Exposure process

Abstract

Disclosed is an exposure method comprising preparing an exposure apparatus including an illumination system and a projection lens, setting, in the exposure apparatus, a photomask having a mask pattern including a plurality of unit circuit patterns arranged like a checkered flag pattern and a plurality of unit auxiliary patterns arranged between the unit circuit patterns, and projecting the mask pattern onto a substrate through the projection lens by irradiating the photomask with light from the illumination system, wherein the unit circuit patterns and the unit auxiliary patterns generate a plurality of diffraction light spots on a pupil plane of the projection lens, and the four diffraction light spots having higher light intensities than the remaining diffraction light spots are distributed on the pupil plane in a cycle of 90°.

Description

[0001] This application is a divisional application of an invention patent application filed by Toshiba Corporation on June 27, 2002 with the application number 02123399.3 and the invention name "exposure method". technical field [0002] The present invention relates to an exposure method, and particularly relates to a technique for reducing the influence of aberration in a lithography process of semiconductor manufacturing. Background technique [0003] In recent years, along with the miniaturization of circuit patterns, the influence of aberration of a projection lens of an exposure apparatus has become a problem. [0004] If the aberration of the projection lens is to be reduced, the aberration of the optical system needs to be converted into the form of wavefront aberration due to the need for physical optics processing. Zernike polynomials are currently widely used as a method of expressing wavefront aberrations as a function of pupil coordinates. The first 16 terms o...

AI Technical Summary

Problems solved by technology

However, it is extremely difficult to adjust the lens for 3θ aberration, so it is extremely difficult to solve the problem of transferring a left-right asymmetrical pattern as described above.

[0025] In particular, when a grid-shaped pattern is formed on the reticle, as will be described later, the influence of 3θ aberration is enhanced due to the intensity distribution on the pupil plane of diffracted light, and left and right asymmetrical patterns are transferred. Questions like pattern will become more profound questions

[0026] In this way, with the miniaturization of circuit patterns, it is difficult to obtain a desired pattern on the wafer due to the aberration of the projection lens, and it is extremely difficult to reduce the influence of 3θ aberration in particular.

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