Measuring nanograins of 50nm-thick metallization layer using a new approach of EBSD pattern matching

Analyzing nanograins smaller than 100nm in semiconductor interconnectors and packages using conventional Electron Backscatter Diffraction (EBSD) in a Scanning Electron Microscope (SEM) can be challenging. The solution for many researchers is the new transmission EBSD (t-EBSD), also known as the transmission Kikuchi Diffraction (TKD) technique, which requires TEM lamella samples with the optimized sample thickness and optimized SEM conditions at 30kV. This work explores the use of conventional EBSD geometry to analyze ultrathin metal thin films (<100nm) produced by advanced semiconductor manufacturing. The new method combines a new indexing method of pattern matching with the conventional EBSD technique, which enables the acquisition of high-quality EBSD maps from a 46 nm-thick Tungsten metallization layer on a Si wafer without the need for TEM sample preparation. The patterns were stored using a sensitive Symmetry S3 EBSD detector during the data acquisition and then reindexed using MapSweeper, the offline pattern matching software. The approach results in the improved orientation map quality with a hit rate increasing from 58.4% to 90% and the increased nanograin detection. The mean grain size was 40nm, obtained statistically from 209 grains. This simple and cost-effective approach provides an alternative to the more complex TKD technique and offers a promising solution for the analysis of nanograined metallization layers down to 50 nm in thickness.