CHARGE SHEET MODEL

Development of Low Temperature Oxidation Process Using Ozone For VLSIBYRaghav Singh Tomar1OutlineIntroduction and MotivationFabrication steps for MOS capacitorsCharacterization techniquesEffect of passivation on oxide qualityEffect temperature on oxide growth and its quality22Introduction and MotivationNeed of Thin oxidesNeed of Low temperature process for oxidationOzone has an alternative of oxygen for oxidationFast oxidation at low temperatures Improved interface characteristics Diminished interfacial transition layer

3Device fabrication Steps4Cont.5Cont.6Silent Discharge ozone generatorOxygen inletNitrogen inlet (For Purge)Generated ozoneOzone outletSubstratePressure: 1atmHot ChuckUV SourceSchematic diagram of Ozone oxidation chamber110W low pressure mercury UV lamp with wavelengths mainly 253.7nm and 184.9nmCont.7Silent Discharge ozone generatorOxygen inletNitrogen inlet (For Purge)Generated ozoneOzone outletSubstratePressure: 1atmHot ChuckUV SourceSchematic diagram of Ozone oxidation chamberCan be Heated up to 3000 CCont.8Silent Discharge ozone generatorOxygen inletNitrogen inlet (For Purge)Generated ozoneOzone outletSubstratePressure: 1atmHot ChuckUV SourceSchematic diagram of Ozone oxidation chamberOzone conc. 5930 ppmCont.9Cont.10

Final structure of MOS capacitor structure Front side metal dots under microscope Characterization Techniques Optical characterization 11

Schematic arrangement of reflectrometric spectroscopy setup Characterization Techniques Optical characterization : Principle of operation12

Incident lightReflected lightPrinciple of measurement for reflectometry spectroscopy Characterization Techniques Optical characterization : Typical reflectance spectrum13

Peak !!Typical measured reflectance spectrum Characterization Techniques Leakage current density (J-V) characterization

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Stair case voltage applicationCharacterization Techniques Capacitance Voltage (C-V) characterization: Principle

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Internal schematic diagram of LCR meterCharacterization Techniques Capacitance Voltage (C-V) characterization: Setup

16LCR MeterSMUCHUCK

Shield BoxInstrumentation arrangement for CV measurementCharacterization Techniques Error Corrections technique for C-V measurement

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Voltage (V)Comparison between Chuck biased and Metal biased configuration Characterization Techniques Error Corrections technique for C-V measurement

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Cm: Measured Capacitance, Gm : Measured ConductanceCc: Corrected Capacitance, Gc: Corrected Conductance, RSERIES: Series ResistaanceMOS equivalent circuitCharacterization Techniques Error Corrections technique for C-V measurement

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Characterization Techniques Conductance vs Frequency (Gp/-f) characterization for Dit extraction

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VG = 0, (b) VG > 0, (c) VG < 0. Electron-occupied interface traps are indicated by the small horizontal heavy lines and unoccupied traps by the light lines and depending on that the charges developed on them is denoted by neutral (O) , positive (+) and negative (-)Characterization Techniques Error correction in Gp/-f characteristics 21

Cm: Measured capacitance, Gm: Measured conductance, Cs: Semiconductor capacitanceCox: Oxide capacitance, Rit: Interface trap resistance , Cit: Interface trap resistance,Cp: Parallel capacitance, Gp: Parallel conductanceMOS equivalent circuits for Gp/-f characteristics Characterization Techniques Error correction in Gp/-f characteristics 22A typical variation of series resistance with frequencyCharacterization Techniques Time dependent dielectric breakdown (TDDB) 23

HARD BREAKDOWNSOFT BREAKDOWN

Characterization Techniques Time dependent dielectric breakdown (TDDB) 24

SOFT BREAKDOWNEffect of passivation on oxide qualityEffect on optical thickness

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Effect of passivation on oxide qualityEffect on bulk defects26-OH Passivated-H passivatedArea: 7.78e-3 cm2-OH Passivated-H passivatedArea: 4.62e-3 cm2-OH Passivated-H passivatedArea: 1.86e-3 cm2-OH Passivated-H passivatedArea: 3.317e-4 cm2Gate leakage current density for different devices of different areas distributed across waferEffect of passivation on oxide qualityEffect on bulk defects27-OH Passivated-H passivatedArea: 5.178e-5 cm2Gate leakage current density for different devices of Area: 5.178e-5 cm2 distributed across waferEffect of passivation on oxide qualityEffect on bulk defects28

Effect of passivation on oxide qualityEffect on Si-SiO2 interface29Dit Vs position within Si band gap for OH passivated SiDit Vs position within Si band gap for H passivated Si

Dit Vs position within Si band gap for thermally grown oxide

E. H. Poindexter etal, J. of App. Phy., Vol. 56, No. 10, pp. 2844-2849, 1984.

Effect of passivation on oxide qualityEffect on oxide lifetime30-OH passivated-H passivatedSoft BreakdownHard BreakdownNoBreakdownFailed in pre testSoft BreakdownHard BreakdownNoBreakdownFailed in pre testPositive/Total7/100/103/104/201/107/102/1012/30Effect of oxidation temperature on oxide qualityAt 500C31

Voltage (V)Capacitance (F)C-V and I-V characteristics of different devices distributed across waferEffect of oxidation temperature on oxide qualityAt 1000C32Voltage (V)Capacitance (F)

C-V and I-V characteristics of different devices distributed across waferEffect of oxidation temperature on oxide qualityAt 2000C33Voltage (V)Capacitance (F)

C-V and I-V characteristics of different devices distributed across waferEffect of oxidation temperature on oxide qualityAt 3000C34C-V and I-V characteristics of different devices distributed across waferEffect of oxidation temperature on oxide quality35T CMaximum Current Recorded (A)Accumulation RegionInversion Region50110-2110-4100110-6110-7200110-8110-9300110-81x10-10Maximum gate leakage current recorded for oxide grown at different temperaturesConclusionsPros with OH passivationLow bulk defect densityHigh quality Si-SiO2 InterfaceImproved oxide lifetimeImproved yieldPros with H passivationHigher oxide thicknessWith increase in temperature, improvement in oxide quality can be seen

3637THANK YOUMaximum Thickness RecordedMinimum Thickness RecordedAverage Thickness Recorded

-OH Passivated1.35 nm1.18 nm1.21 nm

-H Passivated1.89 nm1.65 nm1.80 nm