An optimized parameter guidance system for line/space CD metrology

In semiconductor industry, as physical sizes of integrated circuit (IC) components continue to shrink, critical dimension (CD) metrology plays an important role in manufacturing process monitor and control. However, when prior knowledge of E-beam tool conditions and statistics of underlying imaging samples are limited or missing, metrology parameters (such as imaging conditions and CD measurement parameters) are often selected empirically and not optimized in terms of measurement accuracy or precision. Common practice involved in fine-tuning some of the parameters may result in a time-consuming trial-and-error cycle. In this paper, we propose a guidance system to provide an optimized set of metrology parameters given a line/space pattern image or images of scanning electron microscope (SEM). The proposed system models input condition with a comprehensive set of model parameters and then statistical analysis is done based on modeling outputs. A set of metrology guidelines, such as measurement parameters and achievable precisions, can be recommended by the proposed system. The validity of our method has been demonstrated by comparing the recommended parameters with the optimal parameters found by brute-force search on a set of 100 SEM images of line/space patterns.