Scatterometer for characterization of diffractive optical elements

Diffractive optical elements can control light beyond the capabilities of traditional optical components, which offers great opportunities for numerous applications. However, modern functionalities are related to even smaller feature sizes, which causes remarkable challenges for the structure measurements in the nanoscale. The current methods are not optimal for the characterization of diffractive structures. Optical scatterometry, however, would be a good tool for non-destructive characterization, and in particular, for inline process control of the fabrication. In this paper, detailed information about a goniometric scatterometer built at MIKES (Centre for Metrology and Accreditation), basics of the inverse problem approach for solving the parameters of the structure and first measurements for confirming the functionality of the scatterometer as well as the capabilities of it are discussed.