In this work, the effects of the N2 addition to the SF6 plasma used in the isotropic silicon etching of Microelectromechanical systems (MEMS) with Au components are investigated. A four-variables Doehlert design was implemented for optimizing the etching parameters (power, pressure, gas flow rate, and N2/SF6 ratio) to maximize the lateral etch rate of Si using SF6/N2 gas mixture. The optimized etch condition founded for a lateral etch rate of 1.8 µm/min was: power=143 W, chamber pressure=86 mTorr, flow rate=22 sccm, and N2/SF6 ratio=0.1. Furthermore, it was demonstrated that the established etching process avoids the structure damage of Au components.