Method for computing double absorption layer alternating phase shift mask diffraction field

Abstract

The invention provides a method for computing a double absorption layer alternating phase shift mask diffraction field. The method comprises the following specific steps; 1, setting the number n of spatial harmonics when an electromagnetic field is expanded; 2, performing Fourier series expansion on the dielectric constant of each grating layer, wherein, performing Fourier series expansion on TM polarized light by computing the reciprocal of the dielectric constant; and 3, for TE polarized light and the TM polarized light, solving the characteristic matrix of each grating layer, and obtaining a diffraction field corresponding to the TE polarized light by using continuous boundary conditions in the tangent direction of the electromagnetic field. Through the Fourier series expansion on the TM polarized light by computing the reciprocal of the dielectric constant, the convergence of the TM polarized light while entering a damaged mask grating can be improved, so that the calculated diffraction field has a higher accuracy.

Description

technical field [0001] The invention relates to a calculation method for a diffraction field of a double-absorbing layer alternating phase-shift mask, and belongs to the technical field of photolithographic resolution enhancement. Background technique [0002] The rapid development of the semiconductor industry is mainly due to the progress of micro-processing technology in microelectronics technology, and photolithography technology is one of the most critical manufacturing technologies in chip preparation. Due to the continuous innovation of optical lithography technology, it has repeatedly broken through the expected optical exposure limit, making it the mainstream technology of current exposure. [0003] The lithography system is mainly divided into four parts: illumination system (light source), mask, projection system and wafer. The light incident on the mask is diffracted, and the diffracted light enters the projection system and forms an interference image on the wa...

AI Technical Summary

Problems solved by technology

First, the method only analyzes multilayer grating structures with the same period

Second, this method analyzes the diffraction characteristics of dielectric gratings. When analyzing TM polarized light incident on a lossy mask grating, the convergence becomes poor

[0009] The prior art (J.Opt.Soc.Am.A, 1996, 13:779-784) discloses a method to improve the convergence of TM polarization, but it only analyzes the diffraction of a single-layer grating

However, in the alternating phase shift mask, the period of the etched area in the glass substrate is different from the period of the mask absorbing layer, and the alternating phase shift mask has two absorbing layers, so the above method is not applicable to the alternating phase shift mask. Solution of Diffraction Field

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