This paper reports a method of frequency scaling millimeter wave thin-film lithium niobate (LiNbO3) acoustic resonators using ion beam assisted argon gas cluster etching whilst maintaining a high figure of merit (FoM) and averting ultra-thin-film fabrication difficulties. A transferred 100 nm thick 128° Y-cut LiNbO3 thin film is trimmed to a thickness of 75 nm. Consequently a 24.4 GHz first-order antisymmetric mode (A1) resonator with a high k^2 of 34.3%, a Q of 54, and an FoM of 18.5 is presented. The quality of the film remains intact during the trimming process, proven by material-level analysis, and similar f·Q product compared with resonators fabricated using the original film. These results show a viable and less complex path toward further frequency scaling acoustic devices.
