High-Q above-IC inductors and transmission lines - comparison to Cu back-end performance

In the current trend towards portable applications, high-Q integrated inductors have gained considerable importance. In this paper, wafer level packaging techniques have been used to integrate state of the art high-Q on-chip inductors on top of a five-levels-of-metal (5LM) Cu damascene back-end of line (BEOL) silicon process using 20Ω.cm Si wafers. The inductors are realized above the on-chip passivation layer using thick post-processed low-k dielectric BCB (benzo-cyclobutene) and electroplated Cu layers. The performance of the inductors is compared to inductors with identical lateral dimensions realized in the BEOL using different comparison criteria: Q_L and Q_BW (single ended as well as differential excitation) and maximum available gain (G_max). Next to inductors, high quality above-IC transmission lines have been realized in the WLP layers.