Oxidation enhanced diffusion during the growth of ultrathin oxides

Abstract

Boron-doped marker layers grown by chemical vapor deposition were used to measure oxidation enhanced diffusion (OED) during the growth of ultrathin oxide layers of 3.3 nm. The oxides were grown by three different methods: steam oxidation at 650°C, dry furnace oxidation at 800°C and rapid thermal oxidation at 1050°C. The effective B diffusion length decreases drastically with oxidation temperature, being lower than ∼3 nm for steam oxidation. This demonstrates that steam oxidation is ideally suited for minimizing dopant diffusion during the growth of gate oxides in advanced CMOS processing. Diffusion analysis shows that the enhancement in the equilibrium diffusivity increases from a factor of ∼3 at 1050°C to ∼350 at 650°C. On the basis of these measurements, parameters in a state-of-the-art OED model have been calibrated to enable accurate process modeling of OED in the regime of thin oxide growth.