AN OPTIMIZED FRONT-SIDE MICROMACHINING PROCESS FOR DIELECTRIC MEMBRANES USING TMAH

The etching properties of <100> silicon substrates are known to allow the fabrication of open dielectric membranes by anisotropic etching from the wafer front side. Such structures are needed in several microsystem applications, where the main difficulty in the process consists in finding the right calibration between the lateral underetching of silicon below the membranes and the depth of the underlying cavity, especially when a closed well is needed in the substrate under the suspended structures. This work describes an experimental investigation performed in order to obtain an optimized, CMOS-compatible process for the fabrication of dielectric membranes micromachined from the front side using tetramethyl-ammonium-hydroxide (TMAH)-water etching solutions.