Dielectric microwave characterization of the SU-8 thick resin used in an above IC process

A broadband technique for determining electrical properties of dielectric materials is presented, based on microstrip lines. Relative permittivity and loss tangent are computed from S-parameter measurements and analytical equations. The analytical computation is either direct by using equations derived from Bahl formulas, or iterative by using Jensen-Hammerstad formulas coupled with the efficient secant algorithm. Thin film microstrip transmission lines have been fabricated for the extraction of dielectric electrical properties of SU-8 resin. A relative dielectric constant of 2.85 and a loss tangent of 0.04 were determined. These values are used in an EM simulator for the design of an SU-8 based high-Q inductor implemented on a low resistivity silicon substrate. The good agreement between measurements and simulations validates the characterization procedure and confirms the relevance of SU8 for applications up to 15 GHz.