High speed directional etching of piezoelectric material is still insufficiently developed for producing high aspect ratio microstructures. The ability to realize well-defined structures on the surface of the substrates, with almost vertical side walls, a high aspect ratio, and a relatively low surface roughness, is a key factor for many applications, micro-electromechanical systems, integrated optical devices or Bulk Acoustic Waves resonators for Ultra Stable Oscillators.Current manufacturing technology for quartz BAW resonators does not allow reducing the size and the manufacturing cost in maintaining the ultimate performances (short term stability, long term aging, low acceleration sensitivity...). To achieve collective machining, we performed chemical etching up to now. Unfortunately, the etching rate and the surface roughness strongly depend on the plate orientation. For instance, for the crystallographic orientation commonly used to perform Ultra Stable Resonators (called SC-cut), the surface quality deteriorates sharply with time (differently on the 2 surfaces). Furthermore, the shape of the sidewalls is also orientation dependent.In this paper, we report on deep reactive ion etching of quartz crystal. We give results about the etched rate and the etched depth, the shape of the sidewalls, and especially the quality of the etched surface.
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