A power grid optimization algorithm considering via reliability

Recently, fine-pattern process approaching to physical limit and the rise of heat density become major factors of reliability degradation of LSIs. Especially reliability problems in power grids occur more notably in vias. The optimization of via design in consideration of the influence of heat and current density is increasing the importance. This paper formulates via reliability with the mean life time. It gives the minimum mean life time as design restrictions, and it not only fills design restrictions, but proposes a technique of obtaining the solution of more reliable power supply wiring synthetically in consideration of a trade-off relation with other optimized indices, such as a wiring congestion degree, IR drops, and electro migration. It also includes the function which increases via area to improve the reliability of via, even if it increases wiring congestion.