dopant-rich films on si...3d doping: finfets(1) current dopant ald pagsept20-17 [email protected] 2...
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Dopant-RichFilmsonSi:AnewfrontierforthermalALDprocesses
MichaelI.Current,CurrentScientific,SanJose,CA
with...T.E.Seidel,Seitek50,PalmCoast,FL,J.W.ElamandA.U.Mane,ArgonneNationalLaboratory,Argonne,IL,A.GoldbergandM.D.Halls,Schrodinger,Inc.,SanDiego,CA,J.Despres,O.Byl,Y.Tang,J.Sweeney,Entegris,Danbury,CT.
1. Howtodope3Dstructures?:finFETs,V-NAND2. DFTcalculationsofB&PonSi3. B2F4 ALDgrowthkinetics4. Conformality &thermaldrive-in5. Summary
3DDoping:finFETs (1)
T.Seideletal.,“ALDProcessforDopant RichFilmsonSi”,IIT16.Y.J.Leeetal;.,“Junctionless FETwithsub-5nmShellDoping”IEDM14.
WhenfinFETs shiftfromepi-topcontactstolargerareasidewallmetal-Sicontacts,finsidewalldopingwillneedtobe(1)muchmoreuniformand(2)higheractiveconcentration.
Near-surface“shell”dopinginthinfinscanbeusedforhigh-performancejunctionless channelsIF thedopingisverythin(<2nm)withhigh-activeconcentration.
3DDoping:V-NAND(2)
3D-NANDshippingnowat48/64layers.96layerversionsduein2018.ChannelAF>50:1.
HowtodopethechannelsforVth ?
PIII/PLADdopingisgoodforfinfFETsand“modest”ARtrench/via/channels,butforAR>50?
D.Rajetal.,IIT14
AR≈8:1
RecoilImplants(1)
Recoilimplants(“ionbeammixing”)havebeenusedforalongtime.
Keyadvantages(forglancingangles)are:
1. recoildoseismuchlarger(≈x100)thantheincidentiondose.
2. recoilmixingprofileis“shallower”thantheincidentions.
3. recoildoseisnotverysensitivetoeither(a)incidentionenergyor(b)incidentionangle.
4. implantdamagecanbelimitedto(mostly)thesurface(source)layer.
RecoilImplants(2)
T.Seideletal.,:ALDofDopants forRecoilImplantationforfinFET Sidewalls”,IIT14
RecoilmixingprofilesofBsurfacefilmsaresubstantiallythesameforglancingincidenceAr+ ionsfor>40keV.
ThermalALDofDopants:circa2014
OK,allwehavetodois:
(1)lookuprecipesforALDofthindopant richfilms,(2)growdopant-richALDfilms,(3)dorecoilimplant(orthermaldrivein),(4)shipdevices,(5)enjoyacelebratoryfinewine.
But,asofSept2014,therewereNOPUBLISHEDPAPERS onthermalALD*ofdopant richfilmsonSiintheANLdatabase(>2.5kALDpapers)!
So,callyourfriendswhodoquantumchemistrycalculations.
*Thereareplentyofpapersforthermaldeposition,PECVD/ALD,etc.…allwithquestionsonconformality forextreme3Dsurfaces.
DensityFunctionalTheoryforB&PonSi(1)
Bycomparisonwiththe“GrandDad”ofALDapplications,W-depositionwithWF6,initialcalculationswithPF3 (usingDensityFunctionTheory(DFT)atSchrodinger,Inc.)alsolookedfavorable.
A.GoldbergandM.D.Halls,Schrodinger,Inc.,SanDiego,CA,
DensityFunctionalTheoryforB&PonSi(2)
T.Seidel,etal.,“SimulationofnucleationandgrowthofALDPhosphorousfordopingoffinFETs”.JVST-A36(2016).
MoredetailedDFTcalculationsshowfavorableenthalpiesforPF3,PCl3 andPBr3 combinedwithSi2H6.
DensityFunctionalTheoryforB&PonSi(3)
A.Maneetal.,“ALDofBoron-containingfilmsusingB2F4”,JVST-A43(2016).
DFTcalculationsshowedmorefavorableenthalpiesforB2F4*forsequentialdepositions(forH-terminatedSisurface)thanBF3.
*B2F4 isarelativelynewSiprocesschemicalwithlowerionizationpotentialthanBF3 (goodforionimplantsources).AlsoweakB-Bbonds.
ALDGrowthKineticsofBonSi(1)
A.Maneetal.,“ALDofBoron-containingfilmsusingB2F4”,JVST-A43(2016).
WorkingonB-dopedALD,sequencesofB2F4 alternatedwithH2Oshowedeventualfilmgrowthsaturation.
SequencesofB2F4 alternatedwithSi2H6 showedevensoonerfilmgrowthsaturation.
ALDGrowthKineticsofBonSi(2)
A.Maneetal.,“ALDofBoron-containingfilmsusingB2F4”,JVST-A43(2016).
SequencesofB2F4 alternatedwithSi2H6 andH2Oalsoshowedfilmgrowthsaturationwithin≈300s.
ButadditionofTMA(Trimethyl-Al)tosequencesofB2F4 alternatedwithH2Oshowedcontinuedfilmgrowthpromise.
ALDGrowthKineticsofBonSi(3)
A.Maneetal.,“ALDofBoron-containingfilmsusingB2F4”,JVST-A43(2016).
AsequenceofB2F4 alternatedwithTMAandH2Oshowedlinearfilmgrowthwithnosaturation.
However...
Theresultingfilmisnotreally“dopant rich”,with≈10%B.
B-richFilmswithB2F4:Conformality
Bottomofa40:1hollowSicylinder*
Sicore(8nm)B-AlBO (9nm)ZnO cap(6nm)
*Aixtron teststructure.
B-AlBO thermalALDfilmsshowedexcellentconformalityontheoutsideandinsideofa40:1hollowSicylinder.
B-richFilmswithB2F4:ThermalDrive-in
“RTA”(30s)annealingofB-AlBO ALDfilmsproduced≈5nmXj profilesinSifortemperaturesof700to875C.
Fwastheonlysignificantco-diffuserwithBfromtheB-AlBO ALDfilmsat825C.
Summary&Status
1. Startingfromanopenfieldinlate2014,promisingdopant richfilmgrowthenergetics identifiedforBandPcontainingfilmswithDFTbySchrodingerInc.
2. GrowthkineticsofB-richfilmsexploredbyANLforB2F4,withlineargrowthconditionsestablished.
3. B-containingthermalALDfilmsgrownwithexcellentconformalityandsuccessfulthermaldrivein.
4. PaperswrittenforALDandIITconferences.
5. Projectonhold,pendingarrivalaserioussponsor(withfunding)andambitionstoexploitthesethermalALDpossibilities.
ThecartoonIpastedintomy1st SiliconValleynotebookin1980
Notesformodern(2015)graduatestudentsatChengKungU.(Tianan),whoneverhaveseenatypewriter.