Week-4-5-SiO2 -for hw #1

Week-4-5-SiO2 -for hw #1 - EE-438L :Introduction to...

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10/06/09 Dr. Kian Kaviani - Spring 2009, EE 1 EE-438L :Introduction to Microelectronic Processing Dr. Kian Kaviani Electrical Engineering Dept. University of Southern California Viterbi School of Engineering
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10/06/09 Dr. Kian Kaviani - Spring 2009, EE 2 Thermal Oxidation of Silicon
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10/06/09 Dr. Kian Kaviani - Spring 2009, EE 3 Properties of SiO2 SiO2 and Si/SiO2 interface are the principal reasons for silicon’s dominance in the IC industry. Some of the properties that distinguishes SiO2 from other insulators are: Easily and selectively etches using lithography Masks most common Impurities (B, P, As, Sb) Excellent insulator ( ρ > 10 Mega Ohm-cm , Eg > 8 eV) High breakdown field (10 E7 V / cm) Excellent junction passivation Stable bulk electrical properties Stable and reproducible interface with Si
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10/06/09 Dr. Kian Kaviani - Spring 2009, EE 4 SiO2 : Range of Applications
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10/06/09 Dr. Kian Kaviani - Spring 2009, EE 5 Properties of Thermal Oxide Density 2.27 gm / cm3 Melting Point 1700 C Vapor Pressure E-3 Torr at 1450 ºC Thermal Conductivity 0.014 watt /cm - ºC Linear Coefficient of Expansion 5 X 10-6 / ºC Resistivity 5 – 10 Mega Ohm – cm Dielectric Constant 3.9 Energy Gap ~ 8 eV Oxygen Solubility 5.5 x 10 E16/ cm3 at 1000 ºC Water Solubility 3.4 x 10 E19 / cm3 at 1000 ºC
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10/06/09 Dr. Kian Kaviani - Spring 2009, EE 6 Basic Structure of SiO2
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10/06/09 Dr. Kian Kaviani - Spring 2009, EE 7 Thermal Oxidation of Silicon
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10/06/09 Dr. Kian Kaviani - Spring 2009, EE 8 The Deal – Grove Model for Thermal Oxidation of silicon ( Linear – Parabolic Model ) Flux : Number of atoms or molecules crossing a unit area in a unit time F1 : Oxidizing species moving from the bulk of the gas phase to the gas/oxide interface. F2 : Oxidizing species diffusing through the existing oxide to the Si /SiO2 interface. F3 : Oxidizing species consumed by the reaction at the Si / SiO2 In the Steady State: F1 = F2 = F3 F1 F2 F3
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10/06/09 Dr. Kian Kaviani - Spring 2009, EE 9 The Deal – Grove Model for Thermal Oxidation of silicon ( Linear – Parabolic Model )
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10/06/09 Dr. Kian Kaviani - Spring 2009, EE 10 SiO2
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10/06/09 Dr. Kian Kaviani - Spring 2009, EE 11 The Deal – Grove Model for Thermal Oxidation of silicon ( Linear – Parabolic Model ) x ^2 + Ax = B( t + τ ) Where: x :Oxide Thickness (cm) t :Oxidation time (seconds) τ :Time correction factor B : Parabolic Rate Constant B/A : Linear Rate Constant
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10/06/09 Dr. Kian Kaviani - Spring 2009, EE 12 The Deal – Grove Model for Thermal Oxidation of silicon ( Linear – Parabolic Model ) Special Cases : 1) 0 t >> τ x^2 ~ B t (Long Oxidation Time) where: B : Parabolic Rate Constant Growth rate is limited by arrival of oxidizing species diffusing through the thick SiO2 film 2) t << t x ~ (B/A)(t + τ ) Short Oxidation Time where: B/A : Linear Rate Constant Growth rate is limited by reaction rate at the SiO2 interface
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10/06/09 Dr. Kian Kaviani - Spring 2009, EE 13 The Deal – Grove Model for Thermal
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Week-4-5-SiO2 -for hw #1 - EE-438L :Introduction to...

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