Drastic improvement of as-sputtered silicon nitride thin film quality at room temperature by ArF excimer-laser annealing method

Abstract

Hydrogen-free silicon-nitride films have been deposited on 1200 Å-thick Si (100) wafers by using reactive sputtering at room temperature and annealed by ArF excimer-laser at room temperature. In-situ X-ray photoelectron spectroscopy (XPS) analyses showed that the 1200 Å-thick as-sputtered films were completely and uniformly annealed by ArF excimer-laser with the various energy densities leaving no unannealed portion in the depth direction. An as-sputtered film was also annealed in furnace at 1 000 °C for comparison. The influence of the energy density was further investigated by comparing the etch rate of the SiN film with the N/Si ratio adjusted by separating the unreacted-Si and N components from the SiN film. For the excimer-laser-annealed SiN films, the results of quantitative XPS analysis were in good agreement with the etching characteristics.The as-sputtered SiN film contained slightly higher Si than the stoichiometric ratio, with an adjusted-N/Si-ratio value 0.902, possibly due to sporadic presence unreacted-Si. At the laser energy densities ranging from 100 to 175 mJ/cm2, the excimer-laser-annealed SiN films displayed a much better film quality than the SiN film annealed at 1000 °C, due to a higher N/Si ratio.