Quantitative Comparison of Simulation and Experiment Enabling a Lithography Digital Twin

Digital twins of the semiconductor fabrication process provide means for optimization of the physical layout and nanofabrication process design, studying compatibility between desired structures and a process flow, and a pathway to analyze the root causes of defects for state-of-the-art CMOS and MEMS devices. In this paper, a metric for the geometric differences between structures visualized by CD-SEM images is defined, and a computer-vision-based algorithm is developed to evaluate the metric. One of the major uses of such metrics is to compare experimental and simulated images. For this application, numerical results are presented when the simulator is SEMulator3D (R), a physics-based process modeling software system for semiconductor and MEMS devices. Computer vision tools, such as filters, thresholding, and morphology operations, are used to extract geometric features from CD-SEM images and pattern matching and symmetric difference are used to compute the metric. Examples of using the metrics to quantify the geometric similarity between a simulated nanostructure and an experimental CD-SEM image of the fabricated nanostructure are presented. The data consists of eight classes of nanostructures which are defined, fabricated in the cleanroom with 36 combinations of layout parameters, and imaged with a CD-SEM.