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Radiation hardness of Si-sensors N.Zamjatin, JINR, Dubna. The 3rd Work Meeting of the CBM-MPD STS Consortium “Technical challenges of the CBM and MPD Silicon Tracking Systems 2009” 1 – 4 June 2009, Doctor Winter’s Lodge Resort, Sortavala, Karelia, Russia. Radiation damage of Si:

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Radiation hardness of si sensors n zamjatin jinr dubna

Radiation hardness of Si-sensors

N.Zamjatin, JINR, Dubna

The 3rd Work Meeting of the CBM-MPD STS Consortium

“Technical challenges of the CBM and MPD Silicon Tracking Systems 2009”

1 – 4 June 2009, Doctor Winter’s Lodge Resort, Sortavala, Karelia, Russia


Main effects in silicon at non ionization energy loss niel

Radiation damage of Si:

Removing of the atom Si from crystal lattice with vacancy on stital (V) and interstitalSi (I );

V and Iis electrical activity deep levels:

V V;

VО;

VР;

IС;

IVР;

et al.

Deep level effects:

- generation/recombination

- «traping/detrapinge-h»

- removing donors

Main effects in Silicon at Non Ionization Energy Loss (NIEL)

Ес

е

DL

h

Ev

Compensation donors

Dark current

Charge collection

3-rd meeting CBM-MPD, 1-3 June'09


Radiation hardness of si sensors n zamjatin jinr dubna

  • A. The detector leakage current increases linearly with hadrons fluence:

  • =II  V

  • fluency, Vthe detector bulk,

  • I =(51)10-17 Асм-1for fast neutronsat

  • T = +20º C(no self-annealing)

  • Possible solution at high hadrons fluence:

  • work at low temperature -(30-50)°C, detector leakage current doubles it’s value every 8 degrees;

  • Detectors module design required very good thermo contact between Si-sensor and cooling plate for the excluding of the heating and thermo break down /3/

3-rd meeting CBM-MPD, 1-3 June'09


Radiation hardness of si sensors n zamjatin jinr dubna

  • I-V and C-V measurements for detector RWS-01/01-69-7 before and after neutrons /3/ irradiation 4.9×1014 n/cm2

  • Blue color curves – measurements at +20°C before irradiation

  • Red color curves – measurements at -28°C after irradiation

  • Topology of detector:

  • 32-p+strips;

  • 63×63×0.3 mm3;

  • 5 kOhm×cm n-type Si-Wacker, <111>

3-rd meeting CBM-MPD, 1-3 June'09


7 5 p i v

До облучения:

Рдет=10-6А×150В=1.5×10-4Вт

(Для Vdet=(63×63×0.3)мм3).

После 5 лет (CMS/SE

Фn=1014 см-2):

Рдет=5×10-4А×500В=0.25Вт (при Т = -5º).

! Проблема теплового

пробоя (саморазогрев

облученного детектора)

7.5. Рост мощности рассеяния на ППД (P=IV).

3-rd meeting CBM-MPD, 1-3 June'09


Radiation hardness of si sensors n zamjatin jinr dubna

B.Decreasing of the charge collection efficiency (CCE) with increasing hadrons fluence

  • The CCE decreases 8%/1014 n/cm2 and does not depend on initial silicon type, extrapolation of this curve to 1015 n/cm2 give the value for signal equal 20% from initial amplitude /3/

  • What to do???

  • to change of Si-planes after each 5×1014 n/cm2???;

  • to work with (20-10)% of CCE;

  • to work at low temperatures and at forward bias (experience of RD39, LAZARUS effect /1/ )

3-rd meeting CBM-MPD, 1-3 June'09


Radiation hardness of si sensors n zamjatin jinr dubna

C.The detector full depletion voltage Ufd increases with hadrons fluence (after point inversion of type conductivity for n-type Si). This effect could be diminished /2, 4/ applying the oxygenated Si and low resistivity Si as a starting detectors material:

CZ (MCZ) has higher oxygen concentration in crystal ingot, low resistivity material (100 – 800 Ohm  cm)

FZ-Si-p – no conductivity type inversion

FZ-Si-(n- or p-type) + O2 during the detectors technology fabrication

Remark:in the real experiments with irradiated detectors Ud>Ufd for the attainment of plato CCE=f(Ud) and max S/N

3-rd meeting CBM-MPD, 1-3 June'09


Inversion of bulk type conductivity n type to p type at irradiation si sensors
Inversion of bulk type conductivity (n-type to p-type) at irradiation Si-sensors

  • Sensor (20×20×0.4) mm3at biasUd=15Virradiated by fast neutrons

  • Capacity of detector measured (F=1 кГц) directly at irradiation on the neutrons chanel

  • Initial parameters of Si:

  • n-type, <111>, (FZ-Wacker);

  • ρ=6 кОm×сm(Ufd=80 В)

  • Point inversion for this detector equal (2÷3)×1012n/сm2

Direct method for the measuring of the point inversion bulk type conductivity/5/

3-rd meeting CBM-MPD, 1-3 June'09


Radiation hardness of si sensors n zamjatin jinr dubna

Is it an alternative to SILICON to construct a detector with large area in radiation hard environment???

Possible candidates: CVD-C, CdTe, GaAs and???

CVD-C: (-) commercial wafers with big area???, big cost, small (50-150mkm) CCLength; (+) radiation hardness!!!

CdTe(CdZnTe): (-) small area of wafers (1-5 cm2); high cost (5-10 $/mm3) for mono crystal; (+) high radiation condition of policrystaline (CERN-R&D for luminosity monitor)

GaAs: (-) more expensive that Si-detectors, mechanical conditions lower that Si; (+) bigger radiation hardness that Si! (need to study of rad.hard. for real detectors)

3-rd meeting CBM-MPD, 1-3 June'09


Ds strip detector n side with p stop ring n strip

n+ strips large area in radiation hard environment???

p+ stop rings

DS-strip detector: n+side with p+stop ring/n+strip

3-rd meeting CBM-MPD, 1-3 June'09


Ds strip sensors need to study surface radiation effects on the both sides
DS-strip sensors need to study (surface) radiation effects on the both sides

What difference between n+ and p+ sides for DS-strip sensors?

  • each n+ strip isolated by p+ stop ring

  • inter n+ strip region need bigger value of full depletion voltage in compare with bulk depletion

  • with over depletion increase electric field in inter n+strip region and possible break down n+ strip to p+ stop ring

  • detectors from difference manufactures have individual parameters (thickness of dielectric layers, density of charge in SiO2, profile of implantation layers, et al)

3-rd meeting CBM-MPD, 1-3 June'09


Radiation hardness of si sensors n zamjatin jinr dubna

(I-V) on the both sidesat +20° for Si PAD-detector (8×8×0.3 mm3) after irradiation 2×1012 alpha/cm2,

Eα=3.5 MeV, α-particles illuminated n+ side (Ohmic contact)

U full depletion

3-rd meeting CBM-MPD, 1-3 June'09


Radiation hardness of si sensors n zamjatin jinr dubna

(I-V) for Si PAD-detector (8 on the both sides×8×0.3 mm3) after irradiation 2×1012 alpha/cm2, Eα=3.5 MeV, α-particles illuminated p+ side (junction contact)

3-rd meeting CBM-MPD, 1-3 June'09


Radiation hardness of si sensors n zamjatin jinr dubna

  • References: on the both sides

  • V.G.Palmieri et al., “Evidence for charge collection efficiency recovery in heavily irradiated silicon detectors operated at cryogenic temperatures”, NIM A 413 (1998) 475-478.

  • B.Dezillie, Z.Li et al., “Improved Neutron Radiation Hardness for Si-detectors: Application of Low Resistivity Starting Material and/or Manipulation of Neff by Selective Filling of Radiation-induced Traps at Low Temperatures”, IEEE Transactions on Nuclear Science, Vol.46, No.3, June 1999.

  • Ph. Bloch, N.Zamiatin et al. “Performance of Si sensors irradiated to

  • 5 ×1014 n/cm2”, NIM A517 (2004) 121-127.

  • RD-48, ROSE Collaboration Reports.

  • 5. Н.И. Замятин и др., Экспериментальный метод определения инверсии n–типа проводимости кремния при облучении быстрыми нейтронами. Сообщение ОИЯИ, Р13-2001-281.

3-rd meeting CBM-MPD, 1-3 June'09


Conclusion
Conclusion: on the both sides

  • Bulk damage effects in Si crystal are very good study and understood (big experimental data of ROSE collaboration for LHC experiments, RD48)

  • Surface damage effects dependent from topology and technology sensors (inter strip distance, p+ stop ring on n+ side, thickness of SiO2, et all)

  • DS-strip sensor need to study radiation hardness for both sides n+ and p+ before- and after point inversion (inter strip resistance, inter strip capacitance, cross talk, S/N, break down on p+ or n+ side?)

  • Sensors after high hadron fluence need very good thermo contact with cooling system (special design modules/ladders)

3-rd meeting CBM-MPD, 1-3 June'09