Effect of Nitrogen on the Physical Properties and Work Function of MoN_x Cap Layers on HfO_2 Gate Dielectrics

摘要

In this work, MoN_x films deposited by reactive sputtering are investigated as cap layers on HfO_2 gate dielectrics. A phase transition from body-centered-cubic Mo phase to face-centered-cubic (FCC) y-MO_2N phase is found with increasing nitrogen content and causes a morphology change. It is found that the crystallinity and grain size decrease when MoN_x films are subjected to phase transition. The Mo 3d core levels shift toward higher binding energy due to increments of nitrogen in the MoN_x films. The resistivity and work function are also seen to have positive dependence on the nitrogen content. The work functions extracted from the capacitance vs. voltage curves are 4.58 eV for Mo films and 5.10 eV-5.23 eV for MoN_x films on HfO_2 gate dielectrics, respectively.