Plasma damage to silicon resonators measured by internal friction

Plasma-based processes are widely used in microfabrication for cleaning and etching, but can result in unwanted damage to the device being fabricated. We investigate the effects of two common plasma treatments—cleaning via an oxygen plasma, and a tetrafluoromethane reactive ion etch—on silicon by measuring the internal friction of high quality factor silicon resonators before and after exposure to the plasma treatment. We find that all plasma treatments led to surface damage, as measured by an increase in internal friction, only some of which could be mitigated by post-plasma annealing at 200°C or 400°C. Additionally, there is evidence of an internal friciton peak resulting from a thin fluorinated layer after the tetrafluoromethane etch, which can be mitigated by annealing.