low pressure chemical vapor deposition (LPCVD) silicon oxynitride (SiON) films of various compositions between SiO{sub}2 and Si{sub}3N{sub}4 were grown by changing the relative ratio (Ro) of nitrous oxide (N{sub}2O) to silane (SiH{sub}4) pressures while keeping constant the ammonia (NH{sub}4) pressure. The SiON films were deposited at 700 °C on p-type silicon substrates (with a carrier concentration of 10{sup}15 cm{sup}(-3)), varying Ro from 0.32 to 1.38. Some samples were subsequently annealed at 700 °C for times up to 150 min, whereas other samples were annealed at 1000 °C for times up to 60 min in nitrogen. In this work, we present results of the effect of Ro upon the refractive index, the infrared spectrum, and the growth rate of the LPCVD SiON layers. In particular, we show that as Ro increases, the refractive index decreases from values very close to those of SiN to values very close to those of SiO{sub}2. In addition, the infrared spectrum shows that the peak associated to the SiO stretching vibration mode decreases as compared to the Si-N stretching local mode when Ro increases. The annealing processes seem not to modify the films as thickness and refractive Index remain constant as a function of the annealing time.
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