Sabina Ronchin 1, Maurizio Boscardin 1, Nicola Zorzi 1, Gabriele Giacomini 1, Gian-Franco Dalla-Betta 2, Marco Povoli 3, Alberto Quaranta 2 ; Giorgio Ciaghi 3 1 FBK Trento 2 INFN and University of Trento 3 University of Trento (Italy) A new 3D PIN diode structure for neutron detection 8 th “Trento” Workshop on Advanced Silicon Radiation Detectors (3D and P-type Technologies) FBK-CMM, Trento, Italy February 18-20, 2013

Outline S. Ronchin 8 th “Trento” Workshop Trento, February 18-20, 2013 Introduction Process parameters and technological variations Pictures and morphology of realized devices Electrical characterization Conclusions

New hybrid 3D detectors for neutrons (see presentation of prof. Alberto Quaranta ) Junction scintillator Impinging neutron Reaction products Scintillation Hybrid detectors obtained by pouring polysiloxane scintillator into the 3D silicon detector cavities Increase of the active interaction volume for neutron, giving higher detection efficiencies. metal S. Ronchin 8 th “Trento” Workshop Trento, February 18-20, 2013

Junction n on p P-diff or poly P-type Si back metal p-type wafers: isolation by p-spray on back side and p-plus bulk contact on front side Two DRIE process P-doping by diffusion Front\back contact via diffusion or poly doped S. Ronchin 8 th “Trento” Workshop Trento, February 18-20, 2013 front Process parameters and technological variations DRIE excavation DRIE passing through hole p-type Si

Processed wafer front back S. Ronchin 8 th “Trento” Workshop Trento, February 18-20, 2013

Die picture (1 cm 2 pixel array) front back S. Ronchin 8 th “Trento” Workshop Trento, February 18-20, 2013

Surface and cross- section at optical microscope Impinging neutron Reaction products S. Ronchin 8 th “Trento” Workshop Trento, February 18-20, 2013 after polysilicon definition

SEM images after polysilicon definition (1) Impinging neutron cavities Overview on tilted sample Passing through holes

Cross-section at SEM after polysilicon definition (2) 230  m 200  m 30  m ≈ 7  m Poly-Si 500 nm oxide membrane front back Cavity Passing through holes Cavity

Wafer layout HYDE-1 Die size 1cm 2 Active area≈25 mm 2 p-plus holes contacts

Preliminary tests by by G. Giacomini and G. Ciaghi Total resistance ~ 200 Ohm Back/front contact checking on test structures cavity Passing through holes

Wafer 2: with poly From I-V: leakage current of a few nA/cm 2 and breakdown voltage of 50-60V (lower values due to defects). From C-V: two-phase depletion mechanism: rapid decrease due to lateral depletion, slower decrease of the other regions, with trend compatible with the different geometries of pplus. Electrical test on pixel dies with different geometries

Wafer 10: without poly From I-V: leakage current of a few nA/cm 2 and breakdown voltage of 70-90V (lower values due to defects). From C-V: two-phase depletion mechanism: rapid decrease due to lateral depletion, slower decrease of the other regions, with trend compatible with the different geometries of pplus. Electrical test on pixel dies with different geometries

Conclusions Process successfully concluded: 5 wafers with polysilicon (2 with passivation) 6 wafers without polysilicon (3 with passivation) Preliminary electrical tests show: Good electrical contact between junction on back cavity and front side Leakage current of a few nA/cm 2 and breakdown voltage of V for devices without polysilicon, Functional tests (noise, response to laser pulses and radioactive sources) after mounting on dedicated test board are in progress; Filling with polysiloxane scintillator ok (see talk of A. Quaranta) S. Ronchin 8 th “Trento” Workshop Trento, February 18-20, 2013 Tests with neutrons are planned at Legnaro for April

S. Ronchin 8 th “Trento” Workshop Trento, February 18-20, 2013

Cross-section at optical microscope and at SEM after polysiloxane filling

Deposizione dello scintillatore (1) Foto in sezione al microscopio ottico (campioni tagliati con sega a disco) New polysiloxane based scintillators