Model to predict gate tunneling current of plasma oxynitrides

Two key parameters for silicon MOSFET scaling, equivalent oxide thickness (EOT) and gate leakage current density (J_g) are measured and modeled for silicon oxynitride (Si-O-N) gate dielectrics formed by plasma nitridation of SiO₂. It is found that n-MOSFET inversion J_g is larger than p-MOSFET inversion J_g when the gate dielectric consists of less than 27% nitrogen atoms, indicating substrate injection of electrons is dominant for this range of plasma nitrided Si-O-N. To examine the intrinsic scaling of Si-O-N, we model EOT and n-MOSFET J_g for sub-2-nm physically thick gate dielectrics as a function of film physical thickness and nitrogen content. The model has four free fitting parameters and unlike existing models does not assume a priori the values of the oxide and nitride dielectric constant, barrier height, or effective mass. It indicates that at a given EOT, leakage current of n-MOSFETs with Si-O-N gate dielectrics reaches a minimum at a specific nitrogen content. Through the use of this model, we find that plasma nitrided Si-O-N can meet the 65-nm International Technology Roadmap for Semiconductors specifications for J_g, and we estimate the nitrogen concentration required for each node and application.