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High-quality surface and bulk passivation of crystalline silicon solar cells has been obtained under optimum anti-reflection coating properties by silicon nitride (aSiN x :H) deposited at very high deposition rates of $ 5 nm/s. These a-SiN x :H films were deposited using the expanding thermal plasma (ETP) technology under regular processing conditions in an inline industrial-type reactor with a nominal throughput of 960 solar cells/hour. The low surface recombination velocities (50-70 cm/s) were obtained on p-type silicon substrates (8Á4 cm resistivity) for as-deposited and annealed films within the broad refractive index range of 1Á9-2Á4, which covers the optimum bulk passivation and anti-reflection coating performance reached at a refractive index of $ 2Á1.

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Expanding thermal plasma (ETP) deposited silicon nitride (SiN) with optical properties suited for the use as antireflection coating (ARC) on silicon solar cells has been used as passivation layer on textured monocrystalline silicon wafers. The surface passivation behavior of these high-rate (>5 nm/s) deposited SiN films has been investigated for single layer passivation schemes and for thermal SiO 2 /SiN stack systems before and after a thermal treatment that is normally used for contact-firing. It is shown that as-deposited ETP SiN used as a single passivation layer almost matches the performance of a thermal oxide. Furthermore, the SiN passivation behavior improves after a contact-firing step, while the thermal oxide passivation degrades which makes ETP SiN a better alternative for single passivation layer schemes in combination with a contact-firing step. Moreover, using the ETP SiN as a part of a thermal SiO 2 /SiN stack proves to be the best alternative by realizing very low dark saturation current densities of <20 fA/cm 2 on textured solar-grade FZ silicon wafers and this is further improved to <10 fA/cm 2 after the anneal step. Optical and electrical film characterizations have also been carried out on these SiN layers in order to study the behavior of the SiN before and after the thermal treatment.