Exposure apparatus

#This application claims foreign priority benefit based on Japanese Patent Applications No. 2005-183010, filed on Jun. 23, 2005, and No. 2006-132301, filed on May 11, 2006, each of which is hereby incorporated by reference herein in its entirety as if fully set forth herein.

#The present invention relates, generally, to an exposure apparatus, and, more particularly, to an exposure apparatus that exposes a plate, such as a wafer for a semiconductor device, and a glass plate for a liquid crystal display (“LCD”). The present invention is suitable, for example, for a so-called immersion exposure apparatus that immerses, in a liquid, a space between a plate and a final surface (of a final optical element) of a projection optical system, and exposes the plate via the liquid.

#A conventional projection exposure apparatus uses a projection optical system to expose a circuit pattern of a reticle (or a mask) onto a wafer, etc., and a demand for a high-resolution exposure apparatus has recently increasingly grown. Immersion lithography is one attractive measure to meet this high-resolution demand. Immersion lithography promotes an increase of a numerical aperture (“NA”) of the projection optical system by replacing a medium at the wafer side of the projection optical system with a liquid. The projection exposure apparatus has an NA of n·sin θ, where n is a refractive index of the medium. The NA increases up to n when the medium has a refractive index greater than that of air, i.e., n>1. Immersion lithography intends to reduce the resolution R (which is defined as R=k1(λ/NA)) of the exposure apparatus, where k1 is a process constant, and λ is a wavelength of a light source.

#FIG. 1 is a schematic sectional view of a structure of an exposure apparatus according to one aspect of the present invention.

#FIG. 2 is a schematic sectional view showing one illustrative structure of a measuring unit of the exposure apparatus shown in FIG. 1.

#FIG. 3 is a schematic sectional view showing a structure of a variation of the measuring unit shown in FIG. 2.

#A description will now be given of an exposure apparatus 100 according to one aspect of the present invention, with reference to the accompanying drawings. In each figure, the same element is designated by the same reference numeral, and a duplicate description will be omitted. Here, FIG. 1 is a schematic block diagram of the exposure apparatus 100. The exposure apparatus 100 is an immersion type projection exposure apparatus in which a circuit pattern of a reticle 20 is exposed onto a plate 40 via a liquid 70, which is supplied to a space between the plate 40 and a final surface (of a final optical element) of the projection optical system 30 closest to the plate 40. The exposure apparatus 100 is a step-and-repeat or a step-and-scan exposure apparatus. Of course, the exposure apparatus 100 is applicable to a step-and-repeat manner, and this embodiment discusses the step-and-scan exposure apparatus (“scanner”) by way of example.

#The exposure apparatus 100 includes an illumination apparatus 10, a reticle stage 22, which is mounted with a reticle 20, a projection optical system 30, a wafer stage 42, which is mounted with a plate 40, a distance-measuring means 50, a stage controller 60, a liquid supply/recovery system, and a measuring unit 80.

#The illumination apparatus 10 illuminates a reticle 20 that has a circuit pattern to be transferred, and includes a light source unit 12, and an illumination optical system 14.