Surface interactions of NH2 radicals in NH3 plasmas

Using the imaging of radicals interacting with surfaces (IRIS) technique, t he scattering of NH2 on a variety of substrates has been measured during NH 3, NH3/H-2, and NH3/SiH4 plasma processing. In most cases, NH2 surface scat tering was greater than unity for 300 K substrates, suggesting that NH2 is produced through surface reactions. Removal of the charged species from the plasma molecular beam results in a significant decrease in scattered NH2 s ignal. We have also measured velocity distributions and translational tempe ratures for NH2 radicals scattering from 300 K substrates. Monte Carlo simu lation methods were used to model spatially and temporally resolved profile s of scattered molecules. The model assumes an initial Gaussian distributio n for radicals across the laser beam and calculates time-dependent changes in the profiles using Maxwell-Boltzmann distributions. For NH2 radicals sca ttering from a 300 K Si substrate, the translational temperature, Theta(Tsc ), is 400 +/- 30 K, significantly higher than the substrate temperature. Re moval of the charged species from the plasma molecular beam results in a de crease in translational temperature for scattered NH2 molecules, Theta(Tsc) = 300 +/- 30 K. This suggests ions are important in surface production of NH2 and in the translational temperature of the scattered radicals.