Effects of background gas–plume interaction in the deposition of SiN x films

Abstract

SiN x overlayers have been grown on quartz and single-crystal Si substrates at room temperature by ablating a Si 3N 4 sintered target in a vacuum environment and different gas atmospheres, N 2 and Ar. The film growth was controlled by real time ellipsometry at a fixed photon-energy, 2.5 eV. Once the deposition process is completed, in situ spectro-ellipsometric measurements were obtained in the 1.5 to 5 eV photon-energy range. The best curve fitting of the data is used to find the film composition: a mixture of non-crystalline Si 3N 4, polycrystalline Si, p-Si, and amorphous Si, α-Si. The film crystallinity is confirmed by TEM. The volume fraction of the film components is determined from ellipsometry. The ellipsometric results are complemented by in situ characterization of the film by XPS. The film stoichiometry was found to depend on the gas pressure. In fact, the ideal stoichiometry, x=4/3, was achieved at a critical pressure, a value which depended on the kind of gas used during deposition.