Effect of film composition of nitrogen incorporated hafnium aluminate (HfAlON) gate dielectric on structural transformation and electrical properties through high-temperature annealing

We investigated the effect of nitrogen on the structural and electrical properties of nitrogen incorporated hafnium aluminate (HfAlON) gate dielectrics through high-temperature annealing. It was found that 30 at.% nitrogen substantially suppresses HfO2 segregation after the annealing. An amorphous HfAlON film with a k-value of 17 after 1000degreesC appeared at the composition of Hf ratio = 35% and N = 32 at.%, accompanied by improved boron blocking from the p(+)poly-Si gate. At an Hf ratio higher than 47%, however, cubic-HfN crystals emerged from HfAlON after the annealing. The cubic-HfN significantly increased gate leakage current through the film. We conclude that the applicability of HfAlON gate dielectric to the further scaling down of LSIs is inherently limited by metallic HfN formation at high process temperatures.