Sensitivity improvement by a hybrid scatterometer

Scatterometry is one of the most promising CD profile metrology technologies for future technology nodes. As critical dimension (CD) continues to decrease, sensitivity of scatterometry needs to be improved to measure even more subtle structures. Sensitivity of a scatterometer highly depends on film stack structure and optical properties of the sample and wavelength, incident angle and polarization implemented by the scatterometer. When measuring different types of sample, scatterometer should be capable of optimizing measuring configurations to get best sensitivity. In this work, we attempt to optimize the measuring sensitivity by introducing a hybrid scatterometer, which is able to measure reflected light from a sample through either an angle-resolved method or a spectroscopic method using two complementary measuring arms. In this setup, improvement of sensitivity can be achieved by choosing better measuring method and adjusting light wavelength, incident angle and polarization.