During Czochralski growth of silicon, the furnace is continuosly purged with low pressure argon flow. The gas flow carries away volatile silicon monoxide, which is created as the reactive silicon melt slowly dissolves the silica crucible, and other impurities.
A model for the heat transfer without convection in Czochralski growth is improved here by adding the argon gas flow and heat transfer by convection and conduction within it. The gas flow is compressible, and the equation of state for argon is the perfect gas equation. The model geometry is axisymmetric. The transport equations are time-independent.
Subsequently, the advection-diffusion equation for silicon monoxide in argon is solved. There is a given source of silicon monixide on the melt surface. Argon flows into the geometry from the top, and the outflow is at the bottom of the geometry. Silicon monoxide is advected downstream, but also diffused in all directions. A baffle is included in the model geometry above the heater to guide the impurities more effectively down.
The figures show the global temperature distribution, the argon absolute velocity and the silicon monoxide absolute concentration.