Design investigation for three-dimensional uniformity of the mass transport field
CVD systems require extensive engineering to produce uniform mass transport distribution across the surface of the substrate. In reactors subject to viscous flow effects, design for manufacturing any particular product involves modelling and experimentation particular to the geometrical configuration. Pulsed-Pressure CVD (PP-CVD) accomplishes both the bulk mass transport and uniform precursor concentration through critically rapid expansion of the precursor into the evacuated chamber. The PP-CVD reactor mass transport system was studied through experimental investigation and parameter modelling. A modified naphthalene sublimation technique was employed in an isothermal low pressure reactor to determine 3D flow field convective and pressure conditions. Uniformity of the mass transport field was investigated for various geometries over a wide range of steady and pulsed pressure conditions using nitrogen gas. The results define the design envelope and processing regime in which convective uniformity is achieved by domination of expansion effects over viscous effects.