Qualification of encapsulation materials for module-level-processing

Module-level-processing applies cell processing and/or cell interconnection processes while the silicon wafers are attached to a sub- or superstrate, such as the module glass. This thin-film/wafer-hybrid- silicon (HySi) approach offers unique possibilities when using ultra-thin silicon wafers that can hardly be processed free-standing. Liquid adhesives are one option for attaching the wafers to the module glass. Here, we analyze the compatibility of a selection of adhesives with module-level processing. The adhesives have to be stable during wet chemical steps and during thermal treatments. A further requirement is that outgassing from the adhesives should be sufficiently low to allow efficient surface passivation by e.g. plasma enhanced chemical vapor deposition. The adhesives have to withstand UV-irradiation and thermal exposure in order to fulfill warranty requirements. In this work we develop and apply tests for the screening of adhesives. We find that certain liquid addition-curing 2-part silicones pass all the tests and are thus attractive candidates for module-level-processing.