Off-plane diffraction of extreme ultraviolet light caused by line width roughness

A simple and fast method using extreme ultraviolet off-plane scatterometry for in-line line width roughness (LWR) metrology is proposed. The effect of line roughness on diffraction is numerically investigated. LWR diffracts light into the off-plane of the incidence direction, thereby causing a decrement in specular reflection. The amplitude of LWR can be quantified by detecting the decrement of the specular reflection. The angular distribution of m = 0 and n ≠ 0 diffraction orders is related to the LWR spectrum. LWR spectral analysis is possible by scanning the angular distribution of diffracted light. This study can be applied to both amplitude measurement and spectral analysis of LWR for in-line metrology.

► Simple and fast method for in-line line width roughness (LWR) metrology is proposed.
► The method uses extreme ultraviolet off-plane scatterometry.
► LWR diffracts light and causes the decrement of specular reflection.
► Zero-order decrement and off-plane increment related to LWR, not line edge roughness
► Angular position of diffracted light and spatial frequency of LWR are linked.