Precise 3D profile determination of high aspect ratio hole patterns by transmission small-angle X-ray scattering

Abstract

Abstract The etching process of high aspect ratio (HAR) hole patterns on a wafer surface is a key step for fabricating new-generation semiconductor memory devices with vertically stacked structures. As the stacking number of these memory devices increases, it is getting more challenging to maintain the ideal etching profile of HAR holes. Therefore, detailed profile evaluation of these HAR holes is increasingly important. In this study, we have measured 4.2 μm deep holes by transmission small-angle X-ray scattering (T-SAXS) to determine the precise three-dimensional (3D) hole profile. By applying an improved 3D shape model for a hole, we successfully determined a hole profile whose cross-section parallel to the sample surface changes from elliptical to rectangular along its depth. This 3D profile measurement demonstrated that T-SAXS has sufficient sensitivity to evaluate a cross-sectional shape change along the depth of HAR holes.