| 摘要 |
PURPOSE:To measure the inclination of a mask stably with a simple constitution, by irradiating an array of Fresnel zones, which is formed on the rear face of the mask, with rays and observing an optical image converged by the reflected light of a wafer. CONSTITUTION:Eight Fresnel zone plates similar to a zone plate 13-8 are arranged on the rear face of a mask 11 to form one set of a zone array 13. When the mask 11 is irradiated with a parallel light from above, the third-order focus of the zone array 13 is observed as a light spot by the reflected light from a wafer 12. If the mask 11 and the wafer 12 are parallel with each other, only a light spot 16 looks bright. If the wafer 11 is inclined, plural zone plates have bright centers. Thus, the inclination of the wafer 11 is measured stably with a simple constitution. |
