Electrical and Bias Temperature Instability Characteristics of n-Type Field-Effect Transistors Using HfOxNyGate Dielectrics

The dielectric properties and n-type metal oxide semiconductor field-effect transistor (nMOSFET) positive bias temperature instability (PBTI) characteristics of in situ nitrogen-incorporated plasma-enhanced atomic layer deposited HfOxNygate dielectrics were compared with those of the HfO2films. Although the physical thickness of the HfOxNyand HfO2films were almost identical (∼4.1nm), the capacitance equivalent oxide thickness of HfOxNy(1.43 nm) was much lower than that of HfO2(2.28 nm), suggesting that HfOxNyhas a larger dielectric constant. However, HfOxNyshowed a higher leakage current than HfO2due to a decrease in bandgap. HfOxNyshowed a turnaround effect under a positive gate stress bias in nMOSFET. The threshold voltage (Vth)shifted to the positive direction during the first second due to the trapping of electrons at pre-existing trap sites in Hf-based gate dielectrics. Subsequently, the Vthshifted in the negative direction due to hole trapping, which originated from the generation of electron–hole pairs related to the surface plasmon. HfOxNyshowed a higher initial interface trap density but a lower interface trap generation rate during n-type MOS PBTI stress than HfO2.