GrantAgreementNumber643920

DICOMO

Directconversionhybrid-organicX-raydetectorsonmetaloxidebackplane

Call:H2020-ICT-2014-1

PublishableSummary-DiCoMo

StartDate:01-01-2015 Duration:36months

Consortium:

∂ SiemensHealthcareGmbH(Germany)[Coordinator]∂ BASFSchweizAG(Switzerland)∂ IMEC-InteruniversitairMicroelectronicacentrum(Belgium)∂ TNO-NederlandseOrganisatieVoorToegepastNatuurwetenschappelijkOnderzoek

(Netherlads)∂ ICSenseNV(Belgium)∂ Morphwizes.n.c.(Italy)

www.dicomo-project.eu

DiCoMo–PublishableSummary Page2of10

TableofContent

Introductionandobjectives.......................................................................................................................................3Mainactivitiesandresults..........................................................................................................................................4

Activepixelbackplane...............................................................................................................................................4

ROIC....................................................................................................................................................................................4

Coreshellparticles......................................................................................................................................................5

Frontplaneprocessingandcharacterization..................................................................................................6

Systemintegration.......................................................................................................................................................7

Simulations......................................................................................................................................................................9

Exploitationanddissemination............................................................................................................................10Conclusions.....................................................................................................................................................................10

DiCoMo–PublishableSummary Page3of10

IntroductionandobjectivesX-raysaretheoldestandmostfrequentlyusedformofmedicalimagingwhichhelpsdoctorsin the identification,diagnosis, and treatment ofmany types ofmedical conditions.Today,despite theundiscussedvalidityofX-Ray imaging,still toomanymedicationserrorsdue toincorrect diagnosis occur. In particular Mammography, which is the most widely usedscreeningmodalityforbreastcancer,withsolidevidenceofbenefitforwomenagedbetween40to74yearshasarelativehighnumberoffalsepositiveswithadditionaltestingandanxietyor falsenegativesespecially in caseofhighbreastdensitywith false senseof securityandpotentialdelayincancerdiagnosisandtreatment.DiCoMo aims to improve the specificity (thanks to a higher resolution) and sensitivity ofdigitalflatpanelX-raydetectorsinparticularMammographs.This is achieved by combining radical innovations from leading European players fromvarious disciplines. On the backplane level metal-oxide thin film transistors enable therealizationofanactivepixelreadoutscheme.Incombinationwithacustommaderead-outICthispromisesasignificantenhancementinsensitivity.On the frontplane level a novel solvent-free processing technology for hybrid-organicsemiconductors is used in conjunctionwithhybrid-organic core-shell structures to realizethickhybrid-organicphotodetectorswithintegratedscintillatorparticlesforminimalopticalcross-talkandenhancedresolution.Theoverallobjectivesare:

∂ Advance the backplane sensitivity (compared to the state of the art sensitivity of“passivepixelbackplanes ina-SiTFTprocess)bya technology-enabled“active”pixelbackplaneinmetal-oxideTFTprocessofhigherperformanceandbias-stability.

∂ Advancethefrontplaneresolution(comparedtothestateoftheartresolutionofthickCsIscintillators)byhybrid-organicphoto-conversion layer forminimalopticalcross-talk.

∂ Demonstrate the feasibility of industrially relevant integration of the abovetechnologiesthroughafunctionalprototype.

TheDiCoMoconsortiumbrings togethercommercialandresearchpartners fromacross theOrganicandLargeAreaElectronics(OLAE)andmedicalimagingvaluechain.ThesepartnersaresystemproviderSiemensHealthineers,materialssupplierBASF,innovationcentersTNOand imec, plus SMEs ICsense and Morphwize focusing on customized read-out ICs andmodellingandsimulationrespectively.

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MainactivitiesandresultsActivepixelbackplaneTheproject focusesonadvancingthespecificityandsensitivityof flatpanelX-raydetectorsenabled by the disruptive combination of new OLAE technologies. It has successfullydevelopedanewtypeofactivepixelTFTbackplanetechnologytailoredtodriveahighvoltageX-ray detector frontplane. With its VGA size (640x480 pixels) demonstrator backplane,DiCoMo has delivered an essential building block in order to demonstrate industriallyrelevantintegrationtowardbetterandmoreaffordablehealthcare.

Figure1:PicturesofhighvoltageVGAsizefinaldemonstratorbackplanes.(Left)ChiponFoil(COF);(right)Chiponglass(COG).

ROICAdedicatedRead-OutASIC (ROIC) isdesigned to convert electrical signals from anActivePixel Sensor (APS) into adigital image.Thedesign is optimized to convert signals comingfromlargeareapixels(pitch100µmsquared).ThepixelinputsoftheROICareprotectedandrobusttonotdamagetheASICincaseofdefectivepixels.TheROICcanbefullyprogrammedtobeable toconvertdifferentsensitivity levelsatdifferent speeds.Thisallows to trade-offresolution with accuracy. One ROIC can acquire 128 pixels simultaneously with 14bitresolutionandaverylownoiselevelof1.2LSBrms.

The timingcontrol is flexibleandprogrammable toallowoperationwithanycommerciallyavailablepixeldriverASICs.Thehighestachievableconversionspeedfora4Kpanelisupto130FPS.TheROIChasanLVDSinterfacetoallowforthehugedatatransfertoanFPGA,atfullspeedthedatarateisupto50MB/s.TheROIChasbeenpost-processedwitharedistributionlayerand flattenedgoldenbumps. It canbemountedvia a flip-chipprocesson aChip-On-Glass (COG)orChip-On-Flex (COF)whichallows foreasierand robust integrationwith theimagersystem.

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Figure2:a)8"Waferwith400ROICafterbumping,b)Blackimageshowingverylownoiselevel

CoreshellparticlesThe new “direct conversion” mode developed within the DiCoMo project is based oninnovativematerials andprocesses that allowanefficientpreparationofX-Ray conversionlayers made of blends of X-ray absorbing material (scintillator particles) and chargegeneration materials (organic semiconductors) within this single layer. The overarchingconceptbehind thosematerialsandprocesses isaboutdesign,preparationand scale-upoforganic-inorganic core-shell particles that can be fused by dry sintering. The hybridmonolithicconversionlayerthusformedcanthenbedirectlyintegratedonthebackplaneoftheX-Rayimager.

Careful and creative selection of materials (both photoactive polymer and scintillator),preparation methods and scale-up (continuous process) led to highly homogeneousconvertinglayers.

Figure3:SEM imagesofcross-sectionof twohybridconversion layersmadeoutofsinteredhybridcore-shellparticles(whiteareasarethescintillatorparticleswhiledarkareasthephotoactivepolymer).

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FrontplaneprocessingandcharacterizationAmorphousSe isthebestknownmaterial fordirectlyconvertingX-raydetectors.Dueto itsrelatively low absorption coefficient it is solely used in Mammography today. Chargetransport in P3HT:PCBM was reported to be relatively close to aSe (see Figure4). BeforeDiCoMo,Siemensdidprototypehybrid-organicX-raydiodesbasedonP3HT:PCBM:GOSwithinthe BMBF-funded project HOP-X. The HOP-X prototype provided sufficient conversionefficiency and excellent modulation transfer function (MTF), but was suffering from highleakagecurrentandstrongimagelag.TheworkinghypothesisofDiCoMowas,thatbyusinghighermobilitypolymersandreducingthenumberoftraps,wecouldbringhybrid-organicX-raydiodestoacommerciallyrelevantlevel.

Figure4:LifetimemobilityplotfordifferentsemiconductortechnologiesrelevantforX-Raydetection.Theblackandredlinerepresenttheminimummobility-lifetime-productassuminganabsorberthicknessof200and1000µmrespectivelyandanelectricalfieldof1V/µm.Theindividualdatapointshavebeenreportedas follows:MAPI: Shrestha et al. (2017). Nature Photonics, 11(7), 436–440; aSe: Haugen et al. (1999).Journal of PhysicsD: Applied Physics, 32(3), 200–207; P3HT:PCBM:BHJ: Garcia-Belmonte et al. OrganicElectronics9(5),847–851;Hybrid-Organic:Bücheleetal.(2015).NaturePhotonics,9(12),843–848.

Within DiCoMo, Siemens Healthineers has further developed a process to “soft-sinter”semiconductorpowdersontotheVGAbackplane.Theprocessconsistsofauniaxialpressingstepwhichiscapabletocreateactiveareasup-to10x10cm²atmoderatetemperatures.Theprocess uses hybrid organic-powders consisting of a mixture of amorphous organicsemiconductors and scintillator particles. During the pressing process the powder iscompacted and a high-quality homogeneous layer is attached directly on the backplanesubstrate(seeFigure3).Layers with a thickness of up to 500µm have been achieved, which are required for asufficiently high X-ray absorption. Togetherwith BASF, Siemens Healthineers achieved toreduce the leakage current density of those layers below 1E-6 mA/cm² @ 150 V and tominimizelag.Unfortunately,theconversionefficiencywasreducedatthesametimebecausethechargecarriertransportwasdeterioratedintheseleakage-optimizedlayers.As amitigationactionwe tested thesystemwith thin-filmorganicphotodiodes (OPDs)andmetal-organicperovskiteswhichprovidesuperiorchargetransportproperties(seeFigure4).

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Figure5displaysa finishedVGA-sizedPerovskitedetectorandthecorrespondingMTF.ThecorrespondingMTF israthergoodwith0.4@2lp/mmwhich iscomparableorevenslightlybetterthanCsIscintillatorbaseddetectoratcomparableX-rayconverterthickness.

Figure5:a)VGA-COFactivepixelbackplanewithMAPIperovskitesOPDs,b)Modulation transfer functionunderX-Rayirradiationevaluatedwiththeslantededgemethod.

SystemintegrationThereadinganddrivingelectronicsofthesystemhasbeendesignedbyimecandconsistsofhardware,firmwareandsoftwaredevelopedtoaddressandreadouttheDiCoMoX-rayimager.Thedesignofthereading anddriving electronicsdidnot contain any scientific challengeshowever it comprisequitecomplexengineeringwork.

The finaldemonstratorelectronics isable todriveand readout aVGA imager(640 x480pixels); itusesacommercialgatedriverIC(ST5041)thecustommadeROICbyICSenceandtheKintex-7FPGAchip from Xilinx Inc. The COF solution has demonstrated to best in terms of thermal budgetcompatibility of the different system components. Figure 6 shows the dedicatedROIC in the COFversion.Theentiresystemisshownontherightsideofthefigure.

Figure6:(left)ROICwithChip-On-Flex(COF);(right)ImagerwithFPGAbasedreadouthardware

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AfirstimagebasedonthinfilmOPDsandanactivepixelmetal-oxideTFTbackplaneisshowninFigure7.On the right side a linearityplotof the system is shown.Thenoise floorwith~120LSB isdominatedbyanRFnoise (visiblealsoashorizontal linespattern in theMonaLisa image)whichdegrades the noise performance of the imager andwhich origin is stillunder evaluation. To the best of our knowledge this is the first time that an active pixelbackplane with low-cost IGZO technology in a flat-panel X-ray detector setting has beenpresented.

Figure 7: (left) Image takenwith thin filmOPDs and an active pixel backpalne in visible light; (right)Linearityofthesystemresponse.

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SimulationsInthisproject,Morphwizehassetupcomputationaltoolstomodelthesystemanddominatethe significant complexity ofmultiscale hybrid photodetectors, aswell asmulti-crystallinemetal-organic semiconducting Perovskites. As the projects adopts an innovative dryprocessing based on pelleting,we employedmodels compatiblewith significant positionaland energetic disorder. A coupled optical-electrical simulation framework for primary (X-rays)and secondary (visible)absorptionandcharge transportwasdeveloped for sphericalscintillator particles embedded into an organic hostmatrix. Advanced techniques such askineticMonteCarlowerecoupledwithFiniteElementModeling (FEM),todescribe indirectphoton to electron conversion and charge carrier collection.The software allowed to gaininsight into intrinsic system limitations and strategies to improve conversion efficiency.Perovskite’sdirectX-rayabsorptionandhighmobilitywerethenexplored,byimplementingacoupled electronic and ionic drift-diffusion model. The full development cycle allowedintegrating the modules into the powerful in-memory mPER-INM platform, and furtherperforming the mandatory hardware tuning. The result is an extended version of ourcomputational platform, with unprecedented capabilities, suitable for describing a wholespectrumofphotodetectortypesandeffects.

Figure 8:.Overview of X-ray Photodetector software suite, based onMorphwize’smPER-INM simulator.WithinDiCoMo,mPER-INMwasenrichedofcomputationalmodulesdevelopedtosimulatecomplexhybrid,aswellasPerovskite-basedphotodetectors.

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ExploitationanddisseminationThrough-out the projectwe shared our technical resultswith the scientific community bycontributingseveral talksandposters toconferences.Manyof thesecontributionswereondedicatedinvitationoftheorganizerswhatunderlinestheparticularinterestinourresearch.We receivedmany invitations to give key-notepresentations at various conferences. A fulloverviewof thoseactions canbe foundon theDiCoMowebpage (www.dicomo-project.eu).Additionalscientificpublicationswhichhaveresulted fromDiCoMoactionsareplanned forthefuture.

WefurthersharedourinsightswiththeEuropeanexpertcommunityinthefieldofmedicalX-ray imaging buy publishingpress releases and organizing networking events. A particularhighlightwastheworkshoponorganicmaterialsforradiationdetectionattheIEEENSS-MIC2017inAtlantawhichwasjointlyorganizedbytheLORIX,iFLEXISandDiCoMoprojects.Theworkshopwasverywell receivedandbrought together themost influencial stakeholder inthisarena.Inparallel,allprojectpartnerscommunicatedDiCoMoresultsinternallyintheirorganizationinorder tocontinuouslydiscuss theopportunitieswhicharise from theprojectresults.Weareconfident thatmanyof theprojectresultswillsignificantly influence theroadmapsandfutureactivitiesofthepartners,notonlyinthedirectuse-caseoftheX-raydetector,butalsoinotherdomainssuchasdisplay,sensorandenergyapplications.

ICSence is offering the dedicated ROIC as OEM product at market conditions for thosecompanies/instituteswhichmightbeinterestedin.

ConclusionsDiCoMotestednewinnovativedesignsolutionsforlargearea(X-ray)imagertoimprovethedynamic rangeand sensitivityof the imager readout. In thisproject,we switched from thecommonlyusedpassive (1T1C)pixelarchitecture toan in-pixelamplifierschemesimilar tothe one used in CMOS image sensors. Also, we introduced novel materials and a low-temperatureprocessforlow-costdirect-conversionofX-rayradiationintoelectricalcharges.Thisrequirednewdevelopmentsacrossthefullintegrationchain,fromthematerialsynthesis(BASF),deviceoptimization(Morphwize),X-ray-absorber-processing(SiemensHealthineers),imager design (imec), to newhigh-voltage backplanes (TNO) and custom designedRO-ICs(ICsense).Thefulldevelopmentcyclereliedonprocessflowsandinfrastructureclosetotheoneusedinvolumemanufacturing.DiCoMoshowcasedaremarkablecaseofsynergybetweenEuropean high techmicro-SMEs, large enterprises and R&D excellence institutions, in thequesttodevelopsolutionsclosetothemarket.As a result, the DiCoMo consortium did successfully implement functional VGA-sizeddemonstrators and performed an in-depth analysis and benchmark with state-of-the arttechnology.Tothebestofourknowledgethisdeliverableisthefirsttimeimplementationofanactivepixelbackplanewithlow-costIGZOtechnologyinaflat-panelX-raydetectorsetting.The combination with a low-cost directly converting X-ray absorber made from hybrid-organicmaterialshasthepotentialtoincreasetheresolutionandsensitivityofsuchdetectors.While further improvement of several aspects (collection efficiency of front plane, noiseperformanceofbackplane) is required,DiCoMohas significantly enhanced the competenceand scientific know-how in this domain and we expect to see a plurality of follow-upinitiativestowardsinnovativeproducts.