Thermodynamic analysis of moisture absorption phenomena in high-permittivity oxides as gate dielectrics of advanced complementary-metal-oxide-semiconductor devices

The moisture absorption phenomena in high-permittivity (k) oxides were analyzed from the view point of the thermodynamic process. The Gibbs free energy change (ΔG) in the moisture absorption reactions were calculated with the thermodynamic data of oxides, water (H2O), and hydroxides. It was found from the calculation results that the moisture absorption is a common phenomenon in high-k oxides, especially in rare earth oxides. The results also show that lanthanum oxide (La2O3) has the largest moisture-absorption-reaction speed among main candidates for high-k gate oxides. Doping a second oxide could be a direct and effective method to enhance the moisture resistance of La2O3 films.