Erli chen Fabrication III - Etching

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1、III.WetandDryEtchingWetDryIonBombardmentorChemicalMethodChemicalSolutionsReactiveEnvironmentandAtmosphere,BathVacuumChamberEquipment1)Lowcost,easytoimplement1)CapableofdefiningsmallAdvantage2)Highetchingratefeaturesize(<100nm)3)Goodselectivityformostmaterials1)Inadequatefo

2、rdefiningfeaturesize1)Highcost,hardto<1umimplementDisadvantage2)Potentialofchemicalhandling2)lowthroughputhazards3)Poorselectivity3)Wafercontaminationissues4)PotentialradiationdamageIsotropicDirectionality(ExceptforetchingCrystallineAnisotropicMaterials)AppliedPhysics298r1

3、E.Chen(4-12-2004)PatternGeneration(Transfer):Etchvs.LiftoffEtchingLiftoffMaskMaskMaskFilmFilmLithographyLithographySubstrateSubstrateFilmFilmMaskFilmDepositMaskFilmMaskEtchingFilmSubstrateSubstrateFilmFilmStripRemoveMask(Resist)SubstrateMask(Resist)Substrate(Liftoff)Applie

4、dPhysics298r2E.Chen(4-12-2004)Isotropicvs.AnisotropicEtchingMaskIsotropicEtching:EtchingrateisthesameinbothhorizontalandverticaldirectionAnisotropicEtching:EtchingrateisdifferentinR=1horizontalandverticaldirectionLLateralEtchRatio:MaskHorizontalEtchRate(r)R=HL()VerticalEtc

5、hRaterV0

6、sMaskMaskFilmFilm“UnderCut”SubstrateGoodforLift-offSubstrate(Rl=1,patterndimension(Rl=0.5,patterndimensionispoorlydefined)isbetterdefined)MaskMaskSubstrateSubstrateOver-EtchWorseinthickfilm¬resultsinmoreverticalprofile¬PoorCDcontrolinbutlargerbiasthickfilmusingwetetchAppli

7、edPhysics298r4E.Chen(4-12-2004)MaskErosion:Film-MaskEtchingSelectivity1)filmhorizontaletchrate(r)

8、mV–selectivity)W/2(Bias)2)Iffilmhorizontaletchrate(r)>maskhorizontalfhMasketchrate(r):mhF