Strontium niobate high-k dielectrics: Film deposition and material properties

Strontium niobate ultrathin films were processed by water-based chemical solution deposition, an approach that offers environmental benefits. SrNb2O6 and Sr2Nb2O7 show high-k values, which is important for applications such as alternative gate dielectrics. The study of ultrathin films (thickness <30 nm) is crucial, as this is the thickness range for the application envisaged, and as film properties depend strongly on the film thickness. SrNb2O6 had a lower crystallization temperature, less interfacial silicate, lower carbonate content, and higher roughness compared to Sr2Nb2O7. The k values of amorphous films were limited for both compositions (k = 12–14). Crystallization and complete removal of organics or carbonates were accomplished by high-temperature annealing, but increased the roughness and leakage current. For Sr2Nb2O7, interfacial silicates were formed as well. Intermediate calcination steps improved the surface smoothness and increased the k value of SrNb2O6 up to 30.