KIT – Universität des Landes Baden-Württemberg und nationales Forschungszentrum in der Helmholtz-Gemeinschaft Status Interstrip resistance of n-in-p type sensors with p-stop – T-CAD studies INSTITUT FÜR EXPERIMENTELLE KERNPHYSIK

Martin Printz, IEKP – KIT HW meeting Interstrip resistance of n-in-p (R int ) n-in-p type sensors are baseline for Tracker Phase II Upgrade strip sensors are AC coupled oxide between n+ implant and Alu strip oxide is charged positively positive charge in oxide increases with dose accumulation layer of e - between n+ strips shortcut -> signal diffuses -> bad! need isolation structure p-stop or p-spray p+ material Fluka simulation; current trackerOxide charge from MOS measurments; A. Nürnberg

Martin Printz, IEKP – KIT HW meeting R int – process dependencies of p+ R int dosis energy gas flowtemperature Our (CMS) specs for p+ isolation which we provide to the vendor are always: peak doping concentration doping depth...and probably more ?

Martin Printz, IEKP – KIT HW meeting R int – how we measure Probestation measurement voltage ramp between adjacent strips (on DC pads) Fig.: Probe needles on DC pads. Ramp voltage to 1V or 2V in Δ0.2V steps. Slope of the measured current isthe interstrip resistance. (Schematics from A.Furgeri, Thesis 2005)

Martin Printz, IEKP – KIT HW meeting R int – characteristics our specs: R int > 20*R poly  Rint > 1e8 Ohmcm independent of irradiation R int in n-in-p type sensors depends on p+ doping concentration and depth but both influence the max. electric field in the sensor -> breakdown voltage needs to be calculated carefully HPK campaign – Hoffmann, Thesis 2013R int for different doping conc. - Maier, Bachelor thesis 2014

Martin Printz, IEKP – KIT HW meeting R int – T-CAD simulation simulation of R int until now not satisfying difficult? to realize the SPICE network of measurement method in the simulator we use AC simulation and detrmine R int from: But: with this approach, R int cannot be reproduced!

Martin Printz, IEKP – KIT HW meeting R int – simulation in India, Finnland India introduces third trap non uniform damage model Finnland introduces third trap non uniform damage model Several groups/sw – not consistant – still not validated...

Martin Printz, IEKP – KIT HW meeting R int – new simulation approach KIT goal keep simulation or better „physics“ as easy as possible reproduce measurements reproduce SPICE network (not done so far...) ramp to V bias =-900V then save the physics in a file „vg1.sav“ reload this file ramp c1 (=DC) to 2V and mesure the current on c2(=DC) save again analyse... This should reproduce our probestation network and measurement ! Does it?

Martin Printz, IEKP – KIT HW meeting R int – new simulation approach slope and offset (I leak ) reproduced! p_d=1.0 um n_d=1.5 um p_d=1.0 um n_d=1.5 um p_d=1.0 um n_d=1.5 um

Martin Printz, IEKP – KIT HW meeting Doping depth is also significant when doping concentration is kept constant.

Martin Printz, IEKP – KIT HW meeting Simulation of interstrip resistance and electric field strength in dependence on doping concentration and doping depth  are the measurements reproduced?

Martin Printz, IEKP – KIT HW meeting CNM ITE HPK measurements

Martin Printz, IEKP – KIT HW meeting Measurement: after irradiation R int increases with V bias and saturates at about -200V Simulation: R int increases significantly faster compared to measurement and saturates at about -200V

Martin Printz, IEKP – KIT HW meeting Summary Interstrip resistance is a crucial parameter in n-in-p detectors doping concentration and depth are still not „known“ vendors (if not HPK) want our specs  we should know what is best! Simulation was not sufficient so far considering the reproduction of R int new approach: reproduce SPICE network T-CAD reproduces R int measurements for different doping concentrations and depths before and after irradiation to do: R int ramp  what happens here? p-spray 

Martin Printz, IEKP – KIT HW meeting Backup

Martin Printz, IEKP – KIT HW meeting Interstrip resistance n-in-p type sensor performance dependent on isolation technique p-stop atoll p-stop common p-spray isolation technique affects noise and breakdown behaviour -> known from measurements and T-CAD studies task: find the most suitable p+ isolation doping concentration and depth low maximum electric fields -> high breakdown voltage ensure sufficient R int -> low charge sharing despite of fluence Approach: sensors from 3 vendors with 3 different initial doping concentrations and depths HPK campaign p-stop conc. ~ 1-5e16cm -3 doping depth: ~1.0–2.0μm low noise well working even for F>2e15n eq /cm 2 (n-in-p) CNM run (2013) p-stop conc. ~ 9e16cm -3 dopng depth: ~3.0μm results will be discussed! ITE run (2012) p-stop conc. << 1e16cm -3 doping depth unknown no isolation before irrad. p-stop doping conc. not sufficient! proton, neutron, x-ray irradiation bulk defects surface defectsinterplay!?

Martin Printz, IEKP – KIT HW meeting Measurement technique and analysis probestation for electrical qualification of sensors R int depends on bulk as well as on surface damage R int measurement complicated due to leakage current ramp to +1V between to adjacent strips (DC) measurement of lower limit of R int R int increases with V bias at some point (blue line), R int starts to fluctuate measurement limit reached decreases with increasing leakage current probably not the „real“ R int value for comparability of measurements, a linear regression with Δy/Δx=0 is fitted to data in the range of future detector V bias (500V-800V) this value is extracted and plotted in the next slides Fig.: extract from gds file of a strip sensor

Martin Printz, IEKP – KIT HW meeting CNM p-stop conc. ~9e16cm -3 CNM p-stop concentration extremely high ~9e16 cm -3 strip isolation is given even after very high fluence but more and more noisy strips appear with fluence, especially after neutron irradiation F=1.6e15 n eq /cm 2, -900V local very high fields (>30kv/cm) near p-stop 9e16 cm -3 seems to be to high T-CAD: -900V, T=-20°C p-stop strip

Martin Printz, IEKP – KIT HW meeting Synopsys Sentaurus TCAD sw package developed effective 2-trap model (R. Eber, Phd Thesis, IEKP-KA/ , KIT) in order to simulate irradiated silicon sensors tables show models for neutron and proton irradiation developed on data from HPK silicon sensor for the PhaseII Outer Tracker campaign message: models tuned in order to reproduce data from lab measurements (full depletion voltage, leakage current, charge collection and TCT) can be used to investigate new silicon sensor characteristics and CCE neutron model proton model

Martin Printz, IEKP – KIT HW meeting Scan HPK HPK doping concentrations with CNM geometries vary doping depth of implant and p-stop SPR measurements HEPHY: is 2011 measurement the correct one? n_1um & p_1umn_2um & p_2um 2011: 1.1um 2013: 2.2um ? V=-600V, T=-20°C

Martin Printz, IEKP – KIT HW meeting T-CAD: Scan CNM sensoren F vs. Q f PS12 PS25 CNM doping depth and concentrations known from engineers. „missing“ T-CAD input: Q_f what is our message from this plots? or: why do we show this plots? V=-600V, T=-20°C

Martin Printz, IEKP – KIT HW meeting Electric field strength: F vs. Q_f scanned fluence from 1e14 to 1.5e15 n eq /cm 2 (20 cm) two-defect proton model (Phd Robert) scanned oxide charge from 5e11 to 1e12 cm -2 (XFEL study, Zhang) surface defects still not implemented sufficiently how does surface damage influence overall performance after high radiation dosis?

Martin Printz, IEKP – KIT HW meeting Reminder: HPK FOSTER – signal coupling 1060nm laser at 300 Volt in far and near region respectively a.)b.) a.) The signal shares only between far strips 181 and 183 b.) The signal shares between the near strips 182 and 184 but is also seen on the far strip aluminum aluminium

Martin Printz, IEKP – KIT HW meeting by the way FOSTER paper submitted to CMS DN first comments from Joe and/or Katja recieved next step!? -> submission to NIM