Effects of Bottom Electrode Topography in AlN Nano Plate Resonators on Quality Factor

This paper reports on the experimental study of the effects of bottom electrode topography in AlN nano plate resonators (NPRs) on quality factor. We show that efficient piezoelectric transduction of a high frequency (~744 MHz) lateral-extensional mode of vibration and a quality factor as high as ~1300 can be achieved when a 70 nm thick platinum layer is employed as the interdigitated electrode underneath of a 200 nm thick AlN nano plate. Such a high value of quality factor is comparable to that achieved in reference devices with inversed electrode design (employing an unpatterned floating plate as the bottom electrode). The smoothly-transitioned topography of the bottom electrode, more specifically, the tapered edge of the patterned interdigitated electrode is identified as the key contributing factor to the achievement of high quality factors.