Comparison between ADT and PPT for 2X DRAM patterning

Extreme Ultra-Violet (EUV) lithography is almost only solution reachable for next-generation lithography below 30nm half pitch with relative cost competitiveness. In this study, we investigate the feasibility of EUV lithography for applying 2X nm dynamic random access memory (DRAM) patterning. Very short wavelength of 13.5nm adds much more complexity to the lithography process. To understand for challenges of EUV lithography for high volume manufacturing (HVM), we study some EUV specific issues by using EUV full-field scanners, alpha demo tool (ADT) at IMEC and pre-production tool (PPT) at ASML. Good pattern fidelity of 2X nm node DRAM has been achieved by EUV ADT, such as dense line and dense contact-hole. In this paper, we report on EUV PPT performance such as resolution limit, MEEF, across slit CD uniformity (CDU) and focus & exposure latitude margin with 2X nm node DRAM layers in comparison with ADT performance. Due to less flare and aberration of PPT, we have expected that PPT shows good performance.