Novel embedded Z line (EZL) vertical interconnect technology for eWLB

In this paper, we present the novel embedded Z line (EZL) interconnection technology, which allows fabricating vertical contacts in the embedded wafer level ball grid array (eWLB) package. The presented solution enables the realization of vertical interconnections and passive components of wide range of widths and pitches and high metal-pattern resolution. We discuss the electrical characteristics of interconnections and high-frequency transitions realized using EZLs and compare them to structures realized using through encapsulant vias (TEVs) and through silicon vias (TSVs). We show examples of high-density EZL daisy chain structure and 3D package for RF-powered sensor with EZL interconnections to demonstrate the feasibility of the EZL technology. We present the concept of vertical antenna integration using EZL and show measurement results of a vertical EZL dipole antenna integrated in an eWLB package to demonstrate the flexibility and millimeter-wave capabilities of the EZL technology. The presented examples demonstrate that the new EZL technology is competitive to both TEV and TSV interconnect options and that it is particularly interesting for systems combining RF/high-speed and power devices.