Analysis of LPCVD oxides for the passivation of high efficiency silicon solar cells
LPCVD (Low Pressure Chemical Vapour Deposition) oxides have the potential to be used as doping source and passivation layer and at the same time can reduce thermal Stress to the material. The evolution of passivation quality and homogeneity with different process steps is investigated using Modulated Free-Carrier Absorption (MFCA) lifetime topography. A good correlation between the surface recombination velocities and the underlying oxide characteristics is observed. Field effect passivation by fixed oxide charges is the dominant mechanism. Although a light induced degradation of the passivation quality on the test wafers was observed, a suitable implementation in the solar cell process leads to stable solar cells with 19.4 % efficiency processed completely with LPCVD oxides.