Ground rule slack aware tolerance-driven optical proximity correction for local metal interconnects

Abstract

The current method of communicating process capabilities to the designer is in the form of ground rules. However, due to constraints on the complexity and number of rules, there may exist shapes that are design-rule clean but difficult to manufacture. This problem is exacerbated in local routes drawn on 1x metal (M1) which allows highly bi-directional shapes at tight spacing. On the other hand, local M1 routes have low parasitic resistance and capacitance as compared to device impedances. Hence there exists an opportunity to perturb these shapes to improve their manufacturability without significant performance impact. We propose to guide this perturbation by the amount of leeway available between the designed values and the ground rules - which we refer to as ground rule slack. In this paper, we utilize ground rule slack to generate tolerance bands for layout features. We further develop a tolerance-driven optical proximity correction (TD-OPC) algorithm which utilizes such tolerance bands to find a lithographically optimal mask solution for manufacturing. Our experiments on sample layouts shows that the use of this methodology helps reduce lithographic hotspots by 59% in comparison to process window optical proximity correction.