EUV Scatterometer with a High-harmonic-generation EUV Source

We have developed an extreme ultraviolet (EUV) scatterometer based on the analysis of coherent EUV light diffracted from a periodic array with nano-scale features. We discuss the choice of appropriate orders of the high harmonics generated coaxially along with the intense Ti:sapphire laser pulses for high resolution spatial performance. We describe an inverse-problem methodology for determining the structural parameters, and present preliminary measurement results confirming the functionality of the scatterometer. A rigorous coupled-wave analysis measurement algorithm was developed to extract accurately and quickly the relevant constitutive parameters from a measured diffraction pattern using a library-matching process.