Three-dimensional imaging of CMOS image sensor pixel structures using ptychographic x-ray computed tomography in the tender x-ray regime

Abstract

Nondestructive three-dimensional imaging of nanoscale features in advanced semiconductor devices is crucial for understanding and improving their performance. In this study, we applied ptychographic x-ray computed tomography in the tender x-ray regime. Using 4 keV x rays at the NanoTerasu BL10U beamline, we visualized the three-dimensional architecture of a state-of-the-art CMOS image sensor with a sub-micrometer pixel pitch. The reconstructed three-dimensional electron density map achieved a spatial resolution of 34.1 nm, clearly resolving key components, such as silicon-based photodiodes and deep trench isolation structures. This achievement demonstrates an effective methodology for analyzing complex light-element-based devices, paving the way for identifying performance-limiting defects and guiding the design of next-generation electronics.