Preparing for cost-effective soft x-ray metrology for 3D chip architecture

The soft x-ray regime is gaining adoption, specifically for the extreme ultraviolet (EUV) 13.5 nm wavelength used in today’s leading-edge semiconductor chip manufacturing. As miniaturization progresses and with the goal of continuing Moore’s Law, it becomes more difficult for chip makers to increase device densities in a 2D plane, even with leading-edge EUV photolithography. Chip makers are now turning to 3D-stacked architectures to increase area density. Since these stacked layers consist of micro-features and require precise interconnections, it is imperative that proper metrology be performed on each layer to identify possible defects and optimize the process on subsequent layers. There is a need for non-destructive imaging tools that can resolve nanometer-sized features. Soft x-ray imaging could be a solution using wavelengths from 2-20 nm. There are many methods of generating soft x-ray light, often with relatively high costs and varying outputs. This talk will highlight some cost-effective components that are commercially available. We will also present simulations of effective soft x-ray light output at the sample.