Wafer reconstruction: An alternative 3D integration process flow

Wafer reconstruction is a process of forming an integral handle-able wafer by filling the gaps between the dies after die-to-wafer assembly to allow for further processing on the landing wafer, e.g. thinning, redistribution layer deposition, and bumping. This paper examines key aspects and challenges of different wafer reconstruction process flows. Based on analytical and finite element method modeling, guidelines for material selection and structural design are generated. One selected process flow is successfully demonstrated in a typical 300 mm eWLB production environment, proving the feasibility of wafer reconstruction as a 3D integration process flow.