Wafer-Level Packaging Technology for Extended Global Wiring and Inductors

摘要

Wafer lever packaging (WLP) technology, originally introduced for thin film redistribution layers, offers novel opportunities for extended global wiring and passives and has been used to integrate transmission lines and state-of-the-art high Q on-chip inductors on top of a five-levels-of-metal (5ML) Cu/oxide back-end of line (BEOL) 20Ω.cm silicon process. The transmission lines and inductors are realized above the passivation using thick post-processed dielectric (BCB, ε_r=2.65) and Cu layers. Measurements on the BEOL before and after post-processing show no significant shifts for all 5 metal layers. Post-processed SOD transmission lines have losses below -0.1dB/mm@25GHz; a 1nH inductor has a peak Q-factor of 38 at 4.7 GHz with resonance frequency (F_(res)) of 29GHz, the Q-factor tops 30 over 2.6-8.6GHz. Patterned poly silicon ground shields further improve the performance: a Q-factor increase of 90% was demonstrated at 7GHz for a 2.25nH inductor.