A method and apparatus for measuring a charge on a surface, such as on a semiconductor wafer, arising during plasma processing is provided. Such a charge may be measured on an insulating film applied to such a wafer. By the present invention, the charge on such an insulator exposed to plasma is measured in-situ using micro-cantilevers. The micro-cantilevers include an insulating base positioned on the substrate and a cantilevered beam extending therefrom to over the substrate. The beam is formed of a conductive material. A charge on the beam causes an opposite charge to form on the substrate. The opposite charges attract to move or deflect the beam towards the substrate. The amount of movement or deflection corresponds to the magnitude of the charge. This movement or deflection of the beam can be measured to determine the charge by bouncing a light source, such as a laser, off of the beam. In another embodiment, the cantilever includes a flexible bridge interconnected between the base and a rigid beam. In this embodiment, the surface of the beam does not bend. Rather, movement of the beam is accomplished by the bending of the flexible bridge. This allows for easier measurements of the movement of the beam because the surface of the beam remains planar.