Impact of stochastic process variations on overlay mark fidelity towards the 5 nm node

摘要

In this publication the authors have investigated both theoretically and experimentally the link between line edge roughness, target noise and overlay mark fidelity. Based on previous work1, a model is presented to explain how any given edge of a printed feature could have a mean position that varies stochastically (i.e., randomly, following a normal distribution) due to lithography stochastic variation. The amount of variation is a function of the magnitude of the LER (more accurately, all the statistical properties of the LER) and the length of the feature edge. These quantities have been analytically linked to provide an estimate for the minimum line length for both optical and e-beam based overlay metrology. The model results have been compared with experimental results from wafers manufactured at IMEC on both EUV and ArF lithographic processes developed for the 10 nm node, with extrapolation to the 5 nm node.