Numerical analysis of p~+ emitters passivated by a PECVD AlO_x/SiN_x stack

摘要

Evaluation of the level of surface passivation at highly doped crystalline silicon (c-Si) surfaces is not trivial, particularly when the surfaces are textured. In this work we present an advanced numerical analysis that can be used to evaluate the level of surface passivation at both planar and textured samples. First, using Sentaurus TCAD, we compare two widely used extraction methods of the emitter saturation current density J_(0e), the general definition and Kane & Swanson's method. Experimentally determined doping profiles on planar wafers are used to calibrate two-dimensional process simulations. Process simulations are subsequently used to calculate p~+ emitter doping profiles for textured wafers, which are required to simulate J_(0e). Additionally, while matching simulated and experimentally measured J_(0e) values, we find that a high density of negative fixed charge in a plasma enhanced chemical vapour deposited AlO_x/SiN_x stack has a significant impact on surface recombination at the surface. Furthermore, we compare J_(0e) values from textured and planar wafers and confirm that the difference from the expected geometrical factor can be attributed to surface recombination. Finally, by considering surface charges, we find that the electron surface recombination velocity parameter S_(n0) is around 1x10~4 cm/s for all p~+ emitters studied in this work.