Chip Optimization Through STI-Stress-Aware Placement Perturbations and Fill Insertion

Starting at the 65-nm node, stress engineering to improve the performance of transistors has been a major industry focus. An intrinsic stress source-shallow trench isolation (STI)-has not been fully utilized up to now for circuit performance improvement. In this paper, we present a new methodology that combines detailed placement and active-layer fill insertion to exploit STI stress for performance improvement. We conduct process simulation of a 65-nm production STI technology to generate mobility and delay impact models for STI stress. We then utilize these models to perform STI-stress-aware delay analysis of critical paths using Simulation Program with Integrated Circuit Emphasis (SPICE). We present our timing-driven optimization of STI stress in standard cell designs, using detailed placement perturbation and active-layer fill insertion to improve complementary metal-oxide-semiconductor performance. We assess the proposed analysis and optimization on small designs implemented with a 65-nm production cell library and a standard synthesis place-and-route flow. Our stress-aware timing analysis improves the clock frequency by 4.68% to 6.31% over traditional worst case analysis, and our optimization improves clock frequency by 2.44% to 5.26%. The frequency improvement through exploitation of STI stress comes at practically zero cost in terms of design area and wire length.