Patent ID: 8293568

Claim:
A method of forming a selective emitter in a photovoltaic crystalline silicon semiconductor wafer having front and back side surfaces, a junction between said front and back side surfaces, and an emitter between said junction and said front side surface wherein said emitter has a diffused dopant concentration profile such that said emitter has a dead zone immediately underneath said front side surface in which said diffused dopant concentration is relatively constant and a zone of decreasing dopant concentration adjacent the dead zone in which said diffused dopant concentration is decreasing, the method comprising: forming a mask on said front side surface, to create masked and unmasked areas on said front side surface; electrochemically forming a first silicon oxide layer at said unmasked areas of said front side surface such that said silicon oxide layer extends into said emitter at least as far as said dead zone; removing said mask; etching back said first silicon oxide layer until substantially all of said first silicon oxide layer is removed; and electrochemically forming a second silicon oxide layer on the front side surface after said etching back, said second silicon oxide layer having sufficient thickness to passivate said front side surface.