Are MultiVT Filler cells only NWell or complete MOS devices?

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Hi Guys,

Are multi Vth FILLER cells only Nwell implants or are they full PMOS devices with VDD and VSS taps? As threshold voltage gets mentioned, I assume they have a gate and diffusion regions.

If they are just Nwell implants on P substrate i.e. diodes, what is meant by threshold voltage?

Thanks.
 

Filler cells are only N-well implants. They are used for N-well continuity. Now a day you have multi-Vt libraries. Variation in threshold voltage is obtained by varying channel dopping. So for each Vt an additional fabrication mask is required. Different Vt have their own well continuity as they have different dopping levels and masks. So you have different fillers cells for different VT. Filler doesn't have any threshold voltage.
 

Hi yadavvlsi,
thanks for an answer.

Jack
 

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