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Unformatted text preview: 1 Minority Carrier Diffusion Equations and Semiconductor Device Fabrication • Objectives: – Be able to calculate carrier concentrations and currents in semiconductor devices. – Understand the fabrication technologies used to fabricate integrated circuits • Questions to be Answered: EE360 – Lecture 12 – What is a quasiFermi level? – How do we make an integrated circuit? QuasiFermi levels • Recall that the Fermi level is related to the equilibrium carrier concentration. • BUT, we would still like a way to describe carrier concentrations even when we are not in equilibrium. (For example, when we are in steady state). So we introduce energy levels F and F the EE360 – Lecture 12 • So, we introduce energy levels F N and F P , the quasiFermi levels for electrons and holes. 2 Calculating the quasiFermi levels • The quasiFermi levels obey the same relationships as the equilibrium Fermi relationships as the equilibrium Fermi level. • For a nondegenerate semiconductor: EE360 – Lecture 12 Relating Current to the quasiFermi level • Find and substitute into ( ) ( ) kT F E e n p / i P i − ∇ = ∇ • So, p qD p q ∇ − = P p P E µ J P p P and , F F p ∇ ∇ = µ J J EE360 – Lecture 12 N n N F n ∇ = µ J 3 Semiconductor Device Fabrication • Question: How do we start with a uniform piece of silicon and produce an integrated circuit? • Answer: Combine certain “unit” processes, and repeat them several times on each wafer. • Unit Processes: – Oxidation Diffusion – Lithography Etching EE360 – Lecture 12 – Diffusion – Ion Implantation – Etching – Thin Film Deposition Oxidation • Growth of silicon dioxide (SiO...
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This note was uploaded on 04/20/2008 for the course EE 360 taught by Professor Hastings during the Spring '08 term at Kentucky.
 Spring '08
 Hastings
 Integrated Circuit

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