Temperature homogeneity of polysilicon rods in a Siemens reactor

Siemens process productivity can be limited by non-homogeneous temperature profile in polysilicon rods. To overcome this limitation high-frequency current sources have been proposed. An analysis is presented which, based on electromagnetic and heat transfer theory, studies temperature and current density profiles within the rods. Two linked differential equations have been numerically solved by use of non-linear methods. The solution of these equations shows that by means of an increase in current frequency, skin effect takes place, heat generation in the inner part of the rod is decreased and therefore temperature homogeneity increases. The effect of the reflectivity of reactor walls is also analysed and reveals that temperature homogeneity can be improved by minimizing radiation losses better than by heating with high-frequency current sources.