Thermal stability of hafnium and hafnium nitride gates on HfO 2 gate dielectrics

Abstract

The dependence of the material and electrical properties of HfN x films on the nitrogen flow ratio has been investigated in this work. After annealing at 400 °C in the forming gas, the sputtered Hf thin film oxidizes, but the composition of the sputtered HfN 1.0 and HfN 1.3 thin films remains unchanged. In the case of the Hf/HfO 2/Si structure, it is found that (1) oxygen diffuses from the film surface to the silicon substrate, and (2) oxygen is incorporated into the bulk of the Hf film by reduction of the underlying HfO 2 film, after annealing at 400 °C. The results suggest that HfN 1.3 is a poorer oxygen diffusion barrier than HfN 1.0, and reveal that HfN 1.0/HfO 2/Si MOS capacitors possess better thermal stability than Hf/HfO 2/Si and HfN 1.3/HfO 2/Si capacitors.