Investigation of passivation properties of thermal Al2O3 and SiNx stack layers deposited on solar grade p-type CZ Si wafers

The passivation layer of Al₂O₃ on the p-type CZ silicon wafers were carried out using a thermal ALD (atomic layer deposition), with the objective of realizing an industrial version of the PERL (passivated emitter, rear locally diffused) cells. The experiments were performed on bare wafers and device-like structures which have a textured front surface, phosphorus doped emitter, and antireflection coating layer. Different lifetime characteristics were shown with surface state depending on Al₂O₃ and SiN_x deposition. In the case of Al₂O₃/SiN_x stacked layers on bare wafer, measured maximum minority carrier lifetime and implied voltage were 600 μs and 750mV, respectively. Maximum minority carrier lifetime and implied voltage for emitter sheet resistance of 100Ω/sq are 109 μs and 679mV before patterning and 88 μs and 673mV after patterning, respectively.