Effect of rapid thermal annealing temperature on the formation of CoSi studied by x-ray photoelectron spectroscopy and micro-Raman spectroscopy

The effect of rapid thermal annealing (RTA) temperature on the formation of the cobalt silicide (CoSi) was investigated using x-ray photoelectron spectroscopy (XPS) and micro Raman spectroscopy. With 125 Å of Co deposited on single-crystalline Si wafers and capped by a Ti thin film, the wafers were rapid thermal annealed at 450, 460, 470, 480, and 490 °C. These wafers were then stripped with a sulfuric acid peroxide mixture treatment. XPS was used to determine the chemical composition of the CoSi thin films, and the Co Auger parameter was continuously monitored along with ion sputtering to provide a chemical-state depth profile. Micro-Raman spectroscopy was used as a nondestructive method to characterize the film thickness and uniformity of the CoSi thin films on Si wafers. The Raman shifts at 204 and 220 cm−1 due to CoSi and the Raman shift at 150 cm−1 due to Co2Si are reported. The product αd (α is the absorption coefficient, d is the film thickness), which indicates the CoSi film thickness, was calculated from the Si excitation wavelength of 520 cm1. The behavior of the calculated αd as a function of the RTA temperature confirms the XPS result.