On-Scanner High-Spatial-Frequency Overlay Control using a Distortion Manipulator

As overlay tolerances tighten node-over-node, the measurement and control of overlay has progressed from the low (spatial) frequent domain toward higher spatial frequencies. At present up to 3rd order in the (non-scanning) slit direction can be addressed on high end systems. With the introduction of an advanced distortion-manipulator on an ArFi immersion scanners a significant improvement in the spatial frequency of overlay control can be achieved. This actuator will now enable at least up to 9 th order lens distortion manipulation and control in the (non-scanning) slit direction, with future extendibility to on-the-fly adjustments while scanning. The manipulator setup and distortion control is fully incorporated in the scanner software and allows for lens fingerprint optimization, better dynamic lens heating control, and scanner stability control to maintain overlay performance over time. Also an external scanner overlay optimization interface is made available that enables machine-to-machine matching within the immersion platform as well as for cross-matching to the EUV platform. Via this interface also high spatial-frequent process corrections can be send to the scanner. In this paper, we will show the capability of the scanner-integrated distortion manipulator on abovementioned aspects using on-scanner aberration metrology, and in-resist distortion and overlay metrology.