| 摘要 |
<p>PROBLEM TO BE SOLVED: To make it possible to judge whether or not a board has been separated normally from an electrostatic chuck by measuring the values of currents which flow when a substance to be adsorbed is detached, and calculating the quantities of charges remaining in the electrostatic chuck and their polarities on the basis of these current values. SOLUTION: Since oscillating currents flow to electrodes 21, 22 at the instant of time when a substance 1 to be adsorbed is lifted up, they are monitored by ammeters 12, 13, and the movement of the substrance 1 to be adsorbed on a lift pin 10 is learned. The oscillating currents and a detaching current I3 by electrostatic induction on the occasion of separating the substance 1 to be adsorbed from an electrostatic chuck plate 3 reflect the magnitudes of the residual charges 6, 7 of the electrostatic chuck 2, and the movement of the substance 1 to be adsorbed on the lift pin 10. The detaching current, oscillating currents, and residual charges are measured, and the condition of movement of the substance to be adsorbed from the upside of the electrostatic chuck is learned. It is possible to compute the quantities of charges remaining on the electrostatic chuck, if current values on the occasion of detaching after the flow of discharging currents are measured. Besides, it is also possible to know the polarities of residual charges by the directions of the currents flowing.</p> |
