טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentGeppert Irena
SubjectCharacterization of High-k Materials and their Interface
with Si and Metal
DepartmentDepartment of Materials Science and Engineering
Supervisor Professor Emeritus Moshe Eizenberg
Full Thesis textFull thesis text - English Version


Abstract

The aim of this research is to study and understand how the composition of the high-k dielectric materials affects the electrical and material properties as well as the thermal stability of metal/high-k/Si stacks. This research focuses on three systems of dielectric films. The first system is Al2O3, which is a promising candidate in memory applications, where the low leakage current is the major requirement for the charge storage. The influence of the substrate on the interface properties of the dielectric/Si stack, effect of oxide structure on the band gap and dielectric constant were studied. The second system is HfxSi1-xO2N for x=0, 0.3, 0.5, 0.7 and 1, which is suitable for gate dielectric. It was found that the addition of Si and N to HfO2 increases the crystallization temperature, the band gap and valence band offsets relative to Si, however, it decreases the dielectric constant of the Hf-based films. Therefore, an optimal composition needs to be found in order to use these oxides as gate dielectrics. During thermal treatment at 800˚C, the oxides with higher Hf content separate to amorphous SiO2 and crystalline HfO2 phases with a monoclinic structure. In addition, Pt diffuses though the Hf silicate films and SiO2 layers to the Si substrate where Pt silicide is formed in the samples. The third system is (TbxSc1-x)2O3. The rare earth oxides are also candidates for gate dielectric replacement. Isomorphic miscibility of the rare-earth oxides opens possibility to mix these oxides. An interfacial layer formation was observed at the oxide/Si interface for all compositions. The study shows that the mixing influences the band gap and dielectric constant. It also helps to reduce water absorption, but does not influence the valence band offset. It is possible to tune the properties of functional oxides for future nanoscale devices. The addition of a third element into binary oxides helps to achieve the desired properties of the alternative high-k materials, such as high dielectric constant, high band gap, suitable band offsets relative to Si, amorphous structure, low leakage current, low density of the electrical defects and compatibility with current CMOS processing.