Adsorption of Moisture and Organic Contaminants on Hafnium Oxide, Zirconium Oxide, and Silicon Oxide Gate Dielectrics

Hafnium oxide (HfO₂) and zirconium oxide (ZrO₂) are two high-K materials having the potential to replace silicon oxide (SiO ₂) as the gate dielectric. Atmospheric molecular contamination can affect the quality of the new gate dielectric film in a manner similar to SiO₂. Characterization of contaminant adsorption behavior of these high-K films should assist in deciding their potential for successful integration in silicon metal oxide semiconductor technology. The interaction of moisture and organics (in particular, isopropanol, IPA) as common interfacial contaminants with a 5 nm HfO₂ film deposited by atomic layer chemical vapor deposition (ALCVD), which is a trademark of ASM International) is investigated using atmospheric pressure ionization mass spectrometry (APIMS) ; the kinetics and mechanism are compared to that of ZrO₂ and SiO₂. HfO₂ and ZrO₂ have similar moisture adsorption loading, but are significantly higher than that of SiO₂. However, almost all the adsorbed moisture can be removed from SiO₂ and HfO₂ after a 300°C bake under nitrogen purge, whereas ZrO₂ surfaces retain 20-30% of the adsorbed moisture. Experiments with IPA show that the adsorption loading on the three surfaces has the following order; ZrO₂ > HfO₂ > SiO₂. A multilayer model for adsorption of water and IPA is developed to understand the mechanism of interactions of contaminants with the three surfaces. Results from the application of this multilayer model to the experimental data indicate that ZrO₂ forms the strongest surface-hydroxyl (X-OH) bond.