New technique for optical lithography at low k-factors

The analysis and results show the performance of 150nm pattern features exposed with an advanced step-and-scan system using conventional illumination. Extremely uniform linewidth control of 3(sigma) < 6nm for these features is achieved by implementing the new step-and-scan technique of cross-slot-dose compensation. Examples are presented to demonstrate the improvement achieved using this new technique for grouped features, semi-isolated features, and isolated features. This new technique enhances the performance of a step-and-scan system because it allows the adjustment of the illumination signature along the scanned optical slot to achieve the optimum linewidth-control- performance necessary for advanced microprocessor production. Slot compensation is accomplished by locally adjusting the slot width of the scanning syste. The adjustments are automated and under computer control. This technique is not easily applied to the older optical step- and-repeat systems. The paper demonstrates how this technique, used with standard masks and standard illumination, gives an unprecedented enhancement in both resolution and linewidth control. The combination of this new technique with the step-and-scan system's low optical distortion and highly precise pattern-overlay capabilities allows optical lithography to operate at K-factors significantly below 0.5 in volume production. This paper introduces the improvements required to achieve successful production-level lithography at K-factors of 0.4 and below.