Mechanisms involved in the formation of phosphosilicate glass from a phosphoric acid dopant source

This study focused on how the formation of phosphosilicate glass (PSG) film affects the solar cell emitter profile when using an inline ultrasonic mist phosphoric acid source and an inline diffusion furnace. This investigation used a novel approach, whereby the samples were extracted from the inline furnace mid‐process that allowed for the investigation of incompletely formed PSGs. All experimentation was conducted at BP Solar Australia. Total Gravimetric Analysis found that the dilute phosphoric acid dehydrates to form a high concentration phosphoric acid layer on the top surface. X‐ray photoelectron spectroscopy then showed this top surface reacts with the silicon and is reduced to form silicon phosphide. ECV results then demonstrated that the sheet resistance and emitter surface concentration of phosphorus is dependent upon the ratio of phosphide to total phosphorus in the PSG film. Copyright © 2010 John Wiley & Sons, Ltd. This study utilised a novel approach to analyse how the formation of the phosphosilicate glass affects the solar cell emitter profile. The approach consisted of samples being extracted from the in line furnace mid process allowing the investigation of incompletely formed phosphosilicate glass films. Extensive characterisation showed that the sheet resistance and emitter surface concentration of phosphorus is dependent on the ratio of phosphide to total phosphorus in the phosphosilicate glass film.