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

technical field

[0001] 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

[0002] 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.

[0003] 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 of this Zernike polynomial can be expressed as

[0004] Z1:1

[0005] Z2: rcosθ

[0006] Z3: rsinθ

[0007] Z4: 2r 2 -1

[0008] Z5: r 2 cos2θ

[0009] Z6: r 2 sin2θ

[0010] Z7: (3r 2 -2r)cosθ

[0011] Z8...

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