Thin-Film Lithium Niobate Acoustic Filter at 23.5 GHz With 2.38 dB IL and 18.2% FBW

• Published in: Journal of microelectromechanical systems Vol. 32; no. 6; pp. 622 - 625
• Main Authors: Barrera, Omar, Cho, Sinwoo, Matto, Lezli, Kramer, Jack, Huynh, Kenny, Chulukhadze, Vakhtang, Chang, Yen-Wei, Goorsky, Mark S., Lu, Ruochen
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.12.2023; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acoustic filters; Acoustics; Amorphous silicon; Filtering theory; Insertion loss; lithium niobate; Lithium niobates; Millimeter wave communication; Millimeter waves; millimeter-wave; Optical filters; Piezoelectric devices; Piezoelectricity; Resonator filters; Resonators; Silicon; Silicon substrates; Thin film devices; Thin films
• ISSN: 1057-7157; 1941-0158
• DOI: 10.1109/JMEMS.2023.3314666

This work reports an acoustic filter at 23.5 GHz with a low insertion loss (IL) of 2.38 dB and a 3-dB fractional bandwidth (FBW) of 18.2%, significantly surpassing the state-of-the-art. The device leverages electrically coupled acoustic resonators in 100 nm 128° Y-cut lithium niobate (LiNbO3) piezoelectric thin film, operating in the first-order antisymmetric (A1) mode. A new film stack, namely transferred thin-film LiNbO3 on silicon (Si) substrate with an intermediate amorphous silicon (a-Si) layer, facilitates the record-breaking performance at millimeter-wave (mmWave). The filter features a compact footprint of 0.56 mm2. In this letter, acoustic and EM consideration, along with material characterization with X-ray diffraction and verified with cross-sectional electron microscopy are reported. Upon further development, the reported filter platform can enable various front-end signal-processing functions at mmWave. [2023-0129]