Process and Reliability of Embedded Micro-Wafer-Level Package (EMWLP) Using Low Cure Temperature Dielectric Material

In this paper, we present the evaluation results of low cure temperature (less than 200°C) dielectric materials (LCTDMs) in terms of processability and adhesion to silicon nitride and mold compound substrates. The results showed that the LCTDMs have good adhesion to the above substrates. Integration of thin-film passives such as inductors, capacitors, and band-pass filters were also demonstrated on mold compound wafer platform using electroplated copper (Cu) and LCTDM. Thin-film passives fabricated on the mold compound platform using LCTDM showed better performance by two times when compared to the passives fabricated on a high-resistivity silicon wafer. Reliability test vehicles of multichip embedded micro-wafer-level package (EMWLP) were fabricated using Cu redistribution line (RDL), LCTDM, and electroplated Cu under bump metallization with lead-free (Pb-free) solder bump interconnects. Test vehicles were subjected to various package-level and board-level reliability tests as per the JEDEC standards, and failure analysis was carried out after reliability tests. EMWLP with LCTDM passed package-level reliability tests such as unbiased highly accelerated stress test, thermal cycling (TC), and moisture sensitivity test level 3. Test vehicles with underfill passed board-level TC and drop tests. A complete description of dielectric material evaluation for EMWLP, process development of thin-film passives fabrication, and multilayer RDL integration on reconfigured mold compound wafer and its reliability results are discussed.