Different temperatures leakage mechanisms of (Al₂O₃)_x(HfO₂)_1-x gate Dielectrics deposited by atomic layer deposition

(Al₂O₃)_x(HfO₂)_1-x films with varying compositions were deposited on silicon substrates via plasma-enhanced atomic layer deposition (PEALD), and metal-oxide-semiconductor (MOS) capacitors were fabricated. The impact of varying induced Al content on the dielectric properties of HfO₂ was examined through electrical measurements. The results showed that increasing Al content raised the flat-band voltage, reduced the interface state density (D_it), and significantly lowered the leakage current at a given voltage. Moreover, room temperature I-V measurements indicated that Schottky emission (~ 0.8-4.8 MV/cm), Poole-Frenkel (PF) emission (~ 4.8-7.3 MV/cm), and Fowler-Nordheim (FN) tunneling (~ 7.3-8.3 MV/cm) were the dominant current mechanisms under varying electric fields. At higher temperatures (75-100 °C), the leakage mechanism in Al-rich samples (50-100%) shifted from FN tunneling to PF emission at high electric fields (~ 3.3-6.87 MV/cm). The composition and energy band alignments of the films were characterized using X-ray photoelectron spectroscopy (XPS) and ultraviolet (UV) spectrophotometry, showing that introducing Al into HfO₂ increases the bandgap, reduces the dielectric constant, and significantly lowers oxygen vacancies. Thus, it is further demonstrated that HfO₂ films with the appropriate Al content can effectively enhance dielectric properties and adjust the material parameters of the dielectric layer.