Wafer-level packaging technology for extended global wiring and inductors

Wafer level 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 (5 ML) Cu/oxide back-end of line (BEOL) 20/spl Omega/cm silicon process. The transmission lines and inductors are realized above the passivation using thick post-processed dielectric (BCB, /spl epsiv//sub 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 50/spl Omega/ transmission lines. have losses below -0.1dB/mm@25GHz; a InH inductor has a peak Q-factor of 38 at 4.7GHz with resonance frequency (F/sub res/) of 29GHz, the Q-factor tops 30 over 2.6-8.6GHz. Patterned polysilicon ground shields further improve the performance: a Q-factor increase of 90% was demonstrated at 7GHz for a 2.25nH inductor.