High NA EUV: a challenge for metrology, an opportunity for atomic force microscopy

Abstract

High Numerical Aperture (NA) EUV lithography will require very thin resist films. This reduction in thickness will challenge most metrology techniques, except for Atomic Force Microscopy (AFM). Indeed, thinner resist films allow AFM to reach a better depth accuracy and a higher throughput. In this work, we demonstrate the capabilities of AFM metrology on 16-nm half-pitch resist lines obtained with 5 resist film thicknesses ranging from 10 to 30 nm. As we show, AFM provides relevant information about the pattern dimensions (resist height, line top roughness) as a function of exposure dose, and even about the bottom trench roughness on films with thickness < 10 nm.