Model Based Layout Pattern Dependent Metal Filling Algorithm for Improved Chip Surface Uniformity in the Copper Process

Thickness range, i.e. the difference between the highest point and the lowest point of the chip surface, is a key indicator of chip yield. This paper presents a novel metal filling algorithm that seeks to minimize the thickness range of the chip surface during the copper damascene process. The proposed solution considers the physical mechanisms in the damascene process, namely ECP (which is the process used to deposit Cu in the trenches) and CMP (which is the process used to polish Cu after ECP), that affect thickness range. Key predictors for the final thickness range, which is the thickness range after ECP and CMP, that can be computed efficiently are identified and used to drive the metal filling process. To the best of our knowledge, this is the first metal filling algorithm that uses an ECP model among other things to guide metal filling. Experimental results are very promising and indicate that the proposed method can significantly reduce the thickness range after metal filling. This is in sharp contrast with the density-driven approaches which often increase the thickness range after metal filling, thereby potentially adversely impacting yield. In addition, the proposed method inserts significantly smaller amount of fill when compared to the density-driven approaches. This is desirable as it limits the impact of metal filling on timing.