Abstract
Filters based on film bulk acoustic resonators (FBARs) are widely used for mobile phone applications, but they can also address wideband aerospace requirements. These devices need high electromechanical coupling coefficients to achieve large band pass filters. The piezoelectric material LiNbO3 complies with such specifications and is compatible with standard fabrication processes. In this work, simple metal—LiNbO3—metal structures have been developed to fabricate single FBAR elements directly connected to each other on a single chip. A fabrication process based on LiNbO3/silicon Au-Au bonding and LiNbO3 lapping/polishing has been developed and is proposed in this paper. Electrical measurements of these FBAR filters are proposed and commented exhibiting filters with 8% of fractional bandwidth and 3.3 dB of insertion losses. Electrical measurements show possibilities to obtain 14% of fractional bandwidth. These devices have been packaged, allowing for power handling, thermal, and ferroelectric tests, corresponding to spatial conditions.
Highlights
Acoustic waves, using surface or bulk propagation, are used in numerous applications in frequency generation, control, or filtering in modern wireless communication systems [1,2,3]
To achieve large bandwidth filters with fractional bandwidth over 10%, higher coupling coefficient materials are required. These materials should be compatible with batch processes as those used for the micro-electromechanical systems (MEMS)
bulk acoustic waves (BAWs) filters based on electrical couplings are usually designed with series or shunt resonators
Summary
Acoustic waves, using surface or bulk propagation, are used in numerous applications in frequency generation, control, or filtering in modern wireless communication systems [1,2,3]. Bulk acoustic waves (BAWs) or film bulk acoustic resonator (FBAR) devices can offer many potentialities for smart RF components or systems This technology is used as alternative to surface acoustic waves (SAWs) filters in handset duplexers for UMTS and DCS standards around 2 GHz with aluminium nitride piezoelectric layers [6]. This material is mainly processed for local oscillators or narrowband filtering operations (
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