An integrated circuit (IC) includes a number of electronic devices. One way in which to represent the IC is as a layout diagram (hereinafter, layout). A layout is hierarchical and is decomposed into modules which carry out higher-level functions as required by the IC's design specifications. In some circumstances, a semi-custom design (SCD) project decomposes the modules into macro cells, standard cells and custom cells.
For a given SCD project, a custom cell is designed with an arrangement that is specific to the given SCD project in order to provide (in operation) a higher-level logic function that is specific to the SCD project. By contrast, a library of standard cells is designed with no particular project in mind and includes standard cells which provide (in operation) common, lower-level logic functions. In terms of a footprint within a layout, custom cells are larger (typically much larger) than standard cells. Moreover, for a given library, all of the standard cells have at least one dimension which is the same size (typically, the size being a multiple of a library-specific fixed dimension) in order to facilitate placement of the standard cells into a layout. As such, standard cells are described as being predefined with respect to a given SCD project. Custom cells may or may not have at least one dimension that is the same size as the corresponding dimension of the standard cells.
USPTO Backgrounds
USPTO Backgrounds