A high-speed batch-mode ultrasonic machining technology for multi-level quartz crystal microstructures

This paper describes recent advances in batch-mode micro ultrasonic machining (¿USM) and its application to quartz crystal (QC) microstructures. Acoustic emission sensors are used for close monitoring of this batch process. Multi-level AT-cut QC microstructures have been successfully fabricated at a cutting rate >24 ¿m/min, which is substantially faster than available options for plasma-based etching. Arrays of disks, H-shaped and tuning fork structures are demonstrated with a cutting depth up to ~105 ¿m on the 110 ¿m-thick QC substrate. Micromachined QC structures are also mounted on interconnection substrates. Preliminary electrical tests have been performed for resonance characteristics. A low-thermal-expansion glass ceramic, ZERODUR^®, has also been micromachined at a cutting rate >18 ¿m/min.