Improving local critical dimension uniformity (LCDU) from speckle reduction towards a k1 of 0.25

Even though increasing laser bandwidth can reduce speckle contrast and improve LCDU, this will also reduce image contrast3. This image contrast decrease must be taken into consideration with lower k1 imaging. Extensive co-optimization requires an EDA flow of SMO, OPC and LBW (laser bandwidth) which must be done to maximize speckle reduction from increased bandwidth and maintain image contrast. The figure below are SMO-OPC-LBW are imaging pupils and process windows for a dense feature of 38nm on a 76nm pitch, demonstrating that exposure latitude can be maintained in this co-optimization. In this study, the Authors will review a number of Memory and Logic use cases that towards a k1 of 0.25 with improvements in reducing speckle while maintaining image contrast.