Week-8-9-diffusion

Week-8-9-diffusion - EE-438L :Introduction to...

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10/06/09 Dr. Kian Kaviani - Spring 2009 EE5 1 EE-438L :Introduction to Microelectronics Processing Dr. Kian Kaviani Ming Hsieh Electrical Engineering Dept. Viterbi School of Engineering University of Southern California
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10/06/09 Dr. Kian Kaviani - Spring 2009 EE5 2 Diffusion in Solids
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10/06/09 Dr. Kian Kaviani - Spring 2009 EE5 3 Introduction Diffusion: A natural phenomena by which the substances move from regions of higher concentration to regions of lower concentration. Diffusion process stops when the concentration of material become uniform everywhere. There are three types of diffusion processes which are different in the medium that the diffusion process takes place : 1. Gas phase diffusion 2. Liquid phase diffusion 3. Solid State diffusion
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10/06/09 Dr. Kian Kaviani - Spring 2009 EE5 4 Gas & Liquid State Diffusion
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10/06/09 Dr. Kian Kaviani - Spring 2009 EE5 5 Solid – State Diffusion
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10/06/09 Dr. Kian Kaviani - Spring 2009 EE5 6 Atomic Scale of Diffusion in Solids There are two types of atomic scale diffusion in solids: Interstitial impurities Substitutional impurities Interstitial Impurity Atom
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10/06/09 Dr. Kian Kaviani - Spring 2009 EE5 7 Substitutional Impurities The diffusion of impurities that replace silicon atoms on the lattice – sites ( substitutional impurities , such as P, As, & B) requires one of the following mechanisms: 1. Direct Exchange 2. Vacancy - Assisted Movement 3. Interstitial - Assisted Movement
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10/06/09 Dr. Kian Kaviani - Spring 2009 EE5
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Week-8-9-diffusion - EE-438L :Introduction to...

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