Invited Paper MS+NC-MoM9
What Photoemission Can Tell Us About High-K Dielectrics

Monday, October 20, 2008, 11:00 am, Room 311

Angle-resolved photoelectron spectroscopy is an ideal probe films of candidate high dielectric constant films because the thickness of these very smooth films is comparable to the escape depth of the photoelectrons. We have successfully analyzed silicon oxynitride films of the range of thickness of 1 to 4 nm. From the N 1s spectrum we were able to identify four different binding states for N in these films: N bonded to three atoms: three silicon, two silicon and one oxygen atom, and one silicon and two oxygen atoms. In addition we identified a binding state corresponding to N bound to two silicon atoms with one unsatisfied, dangling bond. We also showed that converting the angle resolved data to a compositional depth profile could be done effectively using the maximum entropy algorithm. Recently we have been studying nitrided (HfO₂)_x(SiO₂)_1-x films. The breadth observed in the N1s peak can be attributed to N binding to varying amounts of Si and the relatively electropositive Hf. There appears to be a tendency for N to preferentially bind to Hf in these films. We used the maximum entropy algorithm to analyze these films. Nitridation at successively higher temperatures results in more incorporation of N into these films, and more of this N is incorporated near the oxide/Si interface. Using maximum entropy we were able to convert the angle resolved data to compositional depth profile that had adventitious oxide on the surface, preferential oxidation at the outer surface and the oxide/silicon interface, and otherwise relatively smooth composition of Si⁺⁴ and Hf⁺⁴ through the film. These results were confirmed qualitatively by medium energy scattering.