Presentation on theme: "Metallization of Submicron Features Case Western Reserve University"— Presentation transcript:
1Metallization of Submicron Features Case Western Reserve University inHigh-End Semiconductor Devices by Copper ElectroplatingUziel LandauDepartment of Chemical EngineeringCase Western Reserve UniversityCleveland, OH 44106Presented at ENERGIZER 2/4/05
2High-Tech: Low-Tech: Technology precedes the science – empiricism CVD, PVD deposition of semiconductorsDrugs developmentCatalysisTechnology precedes the science – empiricismElectroplating (some aspects)Low-Tech:Oil refiningElectrical machinerySteel manufacturingUnderlying science is well-established:
3Outline Overview of Copper Interconnect Metallization Rationale for this workAnalyzing the additives effects*Experimental InvestigationsModeling of Additives Transport + AdsorptionSimulation of the via-fill processScaling Issues & Wafer-scaleConclusions
9Advantages of Copper Metallization Higher conductivityReduced time delayHigher current density at lower powerScalability – finer lines at lower levelsImproved EM performanceFewer steps – Dual Damascene ProcessFewer defectsLess equipment, spaceLower costFaster processingLess costly equipmentEnvironmentally benignIntroduced by IBM (Andricacos, Uzoh, Dukovic, Horkans, Deligianni)Commercially implemented (IBM, Intel, Motorola/AMD, TI,…)
10Issues in Copper Metallization ‘Attitude’-Extending ‘wet chemistry’ to ‘dry’ semiconductor processingDoubting the ability of plating to meet the challengeMeeting unparalleled requirements of purity and precisionTechnical-Via scale:‘Bottom up’ fillSeed layer in aggressive geometries (<0.2 μm) – continuityWafer scale:Thickness uniformity of the copper over-plateResistive substrate (~1000 A seed)Modeling and scaling (300 mm, current density, flow…)Process Integration
14Equivalent resistive network RseedIedgeIcenterRseedRelectrolytevvvvvVVapplied= V+- V- == Icenter Relectr.+ Iseed Rseed.= Iedge Relectr.-vvvvvVvvvvvVvvvvvVvvvvvVvvvvvVvvvvvVvvvvvVIedgevvvvvVvvvvvVvvvvvVvvvvvVIcenterRelectrolytevvvvvVvvvvvVvvvvvVRefer to previous work: Tobias, Alkire, LandauSelected results: Phi, Lanzi’sModified Phi (?), modified Lanzi’s definitionvvvvvVvvvvvVvvvvvVvvvvvV+A high resistivity electrolyte will minimize the resistive seed effect
15Low-acid electrolyte Removing the acid; k : 0.5 0.05 W-1cm-1 Typical acid concentration: MRole of acid: provide conductivityRemoving the acid; k : W-1cm-10.25M CuSO M H2SO4Cu++: l = z = C = 0.25x10-3 M/cm3 kCu++ = W-1cm-1SO4--: l = z = C = 0.25x10-3 M/cm kSO4-- = W-1cm-1H+ : l = z = C = 1.8 x10-3 M/cm kH = W-1cm-1HSO4-: l = z = C = 1.8x10-3 M/cm kHSO4-= 0.09 W-1cm-1kTotal = W-1cm-1
18Flow Simulations Micro-Scale Transport within the via is due to diffusion‘Cell-Design’ Simulations
19Enhancing mass transport Flow - reduce d(but inside via only diffusion pertains...)Raise copper conc.: M M (solubility issue -- reducing acid is helpful -common ion effectt (transport number):
20New electrolyte formulation No or low acidcounteracts the resistive seed effectsupports higher copper solubility‘chemical’ enhancement of transportenvironmental, safety and handling benefitsless corrosiveenhances copper seed stability in the presence of dissolved oxygenHigh copper concentrationenhances transport1~2 M (pH=0) ~ 0.1 M (pH = 1~3.5)M M
24Issues in Copper Metallization ‘BOTTOM-UP’ plating of vias“VOID”“SEAM”“Bottom-up”Special mixture of plating additives can lead to ‘bottom-up’ fill.However, additives selection is empirical and fundamental information about their role is lacking.
26Variable Adsorption leads to Variable Kinetics and to ‘Bottom-up’ fill: ‘Enhancer’, e.g. Organic di-sulfideSuppressor, e.g. PEGSlow depositionFast deposition
27Variable Deposition Rates Due to Non-uniform Inhibition Polarization Curvesi[mA/cm2]Enhanced Kinetics (via)100Suppressed Kinetics(‘flat’ wafer)10300 mVV
28Key Issues in ‘Bottom-up’ Plating All metallization chemistries contain :PEG (inhibitor / suppressor)SPS (accelerator / anti-suppressor)Chloride ionsWHY ONLY THESE and NOT OTHERS ???PEG+SPS+Cl-=GOODSPS+Cl-=BAD=BADPEG+SPSPEG+Cl-=BAD
29Key IssuesAccelerated bottom growth should terminate before top surface is approachedTop surface must remain passivated for only a limited timeOnly negligible amount of additives incorporates in the deposit or decomposes: steady-state models inadequateVia fills in s. – Transient interactions are crucialUnderstanding of transient additives transport, adsorption, and interactions.
30A Few Proposed Mechanisms IBM’s modelWest et al.Moffat et al.Adjustable Kinetics along the Via WallsCurvature Enhanced Accelerator CoverageDiffusion Controlled Additives TransportLimitations:Steady state modelMany arbitrary adjustable parameters.Unaddressed Issues:Additives interactionsUnsteady state effectsUnaddressed Issues:Unsteady state effectsRole of PEGArbitrary initial conditions
31Objectives Characterize the transient additives interactions Explain and model the bottom-up fill processDevelop a Simulation for the Bottom-Up FillShould correlate experimental observationsWithout adjustable parameters or extreme assumptionsSPtime ?
33Cl- essential for PEG assisted polarization PEG Adsorption – Effect of Cl-PEG + Cl-Cl- essential for PEG assisted polarizationNo additiveOverpotential (mV)Only PEGOnly Cl-Time t (s)Injection time
34PEG Adsorption Cl - 200 ppm PEG Overpotential (mV) 100 ppm PEG Effect of Concentration200 ppm PEG100 ppm PEG50 ppm PEGOverpotential (mV)t ~ L2/D ~ 7 sPEG saturation at ≥ 200 ppmCl -Injection timeTime t (s)
35FAST ADSORPTION KINETICS SPS Adsorption on ‘Clean’ Electrode‘Clean’ Electrode50 ppm SPS + 70 ppm Cl-Overpotential (mV)FAST ADSORPTION KINETICSInjection timeTime t (s)
36SLOW depolarization of the electrode* t ~ 100 s SPS Adsorption on ‘PEG-covered’ ElectrodePEG saturated electrode (+ chloride)SLOW depolarization of the electrode* t ~ 100 s20 ppm SPSOverpotential (mV)50 ppm SPSInjection timeTime t (s)* R. Akolkar and U. Landau, AIChE Proceedings (2003).
37Interactions dominant during the via-fill period (~20-50 s) Competitive Adsorption (SPS+PEG)SLOW depolarization by SPS due to displacement of PEGOverpotential (mV)Interactions dominant during the via-fill period (~20-50 s)FAST polarization by PEGInjection timeTime t (s)
38Competitive Adsorption (SPS+PEG) Disc rotation = 50 rpmSPS accelerated kineticst=50st=10sSlow depolarization by SPSt=0sCurrent Density (mA/cm2)TimePEG inhibited kinetics (short time)Overpotential (mV)
39Adsorption on ‘clean’ electrode Displaces PEG slowly (t~100 s) Time Scales for Transport, Adsorption and InteractionPEG + Cl-VPEGSPSTransportSLOW (D~10-6 cm2/s)FAST (D~10-5 cm2/s)Adsorption on ‘clean’ electrodeVERY FASTFAST (t~5 s)InteractionCannot displace SPSDisplaces PEG slowly (t~100 s)t (s)20 ppm SPSVt (s)
41SPS ADSORBS RAPIDLY ON ‘PEG-FREE’ VIA BOTTOM Via-Fill Model: PEG Transport DelayPEG diffuses slowly + Adsorbs on sidewallsPEG reaches via bottom after ~10 st=8st=1st=3st=6sPEG surface coverageSPS ADSORBS RAPIDLY ON ‘PEG-FREE’ VIA BOTTOMTOPNormalized Depth z*BOTTOM*Via is 0.1 μ dia.,1 μ deep
42Accelerated Bottom-up Growth Via-Fill Model: PEG Transport DelayAccelerated Bottom-up GrowthMORE PEG CoverageMORE SPS Coverage*R. Akolkar and U. Landau, J. Electrochem. Soc., 151 (11) C702 (2004)
43Modeling of Via FillTime Dependent Transport Kinetics (‘TTK’) ApproachVia Exterior (I)Via Interior (II)BULKIVIA TOPIElectrolyteII1 μWafer SurfaceVIA BOTTOM0.1 μSolve for C ( z , t ) and θ ( z , t ) in I and II
44Modeling of Via Fill – TTK Approach Additives Transport to the WAFER TOP SURFACEConcentration Profile given by :BULK PEGDiffusion boundary layer NO CONVECTION60 μWAFER TOP SURFACEAdsorption = k ( 1 – θ )small features are neglected
45PEG inhibits flat wafer surface instantaneously (t ~ 3-4 s) Via Exterior: Flat wafer surfacePEG inhibits flat wafer surface instantaneously (t ~ 3-4 s)PEG surface coverageTime t (s)
46Modeling of Via Fill* Model incorporates (NO Adjustable Parameters): Additives Transient Processes INSIDE THE VIAR = 0.1 μ L = μDiffusion INOUTAdsorption on the sidewallsModel incorporates (NO Adjustable Parameters):Additives Transport (PEG diffusion)Adsorption on sidewalls (Kinetics)Additives Interactions (SPS displaces PEG)*R. Akolkar and U. Landau, Abstract No. 157-E1, 205th ECS Meeting, San Antonio (2004).
47Modeling of Via Fill – TTK Approach Transport and Competitive Adsorption of both PEG & SPSNi,TNi,T=0Ni,ANi,Dzz+zz=0z=LDiffusion INOUTPEG Adsorption :SPS Adsorption :PEG Displacement:SPS ‘Intreractive’ Adsorption :
48Additives Transient Processes INSIDE THE VIA Modeling of Via Fill*Additives Transient Processes INSIDE THE VIAAdsorptionR = 0.1 μ L = μDiffusion INOUTDIFFUSIONADSORPTIONPEG-SPS INTERACTPEG TransportPEG CoverageSPS Coverage*R. Akolkar and U. Landau, Abstract No. 157-E1, 205th ECS Meeting, San Antonio (2004).
49Additives-Assisted Deposition Kinetics Modulated current density SPSPEGCOPPER SURFACEModulated current density
50Additives-Assisted Deposition Kinetics Total current density: COPPER SURFACECu++SPSPEGTotal current density:Deposit thickness:
51TRANSPORT-ADSORPTION PROCESS (0 < t < 5 s) ADDITIVES COVERAGE AT SHORT TIMESPEGSHORT TIMESPEG-1sPEG Surface CoverageSPS Surface CoverageTRANSPORT-ADSORPTION PROCESS (0 < t < 5 s)SPSSPS-1sLow PEG High SPSHigh PEG Low SPSVIA TOPVIA BOTTOMDistance Into the Via
52TRANSPORT-ADSORPTION PROCESS (0 < t < 5 s) ADDITIVES COVERAGE AT SHORT TIMESSHORT TIMESPEG Surface CoverageSPS Surface CoveragePEG-3sTRANSPORT-ADSORPTION PROCESS (0 < t < 5 s)SPS-3sVIA TOPVIA BOTTOMDistance Into the Via
53TRANSPORT-ADSORPTION PROCESS (0 < t < 5 s) ADDITIVES COVERAGE AT SHORT TIMESSHORT TIMESPEG-5sPEG Surface CoverageSPS Surface CoverageTRANSPORT-ADSORPTION PROCESS (0 < t < 5 s)SPS-5sVIA TOPVIA BOTTOMDistance Into the Via
54TRANSPORT-KINETICS REGIME (0 < t < 5 s) ADDITIVES COVERAGE AT SHORT TIMESPEG-5sPEG-1sPEG Surface CoverageSPS Surface CoveragePEG-3sSPS-5sTRANSPORT-KINETICS REGIME (0 < t < 5 s)VIA TOPVIA BOTTOMDistance Into the Via
55PEG displacement by the SPS (t~100 s) PEG COVERAGE AT LONG TIMEStime10 sPEG displacement by the SPS (t~100 s)40 s30 sPEG Surface CoverageINTERACTION REGIME (5 < t < 100 s)VIA TOPVIA BOTTOMDistance Into the Via, z*
56SPS displaces the adsorbed PEG (t~100 s) SPS COVERAGE AT LONG TIMESINTERACTION REGIME (5 < t < 100 s)30 sSPS Surface CoverageSPS displaces the adsorbed PEG (t~100 s)20 s10 stimeVIA TOPVIA BOTTOMDistance Into the Via, z*
57SPS adsorbs on ‘PEG-covered’ bottom SPS adsorbs on ‘PEG-free’ bottom SPS - Comparison: Via Top vs. Via BottomVIA BOTTOMSPS adsorbs on ‘PEG-covered’ bottomSPS Surface CoverageSPS adsorbs on ‘PEG-free’ bottomVIA TOPTRANSPORT-KINETICSINTERACTIONSTime (s)
58SPS displaces the adsorbed PEG PEG diffuses to the via bottom PEG - Comparison: Via Top vs. Via BottomVIA TOPSPS displaces the adsorbed PEGVIA BOTTOMPEG Surface CoveragePEG diffuses to the via bottomTRANSPORT-KINETICSINTERACTIONSTime (s)
59Effect of PEG Transport Delay Flat RDE used to simulate transport to the viaSimulated via top (i=15 mA/cm2, rpm)Flow affects PEG transport onlyKinetic Resistance (ohm)Slow PEG transport allows SPS time to adsorbSimulated via bottom (i=30 mA/cm2, 90rpm)Injection timeTime t (s)
60SPS displaces the adsorbed PEG PEG diffuses to the via bottom COMPARISON: Via Top vs. Via BottomVIA TOPKinetic ResistanceTime (s)Corresponds to via topRDE ExperimentsCorresponds to via bottomLONG TIMESVIA BOTTOMSPS displaces the adsorbed PEGPEG Surface CoveragePEG diffuses to the via bottomTime (s)*R. Akolkar and U. Landau, J. Electrochem. Soc., submitted.
61Effect of varying surface area on additives coverage Surface area at via bottom shrinksPEG bonds weakly and re-equilibrates with the electrolyteSPS bonds strongly and does not leave surfaceSPS (or PEG) do not incorporate appreciably within the depositMaterial balance on SPS:
62SPS Surface Coverage on the via bottom SURFACE AREA REDUCTION effectsSPS Coverage from transport modeling + Area Reduction EffectsSPS saturation at the bottomSPS Coverage predicted by Transport-Kinetics model aloneSPS Surface Coverage on the via bottomTime (s)A. C. West, S. Mayer and J. Reid, Electrochem. Solid-State Lett., 4 (7), C50 (2001).T. P. Moffat et al., Electrochem. Solid-State Lett., 4 (4), C26 (2001).
63EFFECT OF LOCAL AREA REDUCTION PEG Coverage predicted by Transport-Kinetics approach alonePEG Coverage accounting for the Local Area ReductionPEG Surface Coverage on the via bottomComplete Removal of the PEGTime (s)
64Uniform additives composition everywhere Modeling the ‘Bottom-up’ Fill*t = 0 sUniform additives composition everywherePEGSPS* R. Akolkar and U. Landau, J. Electrochem. Soc., accepted for publication.
65Modeling the ‘Bottom-up’ Fill t → 0+ sFast inhibition on the flat waferFast adsorption of PEG on via sidewallsPEGSPS
66SPS diffuses fast – 20 times faster than PEG Modeling the ‘Bottom-up’ Fillt = 1-2 sSPS diffuses fast – 20 times faster than PEGInhibited wafer surfaceFast transport of PEG to upper via sidewallsPEGSPSFast diffusion and adsorption of SPS on ‘bare’ copper
67Modeling the ‘Bottom-up’ Fill t ~ 10 sInhibited wafer surface and via sidewallsPEGPEG cannot polarize SPS covered surfaceSPS
68SPS slowly depolarizes the wafer surface by displacing PEG Modeling the ‘Bottom-up’ Fillt ~ 50 sSPS slowly depolarizes the wafer surface by displacing PEGPEGSPS
69Summary of Key Aspects of ‘Bottom-up’ Fill No additives initially inside the via due to the low volume/area ratio.High volume/area ratio on the wafer top surface leads to instantaneous inhibition by PEG.Slow transport of diffusion limited PEG to the via bottom ( t ~ 8-10 s ).The PEG transport delay allows time for fast diffusing SPS to adsorb on the via bottom.Delayed arrival of PEG cannot displace the stronger adsorbing SPS.
70Scaling Analysis of Additives Transport Why is a via with ‘reactive sidewalls’ associated with a large PEG transport delay ?Time constant t ~ L2/DFor a 1 μ via, the time constantt ~ 0.02 sPEG is transported by diffusion from the bulk into the viaNo PEG inside the via at t ≈ 0 due to small V/A ratio
71PEG Transport Delay Non-reactive Sidewalls Numerical Simulation of PEG TransportNon-reactive SidewallsReactive SidewallsPEG surface coverage at via bottomPEG transport delay: no PEG at via bottom for ~8 sTime (s)
72“μ decreases with time” One-dimensional Pseudo Steady-State ModelScaling AnalysisUniform inhibition on the sidewallsInfinite Sink at Via Bottom2RLTransport-Adsorption Model :Adsorption Ratek, μ depends on time –Short times – Low θ – High k, μLong times – High θ – Low k, μ“μ decreases with time”Diffusion RateThiele Moduluswhere :
73One-dimensional Transport Kinetics Model Scaling ApproachConcentration Profilesμ = 1Decreasing ‘μ’ due to gradual inhibition of sidewallsμ = 30PEG Concentration, C*No Transport of PEG to the Bottom at high μ’sNormalized Depth, z*Via TopVia Bottom
74Establishing Relationship Between k and t In time t :Amount of PEG Adsorbed on the SidewallsAmount of PEG Accumulated in the viaAmount of PEG Entering the Via=+Assumptions :Negligible PEG AccumulationAverage Diffusion Flux In :Linear Time Dependence of k :
75Normalized Flux of PEG at the via bottom PEG Transport DelayScaling ApproachNormalized Flux of PEG at the via bottomPEG transport delay: no PEG at via bottom for ~9 sUninhibited via sidewalls θside= 0Inhibited via sidewalls and bottom θ ~ 1Time t (s)
76Effect of Via Radius (L=1 μm) PEG Transport DelayEffect of Via Radius (L=1 μm)Inverse dependence of PEG transport delay on via radius‘Transients’ due to Transport Kinetics significant for high aspect ratiosPEG Transport Delay (s)INTEL 90nm technologyHigh Aspect Ratio ViasLow Aspect Ratio ViasVia Radius (μm)
77PEG Transport in Vias with Sloping Sidewalls How does the via geometry affect the PEG transport characteristic ?2Ro2Ro2RoФФФ = positive (Outward Sloping) RE-ENTRANTФ = (Non-Sloping)Ф = negative (Inward Sloping)
78Diffusion IN = Diffusion OUT + Adsorption + Accumulation One-dimensional Unsteady-State ModelAdsorptionDiffusional Flux INOUTAdsorptionФ > 0Ф < 0Transport Model for a Via with Sloping Reactive Sidewalls :Diffusion IN = Diffusion OUT + Adsorption + AccumulationEffect of varying radius stronger on transportDiffusion =Adsorption =
79Surface Coverage at the via bottom (θPEG) One-dimensional Unsteady-state ModelFASTER TransportФ = 0 oФ = 10 oSurface Coverage at the via bottom (θPEG)Ф = -1.1 oSLOWER TransportTime t (s)
80Transport-kinetics time scale Additives Interaction time scale Quantitative Modeling of Via-FillTime ScalesSHORTLONGTransport-kinetics time scaleAdditives Interaction time scalet ≤ 10 st > 10 sPEGSPS
81Transport Kinetics Time Scale SHORTt ≤ 10 sGeneration of differential plating kinetics between the via top and bottom – initiation of superfill.Copper deposition preferentially occurs at the via bottom.PEGSPS
82Simulation of Via-Fill Requires additives distributionEffect of additives surface coverage on the kineticsNUMERICAL APPROACHSolution of the Nernst-Planck Equations or a simplified case (Laplace’s Equation)Time stepping moving boundarySEMI-QUANTITATIVE APPROACHNeglect concentration variations inside the viaMove electrode boundaries on the basis of local kinetics using Faraday’s law
83Simulation of Deposit Propagation Variable kinetics + Moving boundariesVirtual electrode;Outer edge of diffusion layer 2 =0i = f (η)C 2 C =0Passivated kinetics (PEG->SPS)Variable kinetics [Partially passivated, f(t)]Accelerated kinetics (SPS)
84Numerical Simulation of Via-Fill – Variable Kinetics* SiO2ElectrolyteSiO2ElectrolyteFill Time: 48 sec.Overpotential: mVBottom:i = 60 mA/cm2Top:i = 0.24 mA/cm2 3.4 mA/cm2(Depolarization by SPS)Sidewalls: Interpolated kinetics between Top and Bottom‘Cell-Design’ Simulations MOVING BOUNDARIES* U. Landau, E. Malyshev, R. Akolkar and S. Chivilikhin, AIChE Proceedings (2003).
85Via Fill Simulation Current density has been lowered: Electrolyte SiO2ElectrolyteSeamCurrent density has been lowered: No Bottom-Up FillPlating Time: ~147 sec.Overpotential: - 80 mVBottom:i = 10 mA/cm2i0 = 1.12 mA/cm C = 0.83Top:i = 0.05 mA/cm2 4.8 mA/cm2High Depolarization by SPS:i0 = 3.1 μA/cm2 0.28 mA/cm2C = 0.9Sidewalls: Interpolated kinetics between Top and Bottom1 sec time intervals‘Cell-Design’ Simulations
87‘Conformal Deposition’ Rapid depolarization on the via sidewalls VIA-FILL SIMULATIONS: Effect of SPSη = 120 mV PEG = 100 ppm SPS = 0 ppmSeam after 900 sz*‘Conformal Deposition’15 sr*z*Rapid depolarization on the via sidewalls‘Center-line’ Voidsη = 120 mV PEG = 100 ppm SPS = 100 ppmr*
88z* Growth Profile at Low overpotential Seam after 75 s BAD η = 80 mV PEG = 100 ppm SPS = 20 ppmSeam after 75 sGOODBADz*Bottom cannot escape depolarizing sidewallsLow ‘bottom-up’ current density i ~ 12 mA/cm2r*
89Modeling of Superfill – Effect of Current Density Cpeg=200 ppm Csps=20 ppm Via AR = 10V = 130 mVV = 60 mV200 s30 sBottom-up growth‘Seam’ at the mouth due to depolarization by SPS21 mA/cm21 mA/cm2
90Wafer-scale Modeling Rationale for study Only wafer-scale parameters, e.g., total current (I) or voltage (V) are measurableOptimize the process by identifying current/ potential waveformsTransient nature of wafer-scale processes due to:Transient additives interactionsGeometry changes during via-fill
91Empirical observations during wafer metallization: Wafer-scale Modeling300 mm wafer0.2 μ dia., 1 μ deep vias (via loading ~ 6 %)Empirical observations during wafer metallization:Current is initiated upon wafer immersionInitial overall current is lowCurrent is increased as via-fill is initiated
92Wafer-scale Modeling Current balance on the entire wafer : Assuming inhibited sidewall kinetics similar to the wafer topThe wafer geometric current density :
93Wafer Current Density, mA/cm2 Wafer-scale current transientsη = 0.12 V (constant ‘Driving force’)Wafer current drops at long times (t>25s)Wafer Current Density, mA/cm2Wafer Current, ARapid wafer depolarization at short times (t < 10 s)SPS = 20 ppm PEG = 100 ppmTime, s
94Wafer Current Density, mA/cm2 Comparison with ExperimentsModel predictions in agreement with experimentsSource: J. Reid et. al.*Wafer Current Density, mA/cm2Time, s* Experimental data: J. Reid et al., Electrochem. Solid-State Lett., 6(2) C26 (2003).
95Wafer Current Density, mA/cm2 Wafer-scale i vs. t : Effect of potentialη = 0.13 VVIA-FILL COMPLETIONWafer Current Density, mA/cm2η = 0.12 VSPS = 20 ppm PEG = 100 ppm Via loading = 6.3%Time, s
96Wafer Current Density, mA/cm2 Wafer-scale i vs. t : Effect of SPS conc.SPS = 30 ppm Centerline VoidsWafer Current Density, mA/cm2SPS = 20 ppm ‘Defect-free’ Fillη = 0.12 V PEG = 100 ppm Via loading = 6.3%Time, s
97Wafer Current Density, mA/cm2 Wafer-scale i vs. t : Effect of via loadingVia loading = 12.6%Wafer Current Density, mA/cm2Via loading = 6.3%η = 0.12 V PEG = 100 ppm SPS = 20 ppmTime, s
98Implication of Constant Current Wafer Current Density, mA/cm2Time, sSPS =` 20 ppm PEG = 100 ppmη = 0.12 V (constant ‘Driving force’)CurrentWafer Voltage (mV )VoltageToo high – bottom defectsToo low– centerline defects120Time, s
99Major ConclusionsA comprehensive model for the ‘bottom-up’ fill is presented.WITHOUT invoking any adjustable parametersBased on experimentally characterized additives effectsThe model explains:Specific role of the PEG and SPS in the multi-component additives systemThe effect of operating parameters and via geometryWafer-scale current response.
100Acknowledgements: THANK YOU ALL! Dr. Rohan Akolkar Case Prime Fellowship to Rohan AkolkarGeneral Motors Research and DevelopmentThe Dept. of Chemical Engineering, CWRUJohn D’UrsoDavid RearMark BubnickApplied MaterialsYezdi DordiPeter HeyTHANK YOU ALL!