Strong phase shifting optical maskless lithography for the 65 nm node and beyond

摘要

Ever-increasing reticle cost makes optical maskless lithography an attractive alternative to mask-based technologies, particularly for low-volume runs such as prototypes, ASIC personalization, and engineering short loops. If the resolution and imaging performance of the optical maskless exposure tool can match or exceed standard reticle based scanners, then one can seamlessly integrate mix-and-match strategies into the manufacturing flow or even go to an all maskless strategy since resists and film stacks are unchanged. We have developed optical maskless analogs for a majority of the reticle based strong phase shifting techniques. These include analogs to binary, attenuated PSM, alternating PSM, CPL + assist features, and vortex reticles. We will present simulation of maskless vs. reticle based lithography of all these techniques, demonstrating how to move off grid, change CD, OPC correct through pitch, and present common feature process windows and CD / image placement error sensitivities that suggest that for certain applications, optical maskless will be superior to reticle based lithography.