High-Band AlN Based RF-MEMS Resonator for TSV Integration

This paper reports two types of in-house fabricated aluminium nitride (AlN) based piezoelectric resonators, namely the thickness mode resonator and the Lamb-wave mode resonator, which are capable to be integrated with Through Silicon Via (TSV) technology, forming the basis of advanced filters, duplexers and multiplexers. Both types of the resonators, which are fabricated using a CMOS compatible platform, consist of a layer of 1 μm thick piezoelectric layer and two layers of molybdenum (Mo) electrodes covering the top and the bottom surface of the AlN layer. Resonant frequencies above 2GHz, as well as motional impedance less than 10Ω, are obtained when the fabricated resonators are connected directly to the 50Ω terminations of a network analyzer, making both types of resonators suitable for high-band LTE applications. Furthermore, negligible performance drift was observed for both types of resonators fabricated upon undergoing accelerated thermal cycling test, indicating the superior reliability and long-term stability of the fabricated AlN based MEMS resonators and showing their great potential for communications applications in the automotive industry, where reliability and long-term stability is a key requirement for device performance.