In semiconductor manufacturing, inspection and metrology are crucial to improve the chip production yield. As optical lithography advances into the extreme ultraviolet (EUV) regime using a source wavelength at 13.5 nm, the state-of-the-art 3 nm technology node has achieved a transistor density of more than 200 million transistors per mm2. Meanwhile, the fabrication processes become prone to nanoscale defects, e.g., particles, and demand ultra-precise measurement of structural parameters.

However, imaging nano structures with EUV light for process control presents a significant challenge due to the reliance on imaging systems consisting of complex and expensive EUV mirrors, which requires specially designed multilayer coating and sub-nanometre precision surface polishing. To address this, we investigated a novel approach that combining a compact, table-top high harmonic generation (HHG) EUV source with a ptychography, a computational imaging method, to examine the 3D nanostructures on the wafer. This technique eliminates the need for EUV optics in imaging, drastically reducing system costs while maintaining high-resolution imaging capabilities.

In this talk, I will present the EUV experimental setup developed at TUDelft and our image reconstruction, which leverages machine learning (ML) and automatic differentiation for enhanced flexibility and efficiency.

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Bio

Yifeng Shao obtained his Ph.D. in the Optics Research Group at Delft University of Technology, specializing in solving inverse problems in imaging and imaging systems. In 2018, he worked on a joint project between TUDelft and ASML to develop a computational approach for aberration metrology in CD-SEM, which subsequently led to a series of patent inventions. In 2020, he returned to TU Delft and joined the LINX (Lensless Imaging of 3D Nanostructures using Soft X-Rays) project, led by Prof. Wim Coene, where he contributed to the development of a prototype for imaging wafer nanostructures using ptychography and an EUV high-harmonic generation source.

In 2024, Dr. Shao founded AIM Solutions B.V., a startup dedicated to commercializing this technology for semiconductor inspection and metrology applications.