Noninvasive measurement of charging in plasmas using microelectromechanical charge sensing devices

The plasma induced charging of surfaces in a plasma during semiconductor processing has been measured noninvasively using microelectromechanical devices. We have designed, modeled, and fabricated microcantilevers to act as charge sensing probes. The devices exhibit a mechanical deformation when charged, which is probed in situ by optical techniques, or measured by optical inspection after removal from plasma. Charging voltage measurements in a parallel-plate reactive-ion-etching reactor show that more charging is evident at the electrode edge, and that the charging is a strong function of input rf power, chamber pressure, and flow rate of gases.