Ultrathin zirconium silicate gate dielectrics with compositional gradation formed by self-organized reactions

Abstract

Zirconium silicate gate dielectrics with compositional gradation in depth were fabricated by in situ reoxidation of thin metal layers on oxidized Si surfaces. The silicate is composed of a trilayer structure, in which Si-rich layers are formed both at the top and the bottom of the film. The zirconium element is localized at the center of the silicate and, thus, the advantages of the silicate material can be obtained, while keeping sufficient permittivity. The compositionally graded silicates show promising electrical properties, such as a leakage current of less than 0.11 A/cm2 for an equivalent oxide thickness of 1.1 nm and an improved flatband voltage shift that is a result of postdeposition annealing and oxidation.