Abstract
Native oxides at the Si surface on the electrical properties of MOS devices are crucial problems. To study these issues, the thermal stability and electrical characteristics of MOS devices with clustered vertical furnace-grown, native oxide-free, ultrathin gate oxides and Hf x Ta y metal gates were investigated. Postmetallization annealing (PMA) was carried out to study the metal-diffusion effects. Time-of-flight secondary ion mass spectroscopy analysis results show that the diffusion depths of Hf and Ta in the gate oxide are small and stay almost constant with a PMA temperature of up to 950 °C. Compared to those with conventional horizontal furnace-grown oxides, MOS devices with advanced clustered vertical furnace-grown gate oxides show excellent electrical characteristics, such as equivalent oxide thickness, hysteresis, interface trap density, stress-induced leakage current, defect generation rate, and stress-induced flat-band voltage shift. With an increase in PMA temperature, the electrical characteristics remain almost unchanged, which, in turn, achieve the excellent thermal stability and electrical reliabilities of MOS devices with clustered vertical furnace-grown gate oxides and Hf 0.27 N 0.15 metal gates. © 2007 IEEE.