Bulk micromachining characterization of 0.2 μm HEMT MMIC technology for GaAs MEMS design

Front-side bulk micromachining based on 0.2 mu m GaAs HEMT MMIC technology is presented. Several chemical solutions have been used to perform the etching procedure characterization in respect to the obtained vertical profiles. It has been verified that citric acid solution is the most appropriate selective etchant to build suspended GaAs/AlGaAs mesa-shaped structures, while both H3PO4 and NH4OH based anisotropic systems seem to be the most suitable for the free-standing triangular prism-shaped structures. Moreover, all these three solutions could be applied to suspend only metal and intermetallic materials. Etch rates as well as cross-section profiles were obtained. Furthermore, the compatibility of the etching procedure with the integrated electronics and the pad metallization has been successfully tested. The features and applications linked to the obtained structures are also discussed. (C) 1998 Elsevier Science S.A. All rights reserved.