ION-BEAM-ASSISTED DEPOSITION OF HYDROGENATED AMORPHOUS-SILICON NITRIDE

Hydrogenated silicon nitride films were produced near room temperature by electron beam evaporation of Si and simultaneous bombardment with a 500 eV ammonia ion beam from a Kaufman ion source and for a variety of ratios of incident charge to evaporant fluxes. The composition of N, Si and H in the films as a function of ion current density was measured by means of Rutherford backscattering and elastic recoil detection analyses. Reflection and transmission spectroscopy in the wavelength range 400 nm to 3125 nm were employed to measure optical thickness and refractive index. From the data we extracted the number of nitrogen atoms in the ammonia beam per unit charge collected, the sputtering coefficient for ammonia incident on Si, and the refractive index versus composition of the alloys. At the highest N composition, the films were clear in the visible with the UV cut-off less than 400 nm, the index was 1.80 which is lower than that of pure Si3N4 and the H content was as high as 27 at.%.