Accurate characterization of a thick multilayer structure using the marking-layer-based scanning electron microscopy method

Abstract

A multilayer Laue lens (MLL) is a promising optics to advance the focusing resolution of hard x-rays to below 10 nm with high efficiency. It consists of a thickness-graded multilayer with hundreds or thousands of layers. To realize this nano-focusing optics, a high-precision characterization method is needed to measure the position and thickness of each layer. Scanning electron microscopy (SEM) combined with a marking layer method is illustrated in this paper. By inserting WSi2 layers as marking layers in the original MLL structure, the layer positions in different areas can be determined. All the SEM images can be stitched seamlessly and the thickness-graded multilayer is characterized more precisely compared with the conventional method. This new method can help in depositing a more accurate MLL to achieve near-theoretical focusing performance.