Dynamicallyadjustableslurryfeedarmforwafere.docx
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Dynamicallyadjustableslurryfeedarmforwafere.docx
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Dynamicallyadjustableslurryfeedarmforwafere
DynamicallyadjustableslurryfeedarmforwaferedgeprofileimprovementinCMP
FIELDOFTHEINVENTION
Thisinventiongenerallyrelatestochemicalmechanicalpolishing(CMP)andmoreparticularlytoadynamicallyadjustableslurryfeedarmandmethodforadjustingthesameforimprovingapolishinglayerthicknessuniformityincludingaprocesssurfacewaferedgeprofileinaCMPprocess.
BACKGROUNDOFTHEINVENTION
Insemiconductorfabricationintegratedcircuitsandsemiconductingdevicesareformedbysequentiallyformingfeaturesinsequentiallayersofmaterialinabottom-upmanufacturingmethod.Themanufacturingprocessutilizesawidevarietyofdepositiontechniquestoformthevariouslayeredfeaturesincludingvariousetchingtechniquessuchasanisotropicplasmaetchingtoformdevicefeatureopeningsfollowedbydepositiontechniquestofillthedevicefeatures.Inordertoformreliabledevices,closetolerancesarerequiredinformingfeaturesincludinganisotropicetchingtechniqueswhichrelyheavilyonlayerplanarizationtoformconsistentlydeepanisotropicallyetchedfeatures.
Inaddition,excessivedegreesofsurfacenonplanaritywillundesirablyaffectthequalityofseveralsemiconductormanufacturingprocessesincluding,forexample,photolithographicpatterningprocesses,wherethepositioningtheimageplaneoftheprocesssurfacewithinanincreasinglylimiteddepthoffocuswindowisrequiredtoachievehighresolutionsemiconductorfeaturepatterns.
Chemicalmechanicalpolishing(CMP)isincreasinglybeingusedasaplanarizingprocessforsemiconductordevicelayers,especiallyfordeviceshavingmulti-leveldesignandsmallersemiconductorfabricationprocesses,forexample,belowabout0.25micron.CMPplanarizationistypicallyusedseveraldifferenttimesinthemanufactureofamulti-levelsemiconductordevice,includingplanarizinglevelsofadevicecontainingbothdielectricandmetalportionstoachieveglobalplanarizationforsubsequentprocessingofoverlyinglevels.
Forexample,intheCMPofoxidecontaininglayerssuchasdielectricinsulatinglayersalsoreferredtoasinter-layerdielectric(ILD)layersandinter-metaldielectric(IMD)layers,itisimportanttoachieveahighdegreeofplanarityduringILDremoval.Forexample,followingformationoftheILDlayer,viaformationprocessiscarriedouttoformelectricalinterconnectionsbetweenelectricallyconductiveportionsofanunderlyingILDlayerandanelectricallyconductiveportionofanoverlyingILDlayer.IntheeventthatthethicknessuniformityisnotwithinspecificationsfollowingtheoxideorILDCMPprocess,asubsequentanisotropicetchingprocessinrelativelythickerILDlayerportionstoformtheviainterconnect,forexampleatawaferedgeportion(e.g.,periphery)maynotbesufficientlydeeptomakecontactwiththeconductiveportionoftheunderlyingILDlayer,thusresultinginanopencircuitintheintegratedcircuitsemiconductordevice.Ontheotherhand,ifthewaferedgeportionisrelativelyoverpolishedresultinginarelativelythinnerILDlayerportion,asubsequentviaetchingprocesscanresultinmetalthinningintheunderlyingconductiveregionalteringelectricalresistances.
ThewellknownPrestonequationgenerallyexplainsthepolishingmechanismfordielectriclayers,particularlySiO2containingdielectriclayers.Generallytherateofremovalisproportionaltotheappliedpressure,therelativevelocitybetweenthewaferandthepolishingpadandaproportionalityconstantthattakesintoaccountothervariablessuchasthehardnessofthedielectric,theslurry,andthepolishingpad.
OneprocessthatisasyetnotquantitativelyunderstoodistheroleoftheslurryinformingahydrodynamiclayerunderneaththewaferpolishingsurfaceduringCMP.Thedistributionoftheslurrywithrespecttothepolishingsurfacehasreceivedlittleattentioninthepriorart.Forexample,itisknownthatbothmechanicalandchemicalprocessesaccountforpolishingofthesurface.Forexample,chemicalprocessesareknowntodominateonthemicroscaleinremovingmaterialwhilemechanicalprocessesdominateonthemacroscale,forexampleinremovinghighspotsonthewafersurface.Inaddition,theconditionofthepolishingpadaffectsbothchemicalandmechanicalprocesses.
Priorartprocesseshaveproposedfeedingtheslurrythroughthepolishingpadtomakethedeliveryoftheslurrytothewaferpolishingsurfacemoreuniform.ThisprocesshasmetwithsomesuccessbuthasproveddifficulttocontrolwithrespecttovaryingpolishingpadsurfacesandtheparticularCMPmachineused.Forexample,theedgeofthewafermaytendtogetahigherorlowersupplyofslurryduetothecomplexrelativemotionofthepolishingpadandthewaferpolishingsurfacewhichmaybemovedatvaryingrate
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