HIGH QUANTUM EFFICIENCY NEUTRON DETECTOR WITH A SPATIAL RESOLUTION IN THE MICROMETER RANGE

GÖRAN THUNGSTRÖM

COLLABORATION PARTNERS•Czech Technical University in Prague, Institute of experimental and applied physics (IEAP)

•ACREO, Kista (Stockholm)

•SINTEF, Oslo

• Mid Sweden University, Sundsvall

IMPROVED EFFICIENCY

Czech Technical University in Prague, Institute of experimental and applied physics (IEAP), J. Uher, et. al. (2007)

TEST DETECTOR

DIODE MASKS

GUARD RINGS

LAYOUT OF THE ETCHING MASK

QUANTUM EFFICIENCY

Pordiameter Wallthickn. # pores CoverageHits > 100 keV

Qeff > 100 keV

Hits 1,5-3 MeV

Qeff 1,5-3 MeV

8 5 620967 31,21% 96,20% 30,03% 55,40% 17,29%16 5 240377 48,33% 91,60% 44,27% 34,50% 16,67%32 5 77976 62,71% 73,50% 46,09% 14,50% 9,09%

8 10 353819 17,78% 96,20% 17,11% 54,60% 9,71%16 10 166347 33,45% 91,60% 30,64% 41,10% 13,75%32 10 62505 50,27% 73,50% 36,95% 20,80% 10,46%

8 20 141840 7,13% 96,20% 6,86% 53,60% 3,82%16 20 84937 17,08% 91,60% 15,64% 60,40% 10,31%32 20 40098 32,25% 73,50% 23,70% 39,30% 12,67%

PROCESSINGPore etching in Si is a mature technology

• DRIE• Photochemical etching

Sidewall passivation is critical• Low leakage current• Resistant to the neutron

converter

Other challenges• Bump bonding• Large area structures…

Pore diameter Wall thickness

8 um 16 um 32 um

6 um Detector_1020 1020_1 1020_212 um 1020_3 1020_4 1020_524 um 1020_6 1020_7 1020_8

•D=36 (32) µm• w=8 (12) µm

ACREO, P. Norlin (2013)

PASSIVATION SIO2 ~2000Å

d d d d d d

DRY ETCHING

d d d d d d

CONTACTS

d d d d d d

TESTING WITH ALPHA SOURCE

d d d d d d

FILLING WITH NEUTRON CONVERTER

•Boron and/or Lithium compound• Powder with some filler• CVD-method• ?

THE FINAL GOAL, A PIXEL DETECTOR WITH NEUTRON CONVERTER Pores are etched in the silicon sensor and filled with a neutron converter.

• Electronic readout chip from the medipix consortium, Timepix

• ACREO post-processes the TIMEPIX-wafers with indium bumps

• SINTEF, MIUN and ACREO can then bump bond different types of pixelised neutron detectors

• Characterisation with neutrons is done by IEAP (Prague)

Pixel size 55x55 µm, center of gravity result in an improved spatial resolution