Small angle X-ray scattering (SAXS) overlay measurements for advanced semiconductor technologies.

In the aim of enhancing the density of components in microchips and thus improve their performances, microelectronics components keep downsizing. The
International Roadmap for Devices and Systems (IRDS), announced the need of sub-nanometer metrological sensitivity below the 10 nm node, usually accounting for the grid width of transistors. Current metrology technologies will reach their limits and new methods need to be explored, amongst which small angle X-ray scattering (SAXS) shows great potential. It has been proven efficient for the reconstruction of several parameters such as height, side wall angle (SWA), periodicity or critical dimension (CD) on structures such as line gratings, high aspect ratio lines or deep trenches. Our study aims to apply SAXS to the measurement of overlay (OVL), which designates the misalignment between two layers in a component. In order to do so, we measure the overlay on samples presenting stacks of line gratings with programmed overlay.