| 摘要 |
Positional information of each of wafer stages during exposure and during alignment is measured directly under a projection optical system and directly under a primary alignment system, respectively, by a plurality of encoder heads, Z heads and the like, which a measurement bar placed below surface plates has, using gratings placed on the lower surfaces of fine movement stages. Since a main frame that supports the projection optical system and the measurement bar are separated, deformation of the measurement bar caused by inner stress (including thermal stress) and transmission of vibration or the like from the main frame to the measurement bar, and the like do not occur, which is different from the case where the main frame and the measurement bar are integrated. Consequently, high-precision measurement of the positional information of the wafer stages can be performed. |
