+ R - Center for Nanoscale Systems - Harvard University

Metrology for NanofabricationThe Great Wide World of Measurement ScienceJason TresbackCenter for Nanoscale SystemsHarvard University

Outline• Overview of Metrology– Introduction to Metrology– Metrology for Process Control• Key Metrology Techniques for Nanofabrication at CNS– Optical Microscopy– Ellipsometry– Profilometry– Atomic Force Microscopy (AFM/SPM)– Thin Film Characterization Part-1• Electrical Property Measurements at CNS– Electronic Conduction Overview– Van der Pauw Resistivity and Hall Measurements– Thin Film Characterization Part-2– Device Testing• Q/A

IntroductionMetrology:The Science of Measurement(Experimental and Theoretical Data w/ Any Certainty)-Scientific, Industrial, and Legal(?-1799)d1 Meter (metre) = Million Microns = Billion Nanometers = ?Traceability:-How Certain Are You About a Measurement or EachStep of a Process?-The Ability to Identify Entities and Verify WithDocumented Records and/or Calibration DataCalibration:-Use of a Traceable Standard (NIST, BIPB,…) toDetermine a Tool’s Bias, Accuracy, and Precision“There are two possible outcomes: if the resultconfirms the hypothesis, then you've made ameasurement. If the result is contrary to thehypothesis, then you've made a discovery. “Enrico Fermi(1889-1960)1 metre = d/10,000,000Wikipedia.orgPt/Ir (1960-1983)Krypton-86Wikipedia.org(1983)Speed of Light

lowProbabilityDistributionAccuracyhighMetrology for Process Controlx xx xxxxxxxxxxxAccuracy: (True Value)-How Close to Reference orActual ValuePrecision: (Repeatability)-Degree of Reproducibilityof a MeasurementReference/ActualAccuracyhighPrecisionlowPrecision

Metrology for Process ControlDATADesign, Model, andSimulationMetrology:Optical Microscopy (OM)Profilometry, Ellipsometry, 4-PPStation, Rs-Mapper, AFM/SPM…Cost?Destructive?Nanofabrication Process:(Front-end, Lithography, RIE,CVD, PVD, ALD, RTA, Backend…)DATAYield and PerformancePrecision?Speed?DATAMetrology:Stress Tests, Spectroscopy(Raman/FTIR/PL/XPS..), XRD,SIMS, SEM, TEM,DATA-Statistical ProcessControl (SPC)-Standard Deviation

Key Metrology Techniques forNanofabrication at CNS•Optical Microscopy•Ellipsometry•Profilometry•Atomic Force Microscopy (AFM/SPM)•Electrical Characterization•X-Ray Photoelectron Spectroscopy (XPS)•SEM, FIB, and TEM•FTIR, Raman, Photoluminescence,…•X-Ray Diffraction (XRD)•Secondary Ion Mass Spectroscopy (SIMS)•…

Optical MicroscopyCapabilities– More than 10 OMs at CNS: Stereo, Reflection,Transmission, Inverted, Fluorescence….– Modes: BF, DF, Differential Interference Contrast(DIC), Polarizing– Objective Lenses: 2.5x to 150x– Ultra-High Definition Digital Cameras (6.7um/pixel)-Advance Optical Techniques: NSOM, Confocal, TIRF,TRPL, Raman,…(Contact Jiangdong Deng or Arthur McClelland)Advantages– Rapid– Non-destructive– Lager Area InspectionDisadvantages– Lateral Resolution is Limited by Rayleigh Criterion– Poor Vertical Resolution and No Height (Z)Information100xαR = 0.61λ/ NAN.A = n*sin α0.2 mm WDNA ~ 0.8-0.9520x

Optical Microscopy20x50x50xLateral Measurements:1um or Less but +-0.5um1+mm50x 100xspi.comStage Micrometer’s for Routine Manual CalibrationPhotolithography Masks (Steve Hickman)

EllipsometryCapabilities-Polarized Light for Multi-Layer Film Thickness (t)and Refractive Index (n)-Works Well for Oxide/Nitride/Polymer down to1nm ThicknessAdvantages-Rapid-Non-destructive-200mm Scan Size for Large Area UniformityDisadvantages-Requires Transparent Films (No Metals > 10nm)-Must Have n, t, and K Standardized Values-Interface Must be Clean, No High Roughness–Data Analysis Difficulties:Int.- film is ultra thick (>10um)- ultra thin (1nm)- strong absorption or scatteringr / r tan( )epsThickness (nm)Measured Parameters: tanΨ and CosΔi

EllipsometryGaertner Single WavelengthScanning Ellipsometer (ES-2)J.A Woollam WVASE32 (ES-1)150nm SiO 2 on SiliconRefractive Index (n)30nm SiO 2 on Silicon

ProfilometryTwo Main Types of Profilometry:1) Contact/Stylus Surface Profilometer-Veeco Dektak 6M and KLA-Tencor P16 (PL-3/4/5)-Vertical Step Height (SH): 5nm to 260um-Scan Size: 100um to 50mm-Lateral Resolution: 1-2umDektak 6MCCI HD2) Optical (Interferometer) Surface Profiler-Veeco WykoNT1100 and Taylor Hobson CCI HD (PL-2/6)-Vertical Step Height (SH): 0.1nm to 2mm-Scan Size/Area: 130um to 100mm-Auto Focus/Fringe Find/Scan-Local Film Thickness Measurement: 50nm to 20+umNew Tool at CNS!

Contact Surface ProfilometryDektakmanual.pdfBruker-axs.comLVDT5 umBruker-axs.comWikipedia.orgLinear Variable Differential Transformer (LVDT)or Displacement Transducer

Optical ProfilometryCCI HDWyko NT1100Taylor Hobson CCI HD.pdfTaylor Hobson CCI HD.pdf

Optical ProfilometryCr/NiFe on Si/Ti/Au5nm-Cr 40nm-NiFeNiFe-40nmCr-5nmSiAuTi

Optical ProfilometryAuTiSiNiFe-40nmCr-5nm

Optical ProfilometryMicro-DotsStitchingSH Calibration Standard 5.183um

Optical ProfilometryElectrode Arrays and Photonic Devices

Atomic Force Microsopy (AFM)4 AFM systems at CNS:-Asylum Research MFP3D-SA-Asylum Research MFP3D-BiO-Veeco NanoMan V-WiTec NSOM/Confocal/Raman/SPM-Environment Control-Nano IndentationCombined FluorescenceMicroscopy for Bio-AFMCapabilities and Advantages-Vertical resolution:

Atomic Force Microsopy (AFM)Sub-Micron RIE on Silicon (Nanoman V AFM)Silicon:-1um Grating-2um Pitch~250nm RIE(Ling Xie)

Atomic Force Microsopy (AFM)RIE on Silicon (Nanoman V AFM)5x5um x 200nm Deep Squares/RIE in Silicon

Atomic Force Microsopy (AFM)Ti/Au on p-Silicon (Nanoman V AFM)AuAuSiAu-75nmTi-5nmRMS (Rq):2.97-3.2 nm

Atomic Force Microsopy (AFM)Ti/Au on p-Silicon (MFP3d AFM)NiFeAuNiFeRMS:4.11nmAuTiSiNiFe-40nmCr-5nm

Atomic Force Microsopy (AFM)Si12 umAuAudz = 74.71 nmSiAu-75nmTi-5nm

Thin Film Characterization-1250 °CGrowthRMS:5.06nm250 °CGrowthRMS:4.69nmt = 62.6nmn = 2.48TiO 2 0114 As GrownZnO and TiO 2 Thin FilmDeposition on Si Using ALD(Mac Hathaway)TiO 2 0114 After 550 °C Anneal/30 Minutes150 °CGrowthRMS:1.08nmt = 24.6nmn = 2.24TiO 2 0404 After 550 °C Anneal 30 minutes

Thin Film Characterization-1200 °CGrowthRMS:0.55nmt = 54.3nmn = 1.79ZnO 1006b (550 °C Anneal/30 Minutes)Al-Doped(AZO)RMS:0.60nm200 °CGrowthRMS:1.30nmt = 102.4nmn = 1.97ZnO 111109 (550 °C Anneal/30 Minutes)200 °CGrowtht = 54.3nmn = 1.79

Electrical Property Measurementsat CNS•Electronic Conduction Overview•Van der Pauw Resistivity and Hall Measurement•Thin Film Electrical Characterization•Device Testing•Scanning Probe Microscopy: EFM, CFM, MFM, and SCM•Time Resolved Photoluminescence (TRPL)•Mercury Probe C-V (Non-destructive CV, Hall…)•Deep Level Transient Spectroscopy (DLTS)•Stress Test/Failure Analysis (FA)•…

Electronic ConductionHummel, R.E. Electronic Properties of Materials 3 rd Ed. Springer (2001)Classical Electron TheoryV = I*RBulkQuantum Mechanicsj = σε = I/A = Nve2-d Sheetσ = 1/3v f2 e 2 τN(E f )σ = N f e 2 τ/mALWtρ = 1/σR = ρ(L/A) = ρ(L/t*W) = ρ/t(L/W) = R s (L/W)

Electronic ConductionClassical “Free”Electron Theory-Partially-FilledValence BandMetals and Alloysρ 2 = ρ 1 [1+ α(T 2 – T 1 )]ρ = ρ th + ρ imp + ρ def= ρ th + ρ resIntrinsicSemiconductorsj = σε = I/A = Nveσ = N e u e e + N h u h e-Filled Valence Band-Small Energy Gap toConduction BandHummel, R.E. Electronic Properties of Materials 3 rd Ed. Springer (2001)ExtrinsicSemiconductorsCovalent MaterialsHave Mixed s and pHybrid State’s

Electronic ConductionIntrinsic Semiconductorsj = σε = I/A = Nveσ = N e μ e e + N h μ h eμ = v f /εExtrinsic Semiconductorsσ = N d μ e e + N A μ h en-type SiliconCovalent MaterialsHave s and p HybridState’sσ = 4.84E15 (m e */m o ) 3/2 T 3/2 e(μ e + μ h ) exp[-(E g /2k b T)]Tune E g withDopant/DefectsHummel, R.E. Electronic Properties of Materials 3 rd Ed. Springer (2001)

Electronic ConductionContact Electrode Deployment on Extrinsic Semiconductorsn-typep-typeDiffusion CurrentLower Work FunctionElement ɸ eVAg 4.5-4.7Al 4.1-4.3Ti 4.3Cr 4.5Hg 4.5Si 4.6-4.8In 4.1Space Charge LayersHummel, R.E. Electronic Properties of Materials 3 rd Ed. Springer (2001)Drift CurrentHigher Work FunctionElement ɸ eVAu 5.1-5.5Co 5Pt 5.1-5.9W 4.3-5.2Pd 5.2-5.6Cu 4.5-5.1C 5

Van der Pauw Hall and ResistivityMeasurements1ALV4 14VL1 mmVL123A2 3 2A34R A = V 43 /I 12 R B = V 14 /I 23Van der Pauw Equation: exp(-πR A /R S ) + exp(-πR B /R S ) = 1Ideal Case:R 21,34 = R 12,43R 32,41 = R 23,14 R 43,12 = R 34,21R 14,23 = R 41,32R A = (R 21,34 + R 12,43 + R 43,12 + R 34,21 )/4R B = (R 32,41 + R 23,14 + R 14,23 + R 41,32 )/4DR S = π/ln2*V 23 /I 14= 4.532 (V 23 /I 14 )CDE ResMap (MET-2)40 um WC Tip100 g force

Van der Pauw Hall and ResistivityMeasurements1ALV4 14VL1 mmVL123A2 3 2A34R A = V 43 /I 12 R B = V 14 /I 23Van der Pauw Equation: exp(-πR A /R S ) + exp(-πR B /R S ) = 1Ideal Case:R 21,34 = R 12,43R 32,41 = R 23,14 R 43,12 = R 34,21R 14,23 = R 41,32R A = (R 21,34 + R 12,43 + R 43,12 + R 34,21 )/4R B = (R 32,41 + R 23,14 + R 14,23 + R 41,32 )/4DR S = π/ln2*V 23 /I 14= 4.532 (V 23 /I 14 )CDE ResMap (MET-2)40 um WC Tip100 g force

Van der Pauw Hall and ResistivityMeasurements1.4 Tesla (Variable)

Van der Pauw Hall and ResistivityMeasurementsn s = (I*B)/(q*|V H |)ρ = 1/q(nμ n + ημ h )µ = |V H |/(R S I*B) = 1/(q*n S R S ).bulk resistivity (ρ = R S d) and the bulk density (n = n S /d).SampleGlass Cold Finger300K to 100K(~30 mins!)LISE G27300K to 700K(~30 mins!)

Van der Pauw Hall and ResistivityMeasurements10 mm x 10 mm Max Sample SizeL8.5 mm x 8.5 mm Max Sample SizeLCloverleaf Geometry7.5 mm Center to CenterSpacing Recommended7.5 mm Center to CenterSpacing RecommendedDdDD = 1 mm is recommended:(D/L) α error(d/L) α errorD = 1 mm is recommended:(D/L) α errorOk! Better!! Best!!!

Thin Film ElectricalCharacterizationScanning Capacitance Microscopy (SCM) Using AFMTrapped Charges

Thin Film ElectricalCharacterizationN d (x d ) = - C 3 / (qK s ε o A 2 dC/dV)Agilent b1500 w/ MF-CMUC = ε o ε a A/d

Thin Film ElectricalCharacterizationAgilentEasyExpertSoftwareAgilent 4156cw/ 4x HRSMUAgilent b1500w/ MF-CMULakeShore 1.5K Probe StationSignatone 4ptProbe StationRT up to 450K1.5K up to 450 K

Resistivity (ohm-cm)Thin Film Characterization-2AuTiAl-ZnO (AZO)SiO 2SiZnO and TiO 2 Thin Film Depositionon Si Using ALD (Mac Hathaway)AFM (Height)4.0E-02Resisitivity Vs. Temperature3.0E-022.0E-021.0E-020.0E+000 200 400 600 800Temperature (K)ZnO 1006b (550 C Anneal/30 Minutes)

Thin Film Characterization-2AuTiAl-ZnO (AZO)SiO 2SiZnO and TiO 2 Thin Film Depositionon Si Using ALD (Mac Hathaway)AFM (Height)Temperature (K)Resistivity(ohm-cm)Mobility(cm2/Vs)Density (cm-3)100 3.62E-02 -2.39 7.20E+19200 3.04E-02 -2.79 7.30E+19300 2.69E-02 -3.09 7.64E+19300 2.70E-02 -2.91 7.92E+19400 2.20E-02 -3.2 8.82E+19500 1.77E-02 -4.38 8.02E+19600 1.39E-02 -3.06 1.46E+20ZnO 1006b (550 C Anneal/30 Minutes)

Mobility (cm2/V*s)Resistivity (ohm-cm)Carrier Density (cm-3)Thin Film Characterization-2Resisitivity Vs. TemperatureCarrier Density Vs. Temperature5.57.0E+164.53.52.5275 325 375 425Temperature (K)5.0E+163.0E+161.0E+16275 325 375 425Temperature (K)Mobility Vs. Temperature82.562.542.522.52.5275 325 375 425Temperature (K)P-type Silicon with Au/Pt ContactsTemperature (K)Resistivity(ohm-cm)Mobility(cm2/V*s) Density (cm-3)300 3.38 63.0 2.93E+16325 3.69 45.0 3.75E+16350 4 33.6 4.63E+16375 4.32 25.9 5.55E+16400 4.63 20.7 6.48E+16

Thin Film Characterization-2150 °CGrowthRMS:1.08nmt = 24.6nmn = 2.24TiO 2 0404 (550 °C Anneal/30 minutes)200 °CGrowthRMS:1.30nmt = 102.4nmn = 1.97ZnO 111109 (550 °C Anneal/30 Minutes)Photoluminescence Spectroscopy (PL) (Arthur McClelland)

Device Testing1 & 2-d NanoElectronicsM—O—MAuAu0.5 umNiOMetal-Oxide-Metal (MOM)AuNiO, TiO 2 , SnO 2 …Au2 umTresback, et. al. IEEE Transactions on Nanotechnology, 6 [6] 676-81 (2007)

Device Testing1 & 2-d NanoElectronicsM—O—MAuAu0.5 umNiOMetal-Oxide-Metal (MOM)“Failure”NiO, TiO 2 , SnO 2 …AuAu2 um10 umTresback, et. al. IEEE Transactions on Nanotechnology, 6 [6] 676-81 (2007)

Questions?