Metrology by Reconstruction for Lithography

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Solution Overview

Problem

In lithographic processes, accurately determining the true value of measured characteristics on substrates is challenging due to the presence of systematic errors, which are difficult to distinguish from the true values in measurement results, especially when using different substrate measurement recipes that introduce varying intensity distributions and light polarization at the pupil plane.

Innovation Solution

A method using a computer to reconstruct the pattern from a plurality of measurement results obtained with varying substrate measurement recipes, employing techniques like the Algebraic Reconstruction Technique, Radon transform, or projection-slice theorem, to determine the true value and systematic errors, allowing for edge placement error determination and alignment between layers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If multiple substrate measurement recipes with different intensity distributions and light polarizations are used, then measurement completeness and ability to separate true values from systematic errors is improved, but measurement complexity and data processing requirements increase

Engineering Contradiction:

Improveability to separate true values from systematic errorsVSAvoidmeasurement complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The measurement process is segmented into multiple independent measurement recipes, each using different intensity distributions and light polarizations. This segmentation allows systematic errors to be isolated and separated from true values by comparing results across different measurement configurations, thereby improving measurement precision while managing complexity through structured decomposition

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Measurement parameters such as intensity distribution and light polarization are deliberately changed across different measurement recipes. By varying these parameters and observing how measurement results change, the method enables separation of true values from systematic errors, as systematic errors typically manifest differently under varying parameters compared to true measurements

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If multiple substrate measurement recipes are used to obtain comprehensive measurement results, then the ability to determine true values and systematic errors is improved, but measurement time and processing overhead increase

Engineering Contradiction:

Improvedetermination of true values and systematic errorsVSAvoidmeasurement time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

Multiple measurements using different substrate measurement recipes are performed in advance to collect comprehensive data before reconstruction. This preliminary action ensures that all necessary measurement information is gathered upfront, enabling subsequent computational reconstruction to efficiently separate true values from systematic errors without requiring additional measurement time during the reconstruction phase

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The measurement process creates multiple copies of the pattern under different measurement conditions (different intensity distributions and polarizations). These measurement copies are then computationally reconstructed to extract true values, allowing the system to achieve high precision without repeating measurements during the analysis phase

Inventive Principle:

Principle #26Copying

3Manufacturing precision

If diffraction images with different intensity distributions and light polarizations are used for reconstruction, then edge placement error determination accuracy is improved, but computational complexity increases

Engineering Contradiction:

Improveedge placement error determination accuracyVSAvoidcomputational complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

A computational reconstruction process acts as an intermediary between the multiple diffraction images and the final edge placement error determination. This intermediary reconstruction step integrates information from diffraction images with different intensity distributions and polarizations, filtering out systematic errors and extracting accurate edge placement measurements while managing computational complexity through structured processing

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables precise determination of edge placement errors and alignment between layers by reconstructing the pattern from diffraction images obtained with different intensity distributions and light polarizations, effectively separating true values from systematic errors.

Implementation Method 1

The plurality of measurement results comprise diffraction images

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentUS10437158B2Metrology by reconstruction

Publication Date: 2019.10.08 ASML NETHERLANDS BV

AI summary

Disclosed herein is a method comprising: obtaining a plurality of measurement results from a pattern on a substrate respectively using a plurality of substrate measurement recipes, the substrate processed by a lithography process; reconstruct, using a computer, the pattern using the plurality of measurement results, to obtain a reconstructed pattern.