Chipress

Metal ECO is vital to absorb late design changes before tapeout. It could save millions of dollars in mask cost.

Traditionally, metal ECO takes advantage of spare functional cells sprinkled across the design during the physical design phase.

However, traditional metal ECO has inherent limitations: it is not possible to include all cell types as spare cells, and limited drives of ECO cells could introduce DRV issues.

On the contrary, metal ECO with mask programmable cells uses ECO filler cells instead of ECO functional cells. ECO filler cells have the same footprint as ECO functional cells, but they have no contacts to poly / Active.

Metal ECO with mask programmable cells increases feasibility of ECO implementation, as any required functional cells can be derived from one or more filler cells. In addition, these mask programmable cells will not incur additional leakage power compared to traditional ECO functional cells.

Of course, this approach could add extra mask costs involved for the contact layer to poly / Active.

For more information, we recommend interviewees to refer to this page “Metal ECO implementation using Mask Programmable cells”.

Reference:

1. https://www.design-reuse.com/articles/38868/metal-eco-implementation-using-mask-programmable-cells.html#:~:text=ECO%20filler%20cells%2D,connections%20to%20poly%2Factive.%20(