A micromachining-based fabrication process has been proposed for low-volume production of copies of a mesoscale vibratory gyroscope. The process would include steps of photolithography, metallization, deep reactive-ion etching (RIE), Au/Au thermal-compression bonding, and anodic bonding. In the present state of the art, these process steps are well established and the process as a whole would be considered reproducible.
The basic designs and principles of operation of micromachined vibratory gyroscopes were discussed in several prior NASA Tech Briefs articles. For the purpose of the present discussion, the relevant micromachined components of the mesoscale vibratory gyroscope to be fabricated would be a baseplate; a resonator to be mounted on the baseplate; and a post to be affixed to (and thereby become part of) the resonator.
Although the proposed fabrication process would be simple in comparison with some other micromachining processes, it would nevertheless consist of numerous steps and therefore is only summarized here. The baseplate, resonator, and post would be fabricated separately from silicon wafers. The fabrication of the baseplate would include photolithography and etching steps to form pillars to support the resonator; photolithography, metal-evaporation, and liftoff steps to form metal bonding pads and electrical conductors; and photolithography and deep-RIE steps to form through-the-thickness holes. The fabrication of the resonator would include similar but fewer steps (no pillar-formation steps).
The figure depicts the last joining steps. The resonator would be joined to the baseplate by thermal-compression bonding of surface gold layers on their mating metal bonding pads, at a temperature of 350 °C. Top and bottom parts of the post would be joined to the upper and lower surfaces, respectively, of the resonator by anodic bonding at a potential of 4.25±0.25 kV and temperature of Å400 °C.
This work was done by Kirill Shcheglov of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Manufacturing category.
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Refer to NPO-30288, volume and number of this NASA Tech Briefs issue, and the page number.