Delamination between dielectric layers of FOPLP due to copper residue under high temperature storage conditions

The fan-out panel level package (FOPLP) has its advantage of higher throughput over the fan-out wafer level packages (FOWLP) due to its bigger panel size. It is, however, difficult to maintain uniform quality throughout the panel and secure reliability because there are multiple redistribution layers (RDL) of organic dielectric layers and copper (Cu) conducting paths. In particular, adhesion at various interfaces such as polymer-polymer, polymer-metal, and metal-metal is of great concern because both polymer, and Cu are vulnerable to oxidation at high temperatures in the atmospheric environment. In the present study, we investigated the influence of Cu residue on the degradation of interfacial adhesion in FOPLP under high temperature storage (HTS) conditions. The microstructure and chemistry at the interface were studied using a focused ion beam (FIB) and a transmission electron microscope (TEM). We found that trace amounts of Cu residues prevented two polymers from intermingling during lamination, which is evidenced by accumulation of organosilicon compounds at the interface. We also observed that cracks occurred at the polymer-polymer interface where the Cu residues were present after the HTS test. We propose that the Cu residues should be related to oxidation of polymers at the interfaces during the HTS test and subsequent interfacial delamination.