Irradiation studies of L1 sensors for DØ 2b

Production Readiness Review of L0/L1 sensors for DØ Run IIbR. Demina, August, 2003

Irradiation studies of L1 sensors for DØ 2b

Regina DeminaUniversity of Rochester


Outline

Radiation environment and silicon sensor specs

Results on prototypes Conclusions


Requirements for silicon sensors

Main challenge for silicon sensors - radiation Depletion voltage () Leakage current () noise

Doses comparable to LHC – use their R&D

NB: Uncertainty in estimate– conservative approach: 1.5 safety margin

Flux, in 1.0E14 1MeV n equivalent per cm2

0

1

2

3

0 5 10 15 20 25

Int L, fb-1

L0

L1

L2

10 years of CMS at inner radius


Depletion voltage

fb

Spec L0, L1 Vbreak>700 VT=-10oCwith warm up periods:4 months 1st year, 1month each next year

Specification on breakdown voltage derived based on depletion voltage evolution

Spec L2-5 Vbreak>350 V

Hamburg model


Signal to noise ratio

In present design: S/N> 10 T<-10oC for L0S/N> 18 T<-5oC for L1Important to test Ileak after irradiation on prototype sensors and on test structures during production

Total Ileakin L0 sensor Corresponds to s/n>10

Noise contributions:•Capacitive load: 450+43C(pF)•Al strip resistance + analogue cables (L0)•Shot noise Ileak=I0+Ad (=3E-17A/cm)•Thermal noise in Rbias


Irradiation studies at KSU

More details in T. Bolton’s talk 10 MeV p, sweep the beam using

electrostatic deflector Anneal at 60oC for 80 min, then keep

cold Measure I at 1oC, extrapolate to 20oC

Single sided low sensors with guard band structure produced by HPK


Leakage current

Raw currents measured at T=1oC Vbreak>700V (spec)

HPK-L1 11

10

100

1000

10000

100000

1000000

10000000

0 200 400 600 800 1000

bias (V)

I (nA

)

no fluence

2.61 E11 p/cm2

5.23E11 p/cm2

3.13E+12 p/cm2

8.35E+12 p/cm2

2.79E13 p/cm2

4.74E13 p/cm2

9.35E13 p/cm2 =~19fb-1 at r=1.8 cm


I leak vs T

Measure at 1oC, extrapolate to 20oC Verify temperature dependence

I leak vs T

0.00E+00

5.00E+05

1.00E+06

1.50E+06

2.00E+06

2.50E+06

0 5 10 15 20 25

T. oC

Lea

kag

e cu

rren

t, n

A

201 V

I predicted


I leak vs

leakage currents at T=20C

1

10

100

1000

10000

100000

1E+09 1E+10 1E+11 1E+12 1E+13 1E+14 1E+15

10 MeV proton fluence 1/cm2

I_le

ak (

A/c

m3 ) HPK-L1-11

HPK-L1-12

HPK-L2-059

HPK-L2-62

testdiodes

ROSE data

I= pp

p=11.610-17 A/cm for 10 MeV p Hardness of 10MeV protons vs 1 MeV neutrons =

(10MeVp)/(1 MeVn)=11.6/4.56=2.54 (compared to3.87*)

G.P Summers et al., IEEE Trans Nucl. Sci NS-40,6(1993)1372

D. Bechevet et al. NIM A 479(2002)487At 10 MeV p Montreal

N.B.=3.0e-17A/cm for 1 MeV n, if use =3.87

Extrapolated to @-10oC Ileak=140A in L0 S/n>10


Depletion voltage vs flux

Use 1/c2 vs V to determine V depl – 30-50% uncertainty

Depletion VoltageHPK-L1-11

0

500

10001500

2000

2500

3000

0 100 200 300

bias (V)

1/C

2 (p

F-2

)

0

2.61E+11

5.23E+11

3.13E+12

8.35E+12

2.79E+13

4.74E+13

9.35E+13


V depl vs full size sensors

Parameter: C gc ga ka Eaa gy ky Eay Nc0eff

0Value: 1.13E-13

cm-2

1.9E-2 cm-1

1.81E-2 cm-2

2.4E13 s-1

1.09 eV

6.6E-2 cm-1

1.5E15 s-1

1.325 eV

1

-depletion voltage

0

50

100

150

200

250

300

350

400

450

500

1.0E+10 2.0E+13 4.0E+13 6.0E+13 8.0E+13 1.0E+14

10 MeV p fluence (1/cm2)

U_d

ep (V

)

HPK-L1-11

HPK-L1-12

Hamburg model

HPK-L2-059

HPK-L2-062

Use Hamburg model with stable damage, short and long term annealing termsFlux in protons/cm2 main effect on C (scales with 1/)


Other properties after irradiation

Cint: 3 pF(before) 6 pF (after 9.35E13 = 19 fb-1): NC=1680e(before) 1815 (after)

Interstrip Capacitance After Irradiation

0.00

2.00

4.00

6.00

8.00

10.00

12.00

100 1000 10000 100000 1000000

Frequency (Hz)

Cin

t (p

F)

Ch. 3

Ch. 5

Ch. 4

Ch. 6

Ch. 199

Ch. 201

Ch. 200

Ch. 202

Interstrip Capacitance

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

1.0E+02 1.0E+03 1.0E+04 1.0E+05 1.0E+06

Frequency (Hz)

Ci (

pF

)

Ci-Ch193

Ci-Ch194 S/n>9

No change in R poly after irradiation


Conclusions Single sided low sensor technology with guard band structure is used for the

inner layers L1 sensors produced by HPK were tested up to 9.35E13 10 MeV p/cm2

Hardness factor was found to be 2.54 instead of theoretically predicted 3.87, but in agreement with a study by Rose collaboration

Using this number and 1.5 safety factor we estimate 9.35E13 10 MeV p/cm2 to be equivalent to 19 fb-1 at r=1.8 cm (L0)

After this dose No break down was observed up to 1000 V Sensors deplete at 350-400 V in agreement with the hamburg model Based on the observed increase in leakage current we expect Ileak =140 A for L0

sensors at operating T of –10oC s/n=~10 Cint increased from 3 to 6 pF, which will lead to increase in C noise from 1680e 1815e S/n is expected to be above 9 for L0 after 20 fb-1

We believe that these sensors will perform adequately after 20 fb-1


Back up slidesdo not print


Luminosity profile for damage estimate


Fluence estimations for Run IIb

based on CDF silicon leakage current measurements in Run Ia+b

observed radial dependence ~1/r1.7

measured CDF silicon sensor leakage currents are scaled to DØ sensor geometries and temperatures to give shot noise contributions of leakage currents

for depletion voltage calculations, a 1 MeV equivalent neutron fluence is assumed:

1Mev n=2.19·1013 r[cm]-1.7 [cm-2/fb-1] (Matthew et al., CDF notes 3408 & 3937)

safety factor 1.5 applied


Performance extrapolations for Run IIb

S/N extrapolations assume noise in front end of SVX4: 450+43*C(pF) total silicon strip capacitance: 1.4pF/cm L0 analog cable assumed (and measured):

0.4pF/cm noise due to series resistance of metal traces

in silicon ~210e-700e depending on module length

noise due to finite value of bias resistor: ~250e shot noise due to increased leakage currents:

~1100e for L0 after 15fb-1 if T=-5C ~1000e for L2 (20cm long module) after 15fb-1 if T=0C


V depl vs

Test diods

testdiodes - single proton irradiation

050

100150200

250300

350400

0.00E+00 5.00E+13 1.00E+14 1.50E+14

fluence 10 Mev p/cm2

U_d

epl (

V)

Montreal

model diode

test diodes

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Irradiation studies of L1 sensors for DØ 2b