Nondestructive analysis of Si3N4/SiO2/Si structures using spectroscopic ellipsometry

The electrical properties of Si3N4/SiO2/Si structures, which are currently used in integrated circuits technology, are largely dependent upon the structure and the chemical composition of the interface regions which may be a few Å thick. Such locked-in regions are difficult to analyze by destructive techniques like secondary ion mass spectroscopy (SIMS) or Auger electron spectroscopy (AES) with ion milling. We show that spectroscopic ellipsometry, operating in the 1.5–6 eV range, is capable of nondestructively analyzing the interface region. The method is demonstrated on standard atmospheric pressure chemical vapor deposition (CVD) nitride layers and the results are compared with ion-milling AES data. The effects of O2 annealing and NH3:SiH4 ratios are also investigated.