Large area deposition of a-Si PV modules

Large-area deposition scaling-up (from 30×30 to 50×60 and 60×100 m²) is reported within the context of PV (photovoltaic) industrial development. Production-oriented deposition machine specifications are described, and the various technical solutions are discussed. The selected solutions such as plasma box and plasma etching were investigated in full-scale experiments, and illustrative results are presented. An NF₃ etching process was developed and optimized in order to match the maintenance requirements of the production machines. Thanks to this cleaning process, a very low point defect density is demonstrated (>1/ft² ). The thickness uniformity is shown to be better than ±5%. Material quality is also uniform, which is demonstrated by a mapping of the microcrystalline transition. The plasma box concept is shown to reach very low impurity contamination levels in a classical vacuum machine, comparable to what is obtained in ultrahigh-vacuum technology