Mechanical resonators on CMOS for integrated passive band pass filters

We present CMOS post-processing compatible resonator structures for passive band-pass filtering in the MHz-few GHz range. This article discusses the considerations leading to the choice of materials and process sequence, practical aspects in the fabrication, and resonator performance. Using in-situ boron-doped polycrystalline germanium-silicon as resonator and electrode material, high quality factors over 200,000 are obtained at relatively low motional impedance.