Investigation and Discovery of the Integration of FEOL Process by Electron Beam Inspections

A novel inspection method is proposed for checking the integration of FEOL (front-end-of-line) device fabrication. As the designed electron-beam (as e-beam in the following text) inspection methodology applies to the last step of FEOL device and prior to MEOL interconnection fabrication, the capability of both voltage contrast and physical feature detection discovered the surface and underneath defects in the very narrow space of Nickel Silicide formation. Experiments showed the variation of multiplex parameters involving poly critical dimension, spacer and SMT film thickness with dry, wet, furnace and plasma ashing processes would lead to invisible change of Nickel Silicide formation and can be detected by the designed inspection. Defect count would be high while those majority pre-steps process windows being marginal. After all, the cumulative effect would lead to electrical failures of the device.