Radiative wafer heating during plasma deposition process

Abstract

Wafer heating with visible and infrared radiation is a well established method used in plasma deposition reactors used for solar cell production. A detailed study on radiative heat transfer as presented in this article gives a quantitative description by considering the spectral absorption of radiation in optical components, contamination of these components during plasma growth, the spectral emissivity of the silicon solar cell, and the effect of heat buffer components. Even with a clever implementation of heaters the net power incident on the wafer is shown to decrease to 60%. The wafer temperature ramp up time is shown to be dependent on the surface roughness and dopant level of the silicon solar cell, whereas the steady-state temperature during plasma growth is independent on these properties. Due to contamination during plasma growth, the wafer temperature decreases by 80K within one production shift, but this decrease can be minimized to 10–20K by implementing heat buffer components.