Advanced deep reactive ion etching (ADRIE) is a new tool for the fabrication of bulk micromachined devices. Different sensors and actuators which use ADRIE alone or combined with other technologies such as surface micromachining of silicon are presented here. These examples demonstrate the potential and the design freedom of this tool, allowing a large number of different shapes to be patterned and new smart devices to be realized.
A new method to release MEMS chips from a wafer without dicing is presented. It can be applied whenever SO1 wafers are used that are structured from both the device and the handle side using DRIE. This method enables the release of extremely fragile structures without any mechanical impact on the chips. No more dicing residues or debris are created and deposited onto the wafer. The basic idea consists of etching deep surrounding trenches on the device and the handle layer that are displaced by about 20 pm and thus create overlapping areas. For release, the buried silicon dioxide between the overlapping areas is etched away using hydrofluoric acid vapor phase etching.
Abstract-Micromirror arrays are promising components for generating reflective slit masks in future multiobject spectrographs. The micromirrors, 100 µm × 200 µm in size, are etched in bulk single crystal silicon, whereas a hidden suspension is realized by surface micromachining. The micromirrors are actuated electrostatically by electrodes located on a second chip. The use of silicon on insulator (SOI) wafers for both mirror and electrode chip ensures thermal compatibility for cryogenic operation. A system of multiple landing beams has been developed, which latches the mirror at a well-defined tilt angle when actuated. Arrays of 5 × 5 micromirrors have been realized. The tilt angle obtained is 20• at a pull-in voltage of 90 V. Measurements with an optical profiler showed that the tilt angle of the actuated and locked mirror is stable with a precision of 1 arcmin over a range of 15 V. This locking system makes the tilt angle independent from process variations across the wafer and, thus, provides uniform tilt angle over the whole array. The surface quality of the mirrors in actuated state is better than 10-nm peak to valley and the local roughness is about 1-nm root mean square.Index Terms-Deep reactive-ion etch (DRIE), micromirror, microoptoelectromechanical system (MOEMS), mirror array, multiobject spectroscopy (MOS).
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