Study of natural convection in supercritical CO2 cold wall reactors: Simulations and experiments

Fluid flow patterns and temperature profiles within cold wall, high pressure supercritical fluid (SCF) reactors were investigated by simulation and experiment at conditions relevant to the deposition of copper and other metals for applications in microelectronics. Steep thermal gradients between the heated platen, the bulk fluid, and the reactor walls produce large density gradients in the supercritical fluid. Rayleigh numbers are in excess of 1 × 1010 and the flow is highly turbulent. Natural convection and buoyancy forces dominate the flow within the reactor in both the batch (closed domain) and continuous flow (open domain) configurations. The situation is unlike that in low pressure chemical vapor deposition reactors in which thermal gradients do not give rise to significant density gradients, flow is laminar, and forced convection dominates natural convection. Temperature distributions and flow patterns within cylindrical cold wall reactors containing supercritical carbon dioxide were simulated by computational fluid dynamics (CFD) and conjugate heat transfer calculations. Good agreement with experiment was achieved. The implications of the results for reactor design are discussed.