| 摘要 |
PROBLEM TO BE SOLVED: To make autofocus operations follow smoothly even when an exposed light is started scanning from the outside of a substrate by a method wherein a surface position of the substrate is aligned with a focus surface of a projection optical system, and a surface height of a substrate holding member is substantially aligned with a surface height of the substrate. SOLUTION: A Z stage is driven by a Z stage driver so that a focus face of a projection optical system 26 is aligned with a face of a wafer 24 based on a detection signal of an autofocus light receiving system 40. A recess part 28a to which a wafer 24 is mounted is formed in a center portion of a wafer holder 28, and the wafer 24 is mounted in the recess part 28a with an extremely minute clearance 3 (for example, about 100μm). Further, the wafer holder 28 is comprised so that a surface height of the wafer 24 is substantially alighned with a height of a surface 28b of an outer peripheral part of the wafer holder 28, under a condition that the wafer 24 is set to the recess part 28a. In this connection, a depth of the recess part 28a of the wafer holder 28 is equal to a uniform thickness of the wafer. |
