Metrology Method Correcting Non-Isoplanatic Aberrations

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Solution Overview

Problem

Existing metrology tools face challenges in correcting non-isoplanatic aberrations, which are common in simplified lens systems used to reduce cost and complexity, limiting their accuracy and effectiveness in measuring substrate structures.

Innovation Solution

A metrology method that non-iteratively corrects images for non-isoplanatic aberrations by performing field and pupil non-isoplanatic correction operations in their respective spaces, specifically addressing aberrations describable as a convolution combined with object and/or pupil distortion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If simplified lens systems are used to reduce cost and complexity, then device complexity is reduced, but non-isoplanatic aberrations increase

Engineering Contradiction:

Improvelens system complexityVSAvoidimage accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent extracts the aberration correction function from the optical design phase and moves it to the image processing phase. By separating the correction function from the lens design, the system can use simpler lenses while achieving accurate images through computational correction of non-isoplanatic aberrations.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces complex mechanical/optical aberration correction mechanisms with computational image processing. Instead of using complex lens systems or mechanical adjustment mechanisms to correct aberrations, the system captures aberrated images and corrects them digitally through field and pupil space operations.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If iterative correction methods are used, then measurement precision is improved, but processing time increases

Engineering Contradiction:

Improveaberration correction accuracyVSAvoidcorrection processing time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent performs preliminary characterization of the optical system's aberrations during manufacturing or initial setup. By pre-determining the aberration profiles and preparing correction parameters in advance, the system can apply corrections quickly during actual measurements without iterative processing.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses disposable or single-use calibration data and correction lookup tables that are generated once and then reused. Instead of performing iterative corrections for each measurement, the system uses pre-computed correction parameters that can be applied directly to new images.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Data Source

PatentUS20250138436A1Metrology method and device

Publication Date: 2025.05.01 ASML NETHERLANDS BV

AI summary

Disclosed is a metrology method and associated devices. The method comprises obtaining a first image, said first image being subject to one or more non-isoplanatic aberrations of an optical system used to capture said image; and non-iteratively correcting said first image for the effect of said one or more non-isoplanatic aberrations by performing one or both of: a field non-isoplanatic correction operation in field space for said first image, said field space corresponding to a field plane of the optical system; and a pupil non-isoplanatic correction operation in pupil space for said first image, said pupil space corresponding to a pupil plane of the optical system. Said one or more non-isoplanatic aberrations comprise a class of non-isoplanatic aberrations describable as a convolution combined with an object distortion and/or a pupil distortion.