Structural and electrical properties of Nb/NbNx gates on HfO2 gate dielectrics

This study demonstrates that the nitrogen content of NbNx (0 ≤ x ≤ 0.45) films influences material and electrical properties of Nb/NbNx gate electrodes. With the increase in nitrogen content of NbNx films, the crystal phase changes from body-centered cubic Nb phase to cubic δ-NbN phase, accompanied by an apparent morphological change. The crystallinity of NbNx films decreases and the resistivity increases as the N2 partial flow rate increases. The effective work function of Nb/NbNx gate stacks ranges from 3.83 to 4.17 eV for NbNx films deposited at various N2 partial flow rates.