THE INTEGRATION OF CMOS WITH PLASMA-ENHANCED MICROMACHINING

The integration of micromechanical devices in a microsystem with micro electronic circuitry seems to be one of the most interesting and promi sing directions of the development of silicon technology. Basically, s urface micromachining, which uses a specific sequence of deposition an d etching processes is more compatible with high-volume CMOS technolog y. However, high-temperature annealing, which is necessary to relax st ress in thick CVD layers, could affect the performance of a microelect ronic device if the IC is fabricated first, followed by the fabricatio n of the micromachined device. The reverse of this process would damag e the already created micromechanical structures. In bulk micromachini ng, no such annealing is required, and thus, using carefully selected and optimized etching processes and adequately chosen masking material s, the integration of micromachining and CMOS can be performed. In thi s paper, micromachining techniques and the possibility of their integr ation with CMOS are discussed. The applicability of various possible i ntegration schemes is considered. It is shown that thorough use of the plasma etching technique enables the integration of bulk micromachini ng with CMOS. The technique is demonstrated using an AFM sensor as an example. (C) 1997 Elsevier Science S.A.