A standalone alignment technology was developed as a fundamental solution to improve on-product overlay (OPO). It enables high performance alignment measurements, and delivers state-of-the-art feed-forward corrections to exposure scanners. Dense alignment sampling and high order alignment correction is effective for scanner fingerprint matching and for correcting heavy distortion at a wafer edge. A mark asymmetry correction is detailed as effective solution which improves the OPO performance for heavily processed wafers. An OPO test result showed significant improvement using its feed-forward corrections. A high accuracy topography sensor is described as a new metrology innovation. The standalone alignment technology provides critical metrology tool functions such as process monitoring as well.
One of the main components of an On-Product Overlay (OPO) error budget is the process induced wafer error. This necessitates wafer-to-wafer correction in order to optimize overlay accuracy. This paper introduces the Litho Booster (LB), standalone alignment station as a solution to improving OPO. LB can execute high speed alignment measurements without throughput (THP) loss. LB can be installed in any lithography process control loop as a metrology tool, and is then able to provide feed-forward (FF) corrections to the scanners. In this paper, the detailed LB design is described and basic LB performance and OPO improvement is demonstrated. Litho Booster’s extendibility and applicability as a solution for next generation manufacturing accuracy and productivity challenges are also outlined