GaN micromachined FBAR structures for microwave applications

This paper presents the manufacturing of GaN membrane supported F-BAR structures. The 2.2 μm thick GaN layer was grown using MOCVD techniques on a high-resistivity 〈111〉-oriented silicon substrate. Conventional contact lithography, electron-gun Ti/Au evaporation and lift-off techniques were used to define top-side metallization of the the FBAR structures. Bulk micromachining techniques were used for the release of the GaN membrane. The bottom-side metallization of the micromachined structure was obtained by means of sputtered gold. S-parameter measurements have shown a pronounced resonance around 1.2 GHz. The extracted value of acoustic velocity is in good agreement with those reported by other authors on materials fabricated by other methods. The demonstrated FBAR function in epitaxially grown GaN layers opens new avenues for a low-cost monolithic integration with GaN-based electronics and sensing devices.