Spare Cell Leakage Minimization in Physical Design, part 2 of 2
“Spare cell insertion is a well known technique to reduce the cost of functional fixes, limiting the changes to a few metal masks. Common practice is to tie to ground the spare cells’ input pins, reconnecting them later in the flow, as required by any functional ECOs.
For illustration let’s take a NOR gate spare master which has 2 inputs A1 and A2. This gate will have four different states of A1 and A2 and hence four different state-dependent leakage power values. This gate would be summarized as shown in Table 1.”