Importance

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Abstract

A substrate supporting device includes support elements for supporting a substrate, and positioning elements for contacting outer peripheries of the substrate to check horizontal movement thereof. A substrate sensor is disposed around the supporting device for detecting the substrate supported thereon. The supporting device is surrounded also by light projectors for horizontally projecting light having projection tracks overlapping, in a plan view, the substrate supported by the substrate supported device and extending at an angle to one another, and light receivers for receiving the projected light. The substrate sensor and light receivers input signals to a microcomputer for determining whether the substrate is correctly supported. A light projector may project a light beam toward the surface of the substrate supporting on the substrate supporting device, and cause the light beam to be reflected by the substrate surface. Whether the substrate is correctly supported may be determined based on whether the reflected light beam is received by a light receiver. The determination of the substrate being correctly supported is made while the substrate is supported on the supporting device. When the substrate is correctly supported, the substrate supporting device is rotated about a vertical axis to effect a predetermined treatment of the substrate.

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First Claim