Method, system, and computer program product for designing an integrated circuit using substitution of standard cells with substitute cells having differing electrical characteristics

A method, system, and computer program product for designing an integrated circuit. In one example, a standard library is provided having a plurality of standard circuit cells, and a substitute library is provided having a plurality of substitute circuit cells wherein one or more substitute circuit cells correspond to one or more standard circuit cells and the one or more substitute circuit cells have at least one differing electrical characteristic-such as power consumption, quiescent current consumption, speed/response time, leakage current, etc.-than the corresponding one or more standard circuit cells. An initial circuit design is created using the plurality of standard circuit cells of the standard library; and one or more non-critical timing paths are identified in the initial circuit design, the non-critical timing paths including one or more standard circuit cells. The one or more standard circuit cells in at least one of the non-critical timing paths of the initial circuit design are replaced with one or more substitute circuit cells to form a modified integrated circuit design. The replacement operation may occur after standard circuit cells of the initial circuit design have been placed and routed. In this manner, the modified circuit design may include standard cells on the critical timing paths and substitute cells on the non-critical timing paths wherein the standard cells are faster and the substitute cells consume less power and/or less quiescent current, in one example.