| CPC G01R 29/12 (2013.01) [H01L 21/6833 (2013.01); H01L 21/68742 (2013.01); H01L 22/12 (2013.01)] | 20 Claims |
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1. An electric field measuring apparatus comprising:
an electrostatic chuck provided with a through hole and configured to hold a wafer using an electrostatic force;
a lift pin configured to pick up the wafer and vertically move through the through hole;
a driver configured to vertically move the lift pin along the through hole;
a probe in the lift pin and having a refractive index changed by an electric field of the wafer, the probe including an electro-optical crystal;
an optical waveguide configured to form at least one internal path of light having a polarization characteristic changed by the changed refractive index between the probe and the wafer; and
a control module configured to control the lift pin and the driver,
wherein the lift pin is further configured to move to a first position and a second position at a different vertical level than the first position,
wherein each of the first and second positions is at a lower vertical level than the wafer, and
wherein the control module is further configured to calculate a strength of the electric field of the wafer, using electric field data measured using the probe at each of the first and second positions.
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