Hf-Based High-? Dielectrics: A Review

Abstract

In the last decades, the number of transistors per chip with integrated circuits has increased leading to reduction in the thickness of silicon dioxide used as gate dielectrics. However, at small dielectric thicknesses leakage current formation has begun due to the quantum tunneling effect. Thus, it became essential to replace SiO2 with alternative dielectrics with high dielectric constant to maintain the same capacitance at higher gate dielectric thicknesses. This review analyzes alternative high-kappa dielectric materials substituting for SiO2. For this reason, the properties of materials with high dielectric constant are compared to SiO2 with a special emphasis on HfO2, since it is the most promising high-kappa dielectric to replace SiO2. The fundamental points concerning HfO2 gate dielectrics are their high dielectric constant and their thermodynamic stability when in contact with Si. In this article, properties of HfO2 fabricated with different coating methods and doped with different elements such as N, Si, Al, Ti and Ta have been compared and discussed. In the conclusion part, we have summarized the results of characterization obtained by X-ray diffraction, scanning electron microscopy, leakage current density-voltage (J-V), capacitance-voltage (C-V) and UV-vis spectroscopy of HfO2 thin films.