Structural and dielectric properties of Ru-based gate/Hf-doped Ta2O5 stacks

• Published in: Applied surface science 2011-06, Vol.257 (17), p.7876-7880
• Main Authors: PASKALEVA, A, TAPAJNA, M, DOBROCKA, E, HUSEKOVA, K, ATANASSOVA, E, FRÖHLICH, K
• Format: Article
• Language: English
• Subjects: Annealing; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Dielectric properties; Diffusion layers; Electrical properties of specific thin films; Electrical properties of specific thin films and layer structures (multilayers, superlattices, quantum wells, wires, and dots); Electrodes; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Hafnium; Physics; Secondary ion mass spectroscopy; Stacks; Structure and morphology; thickness; Structure of solids and liquids; crystallography; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Tantalum oxides; Thin film structure and morphology; X-ray diffraction and scattering; X-ray reflectometry
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2011.04.062

Hf-doped Ta2O5 thin films are studied with respect to their composition, dielectric and electrical properties. The incorporation of Hf is performed by sputtering of a 0.7nm thick Hf layer on top of Ta2O5 and subsequent annealing to stimulate diffusion of Hf into Ta2O5 and their intermixing. The elemental in-depth distribution of the films is investigated by the time of flight secondary ion mass spectroscopy (ToF-SIMS), which has revealed that Hf and Ta2O5 are intermixed throughout the whole thickness. Two sub-layers exist in all the samples - an upper homogeneous Hf-doped Ta2O5 sub-layer and a near interfacial region which is a mixture of Ta- and Si-oxides. The X-ray reflectivity (XRR) analysis shows existence of interfacial layer with a thickness of about 1.9-2nm, irrespectively of the total thickness of the stacks. Metal-oxide-Si structures with Ru and RuO2 metal electrodes have been prepared and investigated in terms of dielectric constant, effective work function (EWF) and interfacial layer parameters. The influence of post-metallization annealing steps on these parameters was also studied.