1. Field
One embodiment of the invention relates to a spatial light modulator unit, an illumination optical system, an exposure device, and a device manufacturing method.
2. Description of the Related Art
In a typical exposure device of this kind, a light beam outputted from a light source travels through a fly's eye lens as an optical integrator to form a secondary light source (in general, a predetermined light intensity distribution on an illumination pupil) as a substantial surface illuminant consisting of a large number of light sources. In the description hereinafter, the light intensity distribution on the illumination pupil will be referred to as “pupil intensity distribution.” The illumination pupil is defined as a position such that an illumination target surface becomes a Fourier transform plane of the illumination pupil by action of an optical system between the illumination pupil and the illumination target surface (which is a mask or a wafer in the case of the exposure device).
Rays from the secondary light source are condensed by a condenser optical system to illuminate the mask with a predetermined pattern thereon in a superimposed manner. The light passing through the mask is focused through a projection optical system on the wafer and the mask pattern is projected and exposed (transferred) onto the wafer. Since the pattern formed on the mask is a highly integrated one, it is essential to obtain a uniform illuminance distribution on the wafer, in order to accurately transfer the fine pattern onto the wafer.
There is a conventionally proposed illumination optical system capable of continuously changing the pupil intensity distribution (and the illumination condition eventually) (cf. U.S. Patent Application Laid-Open No. 2009/0116093). The illumination optical system disclosed in U.S. Patent Application Laid-Open No. 2009/0116093 uses a movable multi-mirror system consisting of a large number of microscopic mirror elements arranged in an array form and individually driven and controlled in their inclination angle and inclination direction, to divide an incident beam into small unit rays by respective reflecting faces thereof and deflect the small unit rays, whereby the cross section of the beam is converted into a desired shape or a desired size, so as to realize a desired pupil intensity distribution.