Physical Design Cells
Non-functional cells that keep layouts legal and robust.
Overview
Physical-only cells do not implement logic, but they are required for manufacturability and reliability. They close gaps, protect wells, and stabilize power.
Ignoring these cells leads to DRC violations, latch-up risk, or power integrity issues.
Common Cell Types
Tap cells and well ties maintain substrate and well biasing.
Endcaps seal standard cell rows and avoid boundary DRC issues.
Filler cells close spacing gaps and maintain metal density.
Tie-high/low cells provide stable constants with proper isolation.
Decap cells smooth dynamic IR drop near high-activity logic.
Implementation Tips
Insert tap cells at foundry-specified intervals.
Spread decaps near clock buffers and high toggle logic.
Run DRC after physical-only cell insertion.