Room Temperature Wet Chemical Growth of an Oxygen Enhanced Diffusion Oxide Utilized in a Boron Diffusion Process

Abstract

The Room Temperature Wet Chemistry Growth (RTWCG) technology is a novel technology for growing highly uniform amorphous SiOX layers into silicon substrates [1]. By growing RTWCG SiOX layers on one side of silicon substrates, the hydrophilic nature of the SiOX layer made it possible for the crystallization of boric acid, onto the silicon substrate, from an aqueous solution comprised of boric acid dissolved in dilute hydrofluoric acid solution. The crystallized boric acid layer was used as a p+ dopant source for a p+/n+ structure. A sheet resistance of 70 ohm/sq was achieved in three minutes at 1050°C, ambient air. Since the boron diffusant can be created in an inline chemical bench, this new approach will improve the efficiency of traditional solar cells in a cost effective and, very importantly, process efficient way. This method can lower the cost of producing bifacial cells, rear local-diffused (PERL) cells, front surface field-interdigitated back contact (FSF-IBC) solar cells, and other cell structures which depend on boron diffusion to create a p+ or p++ emitter layer.