High throughput in-line diffusion: emitter and cell results on thin wafers

Abstract

We present new in-line diffusion equipment, consisting of a spray system in connection with an IR lamp heated conveyor furnace, which is used on laboratory and industrial scale to apply emitters to solar cells. The spray system deposits on two sides a uniform layer of phosphorous dopant that is diffused into the silicon wafer in the IR lamp heated conveyor furnace. Uniform emitters are produced of nominal 62 and 82 Ω/sq. Sheet resistance mapping is done using the Sherescan on a larger number of wafers for the different groups. Uniform emitters are obtained with standard deviation of maximum 2.2 Ω/sq. Cells are processed using the ECN in-line 16% process with the new in-line equipment, and compared with cells produced with reference laboratory spin-on applied dopant. Results show about 0.5% increase in Voc and about 1% increase in Isc for the laboratory scale and equal results for the industrial equipment.