ChapterII-EE477-SNAZ-Spring09

ChapterII-EE477-SNAZ-Spring09 - University of Southern...

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MOS VLSI Circuit Design: Fabrication of MOSFETs Nazarian EE477L – Spring 2009 University of Southern California University of Southern California
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2 USC/EE477L/Spring 2009 MOSFET Fabrication – Introduction There are very strong links btn fabrication process, the circuit design process and the performance of the resulting chip Circuit designers must have a working knowledge of chip fabrication to create effective designs and to optimize the circuits wrt various manufacturing parameters Both n-channel (nMOS) and p-channel (pMOS transistors are built on the same chip substrate Well (tub) : special regions created in which the semiconductor type is opposite the substrate’s E.g.: n-well CMOS fabrication technology: pMOS is created in an n-well, which was built in the p-type substrate
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3 USC/EE477L/Spring 2009 Simplified n-well CMOS Fab. Process
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4 USC/EE477L/Spring 2009 Lithography Lithography: A process used to transfer a pattern to a layer on the chip Positive photoresist : A type of photoresist, initially insoluble, but becomes soluble after exposure to UV light Negative photoresist is less common: is more sensitive to light, but its photolithographic resolution is not as high as that of positive Remaining photoresist is stripped with another solvent Electron beam (E-beam) lithography is used instead of optical lithography to generate accurate high- density patterns
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5 USC/EE477L/Spring 2009 Silicon Dioxide Patterning Steps
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6 USC/EE477L/Spring 2009 Silicon Dioxide Patterning Steps - Simplified Without showing the intermediate steps (Fig. 2.2(b) directly to 2.2(g)
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7 USC/EE477L/Spring 2009 nMOS Fabrication I Polysilicon is used as gate electrode and as well for interconnect medium Undoped polysilicon is doped with impurities to reduce its high resistivity
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This note was uploaded on 07/21/2010 for the course EE 477L taught by Professor Parker during the Spring '08 term at USC.

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ChapterII-EE477-SNAZ-Spring09 - University of Southern...

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