Recent research development in metal-only ECO

In order to reduce the re-spin cost, metal-only ECO rewires spare cells to realize incremental design changes by changing only the masks of metal layers. Metal-only ECO is widely adopted at IC design houses to resolve last found functional and/or timing failures. This task is challenging because these errors in modern IC design may be many, but the pre-injected spare cells are limited in quantity, in cell types, and in physical locations. In this paper, we first introduce the metal-only ECO flow and survey recent techniques for logic difference extraction, functional ECO and timing ECO optimization.