Fabrication and Characteristics of Spin-on Dielectric for Multi-level Interconnect in WLP

FOWLP (fan out wafer level packaging) is one of the fastest growing technology due to a smaller form factor, a lower package profile, increased I/O density, and low package cost. With the increasing demand of FOWLP technology, heterogeneous or multilayer FOWLP technology becomes the great subject of interest. However, many challenges such as warpage, mechanical stress, thermal stability, die shift, topography, fine-pitch RDL (redistribution layer), and low k dielectric are still present. Also, FOWLP with multilayer RDLs is required for high performance and high density IC devices, and these challenges become more severe with organic based interlayer dielectrics. To help mechanical, thermal, and chemical stabilities an insertion of inorganic based spin-on-dielectric (SOD) into a multilayer FOWLP structure is investigated. In this study, both low temperature cured inorganic material called SOG (spin-on-glass) and photodefinable organic-inorganic hybrid material called PSSQ (polysilsesquioxane) have been evaluated. SOG thin films were cured in H2O vapor atmosphere at 230oC for 1 hour. There were no cracks, delamination or scratches observed, and good planarization and gap filling for L/S=2µm/2µm patterns were observed. And a patterning process of PSSQ was performed, and the possible pattern of L/S=2µm/2µm was confirmed.