Uniform molecular flux in a vertical reactor with pulsed transition regime gas flow
Pulsed-CVD technology accomplishes reactant delivery by timed injection of gas into a continuously evacuated reactor. The reactor conditions produced by this method are new to CVD processing. Seminal investigations to characterize the flow dynamics and transport phenomena for pulsed-transition regime flow are reported. Non-dimensional parameters for reactor design and process control are proposed, and the theory describing molecular impingement rate as a function of these parameters is presented. An experimental, industrial-scale reactor and experimental methods, including naphthalene sublimation, have been developed to investigate the flow dynamics. Pulses of known volume and pressure N2 were delivered into the reactor at timed intervals, while monitoring the resulting reactor pressure and molecular flux field. Results demonstrate that uniform molecular flux can be achieved by Pulsed-CVD at pressures where steady flow would result in stable boundary layers, and thus non-uniform heat and mass transport fields at the substrate, and throughout the reactor.