Substantial Dose Reduction Using Dry Deposited Underlayer for EUV Lithography While Maintaining Roughness and Minimizing Defects

Abstract

In EUV lithography, the underlayers (ULs) play a crucial role for EUV exposure dose reduction as well as the prevention of the pattern collapse of the resist. In this work, we have focused on the EUV exposure dose reduction which is important for cost reduction and productivity enhancement. To accomplish so, we have developed an dry deposited underlayer engineered for metal oxide resist (MOR). A series of ULs with various chemistry, thickness, and processing conditions were screened with MOR resist using ASML's NXE3400 EUV exposure system to print 14 nm dense line CD. We observed a 27% dose reduction on the best deposited underlayer compared to spin on glass (SOG) UL. In addition to the exposure dose reduction, we observed that unbiased roughness values (LWR 2.44 nm and LER 1.86 nm) is maintained the same as SOG UL (LWR: 2.49 nm and LER 1.86 nm). Furthermore, the defect free window is comparable to the SOG process. Considering all these advantages, the dry deposited ULs could be one of the underlayer candidates for high NA EUV lithography.