Simulation based sensitivity analysis and optimization of Scatterometry measurements for future semiconductor technology nodes

The term scatterometry summarizes a rather great variety of techniques, all of which have in common that they investigate the diffraction spectrum from a periodic array of nanostructures.

During the past years optical scatterometry has proved to be a powerful technique for CD and profile metrology and has established itself as one of the mainly applied methods for CD metrology besides CD-SEM [1]. To reconstruct structure parameters, measured spectra are compared to simulated data obtained using software Maxwell-equations-solvers as for example the rigorous coupled wave analysis method (RCWA) [2] implemented in our software package MICROSIM [3]. Using this approach to solve the inverse problem allows us to reconstruct the real structure even if below the optical Abbe-limit. As the size of semiconductor structures keeps decreasing constantly, due to growing memory requirements and miniaturization, the demands on the scatterometry method keeps growing. Also the growing process complexity leads to a relative increase of phenomena such as line edge roughness. Using optimized measurement configurations can help to get and exploit maximum parameter sensitivity. These optimized configurations can be accessed with a simulation based approach, performing a sensitivity analysis for different structures, parameters and technology