Soft X-Ray Projection Optics,

There is a surprising variety of interesting optical designs for possible use in soft X-ray lithography. The requirements for the projection system are more difficult than those for the beam handling and mask illuminator optics, and it is only the projection optics that will be discussed here. Only normal incidence types of designs, using multilayer coatings to get acceptable reflectance, will be treated in any depth. There are other, grazing incidence, designs that will be briefly reviewed but these are not yet mature designs.