A miniaturized biconvex quartz-crystal microbalance with large-radius spherical thickness distribution

A miniaturized biconvex quartz-crystal microbalance (QCM) with large-radius spherical thickness distribution was fabricated by reactive ion etching (RIE) and photoresist reflow with solvent vapor technology. A conventional polishing method could not manufacture the miniaturized, spherically convex shape, which is necessary to suppress a spurious mode and obtain a high $Q$ factor. Not only can the large-radius spherical convex shape be achieved by this technology, but also miniaturization and batch fabrication. The $Q$ factor of the fabricated QCM (80 000) is two times higher than that of the planar QCM, and the spurious mode around the fundamental vibration mode is suppressed very well. It also has superior resonant characteristic under the viscoelastic liquid.