The a-Si:H growth mechanism:temperature study of the SiH_3 surface reactivity and the surface silicon hydride composition during film growth

摘要

We report on two experimental studies carried out to reveal insight into the interaction of SiH_3 radicals with the a-Si:H surface as assumed essential in the a-Si:H growth mechanism.The surface reaction probability beta of SiH_3 on the a-Si:H has been investigated by spectroscopic means as a function of the substrate temperature (50-450 degC) using the time-resolved cavity ringdown technique.The silicon hydrides-SiH_x on the a-Si:H surface during deposition have been studied by the combination of in situ attenuated total reflection infrared spectroscopy and argon ion-induced desorption of surface hydrogen.For SiH_3 dominated plasma conditions,it is found that the surface reactivity of SiH_3 is independent of the substrate temperature with beta=0.30+-0.03 whereas the silicon hydride composition on the a-Si:H surface changes drastically for increasing substrate temperature (from-SiH_3 to =SiH_2 to ident to SiH).The implications of these observations for the a-Si:H growth mechanism are addressed.