Method for optimizing attenuated phase-shifting mask (ATTPSM) of nonideal photoetching system based on Abbe vector imaging model

Abstract

The invention provides a method for optimizing an attenuated phase-shifting mask (ATTPSM) of a nonideal photoetching system based on an Abbe vector imaging model. The method comprises the following steps of: setting transmittivity of different phase opening parts in the phase-shifting mask; setting a variable matrix Omega; setting a target function D as linear combination of an imaging evaluationfunction of an ideal image surface and an imaging evaluation function of an image surface of which the defocusing quantity is fnm; and guiding optimization on the pattern and the phase of the phasing-shifting mask by using the variable matrix Omega and the target function D. By using the vector imaging model and taking vector characteristic of an electromagnetic field into consideration during acquisition of a space image, the optimized mask is suitable for the photoetching system with small numerical aperture (NA) and also suitable for the photoetching system of which the NA is more than 0.6. By the method, the gradient information of optimizing the target function is utilized and a steepest descent method is combined to optimize the pattern of the phase-shifting mask, so the optimization efficiency is high.

Description

technical field [0001] The invention relates to an optimization method of a non-ideal lithography system ATTPSM (attenuated phase shift mask) based on an Abbe (Abbe) vector imaging model, and belongs to the technical field of lithography resolution enhancement. Background technique [0002] The current large-scale integrated circuits are generally manufactured using photolithography systems. The lithography system is mainly divided into four parts: illumination system (including light source and condenser), mask, projection system and wafer. The light emitted by the light source is focused by the condenser and then enters the mask, and the opening part of the mask transmits light; after passing through the mask, the light is incident on the wafer coated with photoresist through the projection system, so that the pattern of the mask is copied on the wafer. [0003] The current mainstream lithography system is the 193nm ArF deep ultraviolet lithography system. As the lithogra...

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Problems solved by technology

However, the above method has the following three shortcomings: first, the above method is based on the scalar imaging model of the lithography system, so it is not suitable for high NA lithography systems; second, the above method does not consider the different points of the projection system on the light source surface The response to the incident light of the light source is different, but because the incident angle of the light at different positions on the light source surface is different, its effect on the projection system is different. Therefore, there is a large deviation between the aerial image obtained by the above method and the actual one, which will affect the optimization of the mask. Third, the above method does not consider the impact of scalar aberration, polarization aberration and defocus of the lithography system, so it is not suitable for non-ideal lithography systems

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