Hydrogen induced dipole at the Pt/oxide interface in MOS devices. Issue 2 (28th September 2015)

• Record Type: Journal Article
• Authors: Kolomiiets, Nadiia M.; Afanas'ev, Valeri V.; Opsomer, Karl; Houssa, Michel; Stesmans, Andre
• Is Part Of: Physica status solidi. Volume 213:Issue 2(2016:Feb.)
• Page Start: 260
• Page End: 264
• Publication Date: 2015-09-28
• Subjects: dipole layers -- interfaces -- internal photoemission -- oxides -- platinum -- work function; Solid state physics -- Periodicals; Solids -- Industrial applications -- Periodicals; 530.41
• DOI: 10.1002/pssa.201532413
• Languages: English
• ISSNs: 1862-6300

Abstract

Abstract : Thanks to its good thermal stability, including resistance to oxidation, platinum (Pt) is widely used in prototyping a wide spectrum of electron devices ranging from metal‐oxide‐semiconductor (MOS) transistors to resistive switching memory cells. In this work, the energy barriers for electrons between the Fermi level of Pt and the conduction band of several oxide insulators (SiO2, Al2 O3, HfO2, Hf0.8 Al0.2 Ox, Sr0.53 Ti0.47 O3 ) were determined by using internal photoemission of electrons. By combining this barrier value with the electron affinity of the particular oxide, the effective work function (EWF) of Pt was determined for different interfaces. As studied over the reference Pt/oxide/Si stacks de‐gassed in high vacuum at 400 °C, the EWF of Pt is found to differ significantly from the accepted vacuum WF value of 5.6 eV. The EWF is equal to 5.2 eV at the Pt/Al2 O3 interface, 5.1 eV at Pt/HfO2, 5.3 eV at Pt/Hf0.8 Al0.2 Ox, 4.8 eV at Pt/SiO2, and 5.8 eV at the Pt/Sr0.53 Ti0.47 O3 interface indicating the presence of a polarization layer of which the contribution to the EWF depends on the oxide composition. Furthermore, annealing in H2 at 400 °C reduces the Pt EWF by ∼0.5 eV at all interfaces except for the Pt/Sr0.53 Ti0.47 O3 one. This observation indicates the formation of an additional H‐related dipole at the Pt/oxide interfaces and suggests that the vacuum WF of Pt cannot be used as the value relevant for the MOS properties.