Development of an organic micromachining process on silicon for RF/microwave applications

We present the development of an organic micromachining process that enables the realization of low loss structures on lossy substrates at microwave/millimeter wave frequencies. This process is capable of achieving an ultra-thick polymer layer (up to I mm) by spin coating, which enables micromachining integration of high-aspect ratio devices including surface air cavities. This process is low temperature and compatible with monolithic integration and post-processing. This process can be applied to develop low loss micromachined transmission lines and integral waveguides on lossy substrates, which is key to designing distributed passive circuits including filters. The advantages of this technology include: (1) High throughput process that is compatible with standard lithography and spin-coating, (2) Isolation of interconnect structures or waveguides from a lossy substrate, and (3) Ability to create air-gap for electromagnetic field propagation. This paper reports the development of the organic micromachining process on Silicon and demonstrates the integration of a micromachined coplanar waveguide interconnects or RF/microwave applications.