(604b) Atomic Layer Deposition and Characterization of ErxTi1-XOy Films

High dielectric constant (k) materials with superb scalability and negligible leakage current are attractive for use in future nanoelectronic devices, especially in sub-45 nm metal oxide semiconductor field effect transistor (MOSFET) and dynamic random access memories (DRAM). So far, a variety of high-k candidate dielectrics, including La₂O₃, Y₂O₃, ZrO₂, HfO₂ and TiO₂, have been investigated for the replacement of traditional SiO₂ (k=3.9). From all these materials, TiO₂ is of great importance in terms of its high dielectric constant which is 80 or higher; however, issues such as small conduction band offset to Si (1.0 eV) and instability on Si substrate lead to more leakage current and limit the use of TiO₂ for MOS application.

In past years, much attention has been devoted to heterogeneous materials in order to modify film properties and overcome the drawbacks of TiO₂ dielectrics. Among these composite films, lanthanide doped TiO₂ films exhibit excellent electrical and chemical properties such as high dielectric constant, low leakage current and good stability on Si. A challenge in the implementation of Ln dopped TiO₂ dielectric thin films is the development of suitable route for thin film growth; few techniques, such as e-beam evaporation, reactive rf puttering and magnetron sputtering, have been used to deposit these materials. Compared to these techniques, atomic layer deposition (ALD) has been identified as a preferred means of fabricating nanoscale features in semiconductor industry, because it offers distinct advantages and meets the challenge requirements, such as precise thickness control at the required dimensions within transistors and conformal coverage in the deep trenches of DRAM.

In this work, we report on the co-ALD of TiO₂ and Er₂O₃ to grow Er_xTi_1-xO_y thin films on silicon substrates with tunable amounts of Er and Ti; different ligand precursors are used in the deposition of these films, i.e., (CpMe)₃Er and TDEAT. The composite films are analyzed, characterized and discussed in terms of structure and surface morphology as a function of composition in order to evaluate the influence of Er composition on the properties of the resulting Er_xTi_1-xO_y films. Also, post-deposition high temperature annealing of the resulting films is studied and its effects on the properties and performance of the Er_xTi_1-xO_y thin films are presented.