Micro-deformation of flexible substrate for electronic devices during handling prior to lithography patterning
The dimensional stability of poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) foils during the handling and production process, is crucial for the quality of the final multilayer flexible electronic devices. The foil-on-carrier (FOC)  foil/adhesive/Si-wafer sandwich  is a handling method, which is currently used to temporary attach the foil to a Si-wafer carrier during the lithography processing. This handling method ensures good surface flatness of the foils during the processing. However this technique has two drawbacks: (1) it creates an in-plane micro-deformation of the PEN foil and (2) bending of FOC due to the lamination procedure and lithography processing. In this article the temperature dependence of in-plane foil deformation and bending of FOC was reported and the final curing step of lamination procedure was identified as the main source of in-plane deformation and bending. Finally the resultant stresses introduced to FOC by the curing step derived from the experimental measurements were compared to stress values calculated from the Stoneys and Ohrings equations.
flexible electronics bending thermal expansion