A micromachining process for die-scale pattern transfer in ceramics and its application to bulk piezoelectric actuators

This paper reports on a batch mode planar pattern transfer process for bulk ceramics, glass, and other hard, brittle, nonconductive materials suitable for micromachined transducers and packages. The process is named LEEDUS, as it combines lithography, electroplating, batch mode micro electro-discharge machining (/spl mu/EDM) and batch mode micro ultrasonic machining (/spl mu/USM). An electroplating mold is first created on a silicon or metal wafer using standard lithography, then using the electroplated pattern as an electrode to /spl mu/EDM a hard metal (stainless steel or WC/Co) tool, which is finally used in the /spl mu/USM of the ceramic substrate. A related process (SEDUS) uses serial /spl mu/EDM and omits lithography for rapid prototyping of simple patterns. Feature sizes of 25 /spl mu/m within a 4.5/spl times/4.5 mm/sup 2/ die have been micromachined on glass-mica (Macor) ceramic plates with 34 /spl mu/m depth. The ultrasonic step achieves 18 /spl mu/m/min. machining rate, with a tool wear ratio of less than 6% for the stainless steel microtool. Other process characteristics are also described. As a demonstration, octagonal and circular spiral shaped in-plane actuators were fabricated from bulk lead zirconate titanate (PZT) plate using the LEEDUS/SEDUS process. A device of 20 /spl mu/m thickness and 450 /spl mu/m/spl times/420 /spl mu/m footprint produces a displacement of /spl ap/2/spl mu/m at 40 V.