Immersion lithography has been developed in a tremendous pace. Starting in late 2001, the technology now has moved to volume production of advanced flash memories. The immersion exposure system has been the key enabler in this progress. In this paper we discuss the evolution of the TWINSCAN immersion scanning exposure tools, and present an overview of its performance on imaging, lens heating control, overlay, focus and defects. It is shown that stable performance assures 45-nm device volume manufacturing. Extendibility of immersion towards 38-nm and 32-nm is discussed. For NAND the next device half pitch will be around 38-nm and it is shown that with 1.35 NA and low k1 dipole or CQUAD illumination a final extension with single exposure is possible. For the 32-nm node and beyond double patterning methods are required till EUV lithography is ready to be used in volume production. To secure tight CD tolerance the overlay performance of the immersion tools need to be tightened to numbers well below 3-nm. The paper presents overlay improvements towards the requirements for double patterning.

Date Published: 7 March 2008
PDF: 12 pages
Proc. SPIE 6924, Optical Microlithography XXI, 69241P (7 March 2008); doi: 10.1117/12.774958

Published in SPIE Proceedings Vol. 6924:
Optical Microlithography XXI
Harry J. Levinson; Mircea V. Dusa, Editor(s)