Electron avalanche injection on 10-nm dielectric films

Abstract

Uniform electron avalanche injection has been successfully performed on 10-nm SiO2 and on composite 8-nm SiO2+4-nm Si 3N4 gate dielectrics. The films were grown on boron-implanted substrates to obtain the optimum surface impurity concentration for uniform injection. The electrical properties indicated high-quality and low-defect density dielectrics with no deleterious effects introduced by the ion implantation. A voltage flat-band Vfb shift and trap analysis were performed on both structures with and without post oxidation anneal, using metal or n-polysilicon gate. The results obtained have confirmed the trends found in thicker oxides and pointed out the presence of deep water-related centers. The composite structure, SiO2+Si3N4, showed high electron trapping due to two Coulombic centers normally invoked for Poole-Frenkel conduction in Si3N4. These centers are usually undetected by high-field injection experiments.