IF MEMS filters for mobile communication

For the past few years, the mobile phone market has been facing fast growth. However, the first generations of mobile telecommunications were based on several different standards over the world, and even at the time major operators negotiate for the third generation licenses, it seems UMTS, CDMA2000 and TD-SCDMA cannot achieve one single standard. A great challenge would be to develop flexible, re-configurable mobile phone handsets that could switch from one standard to another. To do so, MEMS technology is expected as a promising solution to provide tiny, low-consumption tunable components. Moreover, enhancing MEMS technologies to be compatible with IC processing, a novel architecture can be used for a MEMS-based transceiver that could reach the ultimate goal of a fully-integrated single-chip system. Indeed, it has been recently demonstrated that every off-chip, bulky, and expensive passive component present in a typical superheterodyne transceiver front-end could be advantageously replaced by an RF-MEMS counterpart. For example, micro-mechanical resonators could avoid the use of ceramic, SAW, and quartz off-chip resonators to allow low-loss filtering, mixing and carrier generation. But that kind of micro-scale resonators requires high quality factor and temperature stability to achieve highly selective filtering and low phase-noise frequency references. So, to demonstrate this ability, resonators and filters with center frequency up to 300 MHz were designed, and for their fabrication, two processes have been undertaken: an epitaxial thick-film polysilicon industrial technology and a thin-film polysilicon-based technology made compatible with a CMOS-SOI technology.