Focused Ion Beam BasicsFocused Ion Beam BasicsFEI USA, Hillsboro OregonFEI USA, Hillsboro OregonFEIFEI Corporate HeadquartersFEI Corporate HeadquartersFOCUSED ION BEAM BASICSFOCUSED ION BEAM BASICSuuINTRODUCTIONINTRODUCTIONuuTHE FIB SYSTEMTHE FIB SYSTEM»»The source, LMISThe source, LMIS»»Ion ColumnIon Column»»DetectorDetector»»FIB Compared to SEMFIB Compared to SEMuuUSING THE SYSTEMUSING THE SYSTEM»»Beam InteractionsBeam Interactions»»ImagingImaging»»MillingMilling»»Deposit/Etch using GasesDeposit/Etch using Gases»»ApplicationsApplicationsTHE FIB SYSTEMTHE FIB SYSTEMuuA FIB System consists mostly of:A FIB System consists mostly of:»»Ion SourceIon Source»»ColumnColumn»»DetectorDetector»»Vacuum SystemVacuum System»»Gas DeliveryGas Delivery»»StageStage»»Computer with Integrated Image ProcessingComputer with Integrated Image ProcessingIon SourceIon SourceuuHistoryHistoryuuLiquid Metal Ion Sources, used forLiquid Metal Ion Sources, used fordroplets in high velocity, low massdroplets in high velocity, low massspacecraft engines (spacecraft engines (KrohnKrohn, TRW,, TRW,1973)1973)Direct v. Indirect HeatingDirect v. Indirect HeatinguuIons were also noticed and separately pursued for use inIons were also noticed and separately pursued for use inSIMS.SIMS.uuTube sources too unstable, so liquid metal on sharp substrateTube sources too unstable, so liquid metal on sharp substratepursued.pursued.Basic MechanismBasic MechanismuuLiquid Flow from ReservoirLiquid Flow from ReservoiruuIon FormationIon FormationuuExternal Beam InteractionsExternal Beam InteractionsLMIS in a Extractor FieldLMIS in a Extractor FielduuJet-like protrusion for Ga LMIS atJet-like protrusion for Ga LMIS atvarious currentsvarious currentsuuThe tip is sharper and sharper, andThe tip is sharper and sharper, andthe volume of liquid increasesthe volume of liquid increasesuuDashed line is substrate in TaylorDashed line is substrate in TaylorCone shapeCone shapeDotted line is 2.2uA emission currentSource Want to be Taylor ConeSource Want to be Taylor ConeuuEven without the substrateEven without the substrateat the end, the materialat the end, the materialwants to form into the Taylorwants to form into the TaylorCone shape.Cone shape.Voltage-Current CurveVoltage-Current CurveuuNoteNote““turn-onturn-on”” behavior in looking at behavior in looking atthe VI curve.the VI curve.uuVoltage is the extractor voltageVoltage is the extractor voltageuuCurrent is the total currentCurrent is the total currentuuThis graph is for an Indium source,This graph is for an Indium source,but is relative to a gallium sourcebut is relative to a gallium sourceEnergy Spread Increases with Extractor CurrentEnergy Spread Increases with Extractor Current»»Energy spread v. extractorEnergy spread v. extractorcurrent for several sources,current for several sources,including Gaincluding GaAngular DistributionAngular DistributionuuAngular emitted mass distributionAngular emitted mass distributionfor Ga vs. extractor currentfor Ga vs. extractor currentLMISLMIS»»LMISLMIS’’s s have been made from many materialshave been made from many materialsGallium is the Most PopularGallium is the Most PopularuuA liquid metalA liquid metaluuRoom temperature operationRoom temperature operationuuLong lived (500-1500 hr sources)Long lived (500-1500 hr sources)uuHigh vacuum compatibleHigh vacuum compatibleuuLarge ion for sputteringLarge ion for sputteringHeating the SourceHeating the SourceuuGases in column adsorb to GaGases in column adsorb to GauuSecondary electrons back sputtered from extractor cap Secondary electrons back sputtered from extractor cap ““crackcrack””the gasesthe gasesuuGa flows from end faster than it can be replacedGa flows from end faster than it can be replaceduuHeating the source desorbs these gases andHeating the source desorbs these gases and reflows reflows Ga fromGa fromreservoirreservoirIon ColumnIon ColumnuuSource - LMIS at topSource - LMIS at topuuFocusing OpticsFocusing Optics»»Use Electrostatic lenses since ions are heavier than electrons.Use Electrostatic lenses since ions are heavier than electrons.uuDeflection Electronics/Pattern BoardDeflection Electronics/Pattern BoarduuHigh-speed BlankingHigh-speed Blanking»»Need to prevent milling while blankingNeed to prevent milling while blankingIon Column DiagramIon Column DiagramuuDiagramsDiagramsSuppressor & LMISExtractor CapBeam Acceptance ApertureLens 1Beam Defining ApertureBeam BlankingDeflection OctopoleLens 2Charge Distribution of Ion ColumnCharge Distribution of Ion ColumnuuBeam profile is complexBeam profile is complex»»Optimized spatialOptimized spatial»»Optimized millingOptimized milling»»(1990s technology(1990s technology»»shown here)shown here)DetectorsDetectorsuuElectron multipliersElectron multipliers»»ScintillatorScintillator»»Channel Electron Multiplier (CEM) [ion & electron detection]Channel Electron Multiplier (CEM) [ion & electron detection]uuMass filteringMass filtering»»Secondary Ion Mass Spectroscopy (SIMS)Secondary Ion Mass Spectroscopy (SIMS)uuPositioned above sample and biased to collect Positioned above sample and biased to collect secondariessecondaries..SEM Compared to FIBSEM Compared to FIBSEM FIBElectromagnetic Lenses2 Electrostatic LensesWhat a FIB does that a SEM does notWhat a FIB does that a SEM does notuuRemoves MaterialRemoves MaterialuuAdds MaterialAdds MaterialuuSecondary Ion imaging shows material contrastsSecondary Ion imaging shows material contrastsuuChanneling ContrastsChanneling ContrastsuuPrepares samples in situPrepares samples in situuuCombines high magnification imaging and sampleCombines high magnification imaging and samplemodificationmodificationSECTION II: USING THE SYSTEMSECTION II: USING THE SYSTEMuuTopicsTopics»»Beam InteractionsBeam Interactions»»ImagingImaging»»MillingMilling»»Depositing/Etching with GasDepositing/Etching with Gas»»ApplicationsApplicationsUsing the SystemUsing the SystemuuBeam InteractionsBeam InteractionsNote difference in interaction volumeUsing the SystemUsing the SystemuuRasteringRastering: Forming an Image: Forming an ImageuuImage ModesImage Modes»»Secondary ElectronSecondary Electron»»Secondary IonSecondary IonuuContrast MechanismsContrast Mechanisms»»TopographyTopography»»Voltage ContrastVoltage Contrast»»SE/SI YieldSE/SI Yield»»ChannelingChannelingImaging Detector Modes - CDEMImaging Detector Modes - CDEMuuSecondary