Design of a projection objective with high numeric aperture and large view field

As the primary facility for the manufacturing of integrated circuit(IC), and MEMS devices [1], the lithographic equipment’s improvement is restricted by the projection objective which can decide the capacity of the image transmission of the facility and make the facility be capable of reaching the higher precision or beyond. On the basis of the function, increasing the numeric aperture is coupled with the raising of resolution of the projection objective. In this paper, a design of a projection objective with high numeric aperture and large view field for I-line lithography is proposed. Owning a dual-telecentric structure this optical system owns an angular magnification of -1.25, an effective image field of 90×90mm and an image numeric aperture of 0.2. Two aspheric surfaces are adopted in this projection objective to enhance the quality of imaging that will insure the field curvature lower than a half of the DOF, restrict the distortion lower than±σ/5 and make the MTF approximate the diffraction limits.