1. ICT 1 SINTEF MiNaLab SINTEF Radiation Sensor Activity and Development of Technology for Neutron Detection Dr. Thor-Erik Hansen, Chief Scientist Dr. Angela Kok, Research Scientis

2. ICT 2 SINTEF in short Private non-profit research foundation Founded in 1950 at the Norwegian Technical University NTH (now NTNU) in Trondheim Merged with SI in Oslo in 1992, which became SINTEF Oslo Today ~ 2200 employees: ~ 1900 in Trondheim, ~ 300 in Oslo (also facilities in Bergen, Narvik, Houston and Rio de Janeiro) SINTEF head office located in Trondheim Turnover 2011: NOK 2.789 billion (EUR 379 million)

3. ICT 3 MiNaLab ( Micro- and Nanotechnology Laboratory in Oslo) Moved into new lab in 2004, part of NorFab Shared facility with the University of Oslo Two separate clean room floors: SINTEF: 800 m 2 University of Oslo: 600 m 2 Situated on the University of Oslo campus. R&D and small and medium scale production Silicon production line with annual capacity of 10.000 150 mm wafers on one shift QA System approved to ISO 9001:2008 Also have the ISO 14001

4. ICT 4 Main research and development fields sensors and actuators MEMS Piezo MEMS (PZT) Micro-fluidics Radiation sensors: R&D and production Micro optics

5. ICT 5 Radiation sensor products & technologies Single- and double sided strip detectors (area up to 92 x 92 mm 2 ) DC – readout AC - readout FOXFET Polysilicon resistors Pixel detectors Thick detectors; 1mm, 2mm Drift diodes (SDDs) Edge-on detectors for X- and γ - rays 3D Structures including active edge Technology for neutron detection Photo diodes for the 190 to 1100 nm spectral range PIN-diodes, quadrants and arrays Avalanche photodiodes (reach through RCA structure)

6. ICT 6 Selected radiation sensor reference projects High Energy Physics CERN 1985 - DELPHI, ATLAS, ALICE, ATHENA, CMS macro, micro and double sided strip detectors, photodiodes for scintillator readout, 3D- detectors DESY 1997 -1998 HERA single and double sided strip detectors BROOKHAVEN NL, 1997-1998 STAR detector linear drift chamber FERMI NL, 2004 – CMS double sided pixel detectors, 3D-detectors INFN Pisa, 2006-2007 pixel detectors

7. ICT 7 Selected radiation sensor reference projects Photon Physics Stanford Linear Accelerator (SLAC), USA, 2006 – Linac Coherent Light Source (LCLS) pixel detectors Cornell Univ., USA, 2006 – LCLS pixel detectors DESY, Germany, 2012 - European X-FEL Laser pixel detectors Astrophysics Naval Research Lab (NRL), USA, 2005 – 2011 Gamma Compton Camera, 2mm thick double sided macro strip detector, 2mm thick pixel detectors Lawrence Berkeley NL (LBNL), USA, 2011 – Large scale astronomical experiments Implementing strip detectors on backside of CCDs

8. ICT 8 Selected radiation sensor reference projects Industrial X- and γ- ray detector 7 European and 5 US major industrial customers Single and double sided strip detectors with AC coupling for material analysis, non-disclosed European and US industrial customer, 2003 – Edge-on strip detectors for medical imaging, non-disclosed European industrial customer, 2004 - 2011 Edge-on strip detectors for material analysis, non-disclosed European industrial customer, 2006 – XRF-strip detectors for material analysis, non-disclosed European industrial customer, 2009 – Drift diodes for material analysis (double sided with up to 17 mask layers), 500µm and 1mm thick, 3 non-disclosed US industrial customers, 2004 –, 1 non-disclosed European customer, 2012 – Strip detectors for space applications, 2012 – PIN-photodiodes. Quadrants and APDs, 1985 - high-end industrial, defence, and space applications

9. ICT 99 2 mm thick macro strip and pixel detectors for gamma rays Detector Double sided strip detector 64 x 64 strips 1.3 mm x 90.0 mm 2 1.4 mm pitch detector size ~ 92 x 92 mm 2 typical leakage < 10 nA/cm 2 @ 750 V Pixel detector 36 x 36 pixels 2.4 x 2.4 mm 2 2.5mm pitch detector size ~ 92 x 92 mm 2

10. ICT 10 IV measurements on SINTET standard 0.25cm 2 test diodes 500µm, 1mm and 2mm thickness

11. ICT 11 X-rays enter from the”window side” (backside) where there is a shallow junction, allowing detection of low-energy X-rays Capacitance ≈ 100fF On the”ring side” an electric field parallel to the surface of the detectors is generated by increasingly reverse biased field strips Silicon Drift Detector (SDD)

12. ICT 12 Signal Time Function of Silicon Drift Diode Charge Collection: 1 2 3 GND U BACK U IR Event 1signal 1 Event 2signal 2 Event 3 signal 3 U OR 11 22 33 t Drift3 t Drift2

13. ICT 13 Full 3-D Structure with active edges Previously only made at Stanford NF p - - - + + + + - - + - - - - - - + + + + + 3D - detector Planar- detector 50µm inter-electrode distance gives extreme radiation hardness, better than diamond 300µm 50µm

14. ICT 14 Fully filled electrodes Vertical trenches No widening (notching) at the bottom 64 µm 7.5 µm CMS 2E configuration IV for 4000 pixels in parallel (8000 electrodes) SINTEF 3D -detectors The tool: Iprod DRIE etcher 14 µm dia. holes, 280 µm deep5 µm wide trenches

15. ICT 15 Edge-on detector with active edge p p Front contact Rear side guard ring area Active area Incident photons baba P - diffusion N - substrate N+ diffusion Part of side and rear guard ring Active strips Active edge Saw line Active edge Active strips Guard ring Guard ring at edge facing incident photons replaced by N+ diffusion Dead region a few µm only

16. ICT 16 Edge-on non-cooled TE-cooled CdTe detector Spectra taken with edge-on sensor compared with CdTe detector 57 Co isotope spectrum. Comparison with TE-cooled CdTe detector Edge-on detector efficiency 122keV ≈ 6% (3.4% photoelectric, 2.6% Compton events)

17. ICT 17 MediPix detector chip for CTU Details: Made on 150mm diameter wafers with 300µm, 500µm and 1mm thickness 256x256 pixels 35 x 35µm 2 pixel size 55µm pitch Chip size ≈ 17x17mm 2 larger than standard Medipix chips as distance from connected guard ring to saw line is 1.3mm 37 chips/wafer

18. ICT 18 Wafer stage measurements on CTU MediPix detectors Wafer thickness300µm500µm1mm Wafer resistivity6-12kΩcm 10-30kΩcm Depletion voltage< 50V70 – 90V150V Guard leakage note1 1.5–2nA @100V3-4nA @150V3-4nA @200V Breakdown voltage650-800V900-1100V note2 1100V note2 Note1: Pixels floating, guard may pick up most of the total leakage Note2: Voltage supply compliance 1100V

19. ICT 19 Concept for silicon based neutron sensor Silicon pixel sensor with pores stuffed with neutron converter  Pores, cavities, made by Deep Reactive Ion Etch (DRIE) or TMAH wet etch  Filled with neutron converter ( 6 LiF, 10 B, 157,158 Gd, TiB 2 ). Possible reactions: 10 B + n → 7 Li (0.84MeV) + α (1.47MeV) + λ(0.48MeV) 94% probability 10 B + n → 7 Li (1.01MeV) + α (1.78MeV) 6% probability 6 Li + n → 3 H (2.73MeV)+ α (2.05MeV)  The generated alphas are detected by the silicon sensor structure  Simulated efficiency ≈ 30% with square pores compared to 5% for planar configuration  Detector bump-bonded to readout chip (MediPix)

20. ICT 1. Oxidation 2. P-Implantation 3. Annealing and oxidation 4. Lithography P_CONT  No DRIE, cheaper and easier option, but have a rather large surface area Neutron sensor with V-groove (with a non-disclosed partner) 5. Oxidation – 3000Å 6. TMAH etching Backside N-diff.

21. ICT  No DRIE, cheaper and easier option but have a rather large surface area Neutron sensor with V-groove (with a non-disclosed partner) Active area 6.25 cm 2 Leakage current ~3nA/cm 2 170µm V-groves to be filled with Gd by partner 165µm

22. ICT 22 Layout silicon neutron sensor currently in process Wafer front-side photomask, 4 mask layers: P-Diff, Contact, Metal, Passivation Detail backside etch mask Medipix compatible chip 35 x 35µm 2 pores 22 MediPix compatible chips Various other chips

23. ICT Wafer thinning Primarily wet chemical etching Low cost well established process Etches along 111 plane 54.7 o on 100 wafers Active area can be thinned down to about 10 µm for large cavities Frame of sensors remain to be 300 µm for mechanical support 28 Oct 2012, Anaheim 23 Top view of 100 µm square cavities Cross section of 100 µm square cavities 50 µm 54.6 o Example Active area 54.6 o ~10 µm 290 µm Not in scale Support frame for mechanical stability

24. ICT 24 Challenges  Realizing the pores are rather straight forward using wet etch or modern dry etch plasma tools (DRIE). Double sided photolithography and processing required to make the complete sensor. Main challenge is practical and cost effective deposition of neutron converter into the pores. Possible methods: Mechanical deposition (powder)Manual, not cost effective E – beam evaporationBoron has too high melting point? demonstrated with TiB 2 SputteringLow deposition rates for boron? TiB 2 and Gd more easily? Chemical vapour deposition (CVD)Possible for boron, but expensive? Atomic Layer Deposition (ALD)Possible, but slow Spin-on (converter dissolved in polymer)Promising Ion implant of 10 BPossible, but low dose rate?

25. ICT 25 Future work 1.Establish efficient and cost effective technology for deposition of neutron converter. Cooperation with CTU and Mid-Sweden University. 2. Develop gamma insensitive neutron sensor Si device layer 5µm thick Pores, dia. 10µm Si Support wafer Insulator (SiO 2 ) Neutron sensor fabricated on Silicon-on-Insulator (SOI) wafer. Device layer only 5µm thick, which makes the sensor insensitive to gammas.

26. ICT 26 Thank you for your attention!

27. ICT 27 MiNaLab

28. ICT 28 SINTEF revenues Research Council strategic programmes 4 % Research Council basic grants 3 % Other income 9 % Research Council project grants 13 % Public sector 12 % Industry 45 % International contracts 14 % SINTEF turnover in 2011: NOK 2.789 billion (EUR 379 million)