CHEMICAL-VAPOR-DEPOSITION SYNTHESIS AND CHARACTERIZATION OF CO-DEPOSITED SILICON-NITROGEN-BORON MATERIALS

Si-N-B films have been deposited by LPCVD from SiH4/B2H6/NH3 gas mixtu res. The influence of the temperature and the composition of the gas m ixture on the deposition process and film properties has been investig ated. At 1000 degrees C, for the highest ammonia flow rate (SiH4:B2H6: NH3, 10:25:500), a mixture of turbostratic boron nitride and silicon n itride was deposited. For decreasing ammonia flow rates the Si-N-B ter nary system was formed (1260 cm(-1) band in the infrared spectra), whi ch co-exists with the unstable turbostratic boron nitride structure. F inally, for a low NH3 flow rate of 100 seem, stable amorphous films ar e obtained. On the other hand, at 800 degrees C, stable films with a h igh content in the ternary Si-N-B compound were obtained for a wide ra nge of ammonia concentrations (100-500 sccm). At this temperature (800 degrees C), the composition of the films, as measured by Auger and ph otoelectron spectroscopies, strongly depends on the [SiH4]/[B2H6] rati o in the gas mixture. The improvement in the mechanical and chemical p roperties of the samples has been associated with the increase in the content of Si-N bonds in the Si-N-B films.