Optimization of source, mask and projection optics
First Claim
1. A method implemented by a computer for improving a lithographic process for imaging a portion of a design layout onto a substrate using a lithographic projection apparatus comprising an illumination source and projection optics, the method comprising:
- defining a model of the lithographic process using a plurality of design variables including projection optics-related design variables;
defining a multi-variable cost function representing a lithographic process response, wherein the multi-variable cost function comprises a function of the projection optics-related design variables; and
reconfiguring, using the computer, characteristics of the lithographic process by adjusting the projection optics-related design variables, until a predefined termination condition for the multi-variable cost function is satisfied.
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Abstract
Embodiments of the present invention provide methods for optimizing a lithographic projection apparatus including optimizing projection optics therein, and preferably including optimizing a source, a mask, and the projection optics. The projection optics is sometimes broadly referred to as “lens”, and therefore the joint optimization process may be termed source mask lens optimization (SMLO). SMLO is desirable over existing source mask optimization process (SMO), partially because including the projection optics in the optimization can lead to a larger process window by introducing a plurality of adjustable characteristics of the projection optics. The projection optics can be used to shape wavefront in the lithographic projection apparatus, enabling aberration control of the overall imaging process. According to the embodiments herein, the optimization can be accelerated by iteratively using linear fitting algorithm or using Taylor series expansion using partial derivatives of transmission cross coefficients (TCCs).
66 Citations
20 Claims
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1. A method implemented by a computer for improving a lithographic process for imaging a portion of a design layout onto a substrate using a lithographic projection apparatus comprising an illumination source and projection optics, the method comprising:
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defining a model of the lithographic process using a plurality of design variables including projection optics-related design variables; defining a multi-variable cost function representing a lithographic process response, wherein the multi-variable cost function comprises a function of the projection optics-related design variables; and reconfiguring, using the computer, characteristics of the lithographic process by adjusting the projection optics-related design variables, until a predefined termination condition for the multi-variable cost function is satisfied. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification