High sensitive, miniaturized plano-convex quartz crystal microbalance fabricated by reactive ion etching and melting photoresist

In this paper, high sensitive, miniaturized planoconvex quartz crystal microbalance (QCM) has been fabricated by reactive ion etching (RIE) and melting photoresist technology. Due to the convexity of the resonator surface and the small size of the excitation electrode, the energy of the oscillation is trapped at the center so that very little dissipation occurs at the edge. The fabricated plano-convex QCM has superior resonant characteristics compared with a QCM without the plano-convex formation. For example, the QCM with a high quality value (60000) was realized for a 1-mm-diameter electrode QCM with 1.6-/spl mu/m-deep and 2-mm-diameter convex formation on both sides. A spurious mode around a fundamental vibration mode was also suppressed less than 20% from that before the etching. This technology is useful from a viewpoint of mass production because it needs not polishing.