Reflective high-energy electron diffraction investigation of the crystallization of ultra-thin oxides

We employed in-situ reflective high-energy electron diffraction (RHEED) to demonstrate its effectiveness for determining the crystallization temperature of ultra-thin high-k materials for Metal Oxide Semiconductor Field Effect Transistors at the 65 nm technology node and beyond. The crystallization temperature is determined from the appearance of shoulder peaks, which corresponds to crystallization in the line-intensity profile. In the case of HfAlOx films with Al/(Al + Hf) = 0.48, weak shoulder peaks first appear when the annealing temperature reaches 800 .deg. C, indicating the onset of crystallization. RHEED analysis shows that Al doping suppresses crystallization in ultra-thin HfOx films, resulting in higher crystallization temperatures. We also found that the film thickness had a great effect on the crystallization temperature which increased with decreasing film thickness, in case of Al2O3 films deposited using atomic layer deposition. This study demonstrated that in-situ RHEED can serve as a sufficiently sensitive characterization tool for investigating crystallization of ultra-thin high-k dielectric films.