Filler and DeCap

[Prashanthanilm]

How many type of Filler Cell are used in Digital Layouts?.
What is the significance of each of these Cell?.

Note: Also mention non - functional Cells such as Capacitors and Resistors if any

 

[Prashanthanilm]

Sparefill is used for continuity of cells in Design.
Usually Spare fill will be of 1 or 2 Grid wide.

Filler is used for ECO cell generation.
ECO - Engineering Change Order.
Usually Filler cell will be of 4 or 3 Grid wide. And the rest will be the multiple of the basic Filler.
Eg: Filler4,Filler8,Filler12 .. Filler48.
The Criteria for Filler Cell is to be Vertically symmetry.
Horizontal Symmetry cannot be guaranteed as the Poly overhang of pMOAT and nMOAT might differ.

SpareMOSCap:
Cell used for Capacitance.
Schematic of this cell will be either nMOS cap or pMOS Cap.
The nMOS Cap -> Source and Drain connected to VSS and gate to VDD.
The pMOS Cap -> Source and Drain connected to VDD and gate to VSS.
SpareMOSCAp will be 5,8,16 grid wide.
Why the variation in the Grid?
o Grid varaiation is done to get the maximum capacitance. It there is huge
Cap difference between sparemoscap of 4 and 5 grid, then the sparemoscap_5grid
is chosen to draw. The grid selection in not general. Better the Cap , better the cell.