4H-SiC MIS structures using oxidized Ta 2 Si as high-k dielectric A. Pérez-Tomás 1 , P. Godignon 1 , N. Mestres 2 , D. Tournier 1 , J. Montserrat 1 and J. Millán 1 1 Centre Nacional de Microelectrònica (CNM-CSIC) Campus UAB, 08193, Bellaterra, Barcelona, Spain 2 Institut de ciència de materials (ICMAB-CSIC) Campus UAB, 08193, Bellaterra, Barcelona, Spain ABSTRACT Ta 2 Si silicide has been deposited by sputtering and thermally oxidized on 4H-SiC and Si substrates. A mixture of SiO 2 and Ta 2 O 5 insulator films has been obtained after oxidation in dry O 2 . Among the high-k dielectrics, tantalum pentoxide (Ta 2 O 5 ) could be a valuable alternative due to its high dielectric constant. Atomic force microscopy (AFM), C-V measurements along with x-ray diffraction analysis have been carried out in order to study the feasibility of this material as gate dielectric for 4H-SiC MOS devices. Electrical characteristics of deposited and oxidized Ta 2 Si on 4H-SiC and Si samples have been obtained and compared. At the range of oxidation temperatures considered (850 o C-950 o C), the influence of diffusion processes between the Si substrate and Ta 2 Si layer during oxidation strongly influences the dielectric properties of the resulting insulator layer on Si substrates. INTRODUCTION Silicon carbide is a promising material for power electronics because of its wide band gap and high breakdown field, saturation drift velocity, and thermal conductivity [1]. Additionally, the material is attractive because, like Si, its native oxide is SiO 2 . The use of amorphous, thermally grown SiO 2 as a gate dielectric offers several key advantages in CMOS processing, including a thermodynamic and electrical stable interface, as well as superior electrical isolation properties. However, oxides grown on SiC with high interface-state density and a large amount of fixed charges, especially for the SiO 2 /p-SiC structure, have been reported [2-3]. The development of commercial SiC metal–oxide–semiconductor field effect transistors (MOSFETs) has been impeded by the low effective carrier mobility in the MOS channel that is directly linked to interface defects that either trap or scatter carriers [4]. The use of alternative dielectrics as gate material, with a higher dielectric constant can be considered as a valuable alternative in order to enhance the channel conduction and reduce the oxide degradation due to current injection [5]. Nowadays, extensive research and development efforts to grow high-k dielectrics on semiconductors are underway. Applications include to extend the limits of transistor gate capacitance beyond that of ultrathin silicon dioxide, and to improve passivation layers and gate dielectric reliability in wide band gap semiconductor devices. In this sense, we propose the use of deposited and oxidized Ta 2 Si films on 4H-SiC substrates as dielectric in metal-insulator- semiconductor structures. Tantalum silicide (Ta 2 Si) is oxidized to form Ta 2 O 5 and SiO 2 , with a high effective dielectric constant (ε r ∼ 20). In a previous work [6], the feasibility of this insulator was demonstrated on 6H-SiC substrates. In spite of the very low inversion channel mobility, the Mat. Res. Soc. Symp. Proc. Vol. 815 © 2004 Materials Research Society J3.2.1