Preliminary evaluation of line edge roughness metrology based on CD-SAXS

Abstract

Line edge roughness (LER) remains a predominant measure of pattern quality used to evaluate processing parameters throughout the many steps of fabricating microelectronics. In the effort to minimize LER, a critical component is a metrology capable of rapid and non-destructive characterization of fluctuations in the position of the pattern, or line, edge. Previously, we have demonstrated a non-destructive metrology capable of sub-nm precision in the measurement of pitch and linewidth termed Critical Dimension Small Angle X-ray Scattering (CD-SAXS). Here, we explore the capability of CD-SAXS to measure line edge fluctuations using the diffuse scattering from diffraction peaks. Models of varying forms of line edge roughness are used to explore the effects of different types of line edge roughness on CD-SAXS results. It is found that the frequency and the degree of correlation of the roughness between patterns greatly influences the scattering pattern predicted. Model predictions are then compared to CD-SAXS results from a photoresist grating.