Power and Area Efficient Hold Time Fixing by Free Metal Segment Allocation

Abstract

Hold time fixing ensures correct data synchronization, which is essential and serves as the final step of timing closure for IC design. Conventionally, buffer insertion is adopted to fix hold time violations; buffers, however, induce routing difficulty, increase area utilization, and contribute leakage power. Therefore, in this paper, we propose to fix hold time violations by free metal segment allocation for achieving leakage power efficiency and maintaining utilization for mobile and portable devices. At the final step of timing closure, free metal segments and hold violating nets are both fragmented and scattered over the design. We thus partition a design and perform minimum cost network flow to assign proper free metal segments to hold violating nets. Our experiments are conducted on six industrial smartphone designs with TSMC 16nm process, and our results show that compared with the conventional buffer insertion method, our approach can reduce 37% hold time buffer area, promising for saving leakage power and maintaining area utilization-suited to the final step of timing closure.