A Study of CMOS Technologies for Image Sensor Appl

AStudyofCMOSTechnologiesforImageSensorApplicationsbyChing-ChunWangBachelorofScienceinElectricalEngineeringNationalTsingHuaUniversity,Taiwan,June1990MasterofScienceinElectricalEngineeringNationalTsingHuaUniversity,Taiwan,June1992SubmittedtotheDepartmentofElectricalEngineeringandComputerScienceinpartialfulfillmentoftherequirementsforthedegreeofDoctorofPhilosophyattheMASSACHUSETTSINSTITUTEOFTECHNOLOGYAugust2001©2001MassachusettsInstituteofTechnology.AllRightsReserved.SignatureofAuthor...............................................................................DepartmentofElectricalEngineeringandComputerScienceAugust24,2001Certifiedby............................................................................................CharlesG.SodiniProfessorofElectricalEngineeringandComputerScienceThesisSupervisorAcceptedby...........................................................................................ArthurC.SmithChair,DepartmentCommitteeonGraduateStudentsDepartmentofElectricalEngineeringandComputerScience2AStudyofCMOSTechnologiesforImageSensorApplicationsbyChing-ChunWangSubmittedtotheDepartmentofElectricalEngineeringandComputerScienceonAugust24,2001,inpartialfulfillmentoftherequirementsforthedegreeofDoctorofPhilosophyAbstractCMOS(ComplementaryMetal-Oxide-Silicon)imagertechnology,ascomparedwithmatureCCD(Charge-CoupledDevice)imagertechnology,hastheadvantagesofhighercircuitintegration,lowerpowerconsumption,andpotentiallylowerprice.Theadvantagesmakethistechnologycompetentforthenext-generationsolid-stateimagingapplications.However,CMOSprocessesareoriginallydevelopedforhigh-performancedigitalcircuits.Fabricatinghigh-qualityembeddedimagesensorswithCMOStechnologiesisnotastraightforwardtask.ThismotivatesthestudyofCMOStechnologiesforimagingapplica-tionspresentedinthisthesis.Themajorcontentofthisstudycanbepartitionedintofourparts:(a)Atwo-stagecharac-terizationmethodologyisdevelopedforsensoroptimization,includingthecharacteriza-tionoflarge-areaphotodiodesandcomparativeanalysesonsmall-dimensionsensorarrayswithvariouspixelstructures,junctiontypesofthesensors,andotherprocess-relatedcon-ditions.(b)Themechanismofhot-carrierinducedexcessminoritycarriersoccurredatthein-pixeltransistorsisidentifiedandinvestigated.Theinfluenceoftheexcesscarriersonimagerperformanceisanalyzed.Suggestionsonthepixeldesignareprovided.(c)Signalcross-talkbetweenadjacentpixelsisquantifiedandstudiedusingasensorarraywithaspeciallydesignedmetalshieldpattern,whichexposesthecenterpixelandcoverstheoth-ers.Theinfluenceofcross-talkoncolorimagerperformanceisanalyzed.Processandlay-outimprovementsoncross-talkarealsoproposed.(d)Thetrendofpixelsizereductionisinvestigatedfromtheperspectiveoftheachievableopticallensresolution.Usingthemod-ulationtransferfunction(MTF)asanindex,opticalsimulationsareperformedtoexaminetherelationbetweenthelensresolutionandthelenscomplexity.ThesisSupervisor:CharlesG.SodiniTitle:ProfessorofElectricalEngineeringandComputerScience555.AcknowledgementsIwouldliketothankmythesisadvisor,ProfessorCharlesSodini,forhisinsightfultechni-calguidance,steadyencouragement,andunwaveringsupportthroughoutmyPh.D.jour-neyatM.I.T.Iwouldalsoliketothankmythesiscommitteemembers,ProfessorRafaelReifandDr.ChungWangatTSMC,forprovidinginvaluablesuggestionsandadviceinthethesis.SpecialthankstoDr.Shang-YiChiang,V.P.ofResearchandDevelopmentatTSMC,forofferingmeagreatinternshipopportunitytoworkwiththeirCMOSimagesensorteam.Dr.ChungWangandDr.Shou-GwoWuuhostedmethereforsevenmonths.I’mgratefulfortheirhospitalityandtechnicalinput.IwouldalsoliketothankDr.MarcLoinazforinstructingmetheCMOSimagercharacterizationtechniquesduringthethreemonthsofinternshipatLucentTechnologies.Iwanttothankmyfellowdoctoralstudentsandimagesensorgroupmembers,IlianaFujimoriandPabloAcostaSerafini,forthehelpfuldiscussion,encouragementandassis-tance.Specialthankstotheformergroupmember,Dr.JosephLusky,forprovidinghelpandsuggestionsduringthefirstseveralroughyears.Iwouldalsoliketothanktheothercolleagues,includingDonaldHitko,DanielMcMahill,KushGulati,AymanShabra,AndyWang,MarkPeng,MarkSpaeth,SusanDacy,andYao-JoeYang.Theirassistanceandfriendshipenrichedmylife.I’mgratefulfortheendlesssupportandencouragementIhavereceivedfrommypar-entsandfamilyinTaiwanandalsomygirlfriend,Hui-IngMa.FundingforthisworkwasprovidedthroughtheM.I.T.CenterforIntegratedCircuitsandSystems.TSMCprovidedpartialsupportforchipfabrication..67TableofContents1Introduction................................................................................................................171.1ThesisMotivation............................................................................................171.2ThesisContribution..........................................................................................191.3ThesisOverview..............................................................................................212BackgroundandReview............................................................................................232.1GeneralBackground........