Thermal stability and diffusion in gadolinium silicate gate dielectric films

Abstract

Gadolinium silicate films on Si(100) annealed in oxygen and vacuum at temperatures up to 800 °C were analyzed by Rutherford backscattering and narrow resonance nuclear profiling. Oxygen diffused into the film eliminating oxygen vacancies, but Si diffusion, previously observed in Al and Y oxides and in La and Zr silicate films, was absent. Higher-temperature annealing in oxygen resulted in the formation of an interfacial layer observable in high-resolution electron micrographs. Gd0.23Si0.14O0.63 films crystallize at temperatures between 1000 and 1050 °C. These observations combined with recent electrical measurements show that gadolinium silicate films may be a good candidate for the replacement of SiO2 in deep submicron metal–oxide–semiconductor gates.