Frequency Scaling Millimeter Wave Acoustic Resonators using Ion Beam Trimmed Lithium Niobate

Abstract

SummaryThis paper reports a method of frequency scaling millimeter wave thin-film lithium niobate (LiNbO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> ) acoustic resonators using ion beam assisted Argon gas cluster trimming whilst maintaining a high figure of merit (FoM) and averting ultra-thin-film fabrication difficulties. A transferred 100 nm thick 128° Y-cut LiNbO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> 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 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of 34.3%, a Q of 54, and an FoM of 18.5 is presented. The quality of the film was maintained during the trimming process, proven by material-level analysis, and exhibited a 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.