Hybrid Fan-out Package for Vertical Heterogeneous Integration

A new ultra-thin high-density hybrid package that combines fan-out RDL with a backside laminated interposer is developed for mobile applications. The package features up to six fan-out RDL layers for chiplet integration and two to four routing layers in a backside interposer for a high pin-count module stacking architecture. The laminated interposer is placed conformally to the SOC to create a base package as thin as 250 um. An integration challenge in the CTE mismatch between fan-out RDL and laminated interposer is successfully resolved. For a 14x14 mm2 package, a low package warpage is achieved at RT and HT, measured at 37um and -46um, respectively. The twist index is also controlled within 30um. Despite its thinness, the new hybrid package shows enhanced mechanical strength by incorporating the laminated interposer. It is successfully demonstrated that memory and RF modules can be stacked on this thin base package using the standard production flow. The thin packages pass stringent component and board level reliability tests. The new hybrid package combines the electrical and thermal advantages of fan-out packages and the mechanical advantage of laminated interposers. This hybrid fan-out package has a very high interconnect density, which provides excellent design flexibility for advanced vertical heterogeneous integrations.