Packaging of ISFETs at the Wafer Level by Photopatternable Encapsulant Resins

By applying special thick film photolithography it is possible to realize a highly automative ISFET packaging at wafer level. This is achieved using commercial UV-curable encapsulant resin formulations containing either epoxy acrylate or polyurethane acrylate oligamers together with monomers and photoinitiators. Thick polymeric layers are patterned on wafer substrate containing pH ISFET chips, and by a standard mask aligner system windows are opened over the gate region and contact pads. Best results are obtained with compositions based on epoxy acrylate oligomers. Life-time of encapsulated pH microsensor is also presented.