Rare-earth based alternative gate-dielectrics for future integration in MOSFETs J. M. J. Lopes, M. Roeckerath, E. Durgun Özben, R. Luptak, J. Schubert, and S. Mantl Institute for Bio- and Nanosystems (IBN1-IT) and JARA-Fundamentals of Future Information Technology, Research Center Juelich, D-52425 Juelich, Germany Due to the aggressive downscaling of MOSFETs, several dielectric materials have been extensively investigated as potential substitutes for the SiO 2 -based gate dielectric films. Although the introduction of hafnium-based dielectrics in the latest 45 nm CMOS generation has recently been announced, 1 the International Technology Roadmap for Semiconductor predicts that materials with a dielectric constant (κ) even higher than 20 will be required for coming technological nodes. 2 Rare-earth based dielectrics are promising materials for fulfilling this requirement. Amorphous thin films of scandates such as LaScO 3 and GdScO 3 , or of LaLuO 3 , offer κ values ranging from 20 to 30, large optical band gaps (>5 eV) and band offsets to silicon (2-2.5 eV), and a high thermal stability of the amorphous phase ranging from 800°C to 1000°C. These temperatures are significantly higher than that observed for HfO 2 films (~ 500°C), and comparable to those observed for ternary Hf-based dielectrics films such as HfSiO x and HfAlO x , currently the most investigated materials for replacement of the SiO 2 gate oxide. 3 In this contribution, we will review the properties of REScO 3 (RE = La, Gd, Sm) and LaLuO 3 amorphous thin films, grown on Si substrates by pulsed laser deposition (PLD), e-gun evaporation or molecular beam deposition (MBD). In addition, our recent results on the integration of these oxides in MOSFETs using a high-mobility strained-silicon on insulator (sSOI) substrate will be reported. The composition of the films was investigated by Rutherford backscattering spectrometry (not shown). Independently of the deposition technique employed, the scandates or LaLuO 3 films present a ratio between the metallic elements of about 1:1.1. Regarding the oxygen content, the correct stoichiometry could be achieved by using appropriate growth conditions. X-ray diffraction analysis reveals an amorphous structure for the films, which is confirmed by transmission electron microscopy, as illustrated in Fig. 1 for a LaLuO 3 film deposited by MBD at 500°C. Capacitance-voltage (C-V) and current-voltage (I-V) measurements reveal well-behaving C-V curves and low leakage current density levels for this class of materials. As an example, Fig. 2 shows a typical C-V curve measured at 100 kHz for a 6nm thick LaLuO 3 film, presenting an equivalent oxide thickness (EOT) of 1.4 nm. For this film, a leakage current density (not shown) of ~ 10 -3 A/cm 2 was measured at 1V gate bias (⎟V G –V FB ⎟). The D it levels are in the range of 5×10 11 eV -1 cm -2 . Similar results were measured for the scandate films. In addition, the dielectric constant of the films was determined. Figure 3 shows EOT plots for SmScO 3 films deposited by PLD and LaLuO 3 films deposited by MBD at temperatures of 450-500°C. The κ-values obtained from the slope of the linear fit are around 30. For LaScO 3 and GdScO 3 (not shown), κ lies around 23-25. These values surpass those previously determined for other amorphous alternative high-κ oxide films. 4 Fig. 1. TEM image of a 6 nm thick LaLuO 3 film deposited at 500 ° C.