Fabrication,Physical Properties And Performance Investigation Of MOS Devices With Hafnium-based High-K Gate Dielectrics

With the rapid development of microelectronics industry drived by Moore’s Law, the dimensions of devices continuely scale down. According to the principle of shrinking, the thickness of gate oxide at every technology node should be reduced, which makes the thickness of conventional SiO2 gate oxide reduce to atomic level. In this case, the gate tunneling leakage caused by quantum tunneling will dramatically increase, which will result in an immediate and nagative impact to the device. It is imperative to find novel material with higher dielectric constant to replace conventional SiO2. Through persevering investigation and research, Hf-based gate materials with high dielectric constant have a lot of superior characteristic, such as higher dielectric constant and thermodynamic stability, favorable interface quality with the substrate and internal structure, smaller leakage current and reduced frequency dispersion. There are many potential high k dielectrics, like HfO2, HfTiO, HfLaOx, HfAlOx, HfSiOx, HfON, HfTiN, HfGdO, etc. Among these candidates, TiO2-doped HfO2 gate dielectric material is one of the most worthwhile studying systems. As we know, TiO2 is a gate dielectric material which processes K value of about 80, thereby HfO2 combing TiO2 can obtain smaller equivalent oxide thickness (EOT) and reduced leakage current. In current thesis, more attention has been paied to investigate the optical, electrical and inetrfacial properties of Hf-based high-K gate dielectrics. The main experimental results and originalities of the thesis are as follows.(1) TiO2 doping concentration dependent microstructure, optical and electrical properties of the HfxTi1-xO2 gate dielectric thin films have been investigated systematically and the optimized doping TiO2 concentration has been obtained.(2) Annealing temperature dependent electrical properties of HfTiO thin films and the current-conduction mechanism of MOS capacitors have been investigated. Experimental results suggested that 400℃-annealed sample demonstrates lesser trap and defect and smaller leakage current.(3) Incorporating N into HfTiO thin films can increase the dielectric constant crystallization temperature, suppress interface layer growth and reduce the internal charge defect of HfTiO thin films. Through the analysis of the characteristics of HfTiON thin films annealed at different temperatures, the optimized N2 concentration of 5% has been obtained.(4) HfTiO-HfGdO and HfGdO-HfTiO gate stack dielectrics have been obtained by sputtering. By analysis, it can be concluded that Al/HfGdO-HfTiO/Si MOS capacitor with increase electrical performance and suppressed silicate layer growth has been decided.