Low motional resistance ring-shaped contour-mode aluminum nitride piezoelectric micromechanical resonators for UHF applications

This paper reports experimental results on a new class of ring-shaped, contour-mode aluminum nitride piezoelectric resonators that span a frequency range from 223 MHz to 656 MHz showing high quality factors in air (Q_max=2,900 at 472.7 MHz), low motional resistance (ranging from 56 to 205 Ω), and center frequencies that can be lithographically tuned. These resonators achieve the lowest value of motional resistance ever reported for contour-mode resonators and combine it with high Q factors, therefore truly enabling the fabrication of arrays of microresonators with different frequencies on a single chip. Uncompensated temperature coefficients of frequency of only approximately -25 ppm/°C were also recorded for these resonators.