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 PordiameterWallthickn.# poresCoverage Hits > 100 keV Qeff > 100 keV Hits 1,5-3 MeV Qeff 1,5-3 MeV ,21%96,20%30,03%55,40%17,29% ,33%91,60%44,27%34,50%16,67% ,71%73,50%46,09%14,50%9,09% ,78%96,20%17,11%54,60%9,71% ,45%91,60%30,64%41,10%13,75% ,27%73,50%36,95%20,80%10,46% ,13%96,20%6,86%53,60%3,82% ,08%91,60%15,64%60,40%10,31% ,25%73,50%23,70%39,30%12,67%

PROCESSING Pore 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 um16 um32 um 6 umDetector_ _11020_2 12 um1020_31020_41020_5 24 um1020_61020_71020_8

 D=36 (32) µm w=8 (12) µm ACREO, P. Norlin (2013)

PASSIVATION SIO 2 ~2000Å d d d d d d d d d d d d

DRY ETCHING d d d d d d d d d d d d

CONTACTS d d d d d d d d d d d d

TESTING WITH ALPHA SOURCE d d d d d d 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