Gas-phase xenon difluoride etching of microsystems fabricated through the Mitel 1.5-mu m CMOS process

The field of microsystems technology (MST), comprising both micromechanical and microelectronics components, has a tremendous potential for sensing an d actuation at the micro level of matter in almost every field of interest to mankind, from DNA sequencing to information and communication system. Th e application of microelectromechanical systems (MEMS) devices will become mature only if the integration between the micromechanical, microelectronic s and software systems proceeds at the device level. This paper presents a method of realizing such devices using an industrial CMOS process, namely, the Mitel 1.5-mu m process, and releasing the micromechanical structures by xenon difluoride pulse etching. Further, the paper examines the suitabilit y of the Mitel 1.5-mu m process for making piezoresistive, capacitive and v arious micromechanical structures. Details of the etching apparatus and the etching characteristics of gaseous xenon difluoride etching are presented along with experimental results. The effects of window size and corner sele ctivity on the etch rate and etch pattern are studied and discussed.