5. Wafer defect inspection system - Hitachi High-Tech

The wafer defect inspection system detects defects by comparing the image of the circuit patterns of the adjacent dies. As a result, systematic defects ... Skiptomaincontent Search Global HitachiGroupProducts&Services HitachiGroupCorporateInformation GlobalNetwork Sitemap ContactUs Products&Services AboutUs Support TOP Products&Services SemiconductorManufacturingEquipment SemiconductorRoom SemiconductorManufacturing 5.Waferdefectinspectionsystem 5.Waferdefectinspectionsystem Waferdefectinspectionsystemdetectsphysicaldefects(foreignsubstancescalledparticles)andpatterndefectsonwafersandobtainsthepositioncoordinates(X,Y)ofthedefects. Defectscanbedividedintorandomdefectsandsystematicdefects. Randomdefectsaremainlycausedbyparticlesthatbecomeattachedtoawafersurface,sotheirpositionscannotbepredicted. Themajorroleofawaferdefectinspectionsystemistodetectdefectsonawaferandfindouttheirpositions(positioncoordinates). Ontheotherhand,systematicdefectsarecausedbytheconditionsofthemaskandexposureprocess,andwilloccurinthesamepositiononthecircuitpatternofallthediesprojected. Theyoccurinlocationswheretheexposureconditionsareverydifficultandrequirefineadjustment. Thewaferdefectinspectionsystemdetectsdefectsbycomparingtheimageofthecircuitpatternsoftheadjacentdies. Asaresult,systematicdefectssometimescannotbedetectedusingaconventionalwaferdefectinspectionsystem. Inspectioncanbeperformedonapatternedprocesswaferoronabarewafer. Eachofthesehasadifferentsystemconfiguration. Belowisanexplanationoftypicalinspectionsystems;PatternedwaferinspectionsystemandNon-patternedwaferinspectionsystem. Principlesofdefectdetection Patternedwaferinspectionsystem Therearemanytypesofpatternedwaferinspectionsystems,includingtheelectronbeaminspectionsystems,thebright-fieldinspectionsystems,andthedark-fieldinspectionsystems.Eachofthesehasitsownfeatures,butthebasicdetectionprinciplesarethesame. Onasemiconductorwafer,electronicdevicesofthesamepatternaremadesidebyside.Randomdefectsareoftencausedbyparticlessuchasdustandoccurinrandompositions,asthenamesuggests.Thepossibilitythattheywilloccurrepeatedlyinaspecificpositionisextremelylow. Patternedwaferinspectionsystemcanthereforedetectdefectsbycomparingthepatternimagesofadjacentchips(alsocalleddies)andobtainingthedifference. Fig.5-1.Principlesofdefectdetectiononapatternedwafer Fig.5-1showstheprinciplefordetectingdefectsonapatternedwafer. Thepatternonthewaferiscapturedalongthediearraybyelectronbeamorlight.Defectsaredetectedbycomparisonbetweenimage(1)ofthedietobeinspectedandimage(2)oftheadjacentdie. Iftherearenodefects,theresultofthesubtractionofImage2fromImage1bydigitalprocessingwillbezeroandnodefectsaredetected.Incontrast,ifthereisadefectintheimageofdie(2),thedefectwillremaininthesubtractedimage(3)asshowninthefigure.Thedefectisthendetectedanditspositioncoordinatesareregistered. Non-patternedwaferinspectionsystem Thenon-patternedwaferinspectionsystemisusedinthewafershippinginspectionbywafermanufacturers,thewaferincominginspectionbydevicemanufacturersandtheequipmentconditioncheckusingdummybarewaferstomonitorthecleanlinessofequipment.Theequipmentconditioncheckisalsoperformedbytheequipmentmanufacturerattheshippinginspectionandbythedevicemanufacturerattheequipmentincominginspection. Tocheckthecleanlinessofequipment,abarewaferforcleanlinessmonitoringisloadedintotheequipmentandthestageinsidetheequipmentisthenmovedtomonitortheincreaseinparticles. Fig.5-2.Principleofdefectdetectiononanon-patternedwafer(1) Fig.5-2showstheprinciplefordetectingdefectsonanon-patternedwafer. Sincethereisnopattern,defectsaredetecteddirectlywithoutimagecomparison. Alaserbeamisprojectedtotherotatingwaferandismovedintheradialdirectionsothatthelaserbeamisabletoirradiateentiresurfaceofthewafer. Fig.5-3.Principleofdefectdetectiononanon-patternedwafer(2) Whenalaserbeamisprojectedontoaparticle/defectofarotatingwafer,thelightwillbescatteredanddetectedbyadetector.Thus,theparticle/defectisdetected.Fromthewaferrotationangleandtheradiuspositionofthelaserbeam,thepositioncoordinatesoftheparticle/defectarecalculatedandregistered.DefectsonamirrorwaferalsoincludecrystaldefectssuchasCOPinadditiontoparticles. Fig.5-4.Anexampleofdetectingtheresidueatthebottomofacontacthole. Ingeneral,thebright-fieldinspectionsystemisintendedforthedetailedexaminationofpatterndefects.Ontheotherhand,thedark-fieldinspectionsystemcandetectathighspeedandisintendedforthedefectinspectionofalargenumberofwafers. Intheelectronbeaminspectionsystem,electronbeamisirradiatedontothesurfaceofthewafer,andtheemittedsecondaryelectronsandbackscatteredelectronsaredetected. Moreover,theelectronbeaminspectionsystemdetectstheamountofthesecondaryelectronsasanimagecontrast(voltagecontrast)accordingtotheconductivityofthedevice’sinternalwiring.Iftheconductivityatthebottomofthecontactholeofthehighaspectratioisdetected,theSiO2residueofultra-thinthicknesscanbedetected. Products IntroducingtheproductlineupofDefectReviewSEM&DefectInspectionSystems WaferSurfaceInspectionSystemLSSeriesWafersurfaceinspectionsystemtodetectvarioustypesofsmalldefectsonnon-patternedwaferofnextgenerationdevice. DarkFieldWaferDefectInspectionSystemISSeriesDeliveringhighdetectionsensitivityandhighinspectionthroughputwhichenablesyieldimprovementandproductioncostreduction. Page5of7 FirstPagePreviousPageNextPageLastPage Whataresemiconductors? 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