Packaging of RF Mems Switching Functions on Alumina Substrate

The expending development of wireless communication requires strong demands for components with improved capabilities. RF MEMS devices offer a variable alternative to conventional communication components because they consume less DC power, have lower losses, higher linearity and higher Q factor. However, the commercialization of RF MEMS devices is hindered by technological issues such as their packaging , which is the most critical problem to be solved. Compared with conventional IC packaging technologies, packaging of RF MEMS is for more challenging, because it implies both electrical and mechanical aspects. The mechanical nature of RF MEMS requires low temperature, hermetic wafer level packaging [1,2]. An interesting approach consist in encapsulating the component or a group of components on ceramic alumina substrate using simple techniques with limited technological stages. Our approach for the packaging of MEMS based switching networks consist in the encapsulation of the whole switching function instead of each MEMS switch alone, which simplify the design in terms of size and costs. 1. BASIC MEMS SWITCHING ELEMENTS MEMS devices can easily be integrated on a large variety of substrates (silicon, AsGa, quartz...). In this work, we present designs on alumina substrate. The switching devices that we are presenting in this work are designed on alumina substrates, since many microwave applications are using this type of substrates and they can be easily post-processed, once the MEMS fabrication sequence was finished. Fig.1 shows a SEM and a schematic view of the basic MEMS switch integrated in the switching networks presented in this paper. It is a DC contact switch with a cantilever structure made in gold (150μm in length, 120μm in with and a thickness of 3.5μm). this types of switches shows good performance on a relatively wide frequency range (from DC to 30 GHz) and is much less prone to self-actuation compared to standard capacitive switches [3]. Contact fingers cantilever Biasing pad