Abstract
As the chip industry enters 45/40 nm technology node and beyond, Via photolithography process is becoming more and more challenging due to decrease of critical dimension (CD) and narrow process window. The effective control on Via CDU becomes more important to improve SRAM yield, however, the CDU has shown highly sensitive to the variations of wafer topography and the leveling capability of a scanner. The Air Gauge Improved Process Leveling (AGILE) function of ASML immersion scanner is a very effective leveling system for the improvement of CDU performance. This paper studies on the implementation and performance of AGILE focus corrections for advanced photo lithography in volume production as well as advanced development in Huali’s 300 mm facility. In particular, a logic hierarchy that manages the air gage sub-system corrections to optimize tool productivity with sufficient sampling frequency to ensure focus accuracy for stable production processes is described.
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