Advantage of using standard cells
• Independent blocks became too big and complex for a full-custom design,
so there was a need to speed up the circuit and layout design processes.
• There was a shortage of specialized personnel capable of hand-crafting
complex full-custom designed blocks; automation alleviated this problem.
• Advances in the typical manufacturing process included increasing the
number of routing layers from one to two or three metal layers. This added
further complexity to the full-custom layout design process for optimal
• Even in a full-custom design flow, the placement of more than 20 cells is
easier when the building-block cells are implemented with predefined standards.
The standardization of cell interfaces is a concept that is implemented
in a library.