Image-noise effect on discrete power spectrum of line-edge and line-width roughness

The authors investigated the effect of scanning-electron-microscope image noise on the accuracy of line-edge-roughness and line-widthroughness (LER/LWR) statistics extracted from power spectral densities (PSDs). To do this, they numerically prepared pseudo-experimental PSDs of LWR using the Monte Carlo (MC) method. The estimation error n decreased with the total number N_ALL of width data points in the same way as that observed in the absence of the image noise. n first increased gradually with the image-noise intensity R but markedly when R went beyond the threshold value Rth determined by the ratio of the sampling interval δy to the correlation length δy. The PSDs with these R_th's had the same maximum-to-minimum ratio γ (= 10 in this study). The authors approximated n by BN_ALL-3/4(1+g(R,δ;- 3/8 [1 + g(R;δy/epsi;γ where B is 49. They also empirically determined the functional form of g(R;δy/γεγ). Because these functions well fitted massive MC simulation results, they provide guidelines for setting up analysis conditions for securing arbitrarily prescribed accuracy.