Evaluation of EUV Mask Impacts on Wafer Line-Width Roughness Using Aerial and SEM Image Analyses

As more aggressive EUV imaging techniques and resists with lower intrinsic roughness are developed for patterning at 7nm and 5nm technology nodes, EUV mask roughness will contribute an increasing portion of the total printed linewidth roughness (LWR). In this study, we perform a comprehensive characterization of the EUV mask impacts on wafer LWR using actinic aerial images and wafer SEM images. Analytical methods are developed to properly separate and compare the LWR effects from EUV masks, photon shot noise, and resist stochastics. The use of EUV AIMSTM to emulate and measure incident photon shot noise effects is explored and demonstrated. A sub-10nm EUV mask is qualified using EUV AIMSTM with scanner equivalent dose settings that are required for patterning 16nm and 18nm half-pitch L/S features with low- and high-dose CAR resists. The variance and spectral components contributing to wafer LWR are quantified and compared.