Importance

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Abstract

A chamber 25 comprises a support 45 for holding a substrate 20 and a sensor system 135 adapted to detect the presence or proper placement of the substrate 20 on the support 45. The support 45 comprises a window 155 that is transparent and adapted to transmit light therethrough. The sensor system 135 comprises a light source 140 adapted to direct a light beam 150 through the window 155 and a light sensor 160 in the path of the light beam 150. The light beam 150 is sensed by the light sensor 135 when the substrate 20 is properly positioned and the light beam 150 is blocked from the light sensor 135 when the substrate 20 is improperly positioned or vice versa. Preferably, the support 45 comprises an electrostatic chuck 55 adapted to electrostatically hold the substrate 20, the electrostatic chuck 55 comprising a window 155 composed of transparent material or a cut-out or a hole therein.

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First Claim