New spare cell design for IR drop minimization in Engineering Change Order

Abstract

Unused spare cells occur inevitably in traditional ECO design flow. It results in inefficient area usage, more leakage, and more IR drop impacts. To tackle these problems, a reconfigurable cell is proposed which serves the dual purposes of decoupling capacitance and spare cell in this paper. Before Engineering Change Order (ECO) is applied, these cells are pre-placed as decoupling capacitors. When ECO is applied, these cells are configured as functional cells. To demonstrate the efficiency of our configurable cell, we propose an algorithm for timing closure and IR drop minimization. Compared with traditional ECO flow, our method shows 16% reduction in maximum IR drop and 56% reduction in leakage before applying ECO, and 8% reduction in maximum IR drop after applying ECO, with 10% area of spare cells. In addition, we show that there are less unsolved ECO timing paths left after applying our ECO timing optimization algorithm due to free selection of ECO gate type.