WAT-Training-3-3-2004

WATvs.InlineprocessforLogicOUTLINE•1.WhatisWAT?•2.WhyWAT?•3.HowWATmonitorinlineprocess?•4.Generalstructuresusedtomonitorinlineprocess•5.WATparameterstodescribedevicecharacterization•6.Troubleshootingexamples•WATistheabbreviationforWaferAcceptanceTest•WATisdifferentfromCPtest.–WATtestonstructurelevel.Thesestructurescanbearesistor,acapacitororatransistor.–CPtestoncircuitlevel,thecircuitisthecombinationofthousandsoftransistors,resistorsandcapacitors.1.WhatisWAT?•WATisusedtomonitorinlineprocess.•WATisusedtomonitordevicecharacterization.•WATisthenecessarysteptosetupspicemodel.2.WhyWAT?3.HowWATmonitorinlineprocess?DesignanddrawstructuresTapeoutandmaskmakingFABprocessWATDataanalysisBenchconfirmtotheabnormaldataFailureanalysistothefailpointandfoundtheissueinin-lineprocess.Tunedevicerelatedprocesscondition4.Generalstructuresusedtomonitorinlineprocess•4.1Spacingstructures–Spacingstructureisusedtomonitorthelithoandetchcapacityofcriticallayers.SuchasAA,poly,metal.–Measurementmethod:Forcevoltagebetweenpad1andpad2,sensecurrent.orforcecurrentsensevoltage.Pad1Pad24.Generalstructuresusedtomonitorinlineprocess•4.2Continuitystructures–Continuitystructureisusedtomonitorthelithoandetchcapacityofcriticallayers.SuchasAA,poly,metal.–Measurementmethod:Forcevoltagebetweenpad1andpad2,measuretheresistanceofthestructure.Pad1Pad24.Generalstructuresusedtomonitorinlineprocess•4.3Contactchainstructures–Contactchainstructureisusedtomonitorholeprocess.Suchascontactandvia.–Measurementmethod:Forcevoltagebetweenpad1andpad2,measuretheresistanceofthestructure.AAorPolyMetal1Pad1Pad24.Generalstructuresusedtomonitorinlineprocess•4.4Sheetresistancestructures–SheetresistancestructureisusedtomonitorRsofcriticallayers.SuchasAA,Po,bothsilicideandnon-silicide,wells,metals–Measurementmethod:Forcevoltagebetweenpad1andpad2,measuretheresistanceofthestructure.Pad1Pad24.Generalstructuresusedtomonitorinlineprocess•4.5Gateoxidestructures–Gateoxidestructureisusedtomonitorgateoxidethickness.–Measurementmethod:measurethecapacitanceofthisMOScapacitor,andthencalculatethegateoxidethickness.–InversionmodeandaccumulationmodePad1Pad2poly4.Generalstructuresusedtomonitorinlineprocess•4.6Junctionleakstructures–JunctionleakstructureisusedtomonitorthejunctionleakcurrentoftheS/Djunction.includingbulkpattern,AAedgepattern,polyfingerpattern–Measurementmethod:Forcevoltagebetweenpad1andpad2,sensecurrent.orforcecurrentsensevoltagePad1Pad2metal4.Generalstructuresusedtomonitorinlineprocess•4.7Fielddevicestructure–Fielddevicestructureisusedtomonitorisolationperformance,therearetwokindsofstructure:polygateandmetal1gate.–Measurementmethod:connectbulktoground,sweepgatevoltage,sensethecurrentbetweenpad1andpad2Pad1Pad2gatebulk4.Generalstructuresusedtomonitorinlineprocess•4.8Silicidebridgingstructure–Silicidestructureisusedtomonitorifthereissilicideresidueonthespacer.–Measurementmethod:forcevoltagebetweenpad1andpad2,senseleakcurrent.Pad1Pad2gate4.Generalstructuresusedtomonitorinlineprocess•4.9Devicestructure–DevicestructureisusedtomonitorMOStransistorperformance–Measurementmethod:chapter5havethedetailPad1Pad2gatesourcedrainsubstrate4.Generalstructuresusedtomonitorinlineprocess•4.10otherstructures•Designrulecheckstructures,suchasjunctiontowellspacingrulecheck,wellenclosurerulecheck,polyendcaprulecheck,contacttopolyspacingrulecheck,etc.•H-devicetomonitordevicehumpphenomena•MillercapacitortomonitorpolyE-CD•UsesmallresistortomonitorWATprobingcardcontactresistance5.WATparameterstodescribedevicecharacterization•5.1Thresholdvoltage(Vt)•Thresholdvoltageisthegatevoltageattheonsetofstronginversion.•Measurementmethod:–Vt_linear:VD=0.05V(0.1V),VS=VB=0V,VG=0to0.8*VDD,MeasureVt_linear=VG@ID=0.1uA*(W/L)–Vt_gm:VD=0.05V,VS=VB=0V,VG=0to0.8*VDD,extrapolatetoVGatmaxslope,measureVT_gm=VG(INTERCEPT)-0.5*VDVGID5.WATparameterstodescribedevicecharacterization•5.1Thresholdvoltage(Vt)•Vt_gmmeasurementmethodmathematicalillusion:•LinearId=1/2(μCoxW/L)(2(Vgs-Vt)Vds-Vds2)Gm=μCoxW/Lμ•Saturation:Id=1/2(μCoxW/L)(Vgs-Vt)2Gm=μCoxW/L(Vgs-Vt)•Pinch-Off:Vds=Vgs-VtGm=μCox(W/L)Vdsβ=μCox(W/L)•MaximumGmhappenedasPinch_offhappened,whenVg=Vd+Vt,Id=1/2βVd2,replace(x,y)intheformulay=Gm(x-intercept)Getintercept=Vt+1/2VdVGID5.WATparameterstodescribedevicecharacterization•5.2Drivecurrent(Idsat)•DrivecurrentisthedraincurrentwhenMOSworksatsaturationarea.•Measurementmethod:–VD=VG=VDD,VS=VB=0,MeasureIdsat=ID(thendividebyWinsomecalculation)5.WATparameterstodescribedevicecharacterization•5.3Offcurrent(Ioff)•OffcurrentisthedraincurrentwhenMOSworkatcutoffarea.•Measurementmethod:–VD=1.1*VDD,VG=VS=VB=0,MeasureIOFF_N=ID5.WATparameterstodescribedevicecharacterization•5.4Swing•SwingparameterisusedtoindicatehoweffectivelyaMOSFETcanbeturnedoffversusVgs.Theinverseoftheslopeisdefinedasthesubthresholdswing.•Measurementmethod–Vg1=VgwhenId=1e-10*W/LA–Vg2=VgwhenId=1e-8*W/LA–Swing=(Vg2-Vg1)*5005.WATparameterstodescribedevicecharacterization•5.4Swing•theoreticalformulaofswing–Swing=ln10(dlnId/dVgs)=2.3(kT/q)(1+Cd/Cox)–OntheassumptionthatTox0swing60mV/dec5.WATp