High-NA EUV lithography: The next step in EUV imaging (Conference Presentation)

Abstract

Moore’s law drives the doubling of the number of transistors per unit area every 2-3 years. To enable cost-effective shrink of these future devices, a new High-NA EUV platform is being developed. The High-NA EUV scanner employs a novel POB design concept with a numerical aperture of 0.55NA that enables 8nm HP resolution and a high throughput. The novel POB design concept tackles the limitations in angular acceptance of the EUV multilayer masks at the increased NA, but also has implications on the system design and usage of the tool. The introduction of a central obscuration in the POB reduces the angular load on the ML mirrors inside the POB, enabling a high transmission and therefore high throughput. The obscuration size has been chosen such to have minimal impact on imaging performance. Furthermore, the High-NA scanner will be equipped with a highly flexible illuminator, similar to ASML’s NXE:3400 illuminator, that supports loss-less illumination shapes down to 20% PFR. Since imaging is done with unpolarized EUV light, so-called vector effects at high resolution need to be accounted for appropriately. In this paper we will show the implications of the High-NA EUV system design on key performance metrics such as global CDU, pattern shift uniformity (overlay) and contrast for low local CDU at high throughput for several relevant use-cases.