Complex Imaging Reflectometry Using Tabletop Coherent EUV Beams for Spatially and Depth-Resolved Imaging

Next-generation nano and quantum devices have intricately designed complex structures. Moreover, there is a need to integrate advanced 2D and spintronic materials, with control over the electronic, magnetic, transport and interfacial properties. For optimizing these systems, new characterization techniques with high spatial resolution and sensitivity are needed. We present a tabletop complex imaging reflectometer illuminated by coherent high harmonic extreme ultraviolet (EUV) light. It uses coherent diffractive imaging algorithms to generate phase and amplitude reflectivity maps of a sample at many incidence angles. Both the phase and reflectance of EUV wavelengths are very sensitive to the structure and material of the sample, yielding ~50 nm transverse resolution and ~Å axial precision. From the angle-dependent reflectivity, we can solve for the 3D composition in a spatially-resolved and non-destructive manner. Using a semiconductor sample, we solve for layer thicknesses, structure heights, interface quality and dopant levels, which were verified using correlative metrology.