1 / 31

Monolithic Active Pixel Sensors for the TESLA Vertex Detector

Monolithic Active Pixel Sensors for the TESLA Vertex Detector. - Student Seminar, 13 June 2003 -. Devis Contarato University of Hamburg. Outline. Introduction: TESLA requirements Principles of operation of MAPS Activities of the DESY/Uni-HH group Charge collection simulations

aderes
Télécharger la présentation

Monolithic Active Pixel Sensors for the TESLA Vertex Detector

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Monolithic Active Pixel Sensors for the TESLA Vertex Detector - Student Seminar, 13 June 2003 - Devis Contarato University of Hamburg

  2. Outline • Introduction: TESLA requirements • Principles of operation of MAPS • Activities of the DESY/Uni-HH group • Charge collection simulations • Test-stand measurements • Conclusions D. Contarato STUDENT SEMINAR - 13 June 2003

  3. B=4 T Introduction: requirements of TESLA VXD • High impact parameter resolution • spatial resolution<5 m • multiple scattering<0.1% X0 • thin layers ~50 m • High granularity (high jets multiplicity) • pixel pitch of ~20x20 m2 • High occupancy (e+e- pairs background) • fast read-out • on-line data sparsification The technology needs to combine high granularity, little multiple scattering, high read-out speed and radiation hardness: • Harsh radiation environment: • neutron5·109 n(1 MeV)/cm2/5 years • Dionisation= 100 kRad/5 years Pixel detectors D. Contarato STUDENT SEMINAR - 13 June 2003

  4. Technological options for the TESLA VXD • Charge Coupled Devices (CCD) • Active Pixel Sensor (APS) • - Hybrid Active Pixel Sensors (HAPS) • (present day technology for pixel detectors in HEP) • - Monolithic Active Pixel Sensors (MAPS) • (the technology for future LC?) D. Contarato STUDENT SEMINAR - 13 June 2003

  5. Charge Coupled Devices (CCDs) • thin detectors • charge is transferred through the bulk (radiation hardness?) • column-parallel read-out (to improve the limited read-out speed) • low power dissipation D. Contarato STUDENT SEMINAR - 13 June 2003

  6. chip sensor Hybrid Pixels • The read-out chip is mounted directly on top of the pixels (bump-bonding) • Each pixel has its own read-out amplifier • Fast read-out and rad-hard • … but: • Pixel area limited by the size of the read-out chip • High material budget and high power dissipation D. Contarato STUDENT SEMINAR - 13 June 2003

  7. Principle of operation of MAPS 15 µm • double-well CMOS process with epitaxial layer • the charge generated by the impinging particle is reflected by the potential barriers due to doping differences and collected by thermal diffusion by the n-well/p-epi diode • 100% fill factor • integration of the circuitry electronics on the same sensor substrate Reset Collection Output Reset… D. Contarato STUDENT SEMINAR - 13 June 2003

  8. MAPS: a technology for the TESLA VXD? • CCDs • thin (low material budget), good granularity • low read-out speed and neutron radiation tolerance to be proved • Hybrid pixels • fast and (presumably) more radiation-hardened thick (high material budget), poor granularity • MAPSseem to combine the positive features of both: • high granularity and possibility ofthinning down • improved read-out speed • radiation tolerance • use of a standard and cheap CMOS technology D. Contarato STUDENT SEMINAR - 13 June 2003

  9. First prototypes: MIMOSA I – II MIMOSA = Minimum Ionising MOSActive pixel sensor MIMOSA I: technology demonstration • standard 0.6mm CMOSof AMS • 14m thick EPI layer (1014cm-3) • pixel pitch 20x20 m2 • 4 arrays 64x64 pixels • analogue readout - max. clock freq.: 5MHz die size 3.6x4.2mm2 MIMOSA II: noise and radiation tolerance studies (use of different pixel layouts) • standard 0.35mm CMOS of MIETEC • 4.2 mthick EPI layer (1015cm-3) • pixel pitch 20x20 m2 • 6 arrays 64x64 pixels; • radiation toleranttransistor design • analogue readout - max. clock freq.: 25MHz die size 4.9x3.5 mm2 D. Contarato STUDENT SEMINAR - 13 June 2003

  10. 128x128 APS array max 40 MHz readout test APS arrays First prototypes : MIMOSA III – IV MIMOSA III: trial of a deep-submicronic process • standard 0.25 mCMOS of IBM • 2.5 m thick EPI layer(~1015 cm-3) • pixel pitch 8x8 m2 • 2 arrays 128x128 pixels • analogue readout - max. clock freq. 40 MHz die size 4.0x2.0 mm2 MIMOSA IV: study of substrate contribution and of new charge sensing elements • standard 0.35 m CMOS of AMS • p-substrate process(~1014cm-3): no EPI layer • pixel pitch 20x20 m2 • 4 arrays 64x64 pixels • radiation tolerant transistor design • analogue readout - max. clock freq.40 MHz die size 3.7x3.8 mm2 D. Contarato STUDENT SEMINAR - 13 June 2003

  11. MIMOSA V: first real-size prototype chip size 1.73x1.73 cm2 Wafer view • standard 0.6mm CMOS of AMSwith 14m thick EPI layer(1014cm-3) • pixel pitch17x17m2 • 4 independent matrices of 510x512 pixels read-out in parallel • first real size prototype: 3.5 cm2, 1M pixels • serial analogue readout - max. clock freq.: 40 MHz • back-thinning down to 120 mm • coarse stitching (~100 mm) D. Contarato STUDENT SEMINAR - 13 June 2003

  12. Achievements of first MAPS prototypes (Ires-Lepsi, Strasbourg,France) • Good and promising tracking performances of the small-scale prototypes: ~99%,sp~1.5-2.5 m, S/N~30. • Preliminary results with MIMOSA V show that these performances are reproducible with real-size detectors (…BUT: problems connected with large area chips: yield, noise) • Tolerance to neutrons exceeds TESLA requirements (…BUT:degradation after ionizing radiation, not understood) • Technology without EPI-layer (MIMOSA IV) has also shown good perfomances (…BUT: poorer resolution due to larger charge spread) • R&D collaboration started from Strasbourg and joined by several centers in Europe (F-D-CH-NL) D. Contarato STUDENT SEMINAR - 13 June 2003

  13. DESY/Uni-HH activities on MAPS • Detector performance and radiation damage studies • Simulation of charge collection (ISE-TCAD) • Test-stand and test-beam measurements (MIMOSA V) • Radiation damage and material investigations • Mechanical design and cooling • Mechanics: CAD design of VXD layers layout • VXD cooling: simulations, material budget, power switching • General detector design and optimization • - Physics simulation of Vertex Detector D. Contarato STUDENT SEMINAR - 13 June 2003

  14. Issues for device simulation (ISE-TCAD) • 3-D device physics simulations are performed in order to: • understand the charge collection mechanism and its time properties • estimation of the charge collection efficiency • study of the spatial charge spreading onto neighboring pixels • study of theinfluence of technological parameterson the sensor charge collection properties • optimisation of the sensor design D. Contarato STUDENT SEMINAR - 13 June 2003

  15. Boundaries… Doping… Mesh… Physics… Parameters… Solve… + Description of boundaries, doping and mesh Overview of ISE-TCAD simulations MESH GENERATOR Physical models and parameters DEVICE PHYSICS SIMULATOR SIMULATION RESULTS VISUALISATION TOOLS D. Contarato STUDENT SEMINAR - 13 June 2003

  16. Particle track • Simulated structure: 3-dim model of 3x3 pixel cluster (3 pixels in 2-dim) • Technological details and doping profiles from foundry (approximate) • The passage of a MIP is simulated introducing an excess charge (80 e-h pairs/µm) • Transient simulation: relaxation process of achieving equilibrium after the particle passage • Study of different impact positions for the simulated MIP Simulation of charge collection 0 nsec 1 nsec 10 nsec 20 nsec D. Contarato STUDENT SEMINAR - 13 June 2003

  17. MIMOSA V Simulation Central hits particle track Pixel pitch 17 mm, diode 3 mm, EPI-thickness 14 mm, 3x3 pixels cluster • larger diffusion in the epilayer, fast recombination in the substrate (different carrier lifetimes) • expected signal ~1100 e: large charge sharing (clustering) • charge collection times <100 ns • ratio Qsingle/Q3x3~60% agrees well with measurements D. Contarato STUDENT SEMINAR - 13 June 2003

  18. Going to deep-submicron technology Configuration of the collecting diode in a sub-m process with Shallow Trench Isolation Example of simulated structure and geometrical parameters used in the simulations • Future: probably only deep-submicron technology available • smaller epilayer thickness (smaller signal) • latch-up of the transistors requires trench isolation • radiation-induced interface states at the Si/SiO2 interface • substrate contribution to the collected charge D. Contarato STUDENT SEMINAR - 13 June 2003

  19. Charge collection in deep-submicron MAPS Pixel pitch 20 mm, diode 1 mm, EPI-thickness 28 mm, typical doping profiles Mean • Linear dependence of collected signal on epilayer thickness • Important substrate contribution • A thinner epilayer results in smaller signal, butlimited charge spreadingand shorter collection times(faster collection) D. Contarato STUDENT SEMINAR - 13 June 2003

  20. Simulation of interface damage No shallow trench isolation Shallow trench isolation Epi 8 µm (Interface traps concentrations: 1011, 1012 1/eVcm2~500 krad, Wüstenfeld 2001, Ph.D. thesis) • Significant dependence of the collected charge on the trench geometry (mainly on depth, less dependence on trench width) • Collection times are not affected • How to overcome the problem: PolySi instead of Si02? D. Contarato STUDENT SEMINAR - 13 June 2003

  21. Test stand • MIMOSA V chip(256K pixels/matrix) • clocked with 10 MHz • chip read-out 26ms • Cooling unit • VME-Based readout • - clock & reset signals • - ADC board • Source tests • 55 Fe - X ray, 106 Ru - electrons • Planned tests: • Test-beam • IR laser light injection • Temp. and B-field dependence • on/off power switching D. Contarato STUDENT SEMINAR - 13 June 2003

  22. Data acquisition system Interface board -Repeater Cooling block (0oC<T<40oC) Imager board – VME Flash ADC unit Repeater board Chip MIMOSA V chip on front-end board and cooling unit Source Serial analog output VME-based read-out system and hardware data processing units Software for data acquisition and analysis ADC & Imager board Cooler & Thermostat D. Contarato STUDENT SEMINAR - 13 June 2003

  23. Signal processing and Analysis source • Correlated Double Sampling (CDS) on-line: Signal=(Frame2-Frame1) • Analysis: • - central pixel with S/N>10 required • - when found array of 5x5 pixels investigated: neighbors with S/N>2 included in cluster signal • Software for analysis (and DAQ) under development! Fe55 HIT MAP y [pixel] x [pixel] D. Contarato STUDENT SEMINAR - 13 June 2003

  24. Pedestals Pixel pedestal distribution Mean pedestal vs. temperature • T of the coolant and not of the detector is given: there may be a systematic shift • Common-mode noise subtracted • Asymmetrical distribution • Error bars are RMS of the pixel pedestal distribution • Good agreement with fit function: Pedestals ( Ileak ) can be used to measure Ileak after irradiation Leakage current term D. Contarato STUDENT SEMINAR - 13 June 2003

  25. Noise Pixel noise distribution Mean noise vs. temperature T=287 K • Error bars are RMS of the pixel distribution and not the error of the mean • The fit function shows good agreement with the expected behavior: Noise  (Ileak)1/2 Leakage current term D. Contarato STUDENT SEMINAR - 13 June 2003

  26. Calibration with 55Fe 5.9 keV line 6.4 keV line T=287 K • Looking for conversion of the photon in the n-well diode: no charge should appear on the neighbors. • A pixel with S/N>10 is required and NO pixel around it with S/N>1! • 5.9 keV peak used to calibrate the noise:ENC~30-35 • (average pixel noise ~3 ADC counts) • Expected signal from m.i.p. are around 1000 e S/N~30 D. Contarato STUDENT SEMINAR - 13 June 2003

  27. 106Ru - electrons Cluster size distribution Cluster Signal single pixel 3x3 array 5x5 array S/Nneig.=2 Landau fit • S/Ncluster~28(close to that predicted from Fe X-source and noise) • Small difference in most probable signal between 3x3 and 5x5 pixel arrays • Average cluster size ~6 • Spectrum broader than for m.i.p. D. Contarato STUDENT SEMINAR - 13 June 2003

  28. Current developments • Current plans • MAPS with integrated functionalities and on-pixel data processing • New charge-sensing elements: photoFET • Basic radiation studies (test structures) • Exploring fabrication processes (optimum EPI thickness ~8 m) • Goals • Optimisation of detector performances, read-out architecture (CP) and speed (~50 MHz), material and power budget • Fabrication of ladders, improvement of thinning processes • Improvement of radiation tolerance D. Contarato STUDENT SEMINAR - 13 June 2003

  29. MIMOSA VI: integrated data processing AC coupling capacitor Charge storage capacitors Single pixel layout Chip layout • standard 0.35mm CMOS of MIETEC • 4.2 mthick EPI layer(1015cm-3) • pixel pitch 28x28m2 • 1 array 30x128 pixels – 29 transistors/pixel • 24 columns read-out in parallel - max. clock freq.: 30 MHz • Amplification and Correlated Double Sampling on-pixel D. Contarato STUDENT SEMINAR - 13 June 2003

  30. MAPS show good and promising performances for VXD tracking • DESY/Uni-HH group active on chip tests, radiation studies, physics simulation and engineering issues • Full detector simulation tools available • - charge collection simulations • - potential danger of deep-submicron technologies • First results on large-scale prototype • - pedestals and noise resemble leakage current behavior • - cooling is needed to reduce noise • - calibration with 55Fe: ENC~30e -> S/N~30 • - next steps: test-beam studies, irradiations Conclusions D. Contarato STUDENT SEMINAR - 13 June 2003

  31. Open questions • Radiation-tolerance: mechanisms not fully understood. Need for: • test structures for basic studies • device simulations based on measured microscopic parameters • Problems: availability of test structures, lack of technology details • - high energy electrons: might represent an issue? • Mechanics: design of mechanical support in terms of material budget, handling, backthinning • Cooling: power dissipation ~1 kW for the full VXD. Is it possible to switch off between bunch trains?  switch on/off tests • Technological choice for the TESLA VXD not before 2004: will MAPS be ready? D. Contarato STUDENT SEMINAR - 13 June 2003

More Related