Applications of laser ablation inductively coupled plasma mass spectrometry for the analysis of solids

170 Pages·2000·6.6 MB·English

by  Bi, Melody, 1968-

APPLICATIONSOFLASERABLATIONINDUCTIVELYCOUPLEDPLASMA
MASSSPECTROMETRYFORTHEANALYSISOFSOLIDS
By
MELODY(XIANGQING)BI
ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOLOFTHE
UNIVERSITYOFFLORIDAINPARTIALFULFILLMENTOFTHE
REQUIREMENTSFORTHEDEGREEOFDOCTOROFPHILOSOPHY
UNIVERSITYOFFLORIDA
2000
ToMyFamily
ACKNOWLEDGMENTS
I would like to express my immense gratitude to my advisor, Dr. James D.
Winefordnerwhohasofferednotonlyhisintellectualguidancefortheprojectbutalsohis
patienceformymistakesandstubbornnessinpursuitoftheproject. Dr.BenjaminW.
SmithisthenextpersontowhomIwouldliketoexpressmygratitudeforinvaluable
suggestionsandcommentsonthisresearch. Hehasalsogivenmealotofhelponother
issues.
IwouldliketothankDr.AntonioM.RuizandDr.IgorGomushkinwhohave
contributeddirectlytomyexperiments. IwouldalsoliketothankDr.ChenglongYang
formanyusefuldiscussionsconcerningmyresearch.
IwouldliketothankDr.StephenJ.PeartonandDr.RajivK. Singh(fromthe
MaterialsScience&Engineeringdepartment)whoprovidedsemiconductorsamplesand
usefulinformationformyresearch. IwouldalsoliketothankDr.LuisaAmeliaDempere
andMr.WayneAcreefromtheMajorAnalyticalInstrumentationCenter,whohelpedme
withtheSEM-EDSstudy. IwouldliketothankMr.GillBrubakerfromEnergyResearch
CenterforlettingmeusetheICP-AESinstrument.
MygratitudealsogoestoDrs.WillardW.Harrison,DanielR.Talham,Martin
ValaandPaulH.Hollowayfortheirkindnessinservingonmycommittee. Theywere
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alsosupportiveofmyresearcheffort. IespeciallythankDr.Harrisonwhoattendedour
regularresearchgroupmeetingandgavemeusefuladviceeverynowandthen.
IwouldliketothankDr.BurtronH.DavisfromtheCenterforAppliedEnergy
Research,UniversityofKentuckyforrecommendingmetotheUniversityofFloridaand
forhishelpwithmyoralproject. Ifeelveryluckytoknowhim.
IwanttothankmybrotherSeanforhisencouragement. Iwanttothankmymom
YuanteBiandmydadJunkeBiwholiveontheothersideoftheglobe,andwhohave
givenmetheloveandsupportthat1neededthemosttopursuemylifegoalanddreams.
Ialsothankmyfriendsandcolleagues,theentireWinefordnergroup.MerryZhang,Lisa
Lang,DetongSun,CaijunSun,JunqiangSun,JohnathanBishop, QianrongMa,Dale
Cheng,BobandGayGreningeretc.whohavemademytimeattheUniversityofFlorida
apleasantandinterestingexperience.
FinallyIwouldliketoacknowledgefinancialsupportfromaTexacoFellowship
formyresearch.
IV
TABLEOFCONTENTS
page
ACKNOWLEDGMENTS
iii
LISTOFACRONYMS viii
ABSTRACT ix
CHAPTERS
1 INTRODUCTION 1
2 BACKGROUND 7
2.1.PrinciplesofLaserAblation 7
2.1.1.PrinciplesofLasers 7
2.1.2.Q-switchLasers 9
2.1.3.LaserMaterialInteraction 9
2.2.PrinciplesofInductivelyCoupledPlasmaMassSpectrometry 12
2.2.1.Inductivelycoupledplasmas 12
2.2.2.SampleIntroduction 15
2.2.3.SamplingInterface 15
2.2.4.IonLensinICP-MS 17
2.2.5.SpaceChargeEffect 17
2.2.6.QuadrupleMassSpectrometer 18
2.2.7.MassDetectors 19
2.3.PrinciplesofLA-ICP-MS 20
2.3.1.CalibrationStrategies 21
3 INSTRUMENTDIAGNOSTICSANDOPTIMIZATION 36
3.1.Introduction 36
3.2.Experimental 36
3.2.1.Instrumentation 36
3.2.2.Samples 39
3.3.ResultsandDiscussion 39
3.3.1.LaserOutputEnergy 39
3.3.2.LaserFocusingPositions 41
3.3.3.AnalysisofSiC 41
3.3.4.PlasmaOperatingConditions 42
V
4
STUDYOFSAMPLINGSTRATEGYFORLA-ICP-MSANALYSIS 52
4.1.Introduction 52
4.2.Experimental 53
4.3.ResultsandDiscussion 54
4.4.Conclusions 56
5 STUDYOFSOLUTIONCALIBRATIONOFNISTSOILANDGLASS
SAMPLESBYLASERABLATIONINDUCTIVELYCOUPLEDPLASMA
MASSSPECTROMETRY 64
5.1.Introduction 64
5.2.Experimental 66
5.2.1.Instrumentation 66
5.2.2.Samples 68
5.2.3.Solution-basedCalibration 68
5.3.ResultsandDiscussion 71
5.3.1.SelectionofanInternalStandard 71
5.3.2.StudyofFractionationEffect 73
5.3.3.AnalysisofNISTStandardMaterials 74
5.4.Conclusions 76
6 ELEMENTALANALYSISOFSPANISHMOSSUSINGLASER
ABLATIONINDUCTIVELYCOUPLEDPLASMAMASS
SPECTROMETRY 87
6.1.Introduction 87
6.2.Experimental 89
6.2.1.Instrumentation 89
6.2.2.Samples 90
6.3.ResultsandDiscussion 91
6.3.1.ElementalanalysisofSpanishmossusingNISTleafSRMsasmatrix
matchedstandardsbyLA-ICP-MS 91
6.3.2.StudyofFractionation 93
6.3.3.AnalysisofMossSamplesbyLIBS 94
6.3.4.StandardAdditionMethod 94
6.4.Conclusions 96
7.2.1.
7 LOWLEVELCOPPERCONCENTRATIONMEASUREMENTSON
SILICON-WAFERSURFACEUSINGDIRECTLA-ICP-MSAND
SOLUTIONSAMPLINGICP-MS 110
7.1.Introduction 110
7.2.Experimental 112
Instrumentation: 112
VI
7.2.2.
Samples 113
7.3.ResultsandDiscussion 114
7.3.1.DirectAnalysisofWaferStandards 114
7.3.2.AnalysisofSolutionSamples 115
7.4.Conclusions 116
8 PROFILINGOFPATTERNEDMETALLAYERSBYLASERABLATION
INDUCTIVELYCOUPLEDPLASMAMASSSPECTROMETRY 120
8.1.Introduction 120
8.2.Experimental 122
8.2.1.Instrumentation 122
8.2.2.Samples 123
8.3.ResultsandDiscussion 124
8.3.1.EffectofAblationChamber 124
8.3.2.OptimizationofArgonFlowrates 124
8.3.3.OptimizationofLaserFocus 125
8.3.4.ComparisonofLA-ICP-MSwithLA-OES 126
8.3.5.ProfilingofPatternedMetalLayersonSiliconWafers 128
8.4.Conclusions 129
9 CONCLUSIONSANDFUTUREWORK 142
9.1.Conclusions 142
9.2.FutureWork 145
REFERENCES 150
BIOGRAPHICALSKETCH 159
vii
IJS^OFACRONYMS
LA-ICP-AES LaserAblationInductivelyCoupledPlasmaAtomic
EmissionSpectrometry
LA-ICP-MS LaserAblationInductivelyCoupledPlasmaMass
Spectrometry
LA-ICP-OES LaserAblationInductivelyCoupledPlasmaOptical
EmissionSpectrometry
LIBS LaserInducedBreakdownSpectrometry
MD-ICP-AES/MS MicrowaveDigestionInductivelyCoupledPlasmaAtomic
EmissionSpectrometry/MassSpectrometry
RSF RelativelySensitivityFactor
RSD RelativelyStandardDeviation
SEM SecondaryElectronMicroscopy
SIMS SecondaryIonMassSpectrometry
SRM StandardReferenceMaterial
AbstractofDissertationPresentedtotheGraduateSchool
oftheUniversityofFloridainPartialFulfillmentofthe
RequirementsfortheDegreeofDoctorofPhilosophy
APPLICATIONSOFLASERABLATIONINDUCTIVELYCOUPLEDPLASMA
MASSSPECTROMETRYFORTHEANALYSISOFSOLIDS
By
MelodyBi
August2000
Chairman;Dr.JamesD.Winefordner
MajorDepartment:Chemistry
Laser-sampling techniques, such as laser ablation (LA) inductively coupled
plasma (ICP) mass spectrometry (MS), have gained popularity for analyzing solid
materialsbecauselittleornosamplepreparationisrequired. Practicalconcernssuchas
thedifficultyofobtainingormakingmatrix-matchedstandardspreventsuchtechniques
from becoming analytical tools. This work was largely concerned with studies of
calibrationstrategiesfortraceanalysisinsolidsandthefeasibilityofsurfaceprofilingby
LA-ICP-MS. ThecapabilitiesofsurfaceprofilingbyLA-ICP-MSwerealsoexplored.
ByanalyzingNISTsoil andglass samples, amethodforthedeterminationof
traceelementconcentrationsbyLA-ICP-MSusingsolutioncalibrationandaninternal
standard has been studied and evaluated. In most cases, the measured element
concentrationswerewithin±15% ofthe certified values. The choice ofan internal
IX
standard andthe fractionationeffectcausedby laserirradianceonthe surface ofthe
samplewerestudiedanddiscussed.
NISTarchivalleafstandardswereusedforreliablequantitativeelementalanalysis
ofSpanishmosssamplesbyLA-ICP-MS. Theresultswerecomparedwiththatobtained
frommicrowavedigestion(MD)ICPatomicemissionspectrometry(AES)analysis. For
most ofthe elements studied, the results for the two techniques agreed. A standard
additionmethodwasalsostudiedandtheresultsshowedthatitisaneffectivemethod
whenmatrix-matchedstandardsarenotavailable.
LA-ICP-MS was applied to profiling of patterned thin metal layers on a
polymer/siliconsubstrate. TheparametersofthelaserandICP-MSoperatingconditions
havebeenstudiedandoptimizedforthispurpose.LA-ICP-MShasgoodsensitivityand
wasabletoprofilethinmetallayersontheorderofafewnmonthesiliconsurface. A
lateralspatialresolutionof45pmwasachieved.
Finally,LA-ICP-MSwasusedtomeasuretheamountofcoppercontaminationon
a silicon wafer surface. A detection limit of6.1 x 10'^ atoms/cm^ was obtained.
X