Particle contamination in low pressure organometallic chemical vapor deposition reactors: Methods of particle detection and causes of particle formation using a liquid alane (AIH₃) precursor

Two methods of analyzing particles were interfaced to a low pressure chemical vapor deposition reactor used to deposit A1 films from the liquid precursor dimethylethylamine alane. A laser light scattering particle counter was used to monitor particles (200 nm) in real time and established that the appearance of particles corresponded to the flow of precursor into the reactor. A particle impaction system was used to collect particles (20 nm) for analysis using analytical transmission electron microscopy and electron diffraction. Typical sizes of the A1 particles were in the range 20–1000 nm. Purposely introducing trace amounts of H₂0, CO, and 0₂ into the reactor during the flow of the precursor caused an increase in the number of particles. Our results suggested that A1 particle formation was induced by impurities in the gas phase (particularly H₂0) although competing mechanisms could not be ruled out.