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 WOx phase and the hafnium silicate HfSixOy 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 Cmax 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 HfxSiyWzO oxide layer and further decrease in Cmax. 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.