High-frequency surface acoustic wave (SAW) devices fabricated by contact-transferred and mask-embedded lithography

This paper reports the application of a newly developed lithography method, the contact transfer and mask-embedded lithography (CMEL), in fabricating high-frequency (~2 GHz) surface acoustic wave (SAW) filters. In sort, CMEL utilizes a thin metal film deposited on an anti-adhesion layer and a silicon mold with pre-fabricated features. The metal film bearing the mold´s surface pattern can be transferred into a photo-resist layer deposited on a substrate. Subsequent etchings complete the lithography and the micro/nano-fabrication. To demonstrate CMEL and its potential, we apply CMEL for fabricating inter-digital transducers of SAW filters with a line width down to 500 nm. Using a LiNbO₃ substrate, the operating frequency can reach 1.8 to 2 GHz based on this simple and easy-to-implement lithography method. Details in the CMEL, the lithography results, the high-frequency performance of the fabricated SAW devices, as well as future developments of this simple lithography method will be addressed.