Sub-100nm Al0.7Sc0.3N Thin Films for Next Generation Bulk Acoustic Wave Resonators and Filters

Thin piezoelectric films with thickness around 100nm are critical for high frequency bulk acoustic resonators and filters, especially in mm-wave frequency range. In this work, 100nm and 50nm 30% Sc doped AlN (Al0.7Sc0.3N) films have been deposited and the high-tone bulk acoustic wave resonators (HBAR) have been fabricated to characterize the thin piezoelectric films. The intrinsic electromechanical coupling coefficient (K-t(2)) of the sub-100nm Al0.7Sc0.3N thin films has been extracted by measurements and modeling of the fabricated HBAR devices. The coupling coefficient of the deposited 100nm and 50nm Al0.7Sc0.3N thin films is 7.9% and 5.6% respectively. These results show that the sub-100nm Sc doped AIN films are promising for the nextgeneration acoustic resonators and filters for mm-wave applications.