In-Situ Transmission Electron Microscopy Investigation of the Interfacial Reaction between Er and SiO₂ Films

Abstract

We fabricated metal-oxide-semiconductor (MOS) devices with a high-k Er-silicate gate dielectric, and demonstrated their electrical performance. The increase in the rapid thermal annealing (RTA) temperature leads to a reduction of the equivalent oxide thickness (EOT), which is attributed in par to the thickness evolution of Er-silicate film and to the chemical bonding change from an Si-rich to an Er-rich silicate. The in-situ investigation of the interfacial reaction between the Er and SiO₂ film using a high-voltage electron microscopy (HVEM) revealed a linear relationship between the squared thickness of Er-silicate layer and in-situ annealing time, indicating that the Er-silicate growth is a diffusion-controlled process. The parabolic growth constants of the Er-silicate film were calculated to be 2.3×10⁻¹⁶ and 9.3×10⁻¹⁶ cm²/s for in-situ annealing temperatures of 350 and 450°C, respectively.