12th RD50 Workshop
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Europe/Zurich
Ljubljana, Slovenia
Ljubljana, Slovenia
Michael Moll
(CERN),
Vladimir Cindro
(JSI, Ljubljana, Slovenia)
Description
12th RD50 Workshop on Radiation hard semiconductor devices
for very high luminosity colliders
Participants
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Registration
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Workshop Welcome
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WelcomeSpeakers: Jadran Lenarčič (Director of Jožef Stefan Institute), Marko Mikuz (University of Ljubljana)
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IntroductionSpeakers: Prof. Mara Bruzzi (INFN and University of Florence), Michael Moll (CERN), Vladimir Cindro (Jozef Stefan Institute)
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Defect and Material Characterization
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Overview of results from the WODEAN collaborationQUANTITATIVE EFFECTS OF NEUTRON IRRADIATION ON SILICON RADIATION DETECTORS -Overview of results from the WODEAN* collaboration- M.K. Bocka, G. Daviesb, D. Ecksteina, E. Fretwursta, E. Gaubasc, A. Junkesa, P. Kaminskid, K. Kaskae, V. Khomemkova, G. Krambergerf, J. Langea, G. Lindströma, L. Makarenkog, D. Menichellih, M. Molle, R. Morih, L. Murinj, M. Pawlowskid, I. Pintiliek, B. Surmad, B.G. Svenssonl, J. Vaitkusc, J. Zelazkod a University of Hamburg , Physics Department, Germany: b Kings College, London, Great Britain: c University of Vilnius, Lituania: d ITME, Warsaw, Poland; e CERN, Geneve, Switzerland; f Jozef Stefan Institute, Ljubljana, Slovenia; g Belarus State University, Minsk, Belarus; h University and INFN Florence, Italy; j Joint Institute of Solid State and Semiconductor Physics, Minsk, Belarus; k National Institute of Materials Physics, Bucharest, Romania; l Oslo University, Physics Department, Norway Silicon detectors for the Large Hadron Collider must tolerate lifetime fluences of up to 1016 cm-2 high-energy hadrons. However, current understanding of the defects created by the damage is poor. Here, we present the results of a multi-technique experimental study of detector grade silicon, irradiated with 1011 to 1016 cm-2 1-MeV equivalent reactor neutrons. We suggest to separate the damage into two classes. The most probable damage events involve a very small number of atomic displacements, while the majority of the damage occurs when a knocked-out atom creates up to hundreds of defects in a disordered region. The small damage events produce mobile single vacancies and self-interstitials that undergo reactions similar to those well-known from electron damage. Isolated divacancies are generated, and, in almost equal numbers, di-interstitials (I2) which are captured by oxygen (O). The I2O complex is thermally unstable above room temperature, affecting the damage production rates. Comparison of infrared absorption and DLTS suggests that the I2O centre produces the two DLTS levels, ‘E4 and E5’ at Ec–0.37 eV and Ec–0.45 eV, which act as traps in detector material. In contrast, the disordered regions evolve mainly by restructuring within themselves, especially, as seen by DLTS, photoluminescence and photoconductivity data, on annealing near 200 oC. They pin the Fermi level in the region of the disordered structures, so that DLTS measurements of the concentrations of defects near the disordered regions are unreliable. For example, only about one third of the VO centres near the disordered regions can be detected by DLTS: Fermi-energy pinning occurs over a volume that is considerably larger than the physical size of the disordered region. This work establishes a quantitative understanding of the defect species and their concentrations for the small damage events, and identifies the major problems in understanding the evolution of defects in the disordered regions. * WODEAN: “WOrkshop on DEfect Analysis” Subgroup of the CERN-RD50 Collaboration; http://sesam.desy.de/WODEAN/Speaker: Gordon Davies (King's College London)
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Analysis of deep level system transformation by photoionization spectroscopyThe photoconductivity spectrum in extrinsic regiono was measured in irradiated Si samples at 18 K temperature. The samples were treated by isochronal annealing in a range 80-250 C. The deep levels were resolved by use of Lucovsky model. A series of levels was observed and a number of deep centers and their contribution on the photoconductivity were dependent on annealing. The comparison of photoconductivity spectra data and the results obtained by DLTS and TSC in other groups in the same series of samoles was performed.Speaker: Prof. Juozas Vaitkus (Inst. of Mater. Sci. & Appl. Res. (IMSAR) - Vilnius University)
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Study of cluster related effects in n-irradiated Epi-Do and MCz diodesIsochronal annealing studies have been performed on neutron-irradiated Epi-Do and MCz diodes. The MCz diode, irradiated with 3E11 n/cm², was investigated with DLTS. The annealing results of cluster related defects will be presented and compared to reverse current data. After injection of 1 Ampere forward current, a bistable effect of the cluster related defects E4 and E5 was observed. Further annealing experiments were performed, with alternating isochronal and isothermal annealing. The Epi-Do diode, irradiated with 1E13 n/cm² has been treated in the same way and TSC measurements were performed. The aim of this study is, to characterize the bistable effect of E4 and E5 and the influence of the cluster related defects on the reverse current as well as on the filling conditions of point defects.Speaker: Alexandra Junkes (Unversity of Hamburg, Germany)
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10:40
Coffee Break
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Fluence and isochronal anneal dependent variations of recombination and DLTS characteristics in neutron and proton irradiated MCz , FZ and epi-Si structuresA comparative analysis of the recombination, generation and reverse recovery lifetime dependent on stopped protons fluence and isochronal anneal temperature is presented for FZ Si structures. In DLTS, heat treatments indicate transformations of majority and minority carrier traps. These changes are also revealed by variations of the excess carrier decay lifetime. The main transformations can be attributed to hydrogen implantation related defects (VOH etc). Also, a comparative study of the impact of penetrative neutrons and protons on recombination and DLTS characteristics in MCz, FZ and epi-Si structures has been carried out. A nearly linear decrease of the recombination lifetime with fluence of the reactor neutrons from 1012 to 3×1016 n/cm2 in the MCz grown Si samples corroborates a non-linear introduction rate of dominant recombination centers. An increase of lifetime and a change of carrier decay shape (process) in reactor neutrons irradiated MCZ Si, dependent on fluence, appears under annealing at elevated temperatures (>180 C, for 24 h). Lifetime behavior with heat treatment temperature shows an enhancement of competition between recombination and trapping centers which is the most pronounced for moderate fluences irradiated material.Speaker: Prof. Juozas Vaitkus (Inst. of Mater. Sci. & Appl. Res. (IMSAR) - Vilnius University)
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Discussion Session on Defect and Material CharacterizationSpeakers: Gordon Davies (King's College London), Mara Bruzzi (INFN and University of Florence)
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12:00
Lunch Break
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3
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Defect Engineering & Pad Detector Characterization I
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Electrical characterization of p- and n- type 150um epi-Si diodes irradiated by protons and neutronsEpi-Si 150 um thick diodes on p- and n-type bulk were studied after irradiation by 24 Gev/c protons (CERN PS) and reactor neutrons (Ljubljana) up to equivalent fluence of several times E15/cm2 and following isothermal annealing at 80C.Speaker: Volodymyr Khomenkov (Hamburg University)
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Annealing studies on MCz after 23 GeV proton irradiation and CCE of 150um epitaxial silicon devicesMCz (n- and p-type) and FZ (n-type) diodes were irradiated with 23 GeV protons and investigated with CV,IV and CCE (beta-source, 2mus shaping) measurements. Isothermal annealing studies at 80° C were performed on a subset of samples irradiation with 3.5e14 protons/cm2. Finally, these detectors were used for isochronal annealing studies between 100° C and 220° C, for which the charge collection efficiency was measured after each annealing step. In addition an measurements on epitaxial detectors of 150 mum thickness irradiated with protons and neutrons were performed.Speaker: Mrs Katharina Kaska (CERN)
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Systematic TCT Investigation of Equal-Double-Junctions in 24 GeV Proton Irradiated MCZ n and p-type Si DetectorsSystematic TCT studies (both electron and hole current shapes are measured for each sample) have been carried out on three sets of samples irradiated by 24 GeV protons to fluences ranging from 1.6x1014 to 2.4x1015 p/cm2 (and after 22-day room temperature beneficial anneal): 1) MCZ n-type Si detectors; 2) MCZ p-type Si detectors; and 3) FZ n-type Si detectors (control sample set). For the control sample set, there are no surprises: SCSI has already taken place at the lowest fluence (1.6x1014 p/cm2), and the double junction/double peak effect is readily seen, with the first junction near the p+ contact as the minor one that changes very little with bias voltages, and it is taken over by the second junction near the n+ contact (- space charge) at higher biases than the full depletion voltage. However, for both MCZ n-type and p-type detectors, the double junction/double peak effect starts to take place also at the lowest fluence, and the standard SCSI in n-type detectors (- space charge dominates the entire detector) has not been seen in the fluence range here. But this double junction/peak effect persists into the subsequent higher fluence with about equal junctions near the p+ contact and n+ contact, regardless of bias voltages that may be much larger than the full depletion voltages. This new effect, termed as the Equal-Double-Junction effect is unique only for the 24 GeV proton-irradiated MCZ (n and p) Si detectors, and it is evident by the almost identical TCT current shapes, before trapping corrections, for both electrons (red laser on the p+ contact) and holes (on n+ contact), with the first peak always dominating a small second peak at any biases voltages. After trapping corrections, the two peaks are expected to have about the same heights, indicating an about equal double junction in the detector. TCT data will be fitted in the future to determine the electric field profiles in these detectors.Speaker: Dr Jaakko Harkonen (HIP)
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On MCz SCSI after 24 GeV/c proton irradiationSeveral MCz diodes from the SMART production, of both n- and p-type, have been irradiated on the 24 GeV/c proton beam at CERN up to a fluence of 1.59 1015 neq.In the framework of a common RD50 research program, electrical characterization and TCT studies have been performed as a function of the annealing time. All irradiated samples show a clear double junction effect. Both annealing and TCT studies seem to indicate the occurrence of type inversion of p-type diodes at high fluences.Speaker: Donato Creanza (University/INFN Bari)
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14:50
Coffee Break
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Comparison of proton damage in thin FZ, MCz and epitaxial silicon detectorsWe present results on 24 GeV/c proton irradiated thin n-type FZ (50 µm, 100 µm), MCz (100 µm), epitaxial (72, 100, 150 µm, standard and oxygenated) pad detectors. Annealing experiments at 80°C have been performed. The extracted macroscopic damage parameters and charge collection measurements with alpha particles will be presented.Speaker: Doris Eckstein (Hamburg University)
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C-V/IV and CCE measurements of MCz and FZ p and n type diodes after mixed irradiationsThe set of MCz and Fz p and n type diodes was irradiated first with fast charged hadrons (200 MeV pions or 24 GeV protons) and afterwards with reactor neutrons. The measurements showed that damage of both irradiation particles adds for Neff and leakage current. The space charge of MCz-n detectors after charged hadron irradiations should be positive as the additional irradiation with neutrons reduces the Vfd. The measurements of CCE confirm above observations.Speaker: Gregor Kramberger (Jozef Stefan Institute)
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Discussion Session: Defect Engineering & Pad Detectors (MCZ, EPI, FZ)Speakers: Eckhart Fretwurst (Unversity of Hamburg, Germany), Gregor Kramberger (Jozef Stefan Institute)
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Welcome Drink
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Collaboration Board Meeting
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RD50 - Spokespersons ReportSpeakers: Mara Bruzzi (INFN and University of Florence), Michael Moll (CERN)
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RD50 funding request - Fabrication and testing of new AC coupled 3D stripixel detectorsThe project aims to fabricate and fully characterize stripixel silicon detectors with a new 3D structure. A mask set will be produced for the production of simple test structures, pixel and strip detectors configurations based on the detector technology. This new 3D structures have some new features either in configuration and/or in processing: (1) all electrodes are processed on one side of the wafer to ensure a simple, true one-sided processing; and (2) stripixel electrode configuration can be arranged to get 2D position sensitive strip-like detectors with single-sided processing. Finished devices will be distributed to the test sites for electrical, (IV, CV, TSC), and source, (alpha, beta, laser), characterization.Speaker: Giulio Pellegrini (Centro Nacional de Microelectronica CNM-IMB-CSIC)
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Pad Detector Characterization II
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Observation of Gamma Irradiation-Induced Suppression of Reverse Annealing in Neutron Irradiated MCZ Si DetectorsFor the development of radiation-hard Si detectors for the SiD BeamCal program for ILC, n-type MCZ Si detectors have been irradiated first by fast neutrons to fluences of 1.5x10^14 and 3x10^14 neq/cm2, and then by gamma up to 500 Mrad. The motivation of this mixed radiation project is to develop a Si detector that can utilize the gamma/electron radiation that exists in the ILC radiation environment, which also includes neutrons. By using the positive space charge created by gamma radiation in MCZ Si detectors, one can cancel the negative space charge created by neutrons, thus reducing the overall/net space charge density and therefore the full depletion voltage of the detector. It has been found that gamma radiation has suppressed the room temperature reverse annealing in neutron-irradiated detectors during the 4 month of time needed for the 500 Mrad radiation dose. The reverse annealing in control detectors (detectors having the same neutron fluences, but going through this 5-month room temperature annealing without gamma radiation) was clearly taking place. This suppression is in agreement with our previous predictions, since negative space charge is generated during the reverse annealing, any suppression of that would mean creation of positive space charge by gamma radiation. The suppressing and interesting effect is that, it seems that regardless of the fluence (two in our case: 1.5x10^14 and 3x10^14 neq/cm2), the reverse annealing is totally suppressed by the same dose of gamma (500 Mrad): the full depletion voltage for the two detectors irradiated to these two different fluence stay the same before and after gamma radiation. Meanwhile, for the control detectors, the full depletion voltages have gone up by the amount of 204 V and 583 V for the two fluences, 1.5x10^14 and 3x10^14 neq/cm2, respectively. This would imply positive space charge created in these two samples are different at the same gamma dose and/or the reverse annealing is affected by gamma radiation, suggesting some non linear effect or interaction. More samples and fluences will be studied in the future to verify the effect.Speaker: Jessica Metcalfe (University of New Mexico)
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Can Li passivate radiation damage in Si?Li has been used to passivate acceptors in Si to allow large volume radiation detectors to be fabricated. This study looks at whether Li drifting can be used to passivate radiation induced accceptors. Results of C-V measurements used to characterise the effect of drifting Li in Si(Li) detectors that have been irradiated with neutrons are presented.Speaker: Dr Chris Parkes (Department of Physics and Astronomy)
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10:10
Coffee Break
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Full Detector Systems
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Summary: 3rd Workshop on Advanced Silicon Radiation Detectors (3D and P-type Technologies)A summary on the presentation given on the "3rd Workshop on Advanced Silicon Radiation Detectors (3D and P-type Technologies) ", held 14-16 April 2008 at the Residencia CSIC-Generalitat de Catalunya, Barcelona, Spain will be presented. Main focus will be on presentations and topics that are not covered by presentations given on this workshop. Workshop pageSpeaker: Lozano Manuel (CNM)
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Beam telescope for testing p- and n-type detectorsWe constructed in 2007 a beam telescope based on CMS Tracker data acquisition prototype cards and APV25 readout chips. The telescope has 8 silicon strip reference detectors and slots for a couple of test modules. The impact point precision of the reference tracks at the location of the test modules is 4 um, the S/N of the telescope is 25 and it has an active area of 4 cm x 4 cm. The telescope and the test detectors are housed inside a cold chamber, which allows testing of highly irradiated sensors. The stup provides means of probing the cluster resolution, signal-to-noise and charge collection efficiency properties of silicon microstrip detectors.Speaker: Dr Panja-Riina Luukka (Helsinki Institute of Physics HIP)
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Irradiated MCz sensors for a testbeamFor testing signal-to-noise, efficiency and resolution of highly irradiated MCz-sensors, a beamtest will take place at CERN this summer, making use of the new beam telescope SiBT. The sensors were produced at the Helsinki Institute of Physics and were irradiated with protons in Karlsruhe and with neutrons in Louvain-la-Neuve. The data of the measured sensor parameters before and after irradiation will be presented.Speaker: Martin Frey (IEKP, Universität Karlsruhe)
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Charge collection measurements on MICRON RD50 strip detectors and diodes irradiated with protons, pions and neutronsThe systematic studies of charge collection were performed on strip and pad detectors of n and p type produced on Fz and MCz silicon. The detectors were irradiated with 24 GeV protons, 200 MeV pions and reactor neutrons up to equivalent fluences of 1.2e15 cm-2. It was shown that the to larger extent the CCE is determined by Vfd for both strips and pads. Although strip detectors perform better in terms of CCE particularly at lower voltages, but the Q-V plots are similar. The correlation of Vfd from C-V and Q-V agrees well. Charged hadrons appear more damaging for CCE at the same equivalent fluence.Speaker: Gregor Kramberger (Jozef Stefan Institute)
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12:10
Lunch Break
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New CCE results with microstrip detectors made on various substratesThe charge collection efficiency of µ-strip sensors made with the RD50 mask set with various silicon substrates (n and p FZ and MCz) have been compared to different high doses of neutron and protons, well in the range of the anticipated fluences in SLHC.Speaker: Gianluigi Casse (Department of Physics)
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Measurement of charge collection in p-type microstrip sensors with SCT128 chipResults of charge collection measurements with SCT128 chip will be presented. Measurements were made with miniature p-type microstrip sensors with n-side readout produced by Micron. Sensors were irradiated with neutrons up to 1 MeV equivalent fluence of 3e15 n/cm2. Collected charge as a function of bias voltage was measured up to 2000 V.Speaker: Igor Mandic (Jožef Stefan Institute)
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Discussion on Full Detector SystemsSpeaker: Gianluigi Casse (Department of Physics)
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14:50
Coffee Break
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Excursion
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Workshop dinner
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3D detectors & New structures
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Developement of an Indium Bump Bonding Process for Silicon Pixel Detectors at PSIThe hybrid pixel detectors used in the LHC experiments use a vertical interconnection technique, the so-called bump bonding. As the pitch below 100 µm, required in these applications, cannot be fullfilled with standard industrial processes (e.g. the IBM C4 process), an in-house bump bond process with reflowed indium bumps was developed at PSI as part of the R&D for the CMS-pixel detector. Its reliability of this process was demonstrated in the successful construction of the PILATUS 6M (about 60 modules) and the barrel part of the CMS pixel detector (about 800 modules). The talk describes the process and discusses it advantages and limitations.Speaker: Tilman Rohe (Nuclear and Particle Physics Department)
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3D Detector TestingDetectors with a “double sided” 3D configuration have been fabricated at CNM, where the n- and p-type columns are etched from opposite sides of the wafer and do not pass through the full substrate thickness. Strip detectors have been wire bonded to Beetle analogue front-end read-out chips. Pixel detectors have been bump-bonded to Medipix read-out chips at VTT. The initial results obtained from testing these devices in Glasgow are presented.Speaker: Chris Parkes (University of Glasgow)
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10:00
Coffee Break
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Status of 3D Detector R&D in FreiburgWe will report on the status of the test performed with 3D strip detectors that were fabricated at FBK-irst. Modules made by joining 3D detectors of several designs and ATLAS SCT read-out electronics exist, and were tested both before and after irradiation. Results from the 2007 3D test beam at CERN will also be shown.Speaker: Ulrich Parzefall (Fakultaet fuer Physik)
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Discussion on 3D detectors & New StructuresSpeaker: Chris Parkes (Glasgow)
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Visit to Ljubljana Research Reactor
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13:30
Lunch
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13:30
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