Computer generated hologram, exposure apparatus and device fabrication method

A device fabrication method comprising steps of:

• exposing a substrate using an exposure apparatus;
• and
• performing a development process for the substrate exposed,
• wherein said exposure apparatus includes:
• an illumination optical system configured to illuminate a reticle with light from a light source;
• and
• a projection optical system configured to project a pattern of the reticle onto the substrate,
• wherein said illumination optical system includes a hologram including a plurality of cells which form a light intensity distribution on a predetermined plane,
• the plurality of cells including
• a plurality of first cells including isotropic media and anisotropic media, and
• a plurality of second cells including anisotropic media alone,
• wherein the plurality of cells change a phase of incident light which impinges on each of the plurality of cells to form a phase distribution including N phases (N is the number of phases, N≧2) for each of a wavefront of a linearly polarized light component in a first direction and a wavefront of a linearly polarized light component in a second direction perpendicular to the first direction,
• each of said anisotropic media of said plurality of first cells and said plurality of second cells includes one of an anisotropic medium having an optic axis in the first direction and an anisotropic medium having an optic axis in the second direction, and
• letting λ be a wavelength of the incident light, and Δna be a difference between refractive indices, with respect to linearly polarized light components in the first direction and the second direction, of each of said anisotropic media of said plurality of first cells and said plurality of second cells, an anisotropic medium thickest of said anisotropic media of said plurality of first cells and said plurality of second cells has a thickness of λ/Δna×(N−1)/2N.