| Tunneling spectroscopy has been overlooked as a viable characterization tool for the silicon metal-oxide-semiconductor system because the ultra-thin dielectrics required were not representative of gate oxides used in industry. However, the development of demonstrable transistors with sub-20 A gate dielectrics makes the application of inelastic electron tunneling spectroscopy to this material system more pertinent. Utilizing this technique we have observed vibrational modes in ultra-thin silicon dioxide films that are consistent with reported bulk infrared and Raman data. Without the use of special test structures, we have been able to non-invasively observe the changes and variations of this material system, in full-flow encapsulated devices, as a function of process and stress conditions. We report the detection of specific silicon dioxide mode changes resultant from electrical stress and thermal annealing, and present models for explaining these results. |
