One embodiment relates to an apparatus for virtual grounding of a target substrate in a charged-particle beam apparatus. A primary gun generates charged particles for a process beam that is focused on a frontside surface of the target substrate, and the target substrate is held by a stage. An electrostatic voltmeter measures a voltage potential of the target substrate, and a charge-control gun impinges a beam of charged particles to the target substrate. A feedback control loop is used to control the flood gun depending on the voltage potential measured by the electrostatic voltmeter. Other embodiments, aspects and features are also disclosed.