Patent EP-2031659-A1 (EP)
Inventor: TRASSL ROLAND
IPC: H01L31/0224
Filed: 2007-08-30
Abstract: The method for producing a back contact (21) of a silicon-based solar cell (20), comprises applying a metallic layer (24) of the back contact on a back side of a substrate (22) in an inline-vacuum coating plant by sputtering a target or by evaporating, and applying further layers of the solar cell on a front side and/or the back side of the substrate in the inline-vacuum coating plant before or after applying the metallic layer without interruption of the vacuum. The layers are applied by coating tools. A passive layer (23) is applied before applying the metallic layer. The method for producing a back contact (21) of a silicon-based solar cell (20), comprises applying a metallic layer (24) of the back contact on a back side of a substrate (22) in an inline-vacuum coating plant by sputtering a target or by evaporating, and applying further layers of the solar cell on a front side and/or the back side of the substrate in the inline-vacuum coating plant before or after applying the metallic layer without interruption of the vacuum. The layers are applied by coating tools. A passive layer (23) is applied before applying the metallic layer and a barrier layer is applied after applying the metallic layer. The coating tools for applying the layers on the back side of the substrate are oppositely arranged to the coating tools for applying the layers on the front side of the substrate in relation to the alignment of the vacuum coating plant. The substrate lies on a punctiform support of a carrier to avoid a shadowing of the substrate by the carrier. The substrate is moved past at the coating tools in a horizontal alignment, so that the coating direction vertically runs. The metallic layer is separated with a thickness of 2 mu m. After applying the metallic layer, the metallic layer is partially melted with the substrate by an intensive laser beam for contacting the metallic layer on the back side of the substrate, so that a laser-fired contact (LFC) forms itself. A solderable layer (25) is applied after applying the metallic layer and/or the barrier layer. Two layers are applied in a vacuum treatment chamber. The layer is applied on the front side during applying the layer on the back side. Several substrates are arranged in a common carrier and simultaneously provided with the layers. Two coating tools in the vacuum treatment chamber are provided in a common plug-in unit in drawer-like manner. A first coating tool points on the front side and a second coating tool points on the back side. One of the layers of metallic layer, barrier layer and solderable layer is evaporated. The corresponding materials are supplied as filament to an evaporator through vacuum execution. The corresponding materials in two subsequent vacuum treatment chamber are evaporatable in a first- and a second evaporator, are evaporated so long in the first evaporator up to the material is introduced in the first evaporator, and then the materials are evaporated in the another vacuum treatment chamber with the second evaporator without interrupting the evaporation when the material is introduced in the first evaporator, where the first evaporator is waited. One of the layers is sputtered with a rotatable cathode in a direct current sputtering process for metallic layers or dielectric layers of ceramic sputtering targets or by reactive medium frequency sputtering for dielectric layers of metallic sputtering targets. The number of cathodes in depending of the sputtering yield of the cathodes is chosen to obtain a thickness of the layer and throughput of the vacuum treatment plant.