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 (similar to 0.8-4.8 MV/cm), Poole-Frenkel (PF) emission (similar to 4.8-7.3 MV/cm), and Fowler-Nordheim (FN) tunneling (similar to 7.3-8.3 MV/cm) were the dominant current mechanisms under varying electric fields. At higher temperatures (75-100 degrees C), the leakage mechanism in Al-rich samples (50-100%) shifted from FN tunneling to PF emission at high electric fields (similar to 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.