Unique spectral interferometry solutions for complex high aspect ratio 3D NAND structures

We have demonstrated the unique capabilities of spectral interferometry (SI) with vertical traveling scatterometry algorithms (VTS) to solve 3D NAND challenges by measuring complex layer thicknesses of the multideck 3D structures directly from the VTS signals, without modeling, with Cell Over Periphery (COP) underlayer filtering. Multiple examples are presented in the paper, including the measurement of the thin and thick layers of memory structures above the complex logic arrays and the remaining thickness of the fully processed Si wafer from the back side after thinning. In addition, VTS and AI enable direct profiling of the deep through-type cell metal contacts in the areas with nonperiodic staircases and significant lateral variations under the measurement spot.