3-D construction of monolithic passive components for RF and microwave ICs using thick-metal surface micromachining technology

As a viable technological option to address today's strong demands for high-performance monolithic low-cost passive components in RF and microwave integrated circuits (ICs), a new CMOS-compatible versatile thick-metal surface micromachining technology has been developed. This technology enables to build arbitrary three-dimensional (3-D) metal microstructures on standard silicon substrate as post-IC processes at low temperature below 120/spl deg/C. Using this technology, various highly suspended 3-D microstructures have been successfully demonstrated for RF and microwave IC applications. We have demonstrated spiral inductors suspended 100 /spl mu/m over the substrate, coplanar waveguides suspended 50 /spl mu/m over the substrate, and complicated microcoaxial lines, which have 50-/spl mu/m-suspended center signal lines surrounded by inclined ground shields of 100 /spl mu/m in height. The microwave performance of the microcoaxial transmission line fabricated on a glass substrate has been evaluated to achieve very low attenuation of 0.03 dB/mm at 10 GHz with an effective dielectric constant of 1.6. The process variation/manufacturability, mechanical stability, and package issues also have been discussed in detail.