Atomic layer controlled growth of Si₃N₄ films using sequential surface reactions

Si₃N₄ thin films were deposited with atomic layer control on Si(100) substrates using sequential surface chemical reactions. The Si₃N₄ film growth was accomplished by separating the binary reaction 3SiCl₄+4NH₃→Si₃N₄ + 12HCl into two half-reactions. Successive application of the SiCl₄ and NH₃ half-reactions in an ABAB... sequence produced Si₃N₄ deposition at substrate temperatures between 500 and 900 K and SiCl₄ and NH₃ reactant pressures of 1-10 Torr. Transmission Fourier transform infrared (FTIR) spectroscopy studies indicated that the SiC₄ and NH₃ half-reactions were complete and self-limiting at substrate temperatures ≥ 700 K. In situ spectroscopic ellipsometry monitored the Si₃N₄ film growth versus substrate temperature and reactant exposure time. The maximum Si₃N₄ deposition rate per AB cycle was 2.45 Å per AB cycle at 700 K for reactant exposures > 10¹⁰ L. The Si₃N₄ deposition rate decreased slightly in the temperature range 700-900 K. Rutherford backscattering measurements revealed an Si/N ratio of 1:1.35 as expected for stoichiometric Si₃N₄ deposition. The surface topography of the Si₃N₄ films measured with atomic force microscopy (AFM) was nearly identical to the initial Si(100) substrate indicating extremely smooth and conformal Si₃N₄ deposition.