Electrostatic Force Detector With Improved Shielding And Method Of Using An Electrostatic Force Detector

摘要

An electrostatic force detector (“EFD”) for measuring electrostatic force of a surface under test (“SUT”) includes a force detector comprising a cantilevered arm and a probe. The EFD has a shield with a hole through which the probe extends and is positioned to prevent electromagnetic energy from the SUT from reaching the cantilevered arm and most of the probe, and preventing light from reaching the SUT. A method for selecting a voltage range for an EFD measuring a charge on an SUT includes measuring with the EFD two voltages at or near the end-points of an estimated voltage-range, and then comparing the polarities. If the polarities differ, the estimated voltage-range is selected. However, if the polarities are the same, then the estimated voltage range is adjusted to provide a new estimated voltage-range, which is then tested for purposes of determining whether the charge on the SUT is within the range.