSDs impacts the cost and operation of the tracker.

- What is wrong with using the p-on-n SSD a la SCT in the upgrade?

- Type inversion requires full depletion of the detector - Anti-annealing of depletion voltage constrains thermal management - Large depletion voltages require high voltage operation - Slower collection of holes wrt to electrons increases trapping - What is wrong with using the n-on-n SSD a la ATLAS pixels in the upgrade?

- Cost: double-sided processing about 2x more expensive - Type inversion changes location of junction (but permits under-depleted operation) - Strip isolation challenging, interstrip capacitance higher?

-Potential solution: SSD on p type wafers (“poor man’s n-on-n”) - Single-sided processing, no change of junction - Strip isolation problems still persist - Need to change the wafer properties to reduce the large depletion voltages: MCz Hartmut F.-W. Sadrozinski, US ATLAS Upgrade Meeting Nov 10, 2005 3

Charge collection efficiency CCE on n-side

G. Casse, 1st RD50 Workshop, 2-4 Oct. 2002 n-side read-out after irradiation.

1060nm laser CCE(V) for the highest dose regions of an n-in-n (7.10

14 p/cm 2 ) and p-in-n (6.10

14 p/cm 2 ) irradiated LHC-b full-size prototype detector.

Hartmut F.-W. Sadrozinski, US ATLAS Upgrade Meeting Nov 10, 2005 4

Radiation Effects in Silicon Detectors

Basic effects are the same for n-type and p-type materials.

- Increase of the leakage current.

- Change in the effective doping concentration (increased depletion voltage), - Shortening of the carrier lifetimes (trapping), - Surface effects (interstrip capacitance and resistance). The consequence for the detector properties seems to vary widely.

- An important effect in radiation damage is the annealing, which can change the detector properties after the end of radiation. - The times characterizing annealing effects depend exponentially on the temperature, constraining the temperature of operating and maintaining the detectors.

Fluence dependent effects normalized to equivqlent neutrons (“neq”), We use mostly proton damage constants and increase the fluence by 1/0.62.

Hartmut F.-W. Sadrozinski, US ATLAS Upgrade Meeting Nov 10, 2005 5

Radiation Induced Microscopic Damage in Silicon

particle

Si s

Frenkel pair

Vacancy + Interstitial

E

K

> 25 eV

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

E

K

> 5 keV

clusters

V I

Influence of defects on the material and device properties

charged defects



N eff , V dep

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

Trapping (e and h)



CCE

shallow defects do not contribute at room temperature due to fast detrapping 

generation leakage current

Levels close to midgap most effective Hartmut F.-W. Sadrozinski, US ATLAS Upgrade Meeting Nov 10, 2005 6

Leakage Current

• •

Hadron irradiation

Annealing

10 -1 6 10 -2 n-type FZ - 7 to 25 K  cm n-type FZ - 7 K  cm n-type FZ - 4 K  cm n-type FZ - 3 K  cm p-type EPI - 2 and 4 K  cm 5 4

80 min 60



C

10 -3 3 10 -4 10 -5

80 min 60



C

n-type FZ - 780  cm n-type FZ - 410  cm n-type FZ - 130  cm n-type FZ - 110  cm n-type CZ - 140  cm p-type EPI - 380  cm 10 -6 10 11 10 12  eq 10 13 [cm -2 ]

Damage parameter

 10 14

(slope)

10 15 2 1 0 1 oxygen enriched silicon [O] = 2 .

10 17 cm -3 parameterisation for standard silicon [M.Moll PhD Thesis] 10 100 1000 10000 annealing time at 60 o C [minutes]

M. Moll, Thesis, 1999

α 

V

 

I



eq

•

Oxygen enriched and standard silicon show same annealing



independent of



eq and impurities



used for fluence calibration (NIEL-Hypothesis)

•

Same curve after proton and neutron irradiation

6 5 4 3 2 1 Hartmut F.-W. Sadrozinski, US ATLAS Upgrade Meeting Nov 10, 2005 7

V

dep



N eff

and N

eff

depend on storage time and temperature

Stable Damage



N C

0

( 1



e



c

 

)



[

g c



g a e



t



a

(

T

) 

g y

( 1



e



t



y

(

T

)

)]



Beneficial Annealing Reverse Annealing ShallowDonor Removal

10 80min at 60 °C 8 10 4 N a = g a  eq N Y,  = g Y  eq 6 10 3 T = 300K 4 N C 10 2 g C  eq 2 N C0 10 1 10 0 5 k  cm 1 k  cm 500  cm 0 1 10 100 1000 annealing time at 60 o C [min] 10000 G.Lindstroem et al, NIMA 426 (1999) 10 11 10 12 10 13 10 14 Fluence [cm -2 ] 10 15 M. Bruzzi, Trans. Nucl. Sci. (2000)

after inversion and annealing saturation N eff

•

Short term: “

Beneficial annealing” •

Long term: “

Reverse annealing”

time constant : ~ 500 years (-10 ° C)

 b  

~ 500 days ( 20 ° C) ~ 21 hours ( 60 ° C) 30min (80 °C)

8

Charge Collection Efficiency

Limited by: Collected Charge :   

Partial depletion Trapping at deep levels Type inversion (SCSI)

Q  Q o   dep  

trap



dep



d



trap



W e

  

c t

1/



e,h = β e,h ·



eq [cm -2 ]

2.00E+04 1.50E+04 1.00E+04 5.00E+03 Trapping T from Krasel et al Casse et al: p type Trapping T scaled by 2.4

W: Detector thickness d: Active thickness  c : Collection time  t : Trapping time

From TCT measurements within RD50: 2



t ~ 0.2*

10 16

/

, 

t ~ 0.2 ns for

  10 16

cm Luckily this is excludedby CCE measurements:

 

t ~ 0.48*

10 16

/



Fluence



[neq/cm 2 ]

3·10 14 5·10 14 1·10 15 3·10 15 0.00E+00 1.0E+14 1.0E+15 1.0E+16

Trapping time [ns]

16 9.6

4.8

1.6

Hartmut F.-W. Sadrozinski, US ATLAS Upgrade Meeting Nov 10, 2005 9

Defect Engineering of Silicon

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 (V

2

) related deep acceptor levels

•Higher oxygen content  less negative space charge One possible mechanism: V 2 O is a deep acceptor 10 O VO (not harmful at RT) 8 V VO V 2 O (negative space charge) 6 Carbon-enriched (P503) Standard (P51) O-diffusion 24 hours (P52) O-diffusion 48 hours (P54) O-diffusion 72 hours (P56)

V 2 in clusters

4 2 Carbonated 600 500 Standard 400 300 Oxygenated 200 100 E c

VO

0 0 1 2  24 GeV/c proton 3 4 [10 14 cm -2 ] 5

V 2 O(?)

E V

DOFZ (Diffusion Oxygenated Float Zone Silicon) RD48 NIM A465 (2001) 60

Hartmut F.-W. Sadrozinski, US ATLAS Upgrade Meeting Nov 10, 2005 10

Caveat with n-type DOFZ Silicon Discrepancy between CCE and CV analysis observed in n-type (diodes / SSD, ATLAS / CMS, DOFZ / Standard FZ)

500 standard - oxygenated

●

Author radiation Robinson et al., NIM A 461 (2001) 3x10 14 24GeV p/cm 2 Exp. material ATLAS Oxygen. + standard 400 300 200 100 0 0 100 200 300 Casse et al.

Robinson et al.

Buffini et al.

Robinson et al.

Casse et al.

Lindstroem et al.

400 V dep CV analysis [V] 500

■

♦

▲

Casse et al., NIM A 466 (2001) 3-4x10 14 24GeV p/cm 2 ATLAS Oxygen. + standard Lindström et al., NIM A 466 (2001) Buffini et al., NIM A (2001) 1.65x10

24GeV p/cm 2 1.1x10

14 1MeV n/cm 2 14 ROSE CMS

To maximise CCE it is necessary to overdeplete the detector up to :

V

bias

~ 2 V

dep

Hartmut F.-W. Sadrozinski, US ATLAS Upgrade Meeting Nov 10, 2005 Oxygen. <100> Standard <111> 11

Caveat: The beneficial effect of oxygen in proton irradiated silicon microstrip almost disappear in CCE measurements

G.Casse et al. NIM A 466 (2001) 335-344

ATLAS microstrip CCE analysis after irradiation with 3

x

10

14

p/cm

2 Hartmut F.-W. Sadrozinski, US ATLAS Upgrade Meeting Nov 10, 2005 12

CCE n-in-p microstrip detectors



Miniature n-in-p microstrip detectors (280



m thick) produced by CNM-Barcelona designed Liverpool.

by using the a mask-set University of



Detectors read-out with a SCT128A LHC speed (40MHz) chip



Material: standard oxygenated (DOFZ) p-type p-type and



Irradiation: 24GeV protons up to 3 10 15 p cm -2 (standard) and 7.5 10 15 p cm -2 (oxygenated) CCE ~ 60% after 3 10 15 p cm -2 900V( standard p-type) at CCE ~ 30% after 7.5 10 15 p cm -2 900V (oxygenated p-type) G. Casse et al., Nucl. Inst Meth A 518 (2004) 340-342. At the highest fluence Q~6500e at V bias =900V. Corresponds to: ccd~90µm, trapping times 2.4 x larger than previously measured.

Hartmut F.-W. Sadrozinski, US ATLAS Upgrade Meeting Nov 10, 2005 13

Recent n-in-p Results

Important to check that there are no unpleasant surprises during annealing.

Minutes at 80 o C converted to days at 20 o C using acceleration factor of 7430 (M. Moll).

G. Casse et

al

., 6 th RD50 Workshop, Helsinki June 2-4 2005 http://rd50.web.cern.ch/rd50/6th-workshop/.

2 1 0 6 5 4 3 0 0 200 400 600 800 1000 1200

Days @ 20 o C Detector after 7.5× 10 15 p/cm 2 showing pulse height distribution at 750V after annealing. (Landau + Gaussian fit)

8 6 4 2 0 20 18 16 14 12 10 0 900 800 700 600 500 400 300 200 100 0 100 500 300 V 500 V 800 V 300 V 500 V 800 V 200 1000 300 400

Minutes @ 80 o C

1500 2000

Days @ 20 o C Detector with 1.1× 10 15 p/cm 2

Hartmut F.-W. Sadrozinski, US ATLAS Upgrade Meeting Nov 10, 2005 14

Expected Performance for p-type SSD

Details in : “Operation of Short-Strip Silicon Detectors based on p-type Wafers in the ATLAS Upgrade ID M. Bruzzi, H.F.-W. Sadrozinski, A. Seiden, SCIPP 05/09 Conservative Assumptions:  p = 2.5·10 -17 A/cm (only partial anneal) C V s total 2 dep Noise = 2 pF/cm = 160V + b* (= 600V @ = (A + B·C) 2 ( with 2.7* 10 -13  = 10 16 V/cm neq/ cm 2 ) 2 ) (no anneal) + (2·I·  s )/q A = 500, B = 60

S/N for Short Strips for different bias voltages:

35.0

30.0

25.0

20.0

15.0

10.0

5.0

300um, -20deg, 400V 300um, -20deg, 600V 300um, -20deg, 800V 0.0

1.E+12 1.E+13 1.E+14 1.E+15 1.E+16

Fluence [neq/cm 2 ]

35.0

30.0

25.0

20.0

15.0

10.0

5.0

200um, -20deg, 400V 200um, -20deg, 600V 200um, -20deg, 800V 0.0

1.E+12 1.E+13 1.E+14 1.E+15 1.E+16

Fluence [neq/cm 2 ] no need for thin detectors, unless n-type: depletion vs. trapping 600V seems to be sufficient

Hartmut F.-W. Sadrozinski, US ATLAS Upgrade Meeting Nov 10, 2005 15

Expected Performance for p-type SSD, cont.

Noise for SiGe Frontend (see talk by Alex Grillo) Leakage current important: Trade shaping time against operating temperature ( 20 ns & -20 o C vs. 10 ns & -10 o C )

Temperature: -10 deg C Fluence: 2.2·10 15 neq/cm 2 (short strips) 2.2·10 The maximum bias voltage is 600 V 14 neq/cm 2 (long strips)

Noise vs. Shaping time S/N vs. Temperature

1500 1000 500 c=6, f=0 c=6, f=2e14 c=6, f=2e15 c=6, f=2e15, 20deg C=15, f=0 C=15, f=2e14 20.0

15.0

10.0

C = 6, 10 ns C = 6, 15 ns C = 6, 20 ns C = 15, 10 ns C = 15, 15 ns C = 15, 20 ns 5.0

0 5 10 15 20

Shaping Time



[ns]

25 0.0

-35 -30 -25 -20 -15

Temperature [ o C]

-10 -5 Hartmut F.-W. Sadrozinski, US ATLAS Upgrade Meeting Nov 10, 2005 16

Expected Performance for p-type SSD, cont

.

Heat Generation in 300



m SSD

I

(

T

) 

I

(

T

0  ) 

T T

0   2 exp(

E b

2

K

  1

T

0  1

T

0   ) Temperature [ o C]  (T)/  (20) 20 1 0 0.197 -10 -20 0.0797 0.0300 -30 0.0104

Only from active volume

I Volume

    Generated Heat Flux [W/cm 2 ]  neq Vbias [V] w [  m] T = 20°C T=-10°C T=-20°C T=-30°C 3E+14 290 300 1.05E-01 6.75E-03 2.35E-03 7.54E-04 5E+14 1E+15 1E+15 376 400 591 300 247 300 2.27E-01 1.46E-02 5.09E-03 1.63E-03 3.98E-01 2.55E-02 8.90E-03 2.85E-03 7.15E-01 4.59E-02 1.60E-02 5.13E-03 3E+15 3E+15 3E+15 400 600 800 157 193 223 7.62E-01 4.89E-02 1.70E-02 5.46E-03 1.40E+00 8.99E-02 3.13E-02 1.00E-02 2.16E+00 1.38E-01 4.82E-02 1.55E-02 Hartmut F.-W. Sadrozinski, US ATLAS Upgrade Meeting Nov 10, 2005 17

An Italian network within RD50: INFN SMART

n-type and p-type detectors processed at IRST- Trento

Pad detector Test2 Edge structures Test1 Square MG-diodes Microstrip detectors Inter strip Capacitance test Round MG-diodes Wafers Split in:

1.

2.

Materials Process

: :

(Fz,MCz,Cz,EPI)

3.

Standard Low T steps T.D.K.

Isolation

:

Low Dose p-spray High Dose p-spray

Hartmut F.-W. Sadrozinski, US ATLAS Upgrade Meeting Nov 10, 2005 18

SMART News: Annealing behaviour of MCz Si n- and p-type

V dep variation with fluence (protons) and annealing time (C-V): Beneficial annealing of the depletion voltage: 14 days at RT, 20 min at 60 Reverse o C. 3 min at 80 (“anti-”) annealing starts o C.

in p-type MCz: at 10 min at 80 o C , 250 min (=4 hrs) at 60 in p-type FZ : >> 20,000 min (14 days) at RT, at 20 min at 60 o C in n-type FZ: at 120 min at 60 o C .

o C , G. Segneri et al. Submitted to NIM A, presented at PSD 7, Liverpool , Sept. 2005 A.

Macchiolo et al. Submitted to NIM A, presented at PSD 7, Liverpool , Sept. 2005 Hartmut F.-W. Sadrozinski, US ATLAS Upgrade Meeting Nov 10, 2005 19

SMART News: Annealing behaviour of n- type MCz Si

(is n-type MCz inverted?) N-type M. Scaringella et al. presented at Large Scale Applications and Radiation Hardness Florence, Oct. 2005 A.

Macchiolo et al. Submitted to NIM A, Hartmut F.-W. Sadrozinski, US ATLAS Upgrade Meeting Nov 10, 2005 20 presented at PSD 7, Liverpool , Sept. 2005

Inter-strip Capacitance

One of the most important sensor parameters contributing to the S/N ratio Depends on the width/pitch ratio of the strips and on the strip isolation technique (p-stops, p-spray).

Observe large bias dependence on p-type detectors, due to accumulation layer. 2.0E-11 1.8E-11 1.6E-11 1.4E-11 1.2E-11 1.0E-11 8.0E-12 6.0E-12 4.0E-12 2.0E-12 0.0E+00 0

Interstrip Capacitance

100

100



m pitch

14-5 250krad Pre-rad

Cint = 1.5 pF/cm

400 500 SMART 14-5 p-type FZ low-dose spray w/p = 15/50 V dep = 85 V

100



m pitch

J. Wray, D. Larson, SCIPP)

Irradiation with 60 Co reduces the bias dependence, as expected.

Hartmut F.-W. Sadrozinski, US ATLAS Upgrade Meeting Nov 10, 2005 21



Status

Radiation hard materials for tracker detectors at SuperLHC are under study by the CERN RD50 collaboration. Fluence range to be covered with optimised S/N is in the range 10 14 -10 16 cm -2 . At fluences up to 10 and the large area to be covered by detectors is the major problem.

15 cm -2 (Mid and Outer layers of a SLHC detector) the change of the depletion voltage  High resistivity MCz n-type and p-type Si are most promising materials.

 Quite encouragingly,

at higher fluences results seem better than first extrapolated from lower fluence :

longer trapping times ( p-FZ, p-DOFZ) delayed and reduced reverse annealing ( MCz SMART) sublinear growth of the V dep with fluence ( p - MCz&FZ) delayed/supressed type inversion ( p- MCZ&FZ, MCz n- protons)  The annealing behavior in both n- and p-type SSD needs to be verified with CCE measurements.

Hartmut F.-W. Sadrozinski, US ATLAS Upgrade Meeting Nov 10, 2005 22

R&D Plan:

- Need to confirm findings of C-V measurements - Fabricate SSD on MCz wafers, both p- and n-type.

- Optimize isolation on n-side.

- Measure charge collection efficiency (CCE) on SSD, pre-rad, post-rad, during anneal.

- Measure noise on SSD pre-rad, post-rad, during anneal.

Un-irradiated SMART SSD

Hartmut F.-W. Sadrozinski, US ATLAS Upgrade Meeting Nov 10, 2005 23

R&D Plan

Submission of 6” fabrication run within RD50 Goals: -a.

-b.

-c.

-d.

P-type isolation study Geometry dependence Charge collection studies Noise studies -e.

-f.

-g.

System studies: cooling, high bias voltage operation, Different materials (MCz, FZ, DOFZ) Thickness Wafer MCz DOFZ FZ MCz Fz MCz bulk # p p p n n n 7 5 5 3 2 3 Thickness [um] SSD 300 300 300 300 300 200 n-on-p n-on-p n-on-p p-on-n +n-on-n (no backside p-on-n +n-on-n (no backside p-on-n +n-on-n (no backside Hartmut F.-W. Sadrozinski, US ATLAS Upgrade Meeting Nov 10, 2005 24