Mechanisms of process-induced heating of MEMS structures during plasma release etch

The temperature rise on suspended MEMS structures during a Si plasma release etch process is investigated experimentally using in situ infrared imaging. The process is performed on a commercially available inductively coupled plasma etch chamber and comprises an anisotropic, Bosch-type Si DRIE step, an O₂ inhibitor removal step and a SF₆ isotropic Si etch. Temperatures up to 150°C were observed during the isotropic etch and indicate the exothermic reaction of Si and F is the dominant source of heat. Temperature trends with test structure geometry suggest interplay between radiative cooling and etchant transport determines maximum structure temperature.