Layout design rules for one-step dry release and non-stiction wet release of MEMS using DRIE/SOI technology

DRIE (deep reactive ion etching) of SOI (silicon on insulator) wafer is nowadays a popular method to build MEMS for its versatility and simplicity. Yet when the devices using this technology become large in size or have compliant beams, the stiction during the HF wet release is a serious problem that can not be easily solved. In our experiments, we found that some structure patterns can be wet released more easily than others or even can be released without wet process. In this paper, we discuss the relations between patterns and stiction property. Notching effect, which is found to be the mechanism behind this phenomenon, is described. Some mask layout design rules to utilize such effect are given here, which can lead to structure fabrication and release in one DRIE step without any wet process, or, at least, can completely overcome the stiction problem during wet release. Then, the application of these rules on the mask design of a moving stage and its successful fabrication and release is shown.