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Overview History of silicon for tracking detectors & Basics From LHC tracker to SLHC tracker Radiation effects in silicon - defect engineering Device engineering – radiation hard device design Silicon detectors for SLHC n+-p strip detectors n+-p pixel detectors 3D detectors Electronics considerations Conclusions DESY seminar 9.1.2007 Signal formation Isolation techniques G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 1 History and basics DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 2 Position sensitive silicon detectors Planar diodes – structured detectors (Kemmer 1980) photolitografic processing DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 3 First considerations about radiation hardness for HEP - SSC (Detectors and Experiments for the Superconducting Super Collider, pg. 491, Snowmass 1984 1984 considerations for SSC (Detectors and Experiments for the Superconducting Super Collider, pg. 491, Snowmass 1984 Now 105 upra “Silicon strip detectors (near the beam pipe) appear to be limited to…≤ 1032....the 1032 limit could be optimistic.” (PSSC Summary Report pg. 130, 1984) T. Kondo et al, Radiation Damage Test of Silicon Microstrip Detectors, pg. 612, Snowmass 1984 DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 4 And we are we know now … LEP e+e- 1.5∙1031 cm-2 s-1 HERA , Tevatron LHC pp 1.4∙1032 cm-2 s-1 SLHC? pp 1035 cm-2 s-1 •Silicon is a reliable detector technology •Available on large scale (200 m2 CMS) by many vendors with high yield •6’’ wafers are standard, 8’’ are coming •Different silicon growing techniques can be exploited for sensor production (CZ, MCz, FZ, epi-Si) •Many different electronics read-out ASICs were developed •Also other devices are interesting for tracking: CCD, MAPS, DEPFETs … DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 5 Silicon detectors today Signal ~ 22500e in 300mm C~1pF/cm “Standard detector today” for HEP experiments (HERA (all), Belle, LEP, Tevatron) •pitch 25 – few hundred microns •readout strips in p+ side (for SSD) or both sides (for DSD) - around 6 cm long AC/DC coupled •300 mm thick produced on n type-standard float zone silicon •n-type silicon of 2-15 kWcm resistivity •poly-silicon or FOXFET biased on the readout side •Multi guarding structure Physics reasons: •superior position resolution (up to few microns), due to fine segmentation •fast charge collection (tcol~ few ns) for 300 mm thick sensors – high rate operation •dE/dx possible •operational at moderate voltages DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 6 LHC & SLHC DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 7 LHC – new challenge LHC properties Proton-proton collider, 2 x 7 TeV Luminosity: 1034 Bunch crossing: every 25 nsec, Rate: 40 MHz event rate: 109/sec (23 interactions per bunch crossing) Annual operational period: 107 sec Expected total op. period: 10 years Main problems of a tracker at LHC: •Loss of efficiency •fast electronics (high series noise) •charge trapping (loss of signal) •high Ubias , danger of break-down •High power dissipation (8W/module for ATLAS-SCT) •Need for running cool (leakage current) •Need for storing cool to reduce Vfd increase •Large scale – complex services and links DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 8 CMS Overall length: 21.5m, diameter: 15m, total weight: 12500t, magnetic field: 4T ATLAS Overall length: 46m, diameter: 22m, total weight: 7000t, magnetic field: 2T DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 9 • LHC upgrade Super LHC LHC (2007), L = 1034cm-2s-1 f(r=4cm) ~ 3·1015cm-2 500 fb-1 CERN-RD48 Super-LHC (2015 ?), L = 1035cm-2s-1 5 years 2500 fb-1 f(r=4cm) ~ 1.6·1016cm-2 TID=4 MGy CERN-RD50 Phase 1: no major change in LHC L = 2.34 ∙1034cm-2s-1 (higher beam current) Phase 2: major changes in LHC L = 4.6 ∙1034 cm-2s-1 with (BL/2, qc) L = 9.2 ∙1034 cm-2s-1 with (fill all bunches) Phase 3: increase beam energy to 14 TeV (9 to 17 T magnets) DESY seminar 9.1.2007 Pixel (?) Inner Pixel 16 10 Ministrip (?) Q>4000e ~5000e Macropixel (?) 5 eq [cm-2] 10 years SUPER - LHC (5 years, 2500 fb-1) total fluence eq Q>9000e 1015 5 Mid-Radius Short Strips neutrons eq Q>18000e Outer-Radius pions eq “SCT” 1014 5 ATLAS SCT - barrel (microstrip detectors) ATLAS Pixel 13 10 0 10 20 30 40 50 other charged hadrons eq 60 [M.Moll, simplified, scaled from ATLAS TDR] r [cm] Two main problems: •Occupancy increase •Radiation damage G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 10 ATLAS at SLHC (II) Initial studies show that other sub-detectors can be kept with small modifications and some with somewhat degraded performance also at SLHC! ID requires complete replacement, but keeping services at the same level! Long barrel proposal (other “Straw Man” design) ID ATLAS @ LHC ID ATLAS @ SLHC Time plan: R&D 2009, 2010 Construction phase, 2014 Commissioning DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 11 ATLAS at SLHC (III) Simulation studies done to determine optimum segmentation to cope with high track multiplicities: •230 min. bias collisions/BC •10000 tracks for |h|<2.3 Long strips 12 cm x 80 mm Short strips 3 cm x 50 mm Pixels 400x50 mm2 DESY seminar 9.1.2007 LHC SLHC G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC x10 if BCT=25 ns x5 if BCT=12.5 ns 12 Radiation damage in semiconductor detectors DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 13 The CERN RD50 Collaboration http://www.cern.ch/rd50 RD50: Development of Radiation Hard Semiconductor Devices for High Luminosity Colliders formed in November 2001 approved as RD50 by CERN June 2002 Main objective: Development of ultra-radiation hard semiconductor detectors for the luminosity upgrade of the LHC to 1035 cm-2s-1 (“Super-LHC”). Challenges: - Radiation hardness up to 1016 cm-2 required - Fast signal collection (Going from 25ns to 10 ns bunch crossing ?) - Low mass (reducing multiple scattering close to interaction point) - Cost effectiveness (big surfaces have to be covered with detectors!) Presently 260 members from 53 institutes Belarus (Minsk), Belgium (Louvain), Canada (Montreal), Czech Republic (Prague (3x)), Finland (Helsinki, Lappeenranta), Germany (Berlin, Dortmund, Erfurt, Freiburg, Hamburg, Karlsruhe, Munich), Israel (Tel Aviv), Italy (Bari, Bologna, Florence, Padova, Perugia, Pisa, Trento, Turin), Lithuania (Vilnius), Norway (Oslo (2x)), Poland (Warsaw(2x)), Romania (Bucharest (2x)), Russia (Moscow), St.Petersburg), Slovenia (Ljubljana), Spain (Barcelona, Valencia), Switzerland (CERN, PSI), Ukraine (Kiev), United Kingdom (Exeter, Glasgow, Lancaster, Liverpool, Oxford, Sheffield, Surrey), USA (Fermilab, Purdue University, Rochester University, SCIPP Santa Cruz, Syracuse University, BNL, University of New Mexico) DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 14 Radiation damage Two types of radiation damage in detector materials: Bulk (Crystal) damage due to Non Ionizing Energy Loss (NIEL) - displacement damage, built up of crystal defects – I. Increase of leakage current (increase of shot noise, thermal runaway) II. Change of effective doping concentration (higher depletion voltage, under- depletion) III. Increase of charge carrier trapping (loss of charge) Surface damage due to Ionizing Energy Loss (IEL) - accumulation of charge in the oxide (SiO2) and Si/SiO2 interface – affects: interstrip capacitance (noise factor), breakdown behavior, … ! Signal/noise ratio = most important quantity ! DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 15 particle Sis Frenkel pair Vacancy + Interstitial EK > 25 eV Point Defects (V-V, V-O .. ) V I EK > 5 keV clusters Influence of defects on the material and device properties charged defects Neff , Vdep e.g. donors in upper and acceptors in lower half of band gap DESY seminar 9.1.2007 Trapping (e and h) CCE shallow defects do not contribute at room temperature due to fast detrapping generation leakage current Levels close to midgap most effective G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 16 Selecting rad-hard materials for tracker detectors at SLHC Main Selection Parameters High CCE Main Operative Characteristics Main Material Characteristics High crystalline quality & negligible rad-induced deep traps Negligible trapping effects High E field close r-o elect. Low noise Low power High speed Low leakage current No type inversion Low dielectric constant big bandgap Thin thickness Low full depletion voltage High resistivity but: higher e-h High mobility & saturation field creation energy Cost-effective but: higher capacitance Commercially available in large scale DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 17 New Materials: Diamond, SiC, GaN Property Eg [eV] Ebreakdown [V/cm] me [cm2/Vs] mh [cm2/Vs] vsat [cm/s] Z r e-h energy [eV] Density [g/cm3] Displacem. [eV] Diamond 5.5 107 1800 1200 2.2·107 6 5.7 13 3.515 43 GaN 3.39 4·106 1000 30 31/7 9.6 8.9 6.15 20 4H SiC 3.26 2.2·106 800 115 2·107 14/6 9.7 7.6-8.4 3.22 25 Si 1.12 3·105 1450 450 0.8·107 14 11.9 3.6 2.33 13-20 R&D on diamond detectors: RD42 – Collaboration http://cern.ch/rd42/ CCE at high fluences degrades even more in SiC and GaN than in Si. DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC Wide band gap (3.3eV) lower leakage current than silicon Signal: Diamond 36 e/mm SiC 51 e/mm Si 80 e/mm more charge than diamond Higher displacement threshold than silicon radiation harder than silicon (?) 18 Approaches to develop radiation harder tracking detectors •Material engineering •Device engineering •Change of detector operational conditions CERN RD39 “Cryogenic Tracking Detectors” DESY seminar 9.1.2007 Defect Engineering of Silicon Understanding radiation damage Macroscopic effects and Microscopic defects Simulation of defect properties & kinetics Irradiation with different particles & energies Oxygen rich Silicon DOFZ, Cz, MCZ, EPI Oxygen dimer & hydrogen enriched Si Pre-irradiated Si Influence of processing technology Device Engineering (New Detector Designs) p-type silicon detectors (n-in-p) thin detectors 3D and Semi 3D detectors Stripixels Cost effective detectors Simulation of highly irradiated detectors Monolithic devices G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 19 Change of Depletion Voltage Vdep (n-type material – RD48 results) …. with time (annealing): 103 1000 500 102 600 V type inversion 100 50 101 1014cm-2 10 5 1 10-1 100 "p-type" n-type [M.Moll: Data: R. Wunstorf, PhD thesis 1992, Uni Hamburg] 10 0 10 1 10 2 eq [ 10 cm ] 12 10 3 10 10-1 -2 • “Type inversion”: Neff changes from positive to negative (Space Charge Sign Inversion) p+ before inversion DESY seminar 9.1.2007 n+ p+ n+ after inversion neglecting double junction Neff [1011cm-3] 5000 | Neff | [ 1011 cm-3 ] Udep [V] (d = 300mm) …. with particle fluence 8 6 NY NA 4 NC gC eq 2 NC0 [M.Moll, PhD thesis 1999, Uni Hamburg] 0 1 10 100 1000 10000 annealing time at 60oC [min] • Short term: “Beneficial annealing” • Long term: “Reverse annealing” - time constant depends on temperature: ~ 500 years (-10°C) ~ 500 days ( 20°C) ~ 21 hours ( 60°C) - Consequence: Detectors must be cooled even when the experiment is not running! G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 20 The role of the oxygen in the Si (Vfd (I)) 8 Carbon-enriched (P503) Standard (P51) O-diffusion 24 hours (P52) O-diffusion 48 hours (P54) O-diffusion 72 hours (P56) Carbonated 500 MCz-n Helsinki 6 Standard Oxygenated 2 0 0 400 300 4 200 100 1 2 3 4 24 GeV/c proton [10 cm ] 14 -2 In FZ detectors irradiation introduces effectively negative space charge! 600 5 Vdep [V] (300 mm) |Neff| [1012cm-3] 10 For detectors irradiated with charged hadrons RD48: Higher oxygen content less negative space charge For detectors irradiated with charged hadrons RD50: High initial oxygen dimmer (O2i) MCz/Cz and Epitaxial silicon detectors positive space charge (Bi-stable donors) Increase of Vfd at high fluences is roughly the same in all O rich materials |Neff|~7·10-3 cm-1 p ! Almost independent of oxygen content: Donor removal “Cluster damage” negative charge DESY seminar 9.1.2007 After neutron irradiation all materials behave similarly and neutrons are 3x (except epi-Si) more damaging than charged hadrons! G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 21 Proton irradiated oxygen rich detectors (Vfd (II)) 4.00E+02 8.E+12 500 V MCz - n (CNM) 3.50E+02 MCz - n (2e14) 6.E+12 3.00E+02 DOFZ n (2e14) 5.E+12 2.50E+02 7.E+12 Vfd [V] |Neff| [1/cm3] DOFZ n (CNM) 4.E+12 2.00E+02 3.E+12 1.50E+02 2.E+12 1.00E+02 300 mm thick sensors 1.E+12 End of LHC 5.00E+01 0.00E+00 0.E+00 0 2E+14 4E+14 6E+14 8E+14 1E+15 Fluence [24 GeV p/cm2] Do we undergo SCSI NO verified by TCT & annealing curves 1.2E+15 1.00E+00 1.00E+01 1.00E+02 1.00E+03 1.00E+04 Annealing time @ 80C [min] beneficial and reverse annealing similar to that of n-type STFZ, DOFZ materials •Positive space charge is compensated by negative formed during RA •Reverse annealing time constants are prolonged by high concentration of O DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 22 Thin n-type epitaxial Si detectors-CERN-scenario experiment S-LHC: L=1035cm-2s-1 Most inner pixel layer 250 50 mm after 50 min@80C annealing Parameters operational period per year: 100 d, -7°C, Φ = 3.48·1015cm-2 beam off period per year 265 d, +20°C positive stable damage negative space charge during RA 9.1.2007 200 Vfd [V] extracted at elevated annealing fit measurements at room temperatures very well Very good reproducibility and working model (BA, constant damage, 1st order RA, 2nd order RA) DESY seminar (Vfd (III)) 150 25 mm after 50 min@80C annealing 50 mm simulation 100 50 25 mm simulation G. Lindström et al. 0 0 2.1015 4.1015 6.1015 8.1015 eq [cm-2] 1016 Compensation The scenario can be found where the Neff can be controlled. Increase of Vfd is not a limiting factor for efficient use of Si detectors! G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 23 Neutron irradiated epitaxial Si detectors (V fd (IV)) 8.00E+13 neutrons 7.00E+13 no SCSI Neff [cm-3] 6.00E+13 n-type detectors 5.00E+13 SCSI 4.00E+13 3.00E+13 Epi75 - ST (CiS); 150 Ohm cm Epi75 - DO (CiS); 150 Ohm cm 2.00E+13 Epi150 (IRST); 500 Ohm cm 1.00E+13 Epi25 - (CiS); 50 Ohm cm Epi50 - (CiS); 50 Ohm cm 0.00E+00 0.00E+00 2.00E+15 4.00E+15 G. Kramberger et al., 8th RD50 workshop SMART coll., 8th RD50 workshop 6.00E+15 8.00E+15 1.00E+16 1.20E+16 Equivalent fluence [cm-2] Neutrons: smaller increase of |Neff| with fluence than in any other material |gc|~5·10-3 cm-1 no SCSI for r=50 Wcm ; SCSI for r>150 Wcm 20<r<60 cm 200 mm , max=2∙1015 cm-2 Vfd < 300 V Not easy to produce DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 24 Trapping of the drifting charge (I) (-10oC, Vfd) t=min [10-16 cm2/ns] 24 GeV protons 200 MeV/c pions (average ) Electrons 5.6 ± 0.7 Holes 6.6 ± 0.8 1 reactor neutrons 4.1 ± 0.5 6.0 ± 0.4 eff ,e,h e,h (T , t ) eq The e,h was so far found independent on material; resistivity [O], [C] type (p,n) wafer production (FZ, Cz, epitaxial) somewhat lower trapping at eq>1015 cm-2 extrapolated values Remember we have a mixture of pions and neutrons in experiments! r~4cm r~20cm r~60cm electrons for higher fluences eff ,e,h t drift holes DESY seminar 9.1.2007 300 mm 3ns vsat G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 25 Trapping of the drifting charge (II) e,h (T , t ) 0 exp( t t t ) 1 exp( ) ( 0 ) exp( ) ta ta ta Neutron irr. 0 0 Electrons Holes an @60oC Eta[eV] 0.3±0.15 ~650 min 1.06±0.1 -0.4±0.2 ~550 min 0.98±0.1 Ea k BT an 0 exp Confirmed also by ATLAS pixel test beam! T. Lari, Nucl. Inst. Meth. A518 (2004) 349. e,h (T , t ) Trapping probability decreases with temperature, but mobility also! Operation at lower T doesn’t improve CCE ! DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 26 Leakage current 10-2 10-3 …. with particle fluence: -5 10 1012 1013 eq [cm-2] 1014 1015 [M.Moll PhD Thesis] Damage parameter (slope in figure) I α V eq n-type FZ - 780 Wcm n-type FZ - 410 Wcm n-type FZ - 130 Wcm n-type FZ - 110 Wcm n-type CZ - 140 Wcm p-type EPI - 380 Wcm 10-4 10-6 11 10 6 n-type FZ - 7 to 25 KWcm n-type FZ - 7 KWcm n-type FZ - 4 KWcm n-type FZ - 3 KWcm p-type EPI - 2 and 4 KWcm Leakage current per unit volume and particle fluence is constant over several orders of fluence and independent of impurity concentration in Si can be used for fluence measurement DESY seminar 9.1.2007 (t) [10-17 A/cm] I / V [A/cm3] 10-1 with time (annealing): 6 80 min 60C 5 4 5 4 3 3 2 2 . 1 0 1 17 -3 oxygen enriched silicon [O] = 2 10 cm parameterisation for standard silicon 1 [M.Moll PhD Thesis] 10 100 1000 o 10000 annealing time at 60 C [minutes] Leakage current decreasing in time (depending on temperature) Strong temperature dependence: E I exp g 2k BT Consequence: Cool detectors during operation! Example: I(-10°C) ~1/16 I(20°C) G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 27 Device engineering DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 28 Device engineering - Signal in Si detectors (I) t r (t ) t 0 r0 Q Idt q v Ew dt q Ew dr t t 0 Q q[U w (r ) U w (r0 )] p+ 280 mm Weighting field hole electron Qe h Qe Qh U w 0 sensing electrode Uw 1 all other electrodes Uw 0 n+ Contribution of drifting carriers to the total induced charge depends on Uw ! Uw simple in diodes and complicated in segmented devices! For track: Qe/(Qe+Qh)=19% in ATLAS strip detector DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC n+ diode Qh=Qe=0.5 q segmentation 80 mm pitch 18 mm implant 29 Device engineering - Signal in Si detectors (II) I qv Ew Q(t ) drift current tint tint Idt q exp( t 0 t 0 t 0 ) me,h E Ew dt eff ,e , h scalar field in which the carrier drifts Terms different for holes and electrons •trapping term ( eff,e~eff,h ) •drift velocity ( me~3mh ) electrons get less trapped example of inverted p+-n 280 mm fully depleted detector with 25 mm pitch DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 30 Device engineering - Signal in Si detectors (III) E , Ew , E Ew p+ diode good n+ Segmented readout small Ew E worse even worse: p+ readout (p+-n detector) Segmented readout large Ew E better even better: n+ readout (n+-p, n+-n detector) How to get maximum signal? use of n+-n or n+-p device (electron collection) with pitch<<thickness implant width close to pitch (depends on FE elec. – inter-electrode capacitance) for a given cell size of a pixel detector DESY seminar 9.1.2007 pitchx 0, pitchy G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 31 Device engineering - Signal in Si detectors (IV) eff ,e,h tdrift p+ n+ Segmented readout electrons Ew p+ n+ Segmented readout Ew Carriers in this region would be trapped before reaching high Ew! It doesn’t matter if the region is depleted or not - under-depleted detectors would perform almost as good as fully depleted! DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 32 Device engineering Trapping induced charge sharing Incomplete charge collection due to trapping results in appearance of the charge in the neighboring strips! bipolar pulse measuring Idt 0 n+ strips (higher signal) p+ p+ strips (wider cluster) p bulk n+ diode 0 ±U 81% Signals in the neighbors few % of the hit strip observed in atlas test beam Y. Unno et al., IEEE Trans. NS 49(4) (2002) 1868 DESY seminar 9.1.2007 Depends strongly on fluence position of the hit and electrode geometry! G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 33 Device engineering Isolation techniques n+-side readout (I) strip 1 strip 2 ++++++++ oxide isolation structure needed to interrupt the inversion layer between the strip n+ n+ p- substrate electron layer p+ backplane 3 techniques available (from n+-on-n technology): p-stop p-spray S1 S2 high-field regions S1 p-spray/p-stop S2 S1 high-field regions Cint, VBR improve with radiation Cint, VBR degrade with radiation (Oox), better initially (Oox), worse initially S2 high-field region depends on Qox compromise Simulations needed for each design of a detector to find an optimum! DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 34 Silicon detectors for SLHC DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 35 n+-p short strip detectors (20<r<60 cm) Detector geometry: Thickness=300 mm, strip pitch=80 mm, implant width= 18 mm, LHC speed readout (SCT128A-HC), beta source measurements n-in-p : standard FZ p-in-n : oxygenated and standard FZ 25% charge loss after 5x1014 p/cm2 (23 GeV) over-depletion is needed Q/Q0 [%] 100 ~40% charge loss after 3x1015 p/cm2 (23 GeV) ~7000 e after 7.5x1015 p/cm2 (23 GeV) max collected charge (overdepletion) Vfd 80 Vfd~1200 V CCE~60% 60 collected at depletion voltage 40 Vfd>2500 V oxygenated standard 20 CCE~30% M.Moll [Data: P.Allport et all, NIMA 501 (2003) 146] 0 0 1 2 3 4 p [1014 cm-2] P.P. Allport et al., IEEE Trans. NS 52(5) (2005) 1903. 5 Much better performance DESY seminar 9.1.2007 (same charge 6x the fluence + under-depleted operation) G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 36 n+-p short strip detectors (20<r<60 cm) time [days at 20oC] T=-20oC, Vbias=900 V Trapping times tend to longer than predicted at high fluences! CCE (103 electrons) recent neutron irradiated samples 20 18 16 14 12 10 8 6 4 2 0 0 500 1000 1500 2000 2500 800 V 1.1 x 1015cm-2 500 V 3.5 x 1015cm-2 (500 V) 7.5 x 1015cm-2 (700 V) [Data: G.Casse et al., to be published in NIMA] M.Moll 0 100 200 300 400 500 time at 80oC[min] At first unexpected behavior of CCE(t) Possible explanation: •Increase of Vfd (not so important as electric field is still present close to electrodes) •Annealing of electron trapping times CONFIRMED also by simulations! The reverse annealing is not critical as for LHC! DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 37 n+-p short strip detectors – super modules LBNL proposal (evolved from CDF run IIb) Liverpool proposal TPG baseboard DESY seminar 9.1.2007 Bridging structure G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 38 n+-p short strip detectors – shot noise STFZ detectors Short strips at r=35 cm (3 cm x50 mm) P. Allport et al. ENCleak 12 I leak shaping CR-RC shaping 25 ns shaping time Short strips should have noise below 1000 e – dominated by series noise ENCseries C In order to keep the noise below the desired limit ENCleak<500e , T<-15oC DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 39 Long strip detectors (r>60 cm) Present technology (STFZ p+-n) pushed to the higher radii may work – however practical issues cold/warm during the beam-off must be considered Better would be n+-p type detectors (regardless of the silicon type – neutron dominated damage) higher signal and possible use potentially of longer strips to reduce # of channels and have the same S/N No ballistic deficit with BCT=12.5 ns Smaller operational voltage needed and no critical issue if Vfd>operational bias (safety) DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 40 Planar n+-p pixel detectors (r<20 cm) •Pion dominated damage – choice of material for these detectors MCz or epi-Si! •Detectors of some 200 mm almost ideal choice if kept warm during beam-off period Compensation of positive space charge with acceptors during RA (always fully depleted) Annealing of electron trapping times – smaller effect of trapping Smaller power dissipation due to smaller leakage current and bias voltage Smaller shot noise Epi-Si,75 mm n. irr diodes •after annealing (reduction of Vfd and electron trapping times) •after segmentation (higher contribution of electrons) DESY seminar 9.1.2007 ~4000e@1016cm-2 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 41 10 years of LHC (4 cm) at 1034 cm-2 s-1 10 years of SLHC (4 cm) 1034 cm-2 s-1 (60,100,160V) Threshold needed on pixel FE electronics is for ATLAS and CMS pixels around 3500-4000 electrons! Can we hope for better electronics? (500V) more charge at lower voltages (<300 V) with epi-Si (600 V) DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 42 3D n+-p pixel detectors (r<20 cm) Combine traditional VLSI processing and MEMS (Micro Electro Mechanical Systems) technology. Both electrode types are processed inside the detector bulk instead of being implanted on the wafer's surface. The edge is an electrode. Dead volume at the Edge < 5 microns! Essential for forward physics experiments and material budget S.I. Parker, C.J. Kenny, J. Segal, Nucl. Instr. and Meth. A395 (1997) 328. DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 43 3D n+-p pixel detectors (r<20 cm) Pros. •Better charge collection efficiency •Faster charge collection (depends on inter-column spacing) •Reduced full depletion voltage and by that the power •Larger freedom for choosing electrode configuration DESY seminar 9.1.2007 Cons. •Columns are dead area (aspect ratio ~30:1) •Spatially non-homogenous CCE (efficiency=function of position) •Much higher electrode capacitance (hence noise), particularly if small spacing is desired – small drift length •Availability on large scale •Time-scale and cost G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 44 •Volume = 1.2 x 1.33 x 0.23 mm3 •3 electrode Atlas pixel geometry •n-electrode readout •n-type before irradiation - 12 kW cm •Irradiated with neutrons DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 45 Different geometry – 3D sct (RD50) C. Piemonte et al., IRST Sketch of the detector: Functioning: n-columns ionizing particle n+ p-type substrate DESY seminar 9.1.2007 grid-like bulk contact electrons are swept away by the transversal field G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC n+ cross-section between two electrodes holes drift in the central region and diffuse towards p+ Contact (long tail) 46 undepleted 300 or 500 mm 150 mm Different geometry – 3D sct 3D-stc DC coupled detector (64 x 10 columns) 80 mm pitch 80 mm between holes 10 mm hole diameter Inter-column region depleted @ 12 V Active Thickness [um] Diode like structure CCE measurements (slow shaping time) 600 Focused IR laser of 7 mm spot size 3 strips connected to amplifier Thickness calculated from signal 500 400 300 200 100 Florence C-V UCSC 0 0 50 100 150 200 Voltage [V] DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 47 Different geometry – 3D dct 1um 0.4um Passivation Oxide 50mm Designed proposed by RD50 collaboration (IRST, CNM, Glasgow) Metal 5mm n+ doped P-stop p+ 10mm TEOS 2um 300mm Poly 3mm p- type substrate p+ doped 50mm p+ doped •much simplified process – no need for support wafer during production •single sided processing with additional step of etching and B diffusion •Performance equal to original design Oxide Metal 55um pitch DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 48 Electronics – deep sub micron CMOS (ATLAS pixel, CMS all) Vth tox2 DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 49 Electronics – BiCMOS •Short shaping times (12.5 ns) • large capacitances Bipolar transistors perform better in terms of noise-power (CMOS requires larger bias current) BiCMOS in atlas not radiation hard enough and not available anymore 100 1e14 40 Bipolar SiGe transistors “married” to DSM-CMOS 200 3e15 50 @ I c 10mA fT 50 GHz DESY seminar 9.1.2007 Around 4 times smaller power consumption than present design G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 50 Conclusions The ideal detector is the one which can be depleted all the time and kept at room temperature during beam-off periods – we are almost there! Sensor technology for SLHC tracker Long strips (present p+-n cost effective or n+-p) Short strips/pixel (n+-p on rad-hard material) Pixel layers without innermost layer (n+-p pixels on rad-hard material) Pixel layer at 4-6 cm (to be decided between diamond and silicon planar or 3D pixels) Electronics technology: all DSM-CMOS or BiCMOS (with SiGe bipolar part) for strips The most challenging will be engineering work (cooling, cabling, shielding, other services) Prospects are good, but work ahead is enormous! Let’s wait to see first results from LHC, before … DESY seminar 9.1.2007 G. Kramberger, Jožef Stefan Institute, Towards Radiation Hard Silicon Detectros at SLHC 51