Optimizing the Antenna Area and Separators in Layer Assignment of Multi-Layer Global Routing

Abstract

Traditional solutions to antenna effect, such as jumper insertion and diode insertion peformed at post-route stage may produce extra vias and degrade circuit performance. The work in [1] suggests combining layer assignment, jumper insertion and diode insertion together to achieve a better design quality with less additional cost. Based on our observations on global and local antenna violations, this work proposes a dynamic-programming based single-net layer assignment called NALAR, which first enumerates all antenna-violation-safe layer assignment solutions of a net, and then extracts the minimum-cost one for the net. NALAR can minimize via count and separators as well. In addition, an antenna avoidance layer assignment algorithm (ANLA) adopting NALAR as its kernel not only avoids global antenna violations, but also eliminates local antenna violations. Experimental results reveal that, in 11 benchmarks, ANLA can yield 5 violation-free assignments while the algorithms of other works yield no violation-free assignment. As for the total number of antenna violations in all benchmarks, this work and the works in [2], [3] and [4] yield 21, 43506, 41261 and 29671 antenna violations, respectively. However, ANLA performs about 7 times slower than other antenna-aware layer assignment [4].