ASIC ECO flow

ECO: Engineering change order is commonly used flow to  introduce logic changes to fix the bugs found at very late stage of the ASIC implementation flow/ to fix the silicon bug(s) using minimum metal layers to impact the cost. Few years back I have presented a methodology flow and some of the proven methods to implement the ECO in cost effective way (need Synopsys solvnet account to access!)
 http://www.synopsys.com/news/pubs/snug/singapore2008/06_UserPaper_Infineon.pdf