ATLAS Upgrade Planar Pixel Sensor R&D

On this website, you can find information about the ATLAS Upgrade Planar Pixel Sensor R&D (PPS) project. The PPS collaboration investigates the suitability of planar silicon pixel sensors for the ATLAS Upgrade.

News and Schedule

The next PPS meeting will take place at TU Dortmund from 11th to 12th of June, 2015 as a Joint Pixel Sensor Meeting: link


Non-public information repositories of working groups:

External Links:

  • PPS-Proposal: link
  • PPS mailing list: atlas-highlumi-planarpixel(at) , search at e-groups for atlas-highlumi-planarpixel to subscribe.

  • Program and Talks of the twentieth PPS meeting at CERN as part of the ITK week: link
  • Program and Talks of the nighteenth PPS meeting at CERN: link
  • Program and Talks of the eighteenth PPS meeting at CERN: link
  • Program and Talks of the seventeenth PPS meeting at CERN: link
  • Program and Talks of the sixteenth PPS meeting at CERN: link
  • Program and Talks of the fifteenth PPS meeting at LPNHE Paris: link
  • Program and Talks of the fourteenth PPS meeting at CERN: link
  • Program and Talks of the thirteenth PPS meeting at CERN: link
  • Program and Talks of the twelfth PPS meeting at CERN: link.
  • Program and Talks of the eleventh PPS meeting at CERN: link
  • Program and Talks of the tenth PPS meeting at CERN: link
  • Program and Talks of the ninth PPS meeting at Liverpool: link
  • Program and Talks of the eighth PPS meeting at CERN: link

  • Program and Talks of the PPS EVO/phone meeting held on December 13th, 2010: link

  • Program and Talks of the seventh PPS meeting at MPI fuer Physik in Munich: link
  • Program and Talks of the sixth PPS meeting at DESY/Hamburg: link
  • Program and Talks of the fifth PPS meeting at CERN: link
  • Program and Talks of the fourth PPS meeting at CERN: link
  • Program and Talks of the third PPS meeting at CERN: link
  • Program and Talks of the second PPS meeting at LAL Orsay: link
  • Program and Talks of the first PPS meeting at TU Dortmund: link


What this page is for

This page is supposed to serve as general source of information about the ATLAS Upgrade Planar Pixel Sensors R&D activity (PPS) and as file and information exchange platform for institutes participating in the PPS working-groups. The headlines of most topics are based on the workpackages defined in the Planar Pixel Sensor Proposal. Everyone working on a specific package is invited to share his information on the web. If you want to share some of your information only with members of the Planar Pixel Upgrade working-groups please read here.

Table of Contents

Participating Institutes

D. Dobos, B. Di Girolamo, H. Pernegger, S. Roe
AS CR, Prague (Czech Rep.)
V. Vrba, P. Sicho, J. Popule, M. Tomasek, L. Tomasek, J. Stastny, M. Marcisovsky, M. Havranek, J. Bohm, Z. Janoska, M. Hejtmanek
LAL Orsay (France)
A. Bassalat, N. Dinu, E. Gkougkousis, D. Fournier, A. Lounis
LPNHE / Paris VI (France)
M. Bomben, G. Calderini, J. Chauveau, F. Crescioli, C. La Licata, G. Marchiori, P. Schwemling
University of Bonn (Germany)
M. Barbero, F. Hügging, H. Krüger, N. Wermes
HU Berlin (Germany)
H. Lacker
DESY (Germany)
C. Hengler, I. M. Gregor, V. Libov, I. Rubinsky
TU Dortmund (Germany)
S. Altenheiner, M. Andrzejewski, A. Giesen, C. Gö▀ling, B. Hillringhaus, J. Jentzsch, R. Klingenberg, A. Kompatscher, J. Rietenbach, A. Rummler, R. Wunstorf
University of Goettingen (Germany)
J. Grosse-Knetter, M. George, A. Quadt, J. Weingarten
MPP und HLL Munich (Germany)
L. Andricek , A. Macchiolo, H.-G. Moser, R. Nisius, R. Richter, S. Terzo
Università degli Studi di Udine – INFN (Italy)
D. Cauz, M. Cobal, C. del Papa, D. Esseni, M. P. Giordani, P. Palestri, G. Pauletta, L. Selmi
KEK (Japan)
Y. Unno, S. Terada, Y. Ikegami, Y. Takubo
Tokyo Institute of Technology (Japan)
O. Jinnouchi, R. Nagai, T. Kubota, K. Motohashi
IFAE-CNM, Barcelona (Spain)
M. Cavalli, S. Grinstein, Korolkov, M. Lozano, C. Padilla, G. Pellegrini, S. Tsiskaridze
Université de Genève (Switzerland)
D. Ferrere, G. Iacobucci, A. La Rosa, D. Muenstermann, S. Gonzales Sevilla
University of Liverpool (UK)
T. Affolder, P. Allport, G. Casse, T. Greenshaw, I. Tsurin
UC Berkeley/LBNL (USA)
M. Battaglia, T. Kim, S. Zalusky
UNM, Albuquerque (USA)
I. Gorelov, M. Hoeferkamp, S. Seidel, K. Toms
UCSC, Santa Cruz (USA)
V. Fadeyev, A. Grillo, J. Nielsen, H. Sadrozinski, B. Schumm, A. Seiden

Description of Workpackages of the PPS Proposal

Studies on bulk material and radiation hardness

The n-in-n pixel sensor has proven to work well up to large fluences. Unique compensation effects in n-type magnetic Czochralski material lead to full depletion even after very large fluences, hence n-bulk material might also in the future be the best-suited material for the inner part of the pixel detector. P-bulk material on the other hand requires only single-sided wafer processing which might lead to higher yields and reduced cost. It is therefore important to carefully evaluate both bulk materials with respect to their specific performance as pixel detectors at .

n-in-n pixel design

The current pixel design can be taken as a starting point. Many important questions have already been answered for fluences close to those that are expected for the outer pixel layers (e.g. inter-pixel isolation, etc.). To prove the radiation hardness of n-in-n pixels at more than , to enhance the current n-in-n pixel sensor and in acknowledgement of design requests from FE and module/stave designers, R&D on the following topics is necessary:
  • Re-design of the sensor’s geometry to match the FE-I4 and test chips
  • Evaluation of 6” wafers for n-in-n sensors

n-in-p pixel design

The effect of the pixel geometry on the charge collection efficiency at high proton fluences needs to be established. Furthermore, the effect of the wafer material (e.g. FZ vs, MCz) is expected to be large and needs to be evaluated carefully. The optimization of the planar pixel sensors will require a comparative study of several options. n-in-p sensors see high voltage on their edges which could result in discharges into the FE-chips. It has to be examined under which circumstances this could happen and how it can be avoided. To reduce leakage currents, it is possible to design n-in-p sensors with high-voltage implants surrounding the guard ring area. This design feature confines the field gradient to the bulk sensor material thereby leading to an inherently low leakage current. Unfortunately, this raises even more concerns regarding handling and operating FE ASICs in close proximity to high voltage. Therefore, the following studies will be investigated:
  • the amount of leakage current increase incurred without the high-voltage implant on the front side, comparatively with the values from irradiated sensors and
  • feasibility of shielding the affected area with a thin kapton layer.

Improving the performance of planar sensors at high fluences

Test beam results have confirmed that planar sensors still yield signals after very high fluences, however, due to electron trapping the charge collection only takes place in a thin layer (some tens of μm) directly beneath the pixel contacts. The applicable bias voltage is mainly limited by the leakage current escalation. Due to the reduced drift lengths at fluences of above , it is necessary to revise the current strategy concerning tilt and Lorentz angle. Besides, strategies for optimized annealing have to be evaluated and reports of charge collection of up to 15000 electrons after reproduced using pixel devices.

Device Simulation

Device simulations, e.g. by Technology Computer Aided Design (TCAD), use computer simulations to develop and optimize semiconductor processing technologies for planar sensor devices. With the increase of computing power, it becomes a vital tool in exploring efficiently new semiconductor device design and architecture. Using TCAD methods can also reduce significantly development time and number of experimental prototypes, thus lowering new wafer costs.

Integration of new materials like oxygen rich silicon (DOFZ, Cz, MCz,...) and subtle device configuration including inactive edges size reduction, optimization of the number of guard rings together with sensor thinning issues increases the complexity of the design. Comparisons of effective doping concentrations and leakage currents in various irradiated and non irradiated materials (n- in-n and n-in-p design) could be predicted and compared to measurements.


All new sensor designs must be thoroughly tested at realistic fluences, ideally already bonded to an FE-I3 or FE-I4-prototype chip if the FE chip can sustain the fluence. Neutron, proton and/or pion irradiations are intended; besides, high-intensity but low-energy protons could be considered.

Test beams

While charge collection results obtained with radioactive sources and lasers can be useful, for the final qualification of the charge collection efficiency test beams using MIPs are necessary. This is especially the case if a 2D or even 3D map of the CCE is to be recorded to get data on the CCE at (slim/active) edges, in corners and at the bias dot.

R&D on low-cost planar silicon pixel detectors

Due to the occupancy generated by HLLHC’s luminosities, the complete Inner Tracker will be made of semiconductor detectors. This means that an area of about has to be covered with detector modules. At very high track numbers per bunch crossing which are associated with HLLHC luminosities, pixel detectors are a great advantage compared to strip detectors due to their ability of unambiguously determining track points. These are high-quality input to pattern recognition algorithms for track reconstruction and possibly trigger. The area that can be equipped with pixel detectors depends mainly on the cost per area. For the ATLAS pixel detector, bump bonding of sensor tile and FE chips was responsible for the majority of the cost. Sensor, FE chip and support/services had about equal fractions of the remainder. To be able to instrument as large an area as possible, industrially available technologies have to be utilized to reach area-costs comparable to those of silicon strip sensors. To achieve this, R&D on the following fields is proposed:
  • Low cost bump bonding at small pitch
  • Larger Wafer sizes to reduce handling costs
  • Industrial Production methods and appropriate stave design

R&D on active/slim edged and overlapping sensors

Most advanced stave concepts for the Inner Tracker Upgrade strongly prefer to arrange the modules in a ‘flat’ way which improves cooling and facilitates contacting compared to the current ‘shingling’ of modules. It is, however, necessary to keep the Inner Detector’s acceptance at a very high level: Including losses due to failing modules, the overall efficiency must not drop below approximately 97%. Therefore, the anticipation of 98-99% acceptance seems reasonable. To reach this goal and assuming a roughly 20 mm wide FE ASIC, it will be necessary to reduce the inactive gap between two active sensor regions to 100-200 μm for Single Chip Modules and to 400-800μm for 4-FE-MultiChipModules. Without shingling, this acceptance can only be reached by either two-sided staves or – preferably – by active/slim edge sensors.

Minimization of incactive gaps

A first and comparably easy step to reach narrow inactive gaps between active sensor regions is to reduce the number of guard rings as well as their width and the edge widths. To explore these questions, the following studies are proposed:
  • Evaluation of the effects of guard ring numbers and widths after irradiation
  • Study on forceless dicing processes (laser cutting/anisotropic etching)

Feasibility of active edges in planar sensors

It will be important to study how active edges and guard rings can be combined and how the guard rings will reduce the charge collection efficiency underneath of them with respect to the fluence received.

Overlapping sensors

If the measures under evaluation cannot reduce the gaps far enough, evaluation of overlap schemes is proposed in close cooperation with institutes which are developing stave concepts for the ATLAS Upgrade, e.g. two-sided staves with overlapping sensors instead of shingling.


Systematic Monte-Carlo simulation studies are proposed to optimise pixel size and shape as well as the overlap geometry of the pixel detector.

..for optimization of the size of pixel-cells

These studies need to take into account the reduced resolution at high fluences, the physics impact of a modified material budget and the trade-off between reduced noise/capacitance of smaller pixels versus potentially larger heat dissipation by a larger number of pixel cells. evaluate different stave options

Within a concept for the layout of the whole inner tracker, it will be important to compare the different options for pixel sizes/geometries and barrel radii as it is possible that a deviation from the currently discussed concepts (4-3-2 or 5-2-2 layers for pixels-short strips-long strips) could lead to a significant performance improvement. This was also shown by simulation results at the ATLAS Tracker Upgrade Workshop at NIKHEF in November 2008.

FE-development towards low threshhold

In environments with fluences above , all solid state sensors under consideration yield reduced charge. Recent data indicate that planar silicon pixel sensors still work at very high fluences, however, the collected charge will be reduced to only few 1000 electrons. Currently, the ATLAS’ FE-I3 chip is not optimized to run at low thresholds. Besides, enabling low thresholds has up to now no priority in the course of the design of its successor FE-I4.

Non-public Information Sharing: The Group List

This page can be used for sharing information or files only to the members of the Planar Pixel Upgrade working-groups. For that reason a new TWiki-Group was created. Please check whether you are a member of this group. Members of the AtlasPlanarPixelGroup are:

Members: GeorgTroska, DanielMuenstermann, AndreRummler, TobiasWittig, JenniferJentzsch, AnnaMacchiolo, MathieuB, AbdenourLounis, TanakaReisaburo, ClausGoessling, ReinerKlingenberg, JensWeingarten, RenateWunstorf, MichaelBeimforde, YoshinobuUnno, AnthonyAllenAffolder, GianluigiCasse, IlyaTsurin, VitaliyFadeyev, HartmutSadrozinski, CristobalPadilla, PetrSicho, GiovanniMarchiori, GiovanniCalderini, TimGreenshaw, SergioGrancagnolo, NinaKrieger, VladyslavLibov, ValentinaFerrara, IgorRubinskiy, MatthiasGeorge, AlessandroLaRosa, PhilippWeigell, ChristianGallrapp, SebastianGrinstein, ShotaTsiskaridze, PhilipPatrickAllport, RichardNisius, OsamuJinnouchi, NicoletaDinu, PhilipAllport, TakuyaKishida, MarcoBomben, RyoNagai, YosukeTakubo, BranislavRistic, StephenGibson, CristobalPadilla, JohnIdarraga, FabianHuegging, MalteBackhaus, JacquesChauveau, DeanForshaw, JensJanssen, SilkeAltenheiner, OleksandrKorchak, TomonoriKubota, MarkusAlex, PaulDervan, AhmedBASSALAT, VladimirLinhart, LadaDucheckova, KonstantinToms, RuiWang, ZdenkoJanoska, MartinHejtmanek, KateDoonan, ArtemKravchenko, WeiXiang, TillPluemer, LarsGraber, StefanoTerzo, DavideCaforio, KazukiMotohashi, KarolaDette, KojiNakamura, SergeyBurdin, FrancescoCrescioli, JuliaRieger, HongboZhu, KazukiTodome, DaikiYamaguchi, MutsutoHagihara, KazuhikoHara, JuliaRietenbach, ArnoKompatscher, KennethWraight, AndrewBlue, CraigButtar, SimonFeigl, YasutakaArai, NaokiIshijima, AidanRobson, TakanoriKono, MarkoMilovanovic, VagelisG, ClaraNellist, JunyaUsui, BertrandMartin, AndreasJustinGisen, KimihikoKimura, KenYamamoto, RyuichiTakashima, AndreSchorlemmer, MareikeWeers, LingxinMeng, SaverioDAuria

If you are not on the list and want to become a member, please contact (one of) these persons: Members: DanielMuenstermann, JenniferJentzsch, AndreRummler, JensWeingarten, MarkusAlex, MarcoBomben

Creating non-public Topics

If you want to share a topic only with the members of the list mentioned above, 1st create a topic as you have done before. 2nd make sure that you have copied these lines without the hashes (#)

#   * Set ALLOWTOPICVIEW =  AtlasPlanarPixelGroup
#   * Set ALLOWTOPICCHANGE =  AtlasPlanarPixelGroup
#   * Set ALLOWWEBCHANGE = AtlasPlanarPixelGroup
#   * Set ALLOWWEBRENAME = AtlasPlanarPixelGroup
#   * Set ALLOWTOPICRENAME = AtlasPlanarPixelGroup

to the beginning of you new topic. There are 3 spaces in front of the *. They restrict read and write access to the members of the AtlasPlanarPixelGroup.

Last update:
-- AndreRummler - 14-Mar-2012

Major page construction by:
-- JenniferJentzsch, GeorgTroska

Responsible: DanielMuenstermann Last reviewed by: Never reviewed

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Topic revision: r99 - 2015-05-19 - DanielMuenstermann
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