Abstract

ABARCA-JIMENEZ, G.S. et al. Surface micromachining of a micro electromechanical inertial transducer based on commercially available Floating Gate Transistor technology. Superf. vacío [online]. 2018, vol.31, n.3, pp.48-51. ISSN 1665-3521.

This work presents the results of different surface micromachining processes done on a chip from On Semiconductor 0.5 µm commercially available CMOS technology. The intended objective is to fabricate a MEMS inertial transducer in a monolithic substrate, as the electronics for signal processing are based on a Floating Gate MOS transistor, fully integrated in the electromechanical structure. According to the available layers and design rules from the foundry, an inertial sensor chip was designed and fabricated, except the last post-processing step, i.e., the removal of the sacrificial layer and thus releasing the inertial structure based on a surface micromachining process, allowing the completed device to behave as designed. The post-process requires minimizing the damage to the structural metal layers while removing the sacrificial silicon dioxide layer in an efficient way. Taking this into account, the following techniques were proposed: as dry processes, reactive ion etching and hydrofluoric acid vapor; as wet processes, etching with HF solution, buffered HF solution and commercial buffered pad etcher. The related literature shows that any of these techniques could work, but a specific suitable methodology for this CMOS technology and these CMOS-MEMS devices had to be defined. After testing the previously mentioned processes, a specific procedure was determined, which involved wire bonding of the chip in a ceramic package before micromachining, and using a commercial pad etcher in a simple way that minimizes waste, this resulted safer than others described here, and yielded excellent results.

Keywords : FGMOS; surface micromachining; inertial sensor.