Lithium-niobate-based surface acoustic wave oscillator directly integrated with CMOS sustaining amplifier

In this study, a LiNbO₃-based SAW resonator was directly integrated with a CMOS sustaining amplifier using new wafer-bonding-based integration technology. The developed integration technology has overcome the large thermal expansion mismatch between LiNbO₃ (14 to 15 ppm/K along the a-axis) and Si (2.6 ppm/K) by temporary wafer supporting and low-temperature Au–Au bonding. Two kinds of bonding, UV polymer bonding for temporary wafer supporting and Au–Au bonding following plasma surface activation, are key process technologies. A 500-MHz one-chip SAW oscillator was prototyped and evaluated. A low phase noise of –122 dBc/ Hz at 10 kHz offset and –160 dBc/Hz at 500 kHz offset was achieved.