2.1 Full Custom
IC Design
Full
custom design flow is depicted in below figure.
Based on the schematic transistor level
circuit is drawn. W/l ratio is decided; layout does mask set is required for
manufacturing the transistors. A full custom IC includes logic cells that are
customized and all mask layers that are customized. Full custom IC design and
manufacturing take large lead time. Typically full custom design flow includes
CMOS sizing and manual layout. Even today full custom design flow is used for
building analog blocks and analog Ics. There are no efficient HDLs available
yet to model analog blocks owing to inherent characteristics of analog
circuitry.
Thus in full custom flow every transistor is designed and drawn by
hand. Till date this is most successful (only) way to design analog portions of
ASICs. Full custom design flow can give the highest performance but the longest
design time.
Please mention which are the projects that you know that is based on full custom design? Because mostly in India the design are semi or standard cell based design.
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