Formation of W/HfO2/Si gate structures using in situ magnetron sputtering and rapid thermal annealing

The W(150 nm)/HfO₂(5 nm)/Si(100) structures prepared in a single vacuum cycle by rf magnetron sputtering were subjected to rapid thermal annealing in argon. It is found that at an annealing temperature of 950°C, the tungsten oxide WO _x phase and the hafnium silicate HfSi _x O _y phase grow at the W/HfO₂ and HfO₂/Si(100) interfaces, respectively. Herewith, the total thickness of the oxide layeris 30% larger than that of the initial HfO₂ film. In addition, a decrease in the specific capacitance in accumulation C _max and in the dielectric constant k (from 27 to 23) is observed. At an annealing temperature of 980°C, intensive interaction between tungsten and HfO₂ takes place, causing the formation of a compositionally inhomogeneous Hf _x Si _y W _z O oxide layer and further decrease in C _max. It is shown that a considerable reduction in the leakage currents occurs in the W/HfO₂/X/Si(100) structures, where X is a nitride barrier layer.