Methods are disclosed for manufacturing multi-layer film reflection mirrors,
in which a desirable shape accuracy of a reflected wavefront can be obtained after
locally scraping the multi-layer film. In an exemplary method, a multi-layer film
(comprising respective alternating layers of at least two types of substances having
different respective refractive indices) is superposedly formed on the surface
of a mirror substrate. The multi-layer film has a constant period length, and the
multi-layer film on the substrate is locally scraped to correct a phase of a reflected
wavefront from the reflective surface of the mirror. The multi-layer film has an
internal stress of 50 MPa or smaller. Alternatively or in addition, a compensating
adjustment in a film formed on a reverse surface of the substrate can be made to
cancel the stress perturbation caused by scraping of the multi-layer film on the
obverse surface of the substrate.
