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5 th International Workshop on Radiation Imaging Detectors Riga 11 th September 2003

Recent Detector R&D and operational experience. Silicon based detectors Vertexing for Linear Collider Silicon Pixel sensors – MAPs, HAPs, CCDs, DEPFETs Tracking for Linear Collider Silicon drift High radiation environments Lazarus, 3d detectors, edgeless devices, diamond

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5 th International Workshop on Radiation Imaging Detectors Riga 11 th September 2003

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  1. Recent Detector R&D and operational experience Silicon based detectors Vertexing for Linear Collider Silicon Pixel sensors – MAPs, HAPs, CCDs, DEPFETs Tracking for Linear Collider Silicon drift High radiation environments Lazarus, 3d detectors, edgeless devices, diamond Large system operation DELPHI, CDF, CMS 5th International Workshop on Radiation Imaging Detectors Riga 11th September 2003 For Particle Physics applications Paula Collins, CERN

  2. Time Silicon for vertexing @ the LC required performance disentangle complex events Train • Use a silicon based pixel detector • Confine the e+e- background with a high solenoidal field • Keep occupancy reasonable by reading inner layer in 50 msec discriminate b from c and from background d (IP) < 5 mm  10 mm/(p sin3/2q) (best SLD 8 mm  33 mm/(p sin3/2q)) Vertex detector characteristics point resolution 1-5 mm Thickness ~ 0.1 % X0 5 layers Inner radius ~ 1.5 cm

  3. Silicon Trends Basic idea amplifier • Start with high resistivity silicon • More elaborate ideas: • n+ side strips – 2d readout • Integrate routing lines on detector • Floating strips for precision Al strip p+ + + SiO2/Si3N4 - - + n bulk + n+ - + Vbias Hybrid Active Pixel Sensors Chip (low resistivity silicon) bump bonded to sensor Floating pixels for precision chip chip n+ p chip n+ DEPFET: Fully depleted sensor with integrated preamp chip MAPS: standard CMOS wafer Integrates all functions CCD: charge collected in thin layer and transferred through silicon

  4. 15 V 0V 0V + + + DEPFET sensors Kemmer, Lutz, 1987 R&D for tracking ~ 2000 300 mm + Image of toothed watch wheel Resolution: 9 mm (50 mm pixels) • Amplifying transistor integrated into high resistivity silicon detector • Low noise operation possible at room temperature • Thinning possible to 50 mm NIMA 465 (2001) 247-252 R&D: pixel size, power, thinning, speed

  5. R&D issues • Mimimise pixel size • Thin from backside • Minimise power consumption • Speed up readout cycle DEPFET readout scheme • 3 steps for each matrix row • Read all signal currents • Reset pixel row via clear contacts • Read pedestal currents Proposed TESLA Layout

  6. Recent DEPFET R&D Thinning technology NIM A 511 2003 (250-256) Also: Move from circularly shaped JFETs to linear structures to access smaller pixel sizes – currently achieved 30 x 20 mm2 Development of new readout chip NIM A 511 2003 (257-264) 1.5 mm 4 mm Aim for 0.1-0.15% X0 per layer (including chips)

  7.  Monolithic Active Pixel Sensors (MAPS) 1999 – small scale prototypes 1999-2000 first beam tests 2001 – large prototypes 2002 – first circuit with on-line processing • Same unique substrate for detector and electronics • No connections (e.g. bumps) • Radiation hardness (no bulk charge transfer) • Advantages of CMOS process: Easy Design/good yield/low power/Rad hard • Very small pixel sizes achieveable ~ 15 mm Mimosa I II III IV V VI Process 0.6 mm 0.35 mm 0.25 mm 0.35 mm 0.6 mm 0.35 mm Epi layer 14 mm 4.2 mm 2.3 mm 0 (!!!) 14 mm 4.2 mm # pixels 64x64x4 64x64x6 128x128x2 64x64x4 1,000,000x7 24x128x..

  8. MAPS Beam Test Results Signal to Noise Resolution [mm] MIMOSA V MIMOSA I MIMOSA I MIMOSA II MIMOSA V (120 mm) Resolution 1.4 mm 2.2 mm 1.7 mm Efficiency at S/N > 5 99.5 % 98.5 % 99.3% Irradiation of MIMOSA I,II & V up to 1013 1 MeV/c neutrons Gain a constant Noise a constant Leakage current a moderate rise collected charge a 50-70% of initial value (smooth decrease after 1012 or few x 1011 ) NIMA 478 (2002) 311-315

  9. MAPS: Next R&D steps MIMOSA VI: First prototype with column parallel readout • 30 columns (128 Pixels each) with parallel readout • 30 MHz clock, 5 MHz readout (6 clocks per pixel) • New pixel design allows on-pixel signal amplification and double sampling operation Also: MIMOSA VII, <50 um thinning, explore fabrication processes, simulate irradiation, etc.

  10. Charged Coupled Devices - CCDs CCDs invented in 1970 – widely used in cameras, telescopes etc. Tracking applications for HEP: 1980-1985 NA32 120 kpixels 1992-1995 SLD 120 Mpixels 1996-1998 SLD upgrade 307 Mpixels TESLA 799 Mpixels ~1000 signal electrons are collected by a combination of drift and diffusion over a ~20mm region just below surface 10V 2V • Small pixel size – 20 x 20 mm • Possibility of very thin detectors • Column parallel readout: serial register -> direct bump bonding to chip

  11. Layer Radius (mm) CCD lxw (mm x mm) CCD Size (Mpix) Clock / readout time Background (Hits/mm2) Integrated background (kHits/train) 1 15 100 x 13 3.3 50 MHz/50 ms 4.3 761 5 60 125 x 22 6.9 25 MHz/250 ms 0.1 28 CCD R&D for LC requirements I • Speed up readout • 5 MHz readout -> 50 MHz • Reduce clock amplitudes 10V->3V -> 1.5V • Build with high resistivity epitaxial material CCD 55Fe spectrum: 50MHz 3V clocks noise=2.8 counts First ever CPCCD and chip (CPR1) now available! Bonded assemblies for testing this year (watch VERTEX03) More info at: http://hepwww.rl.ac.uk/lcfi/

  12. CCD R&D for LC requirements II Other steps: • Study radiation resistance to LC doses of 100Krad ionising radiation + 5 x 109 neutrons • Temperature dependence • Sacrificial charge • Minimise material in fiducial volume • Unsupported “stretched silicon” option • Highly thinned silicon glued to substrate IEE Trans Nucl Sci, Vol 47, No. 6 • CCD 20 μm CCD bonded with adhesive pads to 250 μm Be substrate • On cooling adhesive contracts more than Be pulls Si down on to Be surface • Layer thickness  0.12% Xo S. Hansen, VERTEX02

  13. Integration into LC design • Baseline design • 5 layers • R_min=15 mm • 3 layer coverage to |cos q|=0.96 • 5 layer coverage to |cos q|=0.9 Cryostat for CCD option flavour tagging performance at s=91 GeV Purity • b jets roughly equal SLD performance • c jets improved by factor 2-3 in efficiency Efficiency

  14. x y Silicon for tracking: Silicon Drift Detectors • Principle of sideways depletion – as for DEPFET sensors • p+ segmentation on both sides of silicon • Complete depletion of wafer from segmented n+ anodes on one side !! Drift velocity must be predictable • Temperature control • resistivity control • Calibration techniques • SDD fully functioning in STAR SVT since 2001 • 216 wafers, 0.7 m2 • 10 mm in anode direction • 20 mm in drift direction • Particle ID

  15. Silicon for tracking: Drift detectors • 5 precise silicon layers to replace TPC • 56 m2 silicon • R&D needed: • Improve resolution to 5 mm • Improve radiation length • Improve rad hardness • Track stamping possible at nanosecond level • SDD are a mature technology – attractive for LC c2 separation for out-of-time tracks for different drift direction configurations

  16. Irradiation L = 1034 cm –2 s-1 The LHC environment will be FIERCE 8 x 108 pp collisions / s Hadron fluences to 1015 cm-2 LHCb vertex detector LHC upgrade/VLHC will be WORSE! Other collider upgrades are hot too e.g. Super Belle/Babar 1014 neq/cm2 per year 1013 L = 1036 cm-2 s-1 Dose ~ 5-10 MRad radius [cm] Improved semiconductor designs/materials are well worth considering

  17. Irradiation Bulk Damage Effects in Silicon • Increased Leakage Current • Noise • Hard to bias • focussing on • Defect engineering • New detector materials • Cryo/forward operation • 3d and thin devices Depletion voltage [V] • Effective Doping Changes • Depletion grows from n+ side • Annealing effects • Buildup of negative space charge worsens in time • Strongly temperature dependent Fluence rd50.web.cern.ch/rd50 Depletion voltage [V] will cover these points time [years]

  18. Irradiation: strips for LHCb Irradiated detectors Underdepletion has two bad consequences Charge spread: A killer for fine pitch detectors! Charge loss • Reminder from Ramo (1939) Q = e * d/w Vbias 1 – 3 x 1014 n/cm2 Vbias Similar story for trapping… NIM A 412 (1998) 238

  19. Mr. Ramo I co-invented the electron microscope I pioneered microwave technology I founded TRW I had a theorem

  20. Irradiation: strips for LHCb • Reminder from Ramo (1939) Underdepletion has two bad consequences Irradiated detectors Charge spread: A killer for fine pitch detectors! Charge loss Q = e * d/w Vbias 1 – 3 x 1014 n/cm2 Vbias Similar story for trapping… NIM A 412 (1998) 238

  21. Irradiation: strips for LHCb p side n side Charge spread causes problems on the p side only Up to ~1014 underdepletion is still more important than trapping LHCb LHCb Resolution [mm] Vbias Vbias NIM A 440 (2000) 17 p side n side ATLAS ATLAS Efficiency For LHCb n-on-n detectors are the technology choice Vbias Vbias NIM A 450 (2000) 297

  22. Irradiation: the Lazarus effect COLD is COOL – as Lazarus knew • Cool detectors have little leakage current • Cool detectors don’t reverse anneal • Possible to control doping – hence underdepleted detectors magically become depleted It’s all about space charge! Neff [cm-3] Vdepl positive space charge “n” Irradiation h-trapping Negative space charge “p” Vdepl | space charge (Neff) | e-trapping

  23. Irradiation: the Lazarus efect Resurrection of a microstrip detector Efficiency COLD Efficiency HOT NIM A 440 (2000) 17 Recovery is temporary – but this can be solved Forward bias Reverse bias 0 min 5 min 15 min charge collection 30 min NIM A 440 (2000) 5 V bias

  24. Irradiation: alternative materials Rule of thumb: Below 1015 neq cunning manipulation of space charge can often save you Above this value, new materials and/or device engineering is better • Defect Engineering • Oxygen enriched silicon • Oxygen dimer in silicon • New Sensor Materials • Silicon Carbide • Amorphous silicon • Compound semiconductors • Diamond • Czochralski silicon Will discuss these

  25. low noise Low Ileak Alternative Materials: Diamonds • Band gap 5 x Si • Cohesive crystal • Room temperature operation Ionisation energy high: MIP gives 2x less signal for same X0 Collection efficiency < 100% Low e low capacitance FWHM/MP ~ 0.95 (for silicon is 0.5) Fast signal collection time Diamonds traditionally grown by CVD New: homoepitaxic monocrystalline films Figure of merit: Collection distance (proportional to mobility and electric field)

  26. Residual shifts measured Lateral field component simulated Alternative materials: Diamonds RD42 in collaboration with Element Six have achieved impressive improvements in collection distances pCVD structures show good radiation hardness + Big step forward in understanding non-uniform response (A. Oh, to be published) 52% loss of S/N at 2.9 1015 p/cm2 23% improvement in resolution

  27. Alternative materials: Diamonds Mono-crystalline diamond shows spectacular performance Charge Collection Distance (mm) E field (V/micron) Future R&D steps Continue monocrystalline diamond studies Push pCVD to 300 mm 40 MHz readout speeds Applications Beam monitoring for BaBar, CMS

  28. Alternative materials: Cz • Single crystal pulled out of melt (High resistivity Czochralski silicon now available) • Oxygen content: • Standard silicon ~1e15cm-3 • DOFZ silicon ~1e17cm-3 • Cz silicon ~1e18cm-3 • First Cz measurements show • Depletion voltage changes less drastically after irradition • No type inversion up to 1015 / cm2 190 MeV pions See Lindstroem et al: http://rd50.web.cern.ch

  29. Alternative materials: Cz First full scale detector prototypes irradiated and operated in test beam at 40 MHz Summer 2003 167V Bias 243V Bias 371V Bias

  30. Irradiation: 3d detectors Planar technology 3-D technology Proposed by Parker, Kenney 1995 Electrode p+ n+ p+ n+ 200mm 200mm • Maximum drift and depletion distance governed by electrode spacing • Lower depletion voltages • Radiation hardness • Fast response • At the price of more complex processing • Narrow dead regions on edges 50mm 10 mm Unit cell defined by e.g. hexagonal array of electrodes • Comprehensive summary: CERN CourierVol 43, Number 1, Jan 2003

  31. Performance after irradiation ~1015 p/cm2 Low leakage currents Low depletion voltages Gaussian X ray lines fast charge collection 14 KeV 17 KeV 59.5 KeV 3d detectors: characteristics Am241 spectrum Fast charge collection rise time ~ 3.5 ns Charge Collection good depletion voltage v 50 V 100 V 150 V

  32. PLANAR PLANAR-3D = PLANAR DETECTOR + DOPANT DIFFUSED IN FROM DEEP ETCHED EDGE THEN FILLED WITH POLYSILICON GUARD RING Sinks surface leakage current E-field p + + Al p + Al E-field n ++ Al n ++ Al n + Al Microcracks, chips etc.. Active Edge Planar Devices A TRENCH IS ETCHED AND DOPED TO TERMINATE THE E-FIELD LINES AFTER THE FULL PROCESS IS COMPLETED THE MATERIAL SURROUNDING THE DETECTORS IS ETCHED AWAY AND THE SUPPORT WAFER REMOVED : NO SAWING NEEDED!!! (NO CHIPS, NO CRACKS)

  33. Active Edge Planar Devices X ray microbeam signal on 1st and 2nd strips of edgeless device MEASURED DEAD EDGE ~ 5 mm 20 Volts Bias July 2003

  34. Silicon for tracking: Large Systems DELPHI 1990 DELPHI 1994 DELPHI 1996 CMS 2006 2 ! CDF 2001

  35. Whoops… Silicon for tracking: Large Systems LHC Tevatron LEP

  36. D0 K p ND=56320 CDF & D0 are demonstrating the possible A huge system is up and running: 19 micron resolution (before alignment) 9 micron resolution (after alignment) S/N > 10 - as expected Silicon participating in trigger Silicon is used for physics!

  37. CDF silicon sensitive to ! Radiation profile measured with high precision (~1 mrad) by 1000 TLD’s ~300 rad/pb at r=3cm (~1010 mips/pb) %1/Ra where 1.5 < a < 2.1 This can be compared to rises in leakage current… … thanks to accurate temperature and current monitoring

  38. CDF silicon sensitive to ! Corrected data give beautiful fits Current (uA) Delivered Luminosity (pb) And very good agreement with TLD’s Also compatible with very small noise increase Fluence (1010 cm-2 pb-1) F (rad)

  39. Systematic assembly line production with decent QA systems Construction: philosopy shift Taken from: DELPHI (888 detectors, 8 geometries) CDF (8000 sensors, 8 geometries) CMS (25000 sensors, 15 geometries) Each sensor treated individually, nurtured into life in many hours of careful handling

  40. Construction: Tales of the unexpected • Range from the glamarous • resonating wire bonds • Endoscopic operations on cooling tubes • super long kapton problems • Chemically active packing materials Through to the less glamarous (Vendors lie)

  41. Cautionary tales I DELPHI “sticky plastic saga” Received sensors from vendor, tested and distributed to assembly labs. All = OK Assembly labs got worse results – confirmed at CERN US TO VENDOR: YOUR SENSORS AGE! VENDOR: YOU ARE RUINING THEM! Zoom on packing Finally found “flakes” A story repeated with variations elsewhere Zoom on flake thru packing Vendor had changed anti static packing plastic – 60 sensors affected, big delay

  42. Ipp ~ 160 mA Cautionary tales II CDF “resonating bond saga” Jumper bond wires route signal from Rf to Rz side of module • Under a very particular set of conditions: • L2 “torture test” or SVT trigger • Bonds orthogonal to 1.4T field • Large current swing (100 mA – only on one bond) If pulsed at the right frequency the tiny Lorentz force (10-50 mg) can excite resonances which fatigue the heel of the wire bond. Eventually cracks are induced and electrical continuity lost

  43. Cautionary Tales III CMS are confronting the enormous challenge of tracker construction with a sophisticated QA scheme 1.3 m 15 different designs 24244 different sensors! To be completed within 2 years! 2.8 m Full testing on pre-series (5% of sensors): IV, CV, strips, optical, irrad Irradiation of 5% of test structures and 1% of strips CMS process control on test structures: (12 measurements) Scheme has weeded out many problems at an early stage and gives confidence in sensor performance

  44. Cautionary Tales III Sample measurements: Depletion Voltage Leakage current Note however that even CMS are not totally immune to the occassional broken bond! Commercial transportation of some modules caused 20% of bonds to break (these modules were fixed in ~1 day) Vibration tests show that transportation can give > 3.4 g force

  45. Cautionary Tales III Used laser to identify cantilever resonances at 88 Hz NASA style vibration test and at 120 Hz Reinforcement glue beds totally solved the problem

  46. Conclusions Detector R&D making a huge impact on the future of HEP Bear in mind: “Even if you think it will take a long time, it will still take longer than you think” H. Bieler, this conference And what about the cost?

  47. Acknowledgements Thanks to all people who provided material, including LC Keith Riles, Paul Dauncey, Ron Settles Silicon Hans Dijkstra MAPSMarc Winter, Grzegorz Deptuch, Wojtek Dulinski, CCD Chris Damerell, Stefania Hansen DEPFETMarcel Trimpl Johannes Ulrici SDD Rene Bellweid, Vladimir Rykov HAPS Massimo Caccia, Wojtek Kucewicz, Peter Chochula, Peter Rosinsky Irradiation Sherwood Parker, Cinzia da Via, Angela Kok, Mahfazur Rahman, Michael Moll, Mika Huhtinen, William Trischuk, Zheng Li Tevatron Alan Sill, Regina Demina, Gino Bolla, Rainer Wallny, Chris Hill, Rick Tesarek CMS Manfred Krammer, b factory David Leith, David Hitlin Dark Matter Hans Kraus, Fabrice Feinstein, Harry Nelson Overview Tejinder Virdee, Guy Wilkinson and not forgetting the organisers of IWORID, Riga 2003

  48. Challenges of Large Systems LHC GPD? The Tower of Babel by Pieter Breugel ack: G. Charpak

  49. More Challenges of Large Systems… mass production, QA, electronics, computing, long time scales (technology, aging), risk factors, mechanics, etc. etc. Example: Calibration systems Will assume huge importance: from cross check to full integration STAR calibration system CMS calorimeter 80,000 crystals Intercalibration ~ 0.4% Will use data and monitoring W g en Z gee 200-400 UV laser beams Measures drift velocity Next step: embed in data stream Huge effort for database

  50. From now on backup transparencies

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