High-rate deposition of high-pure silicon thin films for PV-Absorber layers by crucible-free electron beam physical vapor deposition

In photovoltaics (PV) and microelectronics, there is an ongoing need for fabrication of silicon thin films with excellent material properties and with minimum production cost at the same time. To overcome fabrication gaps we present reached results for depositing silicon thin films by crucible-free electron beam physical vapor deposition (EB-PVD) and for plasma pretreatment of the substrates. The crucible-free EB-PVD process could be improved regarding critical aspects, e.g. occurrence of ingot cracks during heating up of monocrystalline Si evaporation material and spill out of the Si melt on the melting pool edges. Deposition rates above 500 nm/s, corresponding to 30 mm/min, have been reached. Relating heat fluxes will be presented and discussed. By using a double ingot arrangement and superposing vapor from multiple sources the relative deviation of layer thickness could be reduced to < ±5% on a substrate width of 200 mm.