WAT-Basic-Introduction.ppt

WATBasicIntroduction Summary WhatisWAT WhydoweneedWAT Whatcanandcan tWATdo WATbasicconcept device LayoutManualWATprobe 4156 Q A WhatisWAT WATisabbreviationforWaferAcceptanceTest WATisthelastprocessinFAB WATisanimportantprocessinFAB decidewhetherthewafergothroughannormalprocess andshiptocustomer WhydoweneedWAT WATcantestindividualdeviceofstreet notdieorchip WATcancheckelectriccharactersofindividualdevice WATcanmonitorfrontprocessviaelectriccharactersofindividualdevice WATcanprovideoutdevicetestdataforconsumer Whatcanandcan tWATdo Whatcanandcan tWATdo cont Testpattern 1 TestLine TestKey Productionmonitor locatedontheScribeLineandwillbedestroyedafterdiesaw 2 TestChip DesignRulecheck Yieldmonitor ProcessQualification usuallychipsize forinitialprocesstechnologydevelopment WATbasicconcept device layout WATbasicconcept device layout cont WATbasicconcept device layout cont MOSkeyparameters VtandGmIdsatIoffVBDIsubDIBLGAMMASWINGGleak Isubmax Isubvg Gleak2 SUBVTSLP Vt1 Vt2 MFAC1 MFAC2 BETA TypicalWATtestkeylayout DeviceparameterMOS Purpose checktransistorelectricalcharacter ContinuityandSpacingofPoly Metal Spacing Bridging StepincreaseVoltage Breakdown 1uAleakagecurrent FieldDevice Purpose CheckfiledIsolation Gateoxideintegrity Sheetresistance Rs N P NW Po ContactResistance Rc N P Via StackcontactchainCT Viaresistancepattern Purpose TomonitorstackcontactRcfromCTtoV1 mainlyfocusonMET VIAoverlay andmetalislandprocess RC N CT V1 1800Counts VD 1 8V VB 0VMeasure ID thenRC N CT V1 VD ID 900 RS N 2 100 1800 Inlinearregion InSaturationregion WhenId Idsat Vd VG Vth andSo TransistorWATparametersandtestcondition 1 VTGm N VD 0 05V VS VB 0V VG 0to0 8 1 8V whereas1 8VisVDDNextrapolatetoVGatmaxslope measureVTGm N VG INTERCEPT 0 5 VD 2 VTLIN N VD 0 05V VS VB 0V VG 0to0 8 1 8V whereas1 8VisVDDNMeasureVTLIN N VG ID 0 1uA W L Tosimplifythecalculation thetransistorwasconsideredturnedonwhenID 0 1uA W L TypicalValue VTLIN N 10 10 0 37VVTLIN P 10 10 0 44VVTLIN N 10 0 18 0 44VVTLIN P 10 0 18 0 5VVTLIN N 0 22 10 0 31VVTLIN P 0 22 10 0 41VVTLIN N 0 22 0 18 0 36VVTLIN P 0 22 0 18 0 5VVTLIN N3 3 10 10 0 68VVTLIN P3 3 10 10 0 73VVTLIN N3 3 10 0 35 0 72VVTLIN P3 3 10 0 35 0 68VVTLIN N3 3 0 22 10 0 56VVTLIN P3 3 0 22 10 0 68V3 VTSAT N VD 1 8V VS VB 0V VG 0to0 8 1 8V whereas1 8VisVDDNMeasureVTSAT N VG ID 0 1uA W L VD VDDN tomakesurethatthetransistorisworkingatthesaturationstatus 4 IDSAT N VD VG VDDN 1 8V VS VB 0 MeasureIDSAT N ID thendividebyWinsomecalculation TypicalValue IDSAT N 10 0 18 6mAIDSAT P 10 0 18 2 59mA 600uA um 259uA um IDSAT N 0 22 10 4uAIDSAT P 0 22 10 1 1uAIDSAT N 0 22 0 18 180uAIDSAT P 0 22 0 18 60AIDSAT N3 3 10 0 35 6mAIDSAT P3 3 10 0 35 3mAIDSAT N3 3 0 22 10 7 58uAIDSAT P3 3 0 22 10 1 61uA 5 IOFF NVD 1 1 1 8V VG VS VB 0 MeasureIOFF N ID thendividebyWinsomecalculation TypicalValue IOFF N 10 0 18 60pAIOFF P 10 0 18 30pAIOFF N3 3 10 0 35 60pAIOFF P3 3 10 0 35 35pA6 BVD NVG VS VB 0V VD 1 8To3 VDDN whereas VDDN 1 8Vor3 3V MeasureBVD N VD ID 0 1uA WTypicalValue BVD N 10 0 18 4VBVD P 10 0 18 5 21VBVD N3 3 10 0 35 7VBVD P3 3 10 0 35 6 99V 7 ISUB NVD 1 1 1 8V VS VB 0 VG 0 2 1 8Vto1 1 1 8V FindISUB N MAX then dividedbyWinsomecalculation Monitorthehotcarriereffect SweepVgandMeasureIb Isub Abs Isub maxIThesubstratecurrentinann channelMOSFETresultsfromholegenerationbyimpactionizationsinducedbythechannelelectronstravelingfromsourcetodrain Assumingimpactionizationoccursuniformlyinthepinchoffregion nearthedrain thesubstratecurrent Ibs maybewrittenasIbs Id Lwhere ionizationcoefficient L lengthofpinchoffregionWithVg Ibs andreachesamiximumvalue thendecrease TheinitialIbsincreaseisduetotheincreaseinIdwithVg However asVggoesup thelateralfielddecreases causingareductionin Thus thepeaksubstratecurrentoccurswhenthetwocompetingfactorscancelout usuallyat0 5Vd TypicalValue ISUB N 10 0 18 1 6uA ISUB P 10 0 18 0 013uA 8 DIBL DrainInducedBarrierLowering VTLINVD 0 05V VS VB 0 VG 0to0 8 VDDNMeasureVTLIN VG ID 0 1 A W L VTSATVD 1 1 VDDN VS VB 0 VG 0to0 8 VDDNMeasureVTSAT VG ID 0 1 A W L DIBL VTLIN VTSAT 1 1 VDDN 0 05 Thresholdvariationiscausedbytheincreasedcurrentwithincreaseddrainvoltage astheapplieddrainvoltagecontrolstheinversionlayerchargeatthedrain therebycompetingwiththegatevoltage Intheweakinversionregime thereisapotentialbarrierbetweenthesourceandthechannelregion Theheightofthisbarrierisaresultofthebalancebetweendriftanddiffusioncurrentbetweenthesetworegions Ifahighdrainvoltageisapplied thebarrierheightcandecrease leadingtoanincreasedraincurrent Thusthedraincurrentiscontrollednotonlybygatevoltage butalsobythedrainvoltage 9 GAMMA N bodyeffect VD 0 05V VS 0 VB 1 5 1 8 VG 0to1 1 1 8MeasureVTLIN1 N VG ID 0 1uA W L thethresholdvoltagewithsubstratebias VB 0 443744GAMMA N ABS VTLIN1 N VTLIN N ASB VB 2 1 2 2 1 2 Since VT GC QB Cox 2 B Qox Cox VFB 2 B SQRT 2 B VB Where VFB GC Qox Coxand SQRT 2 siqNB CoxVTLIN1 VFB 2 B SQRT 2 B VB VTLIN VFB 2 B SQRT 2 B VTLIN1 VTLIN SQRT 2 B VB SQRT 2 B TypicalValue GAMMA N 10 10 0 5V1 2GAMMA P 10 10 0 57V1 2 10 SWING NVD 0 05V VS VB 0 VG 0to1 8V MeasureVG1 ID 10nA W L VG2 ID 0 1nA W L SWING N 500 VG1 VG2 Intheweekinversion orsub threshold regime thetransistorconductsaverysmallsub thresholdcurrent andthedraincurrentdependsexponentiallyonthegate sourcevoltage Tomeasurethesub thresholdslope SS whenVD 0 05V isdefinedas SUBVTSLP slope 1 VG1 VG2 log Ileak1 log Ileak2 VG1 VG2 log Ileak1 Ileak2 V dec VG1 VG2 log 10 0 1 V dec VG1 VG2 2V dec 500 VG1 VG2 mV dec 11 Gleak NVS VD VB 0 VG VDDN 1 8V MeasureIG If 50nA considerTransistorfailthetest skipallresttransistortests12 Gm NMaxslopeofIDvsVG VB 013 VsubvgVD 1 1 VDDN VB VS 0 VG 0 2 VDDNto0 7 VDDNMeasureVG maxISUB Gatecapacitorkeyparameters 1 TOX 2 Leakage3 BreakdownVoltage4 Cap WATbasicconcept device layout cont WATbasicconceptanddevice cont DiodeKeyParameters CapacitorLeakageBreakdownvoltage Testcondition VD 0 2V VB 0VMeasure ID ComputeRs VD ID L W P Polyresistancepattern RSFV PP D15 400 OHM SQ A Purpose TomonitorsalicideRsresistanceofP PolyB Design L 400 W 0 15 WATbasicconceptanddevice cont SheetResistor Rs ContactResistance Rc N AAContactresistancepattern RCFV NDF D17 3240 OHM EA A Purpose TomonitorN AAcontactRcDesign Under AAUpper Metal 1Holesize 3240ea C Testcondition VD 0 2V VB 0VMeasure ID ComputeRC N VD ID CountCount numberofcontact WATbasicconceptanddevice cont WATfailanalysis processdebugging WATfailuremode OutofSpec Missingorwrongprocesssteps OutofControl Processfluctuation random Processdrift systematictrend Multiplegroup Equipmentchamberoffset WATRe TESTandManualmea