X-ray Microanalysis Background noise reduction by FIB sample preparation

Refractory metals are commonly seen in many structures and defects in Si based semiconductors integrated circuits (ICs). Such defect can be easily identified under x-ray microanalysis conducted with high-beam energies. However, these analyses are typically carried out with a low beam energy to optimize spatial resolution and mitigate background noise from the sample. X-ray microanalysis at low beam energies will generate only M-line X-rays and many of these overlap with the Si-K X-rays line, like W-M line and Ta-M line. In this paper, energy dispersive X-ray (EDX) analysis was study at both low beam energy (5 kV) and high beam energy (15 kV) on un-landed tungsten plug embedded in Silicon dioxide of a post FIB sample. To reduce background noise during high beam energy EDX analysis, further study was carried out on thin slices of samples of about 100nm to a few hundred nanometers prepared by focused ion beam (FIB).