半导体工艺-复旦大学-蒋玉龙-Chapter 4.pdf

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1、Chapter4BasicBipolarandBiCMOSProcessTechnologyOutlineI.RequirementsandstructureofbipolardevicesforhighperformanceICII.MainfabricationprocessofoxideisolationbipolarICIII.Poly-Siself-aligned(PSA)processforbipolarVLSItechnologyIV.SBDclampsforbetterspeedperformanceofbipolarlogicIC(STTL,LSTTL,ALSTTL,

2、SI2L….)V.Hetero-junctionbipolartransistor(HBJTorHBT)technologyVI.BiCMOStechnologyI.RequirementsandstructureofbipolardevicesforhighperformanceIC©Mainrequirements:¾Lowjunctioncapacitance¾Lowseriesresistanceofe,b,c¾Lowbasetransittime(thinnerbase…)¾Highcurrentgain(higheremitterdoping…)¾Highbreakdown

3、voltage¾Highdevicedensity©ConventionalPNjunction-isolatedbipolarIC¾SBC(Standard-buried-collector)NPNtransistor¾Reverse-biasedPNjunctionsurroundstransistorforisolation¾Problems:(1)Consumelargerarea→Lowerdevicedensity(Theactivearea,theregionbelowemitter,onlyroughly5%oftotaldevicearea)(2)Largeparas

4、iticcapacitance→Lowerspeed©Highperformanceoxideisolationbipolardevices¾Areaoccupationreduced→beneficialforhigherdensity¾Parasiticcapacitancereduced(isolation,collectorjunction,emitterjunction)→beneficialforhigherspeedIIMainfabricationprocessofoxideisolationbipolarIC©Anexampleofdopingengineering*

5、StandardBuried-Collector(SBC)transistorprocess1.Substrate,buriedlayerformationandthinepitaxiallayergrowth¾Substrate:Lightlydopedp-Si;(111)/(100),doping∼1014cm-3,ρ∼10Ωcm¾Buriedlayer(subcollector):n+-Sibydiffusionorionimplantation,usinglow-diffusivityimpurities---SborAs¾Epitaxy:N∼1015-16cm-3,ρ∼0.3

6、-0.1ΩcmD---Lightdoping→SmallerB-Cjunctionparasiticcapacitance---Toolight:(1)→Auto-dopingproblemduringgrowth(2)→Basepush-outeffect(basewideningeffect)orKirkeffect(Higher-levelelectroninjection→electronsaddtothespacechargeintheB-Cjunctionspace-chargeregion→wideningofthequasi-neutralbaselayer+widen

7、ingofB-Cspace-chargelayerintothecollector)∴Dopingshouldbehighenoughtomeetthecurrentrequirement:N>j/qvsj---Currentdensity,v—Theelectronscattering-limitedvelocity(7s∼10cm/sec)2.Fullyrecessedoxideisolation--keyoftheisoplanarpro