Difference between Endcap/Decap/Filler cells (Structure wise)

[imsaurabh]

Hi,

I know there are multple threads about this question. But did not find what was I looking for,

I know Endcap at the end of rows and around macro, Fillers in between design to fill the gaps n well continuity, and Decap for IR drop to give exra capcitance...

My question is what End cap has so special that it will be placed at the end of rows/columns/macros.

Cause if it only causes proximity issue it can be fixed with filler or Decap also. Somehwere I have read end cap also does the function of decap cells.

If someoe has clear understanding or knowladge please explain it.

Thanks,
Saurabh

 

[rangermad]

Sounds like you may be confused by "cap" in the word endcap. There is no actual capacitor in and endcap. It is a structure used at times meet well & implant enclosures of mosfets at the end of logic tiers.

 

[imsaurabh]

Okay ..So why cant we use filler cells as end cap cells or vice versa. Why do we need special kind of cells as Endcap cells?

 

[skrishneogg]

End cap cells are also known as boundary cells.

1. Their layout is different from that of a filler or Dcap
2. It is used to isolate several designs and IPs in a SOC. A filler or Dcap cells actually helps in continuity of n-well. Boundary cells does exact opposite of it. It breaks the n-well in a way avoiding any DRCs.
3. Boundary cells protect your design from external signals

Different Boundary cells are used for left, right, bottom, top and also corners. They all have different layouts.

 

[imsaurabh]

I got exact answer as follows,

Main difference between Endcap cell is they have dummy poly. which Dcap or fillers does not have.

SO it prevents any stress or DRC violation on actual circuit and design while fabrication.

Have not seen actual layout of standard cell, will reply again after confirming it.