Gadolinium scandate thin films as an alternative gate dielectric prepared by electron beam evaporation

Abstract

Gadolinium scandate thin films deposited on silicon substrates using electron beam evaporation were investigated. Measurements with Rutherford backscattering spectrometry, high temperature x-ray diffraction, x-ray reflectometry, transmission electron microscopy, and atomic force microscopy were performed. A stoichiometric transfer of material from the source to the substrate in high vacuum could be demonstrated. Homogeneous, amorphous, and smooth films ͑root mean square surface roughness Ͻ1 Å͒ stable up to 1000°C were obtained. Electrical characterization of capacitor stacks revealed a dielectric constant of Ϸ23, C-V curves with small hysteresises and low leakage current densities ͑770 A/cm 2 for a capacitance equivalent thickness of 1.5 nm͒.

Amorphous lanthanum lutetium oxide thin films as an alternative high-κ gate dielectric

“…From the slope of the linear fit, it is possible to calculate the dielectric constant ͑ ͒ of the films excluding the contribution of a lower-interfacial layer. The value obtained for the LaLuO 3 films is Ϸ32, which is higher than those obtained for other amorphous rare earth oxide films 4,5 and amorphous HfO 2 films 13 exhibiting = 22-23. The intersection between the CET axis and the linear fit at 2.6 nm indicates the existence of a lower-interfacial layer between the LaLuO 3 film and the Si substrate.…”

“…The electrical characterization reveals good C-V behavior, a low leakage current density, and a value of about 32, which is larger than those previously determined for other alternative high-amorphous oxides ͑ =22-23͒. 4,5,13,14 One of the authors ͑J.M.J.L.͒ gratefully acknowledges the Alexander von Humboldt Foundation for a research fellowship. The authors thank P. Meuffels for postannealing the target material.…”

“…As shown by Schlom and Haeni, 3 single crystals of these oxides show values of 20-35 which were also observed for amorphous LaScO 3 , GdScO 3 , and DyScO 3 films deposited on silicon ͑ =22-23͒. 4,5 In addition, these materials fulfill the requirements for large optical band gaps ͑5.6 eV͒ and band offsets ͑2 -2.5 eV͒, 6 while their amorphous phase is stable up to 1000°C ͑for GdScO 3 and DyScO 3 ͒. 4,5 Lanthanum lutetium oxide ͑LaLuO 3 ͒, as a member of this class of ternary oxides, is predicted to have similar properties.…”

“…4,5 In addition, these materials fulfill the requirements for large optical band gaps ͑5.6 eV͒ and band offsets ͑2 -2.5 eV͒, 6 while their amorphous phase is stable up to 1000°C ͑for GdScO 3 and DyScO 3 ͒. 4,5 Lanthanum lutetium oxide ͑LaLuO 3 ͒, as a member of this class of ternary oxides, is predicted to have similar properties. 3,7 Experimental data related to high-gate applications of amorphous LaLuO 3 films are, however, still not available.…”

SmScO 3 thin films as an alternative gate dielectric

“…7,8 In contrast, rare earth ͑RE͒ scandates ͑REScO 3 , RE=Gd, Dy, La͒ show higher and, therefore, have attracted significant attention for high-applications. [9][10][11][12][13] The amorphous RE scandates have between 20 and 30 and the crystalline phases have over 30. 12 Christen et al observed band gaps higher than 5.5 eV for these REScO 3 oxides and varying crystallization temperatures depending on the RE atomic number and the Goldschmidt tolerance factor.…”