Advanced overlay target optimization and Integration in optical metrology

In recent years, simulation-based analysis has become an integral phase in metrology targets design process, performances optimization wise to support on product overlay (OPO) reduction, accuracy and robustness to process variation. Moreover, a simulated unit (stack) represented by its optical and geometrical properties can be used as a mathematicalphysical object for obtaining a deeper understanding of the issues faced while an actual measurement performed. Location based stack calibration allows for both, symmetrical and asymmetrical process variation, a noticeable wafer signature to be attained. Using this information, one can analyze the target-design process-compatibility and asymmetry stability. Furthermore, simulated data can be used, combined with measured data, to establish a more exhaustive perceiving of the process characteristics and risks, hence maxims the measurement performances and stability of the process and target behavior. Likewise, simulation tools can equip integration teams with a more holistic apprehension and quantified data, prior or along real time measurements. In the paper we will cover the simulation theory, use-cases and results.