Probing buried interfaces on Ge-based metal gate/high-k stacks by hard X-ray photoelectron spectroscopy

• Published in: Applied surface science Vol. 257; no. 7; pp. 3007 - 3013
• Main Authors: Rubio-Zuazo, J., Martinez, E., Batude, P., Clavelier, L., Chabli, A., Castro, G.R.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.01.2011; Elsevier
• Subjects: CMOS devices; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Ge-based metal gate/high-k stacks; Germanium; Hafnium; Hafnium oxide; HAXPES; Interlayers; Nondestructive testing; Photoelectron spectroscopy; Physics; Stacks; X-rays; 85.30.De; 72.15.Lh; 73.40.Qv; HAXPES; 79.60.Jv; 79.60.−I; 73.21.Ac; CMOS devices; 85.30.−z; 71.30.+h; Ge-based metal gate/high-k stacks; Germanium; 85.30.-z; 79.60.-1; X-ray photoelectron spectra
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2010.10.108

▶ A thin Si interlayer prevents the oxidation of the substrate in Ge based metal-gate/high-k stacks. ▶ Hard X-ray photoelectron spectroscopy enables a non-destructive analysis of interfaces buried several nanometers. ▶ A Hf silicate is formed at the interface between HfO2 and SiO2. In this contribution, we present results of a non-destructive in-depth analysis of concentration of chemical components at buried interfaces on Ge-based CMOS by means of hard X-ray photoelectron spectroscopy (HAXPES) and low angle X-ray reflectivity (XRR). Two samples composed of a Ge/Si/SiO2/HfO2/TiN stack, with layer and interlayer thicknesses of 2500, 0.9, 0.5, 4.9, 3.4nm and 2500, 0.7, 1, 5.8, 3nm have been studied. The use of electrons with kinetic energies from few eV up to 15keV enables to tune the information depth being able to analyze the desired interface in a non-destructive way. XRR enables the determination of the exact layer thickness and density. The results suggest that the Si interlayer prevents the Ge oxidation. Depth profiles of the electronic structure have been obtained for both samples by following the evolution of the photoemission signal from the Hf 2p3/2 core level as a function of the photoelectron kinetic energy. The depth profile of the electronic structure reveals the presence of a chemical shift of the Hf 2p3/2 core level, which is related to an interfacial bonding state. Our results demonstrate the excellent capability of HAXPES to study buried interfaces in a non-destructive way.