Projection optical system, exposure apparatus, and device manufacturing method

摘要

Disclosed is a projection optical system specifically to be used with extreme ultraviolet (EUV) light having a wavelength not less than 10 nm and not greater than 20 nm. The projection optical system has six mirrors sequentially reflecting light in an order from the object side toward the image side and being disposed to define a coaxial system, wherein each of the six mirrors has a curvature radius not greater than 1500 mm.