Layout Rules

With the stick diagram, the layout can be drawn with relative ease.  The only requirement is to follow a few rules known as design rules.  This series will draw using a P-type die that will be used to hold the N-FETs.  The die will have wells of N-type material that will be used to hold the P-FETs.  This configuration is the most common in CMOS technology, but is not the only one possible.

Minimum N-Well enclosure of P type active.....   5 microns
Minimum N-Well enclosure of N type active.....   3 microns
Minimum N-Well space to P type active.........   3 microns
Minimum N-Well space to N type active.........   5 microns
Minimum N-Well width..........................   5 microns
Minimum N-Well space to N-Well................   5 microns

Minimum active width..........................   3 microns
Minimum active space to same type active......   3 microns
Minimum active space to opposite type active..   5 microns

Minimum polysilicon width.....................   2 microns
Minimum polysilicon space to polysilicon......   2 microns
Minimum polysilicon space to active...........   1 micron
Minimum gate space to gate....................   4 microns
Minimum polysilicon endcap length.............   2 microns

Minimum contact width.........................   2 microns
Maximum contact width.........................   2 microns
Minimum contact space to contact..............   4 microns
Minimum active enclosure of contact...........   1 micron
Minimum polysilicon enclosure of contact......   2 microns
Minimum polysilicon contact space to active...   3 microns
Minimum active contact space to polysilicon...   2 microns

Minimum metal1 width..........................   2 microns
Minimum metal1 space to metal1................   3 microns
Minimum metal1 enclosure of contact...........   1 micron

The design rules above will be the set this series will follow.  Rules change from fab to fab, process to process.  Two different fabs owned by different companies will each use different design rules, even if the design process is the exact same.  These rules are based on how small of a geometry can be made, as well as any shift in the location of the mask during the production process.

The meaning of each rule will be explained as they are used.



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copyright Michael Lewis, 1999