Polymer-based zero-level packaging technology for high frequency RF applications by wafer bonding/debonding technique using an anti-adhesion layer

Abstract

This paper describes polymer cap 0-level packaging of RF devices, which is based on successive wafer scale bonding and debonding techniques. Pre-fabricated benzocyclobutene (BCB) membranes on a carrier wafer were directly transferred onto a target substrate by wafer scale bonding process. Using an anti-adhesion layer of hydrophobic octadecyltrichlorosilane (OTS) self-assembled monolayer (SAM), the carrier wafer was mechanically detached from the membranes without any aggressive etching process. As a result, BCB packaging caps in various sizes have been successfully fabricated on a 3 inch Si substrate. BCB cap deformation by thermal residual stress was investigated using ANSYS simulation and the measured results were in good agreement with the simulated ones. Si3N4 film was deposited on the caps for hermetic sealing and the hermeticity was evaluated by N2 leak test. Finally, the suitability of BCB caps in RF applications was assessed by Sparameter measurement of gold coplanar waveguide (CPW) transmission lines. The insertion loss change by BCB packaging was negligible and the return loss was better than 20 dB from DC to 50 GHz.