Spin-coating for fabrication of high-entropy high-k (AlTiVZrHf)O_x films on Si for advanced gate stacks

Spin-coating was performed to fabricate amorphous high-entropy oxide (HEO) (AlTiVZrHf)O_x films on Si substrates. The films were evaluated through X-ray photoelectron spectroscopy and through transmission electron microscopy (TEM)-based energy-dispersive spectroscopy (EDS) mapping, which respectively revealed all constituent elements and the homogenous distributions and no aggregation of those elements. TEM analysis revealed four distinct layers—a crystalline Al metal gate, an amorphous Al₂O₃ interfacial layer, amorphous (AlTiVZrHf)O_x, and native amorphous SiO₂—in a patterned metal–oxide–semiconductor (MOS) gate stack on the Si substrate. The resulting stack exhibited a low leakage current density (J_L) and no frequency dispersion in its capacitance–voltage characteristics after undergoing forming gas annealing. The obtained dielectric constant (k ≈ 32) for the HEO film is promising for advanced gate stacks and transistor applications. Although the film exhibited minor nanocrystallinity and the stack exhibited no interfacial Al₂O₃ layer after rapid thermal annealing at 900 °C, a low J_L, distinct layers, and a clearly defined interface between the (AlTiVZrHf)O_x and SiO₂ were observed, indicating no substantial diffusion among these layers. EDS mapping revealed the homogenous distribution of each constituent element without aggregation. Medium-entropy-oxide films and their MOS devices were fabricated for comparison; however, they exhibited inferior performance.