US Patent 7408760 Charged particle beam application system

During the writing operation, the wafer potential is dynamically detected and corrected. By doing so, the positional accuracy of the circuit patterns written on a wafer can be improved. After a contact resistance between a wafer and a earth pin is measured, the current flowing from the wafer to the ground potential via the earth pin is measured. Then, based on the measurement result, the potential difference is given between the wafer and the ground potential.