EFFECTS OF BACKGROUND GAS-PLUME INTERACTION IN THE DEPOSITION OF SINXFILMS

SiNx overlayers have been grown on quartz and single-crystal Si substr ates at room temperature by ablating a Si3N4 sintered target in a vacu um environment and different gas atmospheres, N-2 and Ar. The film gro wth was controlled by real time ellipsometry at a fixed photon-energy, 2.5 eV. Once the deposition process is completed, in situ spectro-ell ipsometric 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 co mposition: a mixture of non-crystalline Si3N4, polycrystalline Si, p-S i, and amorphous Si, alpha-Si. The film crystallinity is confirmed by TEM. The volume fraction of the film components is determined from ell ipsometry. The ellipsometric results are complemented by in situ chara cterization of the film by XPS. The film stoichiometry was found to de pend on the gas pressure. In fact, the ideal stoichiometry, x = 4/3, w as achieved at a critical pressure, a value which depended on the kind of gas used during deposition. (C) 1998 Elsevier Science B.V.