7F-3 Fabrication of High Stability Oscillators Using AlN/Si High Overtone Bulk Acoustic Resonators

We used a high quality AlN film deposited by sputtering onto a thin silicon device layer (30 mum thick) to fabricate a 2.4 GHz oscillator and to improve the spectral separation. The substrate consists in a 4" thick silicon on insulator (SOI) wafer. The aluminium nitride was deposited by pulsed direct current reactive sputtering onto a platinum electrode. BAW resonators were formed together with patterned top electrodes. Modes separated by 120 MHz have been characterized, and the corresponding resonance used to stabilize oscillators I, the 600-1500 MHz range. Phase noises at 10 kHz from the carrier are found close to -130 dB below 1GHz, and near-120 dB above 1 GHz.