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Abraham Gallas

Timepix Pixel Sensors Tracking & Timestamping for ILC. V Jornadas sobre la participación española en futuros aceleradores lineales. Abraham Gallas. Outline. ILC environment and assumptions Detector design rationale ASIC (Timepix) Sensor thinning Low mass bump bonding

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Abraham Gallas

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  1. Timepix Pixel Sensors Tracking & Timestamping for ILC V Jornadas sobre la participación española en futuros aceleradores lineales Abraham Gallas

  2. Outline • ILC environment and assumptions • Detector design rationale • ASIC (Timepix) • Sensor thinning • Low mass bump bonding • Test beams with Timepix • Next steps Abraham Gallas

  3. ILC in a nutshell • e+ e- linear collider • Center of mass energy range 200-500 GeV • Peak luminosity 2 x 1034 cm-2 s-1 • Bunch timing: • 5 pulses per second (5 Hz) • 1260, 2625, 5340 bunches per pulse • separated by 180, 369, 500 ns • power pulsing • readout speed • 14 mrad crossing angle • Background: • small bunches • create beamstrahlung → pairs Hit density (#/mm2/BX) Abraham Gallas

  4. Forward tracking detector • Relevant physics processes with particles emitted at small : mostly e-, m, t, b- and c-jets • ILD's Forward Tracking Disks • The forward region 6° <  < 30°: 0.1 rad <  < 0.45 rad 0.9 < cos  < 0.995 1.5 < |  | < 3. Abraham Gallas

  5. Detector design rationale • 25x25 mm pixel sensor instrumented with ROC derived from current Timepix (Timepix2-Timepix3) • Both ToT and ToA modes running simultaneously in each pixel • Time resolution of ∼10 ns or better (Timepix2 > 1.5ns (25ns/16)) allowing time stamping (bunch tagging) • Full readout between pulses (5Hz) or every 100BX • Power cycling leading to a 70% reduction on the time the ROC is ON (Timepix2 ∼45mW/pixel). Abraham Gallas

  6. The Medipix Chips bipolar (h+ and e-) Silicon, CdZnTe, CdTe, GaAs, Amorphous Silicon, 3D, Gas Amplification, Microchannel Plates etc… A philosophy of functionality built into the pixel matrix allows complex behavior with a minimal inactive region Configurable ‘shutter’ allows many different applications 55 mm square pixel matrix 256 by 256 3-side buttable

  7. Timepix (2006) Timepix design requestedand funded by EUDET collaboration Time over Threshold Time of Arrival Conventional Medipix2 counting mode remains. sensor Threshold Addition of a clock up to 100MHz allows two new modes. Time over Threshold Time of Arrival Threshold Analogue amplification Digital processing Pixels can be individually programmed into one of these three modes Time of Arrival counts to the end of the Shutter Time Over Threshold counts to the falling edge of the pulse Read-out ASIC

  8. Development history and future 1mm SCAMOS 64 by 64 pixels Photon Counting Demonstrator (1997) Medipix1 250nm IBM CMOS, 256 by 256 55mm pixels Full photon counting (2002) Analogue (ToT) and Time Stamping (ToA) (2006) Medipix2 Timepix Medipix3 130nm IBM CMOS Photon Counting, Spectroscopic, Charge Summing, Continuous Readout (2009) Fast front end, Simultaneous ToT and ToA (2011) Timepix2 VELOpix 130nm/90nm/65nm Future LHCb readout – Data driven 40MHz ToT 12Gb/s per chip (2013) Timepix3 CLICpix 130nm/90nm/65nm Future Hybrid Pixel Time tagging layer for the LCD project (20??) Abraham Gallas

  9. Timepix2 Main Requirements • Lots of different applications → Very demanding specs ! XAVIER LLOPART– CERN PH-ESE

  10. Sensor thinning • Collaboration with CNM to thin 2D-pixel (55x55 μm) sensor from 300 μm down to 200, 150, 100 μm, p-on-n & n-on-p • Read out with TimePix ASIC • Goal: • Measure resolution, efficiency, … thin sensor • Minimal guard ring design. • Production of module/ladder with 3 ASICs Timepix on SOI 150mm 55Fe Abraham Gallas

  11. Low mass bump bonding • Pixel detectors consist of a sensor chip and ROC which are connected with flip chip bumps. • One of the current technologies (FC µ-bump): • 20-30μm (SnPb, SnAgCu, SnAg, … ) • 40-… μm pixel pitch • For 55(25) μm pixel size adds 0.019(0.091) % Xo • Other technologies that can reduce considerably the material budget: • Solid-Liquid-Inter-Diffusion (SLID) Soldering: • 55 μm pixel sensor: 0.0027 % Xo • 25 μm pixel sensor: 0.013 % Xo • Carbon Nano Fiber (CNF) Interconnections (R&D stage): • 55 μm pixel sensor: 0.00087 % Xo • 25 μm pixel sensor: 0.0042 % Xo Abraham Gallas

  12. In SLID tin, indium or other metals with low melting point (MP) are capped on high melting point (MP) pads, because: • Creation of intermetallic compounds (IMC) with the pad metal. • High planarity requirements of metal-metal bonding (e.g., Cu-Cu) are compensated. • Solid-Liquid-Inter-Diffusion (SLID) soldering, AKA Transient-Liquid-Phase (TLP). • Thin layer of solder turns completely into IMC  ultra thin metallic joints! • After the first reflow the MP increases significantly and becomes thermally very stable. • Cu-Sn-Cu structure is the most commonly used, and with an optimized process Sn transforms to Cu3Sn in some minutes. • Step 2: • Cross-hatched Cu6Sn5 phase consumes the Sn aggressively. • Cu3Sn phase grows on at Cu interfaces. • Step 3: • All Sn has been transformed to IMC’s. • Cu3Sn is taking over Cu6Sn5 and grows at the expense of Cu6Sn5 and Cu. • Step 4: • After long heating, the ductile Cu3Sn expands over the whole area and forms the a thin joint. Solid-Liquid-Inter-Diffusion (SLID) Soldering • Step 1 • Sn reacts with Cu and creates IMC’s. • Cu6Sn5 phase grows in big scallops. • Beginning: • Thick Cu pads and < 5 µm of Sn. • Bonding at 270 – 300 ̊C. SAMI VAEHAENEN – CERN PH-ESE

  13. Carbon Nano Fiber Interconnections • CERN has started a small project with Smoltek (Gothenburg, Sweden) to develop fine-pitch CNF interconnection technique for pixel chips. • Goal is set at growing 5 µm – 10 µm long fibres on chips and joining them together. • Electrical contacts will be tested with/without metal contacts. • CNF’s would be ultra-low mass interconnections. • Technology has prospects to be ultra-fine pitch capable. • High planarity of ROC and sensor is required. • First CNF forests have been deposited on CERN test vehicle chips. • Development plan has been made to improve the patterning resolution and to develop suitable flip chip processes. SAMI VAEHAENEN – CERN PH-ESE Abraham Gallas

  14. Timepix Testbeams Six Testbeams with Timepix in 2009 and 2010 Abraham Gallas

  15. 2009 Testbeam - Proving Timepix Main Measurements: Resolution vs. Angle Resolution vs. Threshold Resolution vs. Silicon Bias Efficiency vs. Threshold Efficiency vs. Bias Timewalk Timepix had not been used at all in a particle tracking application We took the opportunity to run parasitically in three beam periods Tested a 300 mm standard silicon Timepix assembly and a DS3D assembly Abraham Gallas

  16. Three Testbeams in 2009 June 2009 : Medipix Testbeam 3 days to demonstrate tracking July 2009 : CMS SiBit beam period Two weeks – parasitic Timepix Telescope 2 Timepix 4 Medipix ~perpendicular 300μm and 3D DUTs Manual angle adjustment 2 Timepix 2 Medipix ~perpendicular No DUT

  17. August 2009 Timepix Telescope 4 Timepix, 2 Medipix planes in telescope Symmetric positioning of planes around DUT Telescope planes mounted at 9° around x & y to boost resolution DUT position and angle controlled remotely by stepper motors 2.3mm Track Reconstruction Error ~100Hz track rate 1 frame per second ~100,000 tracks per measurement point ~1.5 hours per point in SPS North Area

  18. Angled Planes to Boost Resolution Hits that only affect one pixel have limited resolution (30μm region in 55μm pixel) Tilting the sensor means all tracks charge share and use the ToT information in centroid, CoG calculations 55μm 55μm 9o 0o 300μm 300μm 0o ~10μm resolution 9o ~4.2μm resolution Indicative Timepix events

  19. 2009 Results – Resolution Vs Track Angle Operating point of Telescope planes Resolution result from 2009 testbeam demonstrating resolution of a Timepix assembly and the performance of the telescope

  20. Eta distributions 0o incidence 5o incidence 8o incidence 18o incidence Uncorrected Corrected 1 pixel wide clusters 3 pixel wide clusters 2 pixel wide clusters Abraham Gallas

  21. 2010 Testbeam Activity • 3 beam periods as main user • Added Time Tagging System • May • USB2 readout • 300mm Timepix and PR01 fine pitch microstrip sensor (40μm) • June • USB2 readout • 150mm Timepix and PR01 Strip • August • RELAXD readout • 3D irradiated Timepix, FZ, MCZ, BCB strip, 150mm Timepix and 300mm Timepix • Not all data analysed yet so not too many results to show

  22. 2010 Timepix Telescope 6 pixel telescope planes angled in 2 dimensions to optimise resolution Fine pitch strip detector with fast electronics LHC readout Device Under Test moved and rotated via remote controlled stepper motor

  23. 2010 Telescope in Timepix DUT Configuration In this configuration the telescope was optimized for running with a Timepix DUT The USB2 readout allowed a 7 frame per second readout rate (700Hz track rate) The all angled six Timepix telescope gives a ~2.0μm Track Extrapolation Error Timepix DUT beam Timepix ToT Tracking Timepix ToT Tracking Scintillators to set shutter length to e.g. 100 tracks Shutter Generator

  24. Time Resolution for LHC readouts • Asynchronous SPS beam not suited to LHC systems designed for 25ns bunch structure • Implemented a TDC which with Timepix ToA mode gives us ~1ns per track time stamping • Able to provide and record synchronised triggers to 40MHz readout systems (TELL1) • Allows software reconstruction and analysis of asynchronous tracks Telescope in Time Tagging configuration for LHCb Sensor Readout Timepix ToA Track Time Tagging Plane ~100ns beam PR01 DUT Timepix ToT Tracking Timepix ToT Tracking Scintillator Coincidence and TDC ~1ns Logic + TDC Synchronized Trigger

  25. 150μm Sensor Results With a 150μm sensor the optimum resolution point is at twice the angle of a 300μm The higher data rate allows a significant number of measurements to be taken

  26. RELAXD Readout • High Resolution Large Area X-Ray Detector • RELAXD readout from NIKHEF • 50 frames per second over gigabit Ethernet

  27. August 2010 Telescope – Timepix DUT RELAXD system allowed 55 frames per second readout (~2,500 tracks per second) Each 100,000 point measurement now takes 4 minutes Eight angled Timepix tracking planes gives a ~1.67um Track Extrapolation Error Closer tacking planes reduce multiple scattering effects RELAXD interface RELAXD interface RELAXD interface Cooled DUT Timepix ToT Tracking Timepix ToT Tracking

  28. Cooling system Water Block To operate irradiated assemblies its necessary to cool the sensor to below 0oC This system achieved a steady temperature of ~-5oC Sensor+ROC and Pyrolytic Graphite 80W Peltier Abraham Gallas

  29. Telescope Comparisons EUDET. Telescope Abraham Gallas

  30. Next steps • Module0 construction (3-4 ROC) • Minimal guard ring design • Thinning of ROC (50μm) • Thinning of sensor to 80 μm • Bump bonding thin sensor on thin ROC • Support structures (CVD) Abraham Gallas

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