Patent ID: 6943568
Filing Date: 2005-09-13
Classification: G01R

Abstract:
1. A charging voltage measuring apparatus for measuring a charging voltage Vs on the surface of a substrate on a substrate holding unit, comprising: a measuring electrode, for forming an electrostatic capacity Cs with said substrate, being disposed on said substrate holding unit to make contact with or proximate to the back face of said held substrate, and said measuring electrode being electrically insulated from said substrate holding unit; a measuring capacitor connected between said measuring electrode and a ground potential portion, said measuring capacitor having an electrostatic capacity Cm; a voltage measuring unit for measuring a measuring voltage Vm between both ends of said measuring capacitor; and a calculating unit for calculating said charging voltage Vs in accordance with a following numerical expression, Vs=K×Vm where K=(Cs+Cm)/Cs or K=(Cm/Cs) (if Cm>Cs), or its mathematically equivalent numerical expression on the basis of an inverse K of a voltage dividing ratio that is defined by the relation of said electrostatic capacities Cs and Cm and said measuring voltage Vm.