Roles of nitrogen incorporation in HfAlOx(N) gate dielectrics for suppression of boron penetration

Abstract

We have investigated impacts of nitrogen incorporation into HfAlOx films on the gate leakage currents and the flat band voltage VFB shifts. Also, a role of O–Hf–N bonding states in HfAlOx(N) in suppression of boron penetration is discussed. The nitrogen concentration CN in HfAlOx(N) was controlled by changing the NH3 annealing temperature at the step of the layer-by-layer deposition and annealing process as well as the O2 annealing temperature of post-deposition annealing. The CN over 10 at. % in HfAlOx(N) films effectively suppressed boron penetration as revealed by very slow diffusion in Hf3N4 films and the formation of boron-nitrogen remote complex in HfOx(N), preserved the amorphous structure and reduced the VFB shift compared to the case of HfAlOx without nitrogen incorporation, while CN exceeding 13 at. % led to a significant increase of the gate leakage current. This suggests the excess O–Hf–N bond formation enhanced the leakage current.