Realization of High Electrical Performance On-chip Thick Copper Inductor Package by Via Interface Process Improvement for Metal Contact

In 2017 ECTC, we demonstrated an on-chip thick copper "Air-core" inductor integrated with proposed WLCSP-like packaging solution. This year, the spotlight of the upgraded on-chip inductor package is two-fold. The first is a planar magnetic (MAG) film with high permeability is integrated into the inductor. The second is the thickness of the Cu redistribution layer (RDL) becomes 3~4 fold thicker than that used in typical WLCSP. These two paths are used for achieving superior inductance as well as electrical performance. The integrity of "Metal Contact Via" plays an important role on the realization of the on-chip MAG thick Cu inductor package. Two key process issues relating to metal contact at via area will be disclosed and focused for the first time. Two novel concepts ("Patterned Metal-Cut Protection Layer (PMCPL)" & "Multilayer-Etching Stop Layer (M-ESL))" are introduced for the via process improvement. The issues, the fundamental root cause, and the improvement actions will be discussed step-by-step in this paper. In short, without such two imperative improvement approaches as just mentioned, not only will the device function open (fail), but the excellent electrical performance will not be realized as well. At last, compared to the air-core thick copper inductor package reported last year, the results show that the inductance density can boost up 9-fold and the direct resistance (Rdc) significantly reduces 2-fold.