Impact of aberrations in EUV lithography: metal to via edge placement control

In previous work, we have described how EUV scanner aberrations can be adequately simulated and corrected in OPC across the slit to deliver excellent edge placement control. The problem is that the level of aberration variability from tool to tool is currently quite significant and leads to uncorrectable edge placement errors if OPC is done using one tool while exposure happens on a different tool. In this study, we examine the impact of such edge placement errors for single patterning EUV exposure of metal and via layers with variable aberrations in projection lens systems. Two-layer combined CD and overlay edge placement hotspots can be compounded by aberrations which impact CDs and image shifts, and do so differently depending upon design pattern and pupil fill. Aberration values from current 3300 / 3350 EUV scanners are used and compared to hypothetical ideal tool with no aberrations and demonstrate very significant uncorrectable edge placement errors with current aberrations levels. The net result is a significant reduction in the metal-via combined CD-overlay process window.