32 nm Half Pitch Formation with High-Numerical-Aperture Single Exposure

Abstract

According to the International Technology Roadmap for Semiconductors (ITRS), memory half pitch (hp) will reach 32 and 20 nm by 2012 and 2017, respectively. However, it is difficult to fabricate a sub-40 nm node using single-exposure technology with the currently available 1.35-numerical-aperture (NA) ArF immersion lithography. Although it is expected that either double patterning technology or extreme ultraviolet lithography will enable the realization of 32 nm hp, there are still many problems that need to be solved regarding cost reduction. Thus, the study of high-index fluid immersion technology should be pursued simultaneously. ArF water immersion systems with 1.35 NA have already been introduced for 40-nm-hp production. ArF immersion lithography using high-index materials is currently being studied for next-generation lithography. Currently, many studies are being undertaken in order to increase NA for a high-index fluid and a lens in immersion technology. The combination of LuAG (n = 2.14) and a third-generation fluid could be used to realize 1.55 NA. This combination of 0.25k1 and 32 nm hp can be obtained using single-exposure technology. In order to determine the feasibility of this process and possible process hurdles for this high-NA single-exposure technology, 32 nm hp with a 1:1 line and space pattern is tested. Various illumination conditions are tested to realize 1:1 32 nm hp, and the exposure and development conditions are varied to determine whether this single exposure can provide a processible window. As a result, 32 nm hp could be obtained by single-exposure technology with 1.55 NA.