Surface Interactions of NH2 Radicals in NH3 Plasmas

Abstract

Using the imaging of radicals interacting with surfaces (IRIS) technique, the scattering of NH2 on a variety of substrates has been measured during NH3, NH3/H2, and NH3/SiH4 plasma processing. In most cases, NH2 surface scattering 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 signal. We have also measured velocity distributions and translational temperatures for NH2 radicals scattering from 300 K substrates. Monte Carlo simulation methods were used to model spatially and temporally resolved profiles of scattered molecules. The model assumes an initial Gaussian distribution for radicals across the laser beam and calculates time-dependent changes in the profiles using Maxwell−Boltzmann distributions. For NH2 radicals scattering from a 300 K Si substrate, the translational temperature, ϑTsc, is 400 ± 30 K, significantly higher than the subs...