Thermally actuated a-SiC:H MEMS fabricated by a PECVD process

The fabrication of a fully operational thermally actuated MEMS based on PECVD materials is reported. These micro-electro-mechanical systems consist of matrixes of free standing a-SiC:H and a-SiC:H/SiOxNy cantilevers actuated by thermal expansion induced by Joule effect. The structures’ motion is obtained by applying electrical voltage to heating elements integrated in the cantilevers and it is a consequence of the relaxation of the residual stress of a-SiC:H or results from the difference in the thermal expansion of a-SiC:H and SiOxNy. The mobile cantilevers are fabricated by front side bulk micromachining of c-Si substrates. Chromium metal is used as contact metal and heating element. The structures were characterized studying the obtained motion for different applied voltages/currents. The results show that up/down motion with amplitudes of ∼30 μm are obtained for heating currents of 22 mA. If voltage is applied in on/off cycles, up/down motion with frequencies up to 150 Hz is observed, but increasing frequency results in a reduction of the movement amplitude. Further, when the cantilevers are actuated in a synchronized way, ciliary motion is obtained.