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Characterization of P-type Silicon Detectors Irradiated with Neutrons

M.Miñano1, J.P.Balbuena2, C. García1, S.González1, C.Lacasta1, V.Lacuesta1, M.Lozano2,

S. Martí i García1, G. Pellegrini2,3, M. Ullán2

(1) Instituto de Física Corpuscular, IFIC (CSIC-UVEG), Valencia, Spain(2) Instituto de Microelectrónica de Barcelona, CNM-IMB (CSIC), Bellaterra, Spain

(3) Departamento de Electrónica, Informática y Automática, Universidad de Gerona, Spain

3rd Workshop on Advanced Silicon Radiation Detectors, Barcelona, Spain 14 April 2008

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Outline

I. Fabrication process

II. P-type strip detectors irradiated with neutrons

III. Setup (Laser & Radiactive Source)

IV. I-V results

V. Q-V results

VI. Summary and Outlook

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I. Fabrication Process Detectors have been fabricated in the Clean Room facility of CNM-IMB

Rd50 Mask

Designed by the RD50 Collaboration Double side processing One metal layer

Structures

26 microstrips detectors Polysilicon biasing resistors Capacitive coupling P-spray insulation No p-stops

20 pad detectors 12 pixel detectors 8 test structure sets

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II. P-type strip detectors irradiated with neutrons

1 MeV equivalent neutron irradiation at TRIGA nuclear reactor in Ljubljana, Slovenia.

FLUENCES

1X1014 n/cm2

3x1014 n/cm2

1x1015 n/cm2

3x1015 n/cm2

8x1015 n/cm2

• Area: 1x1 cm2

• 130 strips, width: 32 m

• Pitch: 80 m

• Thickness: 300 m

• Multiple guard ring

• Surface isolation: p-spray

Wire bonding

No annealing

DOFZ, MCz substrates to evaluate

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III. Laser Setup

Laser

strip sensorTrigger

Signal

Horizontal scale

20mV

1V

Real signal viewed at 70V in the scope

Laser light is generated by exciting a laser source with an external pulsed signal

(2 V and 1 MHz rate)

Laser properties:

=1060 nm (Near Infrared)

Laser energy of photons=1.170 eV

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III. Radiactive Source Setup

90Sr

strip sensor

Signal

Trigger

Horizontal scale

Photomultiplier

200 mV /div

2 mV /div

Real signal viewed at 300V in the scope

Measurements are used to calibrate the laser measurements

- source

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Laser OscilloscopeFaraday CagePhotomultiplier

and Scintillator

Power SupplyPM power supply

freezer

Sensor cage Source

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0

2

4

6

8

10

12

14

16

0 200 400 600 800 1000

V (volts)

Cu

rren

t (

A) 3E14 n/cm2

1E15 n/cm2

3E15 n/cm2

8E15 n/cm2

IV. Current vs Voltage: DOFZ T = -40oC

For the sensor irradiated with 1x1014 n/cm2 we observed an extremely early break

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IV. Current vs Voltage: MCz

0

0,5

1

1,5

2

2,5

3

3,5

4

0 200 400 600 800 1000

V (volts)

Cu

rren

t (u

A)

1E14 n/cm2

3E14 n/cm2

1E15 n/cm2

T = -40oC

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0

2

4

6

8

10

12

14

16

18

20

22

24

26

0 100 200 300 400 500 600 700 800 900V (volts)

Q (

ke)

Non-irradiated

3E14 n/cm2

1E15 n/cm2

3E15 n/cm2

8E15 n/cm2

V. Charge vs Voltage: DOFZ T = -40oC

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V. Charge vs Voltage: MCz

0

5

10

15

20

25

30

0 200 400 600 800 1000

V(volts)

Q (

ke)

Non-irradiated

1E14 n/cm2

3E14 n/cm2

1E15 n/cm2

T = -40oC Global warming? Effect due to high

current level?

Systematic error?

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Neutron Irradiation:

Comparison DOFZ vs MCz substrates at the same fluences

0

5

10

15

20

25

30

0 200 400 600 800 1000

V (volts)

Q (

Ke

)

DOFZ

MCz

Non-irradiated3 x 1014 neq/cm2

1 x 1015 neq/cm2

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Degradation after neutron irradiation: Q-

0

5

10

15

20

25

30

0 2E+14 4E+14 6E+14 8E+14 1E+15 1,2E+15

fluence (cm-2)

Q (

ke

)

MCz

DOFZ

V=500V

Collected charge is unaffected by the silicon substrate type

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VI. Summary and Outlook P-type strip sensors have been fabricated in CNM-IMB and irradiated with neutrons at several fluences at the TRIGA Nuclear Reactor in Ljubljana.

Detectors on alternative substrates (MCz, DOFZ) have been evaluated.

Current and Collected charge vs Voltage measurements have been done.

Even after the highest neutron fluence (equivalent to 10 years of the sLHC operation) the detectors are still operational.

For instance, at 8.0 1015 n/cm2 ~7300 e- are collected at 900V.

MCz charge collection at high bias voltages to be understood.

The neutron radiation hardness does not depend on the substrate technology.

Near future plans, ALIBAVA system will be used to performance the charge collection measurements and signal characterization.

More neutron and proton irradiated detectores will be characterized in the coming months.