Nonmelt laser annealing of boron implanted silicon

181 Pages·2002·6.6 MB·English

by  Earles, Susan K.

NONMELTLASERANNEALINGOFBORONIMPLANTEDSILICON
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i By
SUSANK.EARLES
ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL
OFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENT
OFTHEREQUIREMENTSFORTHEDEGREEOF
DOCTOROFPHILOSOPHY
UNIVERSITYOFFLORIDA
2002
Copyright2002
by
SusanK.Earles
ThisworkisdedicatedtoLaurieandherfriend,theEnglishmajor.
ACKNOWLEDGMENTS
Iwouldliketothankmyresearchadvisor,Dr.MarkE.Law,forhistimeandsupport
beginninginmysenioryearofundergraduatestudyandcontinuingthroughoutmyentire
courseofgraduatestudy. AlongwithDrLaw,Ihavealsobeenveryfortunatetohave
supportthroughouttheyearsfromDrGisBosmanandDrRobertFox. Theirwonderful
personalities,character,andadvicegavemethecourageanddesiretocontinuewithmy
graduatestudyhereattheUniversityofFlorida. DrShengSLihasalsohelpedmekeep
mysanitybyenduringmanyofmytechnicalquestionsandthoughtsonvarioustopics.
Hisadvice,support,andencouragementhavebeenverywelcomeovertheselastfew
years. ImustalsothankDr.KevinS.Jones. Hiscommentsandadvicehavedefinitely
aidedinprovidingdirectiontomyresearch. LetmealsoacknowledgeDrHollowayfor
steppinginatthelastmomenttoserveonmycommittee.Ithasbeenapleasuretohave
thechancetotalkwithhimafterclassandatvariousmaterialsscienceevents. Iwould
alsoliketoextendaspecialthankstoLauren,Edna,Mary,Erlinda,Jim,andSharon(the
computerandadministrativeassistants)foralloftheirhelpandconversationsoverthe
years.
IwouldliketothankthegroupsfromTexasInstruments,Lucent,Intel,andMotorola
formakingmyinternexperiencesveryenjoyableandsometimeseducational. Each
internshipwascertainlyunique. Mike,Peter,Craig,andTimdefinitelymadeit
believablethatevenworkcanbeentertaining. IalsowanttothankGanaRimpleand
SomitTalwaratVerdantforhelpwiththelaseranneals. Also,althoughtheymaybe
iv
unawareoftheirpositiveinfluence,Iamverygratefulforandwillalwayswelcome
conversationandadvicefromWolfgangWindlandBaylorTriplett. Ialsoneedtothank
theSRCandSEMATECHforthefinancialsupportprovidedforthiswork.
Asformyfriendsandfamily,whichIamveryfortunatetohave,Ithankthemforall
oftheirsupport. IthankSteve,Janet,Marty,Hernan,Jon,Doug,Lahir,Ibo,Dave,
Laurie,Michelle,Lesley,Hugo,Joe,Elaine,Heather,Ming-yeh,Meng,Sushil,Wish,
Aaron,Tony,andtherestoftheformerandcurrentSWAMPgroup,forallofthelunch,
dinner,andphoneconversationsovertheyears. Itissuddenlyobviouswhyittookmeso
longtofinishup. Sowhystopnow,IthankLisa,Juan,andDerekforallofthemuch
neededbabblebreaks. IwouldliketoletPatrickandmyfamilymembers,Ester,Lester,
Beverly,Joe,Beulah,Ron,Angie,Tina,Teresa,Emily,Bob,Gail,Richard,Sandi,Ann,
Brent,Marissa,andDaniel,"Yes,itistimetobuyastove. Iamactuallydone."
1
TABLEOFCONTENTS
page
ACKNOWLEDGMENTS iv
LISTOFFIGURES ix
ABSTRACT xv
1INTRODUCTION 1
1.1MotivationandObjective 1
1.2IonImplantation 2
1.2.1CollisionsandDamage 3
1.2.2Complications 4
1.3Activation 5
1.4AnnealingandDiffusion 6
1.4.1Overview 6
1.4.2RapidThermalAnnealing 8
1.4.3LaserAnnealing 9
1.5AnalysisTechniques 1
1.5.1Chemical 11
1.5.2Electrical 11
1.5.3Structural 13
2LASERANNEALING 20
2.1Overview 20
2.2LaserBeamInteractionwithSilicon 20
2.3TheTemperatureModel 21
2.4LaserInteractionwithImplantedSilicon 23
2.4.1AbsorptionDepthandImplantEnergy 24
2.4.2SiliconInterstitialandBoronDiffusionduringAnnealing 24
2.4.3IncreasingtheNumberofLaserPulses 26
2.5DeterminingtheMeltingPoint 27
2.5.1The308nmMeltingPoint 27
2.5.2The532nmMeltingPoint 28
3EXPERIMENTALINVESTIGATIONSOFTHEEFFECTSOFNLAONBORON
IMPLANTEDSILICON:308NMEXCIMERLASER 38
VI
3.1Overview 38
3.2Experiments 39
3.2.1IncreasingtheNumberofLaserPulses:308nmLaser,5KeVBoronImplant
39
3.2.2IncreasingtheNumberofPulses:308nmLaser,1KeVBoronImplant 39
3.35KeVResultsandDiscussion 39
3.41KeVResultsandDiscussion 41
3.5ConcludingRemarks 43
4EXPERIMENTALINVESTIGATIONSOFTHEEFFECTSOFNLAONBORON
IMPLANTEDSILICON:532NMRUBY:YAGLASER 50
4.1Introduction 50
4.2 IncreasingtheNumberofPulses:532nmLaser,500eVBoronImplant 50
4.2.1Experiment 50
4.2.2ResultsandDiscussion 51
4.3IncreasingtheNumberofPulses:532nmLaser,5KeVBoronImplant 52
4.3.1 Experiment 52
4.3.2 ResultsandDiscussion 52
5EFFECTSOFPOST-PROCESSINGAFTERNONMELTLASERANNEALING....61
5.1Overview.™ 61
5.2High-TemperatureRapidThermalAnnealingafter308nmNLA 61
5.2.1ExperimentalOverview 61
5.2.25KeVResults 62
5.2.3 1KeVResults 64
5.2.4Discussion 65
5.3High-temperaturerapidthermalannealsafter532nmNLA 66
5.3.1 ExperimentalOverview 66
5.3.2 5KeVResultsandDiscussion 67
5.3.3 500eVResultsandDiscussion 68
5.4FurnaceAnnealsandDamageEvolution 71
5.4.1308nmNLA 71
5.4.2532nmNLA 72
5.5Conclusions 72
6EFFECTSOFNLAONMOBILITYANDACTIVATION 89
6.1Introduction 89
6.2ExperimentalResults 90
6.2.1The308nmExperiments 90
6.2.2The532nmExperiments 91
6.3Discussion 92
vn
6.3.1Overview 92
6.3.2BoronActivation,Deactivation,andPrecipitation 93
6.3.3BoronActivation,Deactivation,Interstitials,andDiffusion 96
6.3.4 MobilityandSheetResistance 97
6.3.5Mobility,Activation,andLoops 98
6.4Conclusions 100
7MODELINGTHEMOBILITY 117
7.1Introduction 117
7.2Li'sandLinares'MobilityModel 118
7.3TheImprovedMobilityModel 119
7.4Conclusions 122
8SUMMARY,CONCLUSIONS,ANDFUTUREWORK 130
8.1Summary 130
8.2Conclusions 132
8.3SuggestionsforFutureWork 133
APPENDIX
ATEMPERATURESIMULATIONDURINGNLAUSINGFLOOPS 135
BMODELINGTHEMOBILITYWITHFLOOPS 153
LISTOFREFERENCES 158
BIOGRAPHICALSKETCH 162
vui
LISTOFFIGURES
Figure page
1.1 SchematicofMOStransistorshowinglocationofsourcedrainextensions(SDE) 15
1.2 Topplotshowstheaveragediffusionlengthofasiliconinterstitialafter1nsand10
ns. Thebottomplotshowsthediffusionlengthsforboronafter1nsand10nsfor
intrinsicandtransientenhanced(B-IPairdiffusion)diffusion 16
1.3 Thediffusionlengthofthesiliconisdividedbythediffusionlengthoftheboron
interstitialpairandplottedversustemperature. Thisshowshowmuchfarthera
siliconinterstitialcantravelthanaboron-interstitialpairatthesametimeand
temperature 17
1.4 Thisplotshowshowfastthesurfacecoolsafterreachingapeaktemperatureof
1600K(1327°C). Thetopplotshowshowlongittakestocooltoroom
temperature. Thebottomplotshowshowlongittakestocooltoaround800°C....18
2.1 Thisplotshowsthetemperatureversustimeseenatvariousdepthsinthewafer
duringtheNLA. Thetopcurveisthetemperatureatthesurfaceofthewafer.The
bottomcurveisthetemperatureat100Aintothewafer 29
2.2 Thisfigureshowsthetemperaturedistributioninthewaferduringone20nspulse
withthe532nmlaser. Italsoshowsthebeginningofthecooldownafterthe
pulseisturnedoff(time>2.0xl0"8s) 30
2.3 Thisplotshowsthetemperatureversustimeseenatthesurfaceofthewaferwhen
thesampleisirradiatedwithmultiplepulsesatafrequencyof100Hz 31
2.4 TheseplotsaremagnifiedviewsoftheplotinFigure2.3. Thisshowsamore
detailedviewofhowthetemperatureisdistributedoverdepthduringthe532nm
NLA 32
2.5 Illustrationoftheapproximateamountofthe5KeVboronimplantwhichis
annealedduringa308nmNLA. Theentireareaisannealedduringa532nm
NLA
33
2.6 Sheetresistancevslaserenergydensityin5KeV,lel5B+/cm2samplesirradiated
withone15nspulseusingthe308nmlaser 34
IX
2.7 Reflectivityversuslaserenergydensityafteronepulsewiththe308nmlaseron5
KeV, 2el5B+/cm2samples 35
2.8 Sheetresistanceversuslaserenergydensityforthe5KeV,2el5B+/cm2samples
followingone20nspulsewiththe532nmlaser 36
2.9 Reflectivityversuslaserenergydensityfor5KeV,2el5B+/cm2samplesannealed
withthe532nmlaserusinga20nspulse 37
3.1 SIMSof5KeV,2el5B+/cm2samplesas-implantedandaftertheNLAwith308nm
laser,andafter1040°C,5secRTA 44
3.2 Sheetresistancenumberoflaserpulsesfor5KeV,2el5B+/cm2samplesfollowing
anNLAwiththe308nmlaserat0.6J/cm2. usingapulselength15nsanda
frequencyof10Hz 45
3.3 Plan-viewTEMfor5KeV,2el5B+/cm2samplesfollowingonepulse(topleft),10
pulses(topright),100pulses(bottomright),andaftera1040°C,5secRTA
(bottomright). FortheNLAthe308nmlaserisusedwitha15nspulseata
frequencyof10Hzandalaserenergydensityat0.6J/cm2 46
3.4 SIMSofthe1KeV,lel5B+/cm2samplesas-implanted,aftertenpulses,andaftera
1040oC,5secRTA. The308nmlaserwitha15nspulseat10Hzisused 47
3.5 Sheetresistanceversusnumberoflaserpulsesforthe1KeV,lei5B+/cm2samples
usingthe308nmlaserwitha15nspulseat10Hz. Thepointat pulses
representsthesamplethatjustreceivedthe1040°C,5secRTA 48
3.6 Plan-viewTEMofthe1KeV,lel5B+/cm2samplesafter10pulsesusingthe308
nmlaserwitha15nspulseat10Hz(left)andafterthe1040°C,5secRTA(right)..49
4.1 SIMSoftheboronprofilesas-implanted,followingtheNLA,andfollowingthe
1050°Cspikeannealforthe500eV,lel5B+/cm2samples 54
4.2 Sheetresistanceversusnumberoflaserpulsesfor500eV,lei5B+/cm2samples
annealedwiththe532nmlaserat 0.35J/cm2usinga20nspulse 55
4.3 Plan-viewTEMofthe500eV,lei5B+/cm2samplesannealedwitha1050Cspike
anneal 56
4.4 SIMSoftheboronprofilesas-implanted,followingtheNLA,andfollowingthe
spikeannealforthe5KeV,2el5B+/cm2samples 57
4.5 Plan-viewTEMofthe5KeV,2el5B+/cm2samplesannealedwiththe532nmlaser
at 0.35J/cm2usingone,10,100,and1000pulsesat100Hzand 20ns/pulse 58
4.6 Sheetresistanceversusnumberoflaserpulsesfor5KeV,2el5B+/cm2samples
annealedwiththe532nmlaserat 0.35J/cm2usinga20nspulse 59