Journal of Micro/Nanolithography, MEMS, and MOEMSFabrication of micro suspensions on silicon substrate
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A new technique to remove the silicon from beneath a large structure, by micromachining for making a suspended microstructure both for thermal, as well as electromagnetic, isolations on a complementary metal-oxide-semiconductor (CMOS) chip is reported. Conventional methods require two step front-side etching, an isotropic step, followed by an anisotropic etching step. An alternative technique is based on the backside etching process, which requires extra masks, and processing steps. In order to keep the postprocessing steps to a minimum, a simple technique has been developed that exploits the front-side anisotropic etching to create both undercuttings as well as deep etching in one single step. This method uses the gate oxide and polysilicon layer in CMOS technology as the sacrificial layer for initiating the undercutting needed to make a freestanding microstructure. The microsuspension thickness, width and length of 2 μm, 150 μm×150 μm, respectively, are made out of low-pressure chemical vapor deposition oxide and have been fabricated.