A comparative study on the evolution of the interface chemistry and electrical performance of ALD-driven HfxTiyAlzO nanolaminates

Abstract

In this work, a series of ternary HfTiO and TiAlO films and quaternary HfTiAlO films prepared with different stoichiometric ratios via atomic layer deposition (ALD) were deposited on Si substrates. The interfacial properties, band alignments, and electrical characteristics were analyzed to evaluate the electrical performance of the corresponding metal–oxide–semiconductor (MOS) capacitors. Based on the characterization data, it can be noted that the permittivity of HfTiO increases on increasing the Ti content, while the deterioration of the film quality leads to an increased leakage current. For TiAlO, as the Al content increased gradually, the interface quality improved, but the corresponding permittivity was sacrificed. As for HfTiAlO, the addition of Ti and Al jointly in HfO₂ could improve the interface performance, enlarge the energy band offset, enhance the dielectric constant, and reduce the leakage current simultaneously. The interfacial analysis and electrical characterization demonstrated that HfTiAlO with an ALD cycle ratio of Hf : Ti : Al = 6 : 1 : 1 had the most excellent film quality, interface performance and electrical properties, including a larger dielectric constant of 28.8, a larger conduction band offset with Si of 2.47 eV, and the lowest leakage current density of 1.11 × 10⁻⁵ A cm⁻².