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Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors Graeme Stewart a , R. Bates a , G. Pellegrini b , G. Kramberger c , M. Milovanovic c a: University of Glasgow, School of Physics and Astronomy, Kelvin Building, University Avenue, Glasgow, G12 8QQ b: Centro Nacional de Microelectrónica, Campus Universidad Autónoma de Barcelona, Spain c: J. Stefan Institute, Jamova cesta 39, 1000 Ljubljana, Slovenia

Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

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Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors. Graeme Stewart a , R. Bates a , G. Pellegrini b , G. Kramberger c , M. Milovanovic c a: University of Glasgow, School of Physics and Astronomy, Kelvin Building, University Avenue, Glasgow, G12 8QQ - PowerPoint PPT Presentation

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Page 1: Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

Graeme Stewarta, R. Batesa, G. Pellegrinib, G. Krambergerc, M. Milovanovicc

a: University of Glasgow, School of Physics and Astronomy, Kelvin Building, University Avenue, Glasgow, G12 8QQb: Centro Nacional de Microelectrónica, Campus Universidad Autónoma de Barcelona, Spain

c: J. Stefan Institute, Jamova cesta 39, 1000 Ljubljana, Slovenia

Page 2: Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

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Contents

• Introduction– 3D Detectors– TCT Measurements

• TCT Results– Non-Irradiated Top and Edge TCTs– Irradiated Top TCTs– Annealing Effects

• Conclusions

Page 3: Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

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Introduction• Radiation hard 3D detectors are a candidate for LHC

upgrades.• Transient Current Techniques (TCTs) provide a method

for investigating electric fields in silicon detectors.

• In a TCT measurement, a short laser pulse is shone in a particular line through the detector.

• Charge and current data is collected giving new information on the operation of 3D devices.

• This can be repeated at many points across a detector’s surface to map the electric field.

Page 4: Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

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• Columns etched from opposite sides of substrate and don't pass through full thickness

• All fabrication done at CNM

• Distance between columns is 80 μm, with a 25 μm wide Aluminium strip connecting n-type columns.

• Substrate is 285 μm thick.

• 11 strips were bonded up but with readout only from the central strip.

3D Detector Design

IR Photon

Page 5: Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

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Detector

Co

ole

d s

up

po

rt

y table

Laser

Laser driver

detector HV

Peltier controller

The whole system is completely computer controlled!

z tablex table

1 GHz oscilloscope

cooling pipes

2 fast current amplifiers (2.5 GHz)

trigger line

Cu block

The system is set in dry air atmosphere!Cooling to ~-20oC

Bias T

100 ps pulse200 Hz repetition=1064 nm

G. Kramberger – 15th RD50 Meeting, 2009

TCT setup

Page 6: Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

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Top and Edge TCTs

Advantages of TCTs:• Position of e-h generation can be controlled by moving tables• The amount of injected e-h pairs can be controlled by tuning the laser

power• Easier mounting and handling• Not only charge but also induced current is measured – a lot more

information is obtained

FWHM ~8 μm

Top TCTλ = 1064nm

Edge TCTλ = 1064nm

Page 7: Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

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Top and Edge TCTs

Drawbacks of TCTs:• Applicable only for strip/pixel detectors if 1064 nm laser is used (light

must penetrate guard ring region)• Only the position perpendicular to strips can be used due to widening of

the beam! Beam is “tuned” for a particular strip • Light injection side has to be polished to have a good focus – depth

resolution• It is not possible to study charge sharing due to illumination of all strips

FWHM ~8 μm

Top TCTλ = 1064nm

Edge TCTλ = 1064nm

Page 8: Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

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Example Waveform

Faster electron peak

Slower hole peak

Reflection

Rise time of fastest peak can give velocity profile

Integration of peaks gives charge collected

Page 9: Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

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Non-Irradiated Top TCT

Map is charge collected in 20 ns after laser pulse.

Readout n-type Electrodes

Non-readout n-type Electrodes p-type Electrodes

Laser scans across surface

Unit Cell

Page 10: Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

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Non-Irradiated Top TCT

20V

20V

Page 11: Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

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Non-Irradiated Top TCT

0V 3V 6V

9V 12V 15VInter-column depletion at ~2V

Full, under-columndepletion at 40V

Page 12: Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

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Non-Irradiated Edge TCT

N-type Electrodes

P-type Electrodes

Waveforms collected at 20V

Laser scans across edge

Page 13: Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

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Non-Irradiated Edge TCT

0V 1V 2V

3V 4V 5V

6V

• Full depletion of inter-column region by 3V

• Depletion of the region beneath the electron collecting n-type columns beginning by 4V

• P-type columns not fully depleted by 6V

20V

Page 14: Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

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Irradiation and Annealing• Sample irradiated in Ljubljana facilities.• Irradiation fluence was 5x1015 1MeV Nequ cm-2.

• Sample always annealed in the setup with the Peltier element

• constant laboratory temperature: 21 oC• stable position/laser • sample temperature stabilized to less than 1°C

• Annealing at 60°C for a cumulative time of 600 minutes.• After each annealing step, voltage scans from

0V up to 400V were performed

Page 15: Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

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• Waveforms from the region between n-type columns show a double peak for electron and hole collection and a postive electron signal past 40 μm

• Waveforms from the region across the p-type column show the same peaks without the bipolar signal

60V

Irradiated Top TCT

200V

200V400V

Page 16: Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

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Annealing Effects

• End of beneficial annealing at around 80 mins.

• After type inversion we have a longer term reverse 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]

• Significant annealing beyond beneficial annealing leads to a decrease in the interstrip resistance.

• Eventually, the strips short together.

Resistance vs Annealing time, shown by C. Fleta at 15 RD50, June 2010.

Page 17: Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

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Annealing Effects – 20 mins

0V - 400V in steps of 50V

0V 50V 100V

150V 200V 250V

300V 350V 400V

Page 18: Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

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Annealing Effects – 40 mins

0V - 400V in steps of 50V

0V 50V 100V

150V 200V 250V

300V 350V 400V

Page 19: Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

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Annealing Effects – 100 mins

0V - 400V in steps of 50V

0V 50V 100V

150V 200V 250V

300V 350V 400V

Page 20: Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

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Annealing Effects – 300 mins

0V - 400V in steps of 50V

0V 50V 100V

150V 200V 250V

300V 350V 400V

Page 21: Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

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Annealing Effects – 600 mins

100V - 300V in steps of 100V

100V

200V

300V

Page 22: Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

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Conclusions

• Edge and top TCTs provide a new method to probe 3D devices.

• Substantial depletion occurs at very low voltages.• Irradiation and subsequent annealing alters the collection

of electrons and holes.

Future Analysis:• Compare the velocity profiles of non-irradiated and

irradiated detectors.• From the velocity profiles, electric field can be derived.• Edge TCTs of an irradiated sample, before and after

annealing.

Page 23: Preliminary Analysis of Edge and Top TCTs for Irradiated 3D Silicon Strip Detectors

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