Phenomena and OPC solution of ripple patterns for 65-nm node

The ripple patterns induced by the lithography process will lead to unpredictable necking or bridging risks on circuit patterns. This phenomenon is particularly severe while using the attenuated-phase-shifting mask combined with the strong off-axis illumination. The CD variation induced by the ripple effect is difficult to be accurately corrected by conventional OPC approaches. In this paper, ripples on patterning for the 65nm node have been studied and their problems solved. One of the dominant root causes of ripples is the optical side-lobes from the surrounding patterns. On the L-shape patterns for example, the ripples that occur on the horizontal lines are induced by the side-lobes of the vertical lines. Based on this study of the ripple effect, the layout types resulting in ripple patterns can be classified and predicted. An advanced OPC approach by the segmentation analysis on polygons as well as the correction algorithm optimization has been developed and applied to solve this ripple problem.