Symbolic Moment Computation for Statistical Analysis of Large Interconnect Networks

The shrinking technology feature size and dense large-scale integration make process variation a challenging issue directly confronting the latest design automation tools. Process variation causes severe variation in interconnect networks, including very large-scale integrated interconnect structures, such as clock trees, clock mesh, power-ground networks, and other wiring structures in 3-D integrated circuits. The traditional moment computation techniques are only partly useful for analyzing such variational problems, however, their computational efficiency cannot meet the quickly rising needs, such as statistical analysis. This paper presents a novel symbolic moment calculator (SMC) for variational interconnect analysis. The moment calculator is constructed in a regular data structure that incorporates binary decision diagrams for data storage and computation. Given an interconnect circuit, such a computation diagram has to be constructed only once and can be repeatedly invoked for computation of moments with varying parameter values. Also, the SMC is friendly to interconnect synthesis in that it can be incrementally modified according to the modifications made to the circuit structure. Applications of the SMC for fast moment computation, sensitivity analysis, and statistical timing analysis are addressed. Significant efficiency is demonstrated comparing to other existing methods.