chap3_1 - Principles of VLSI Design CMOS Processing...

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Principles of VLSI Design CMOS Processing Technology CMPE413 1 UMBC U M B C U N IV E R S IT Y O F M A LAN D B L T IM C 1 9 6 6 CMOS Processing Technology Silicon : a semiconductor with resistance between that of conductor and an insulator. Conductivity of silicon can be changed several orders of magnitude by introducing impurity atoms in silicon crystal lattice. • Impurities that use electrons: acceptors (p-type), e.g., Boron. • Impurities that provide electrons: donors (n-type), e.g., Phosphorous. Wafer: 75mm to 230mm (~3” to ~9”) and 0.25mm to 1mm thick. Oxidation : Formation of glass or SiO 2 . Wet Oxidation uses water vapor and Dry Oxidation uses pure oxygen. SiO 2 growth consumes silicon, grows into the substrate. SiO 2 is twice the volume of Si, projects above the substrate as well.
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Principles of VLSI Design CMOS Processing Technology CMPE413 2 UMBC U M B C U N IV E R S IT Y O F M A LAN D B L T IM C 1 9 6 6 CMOS Processing Technology Epitaxy, Ion-Implantation and Deposition/Diffusion: Ways of introducing impurities into pure silicon. Epitaxy : Single-crystal film grown on silicon surface. Deposition : Evaporate dopant material onto surface, high temps drive impurities into silicon bulk (diffusion). Ion implantation : Highly energized donor and acceptor atom driven into the sili- con. How much dopant that is introduced is controlled by energy and amount of time. Where it is introduced is controlled by masks (thin films of special material). Mask materials include: photoresist polysilicon silicon dioxide (SiO 2 ) silicon nitride (SiN)
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Principles of VLSI Design CMOS Processing Technology CMPE413 3 UMBC U M B C U N IV E R S IT Y O F M A LAN D B L T IM C 1 9 6 6 CMOS Processing Technology Selective diffusion: Masks act as a barrier to prevent impurities from diffusing. Process involves:
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This note was uploaded on 08/23/2009 for the course CMSC 711 taught by Professor Chintanpatel during the Fall '04 term at UMBC.

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chap3_1 - Principles of VLSI Design CMOS Processing...

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