Novel approaches to meet the requirements for double patterning

In addition to hardware performance enhancement of exposure tool, new functions are needed to be developed to meet the required performance for realizing double patterning. New functions to improve overlay accuracy are advanced distortion control and stage control. We have developed a real-time lens magnification control system to enhance distortion control, which can make peel type, barrel type and trapezoid type of distortion shape, resulting in improving intra-shot overlay accuracy. Wafer stage grid control function can compensate for shot shift, shot rotation and magnification for each single shot, realizing drastic advancement in overlay accuracy. As for CD performance improvement, dose optimization is effective to compenste for CD uniformity according to CD metrology data from processed wafers. On the other hand, process window enhancement is performed by optimizing illumination mode with Canon's solution software k1 TUNE. In this paper, we will introduce these new functions.