Patent ID: 8040655
Filing Date: 2011-10-18
Classification: H01L,H02N

Abstract:
1. A substrate holding apparatus comprising: an electrostatic chuck for electrostatically attracting and holding a substrate thereon; a push-up member contactable with a position of vicinity of an edge of the substrate on the electrostatic chuck from below for pushing up the substrate; a drive apparatus for driving at least one of the electrostatic chuck and push-up member to thereby allow the push-up member to push up the substrate; a force sensor for detecting a force applied to the push-up member in a pushing up operation; and a control unit, wherein the control unit is configured to measure the force from the force sensor as a first measurement, output a normal state signal when the measured force in the first measurement is equal to or larger than a lower limit value and is equal to or smaller than an upper limit value, and output an abnormal state signal when the measured force in the first measurement is smaller than the lower limit value, only prior to completely removing the substrate from the electrostatic chuck, the control unit is configured to measure again the force detected by the force sensor as a second measurement after waiting for a time when the measured force in the first measurement is larger than the upper limit value, output the normal state signal when the re-measured force in the second measurement is equal to or larger than the lower limit value and is equal to or smaller than the upper limit value, output the abnormal state signal when the re-measured force in the second measurement is smaller than the lower limit value, and output the abnormal state signal when the re-measured force in the second measurement is larger than the upper limit value, only prior to completely removing the substrate from the electrostatic chuck.