Waveguide effect in high-NA EUV lithography: The key to extending EUV lithography to the 4-nm node

One of the main concerns about EUV lithography is whether or not it can be extended to very high numerical aperture. In this paper, rigorous electromagnetic simulation is first used to show that there is an interesting waveguide effect occurring in the 4-nm feature size regime. An exact mathematical analysis is then presented to explain the effect observed in the simulation. This waveguide effect is applied to simulate the printing of 4-nm lines and spaces with excellent aerial-image contrast and peak intensity. The feasibility of EUV lithography for printing logic circuits containing general two-dimensional patterns with 4-nm feature size is also demonstrated. (C) 2015 The Japan Society of Applied Physics