Non-Destructive Characterization of High Aspect-Ratio Structures Using 3D X-Ray Microscopy

Abstract

Hemispherical shell resonators such as the birdbath resonator have demonstrated excellent performance enabling the development of near-navigation grade gyroscopes. Their inherent 3-dimensional nature can make inspecting their geometrical features and abnormalities difficult to do with conventional imaging and characterization methods. This paper demonstrates the capability of 3D X-ray microscopy (XRM) to characterize high aspect-ratio structures in a non-destructive manner with an emphasis on early stages of development. This technique is enormously effective for several reasons. It can be used for failure analysis and characterization of devices before, during, and after field use. It provides detailed 3D images of an entire device, providing the ability to provide 2D views along any given plane. This is a significant capability, especially for millimeter scale 3D devices with sub-micron feature resolution. Because it is non-destructive, it can be used on a variety of samples as they go through manufacturing, and especially after they are packaged and not accessible. Finally, the 3D and 2D profiles can be used to construct models for finite element modeling and device design optimization. X-Ray Microscopy images of fused-silica micro-hemispherical resonators and graphite blowtorch molds are presented to demonstrate the effectiveness of XRM imaging.