Micromachining of multi-thickness sensor-array structures with dual-stage etching technology

A novel bulk-micromachining technique has been developed for the formation of silicon micromechanical sensor-array structures with a scheme of different structural thicknesses of sensing units for different mechanical sensitivities. Using the multi-thickness scheme, a series of sensing units can be integrated to form a sensor array, with each unit having an individual structural thickness and, therefore, an individual mechanical sensitivity. The fabrication is based on a masked-maskless dual-stage anisotropic etching technology. The key to the technology lies in the pattern design of a mask layer and the etching depth control. By using this technique, several sensor-array structures have been successfully micromachined, such as a diaphragm array for multi-range pressure sensor array and beam-mass array for acceleration switch array, etc. The novel fabrication scheme is quite suitable for mechanical sensor arrays or switch arrays, which is attributed to the easily controlled etching process and the integration of many sensing units. Besides, the scheme of thickness variation saves sensing-unit occupation of the planar area, thereby contributing to the high density of array integration.