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 (μUSM) 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 µm/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 µm on the 110 µm-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 µm/min.