Metrology Data Source Separation Using PCA and ICA

Solution Overview

Problem

In lithographic processes, accurately determining the true value of substrate measurements is challenging due to the presence of systematic errors, which complicates the assessment of measurement accuracy and precision.

Innovation Solution

A method using principal component analysis (PCA) and independent component analysis (ICA) to separate contributions from independent sources in substrate measurement results, compiling these into a matrix to identify the true value and assess the accuracy of measurement recipes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If multiple substrate measurement recipes are used to measure overlay, then measurement coverage is improved, but measurement precision deteriorates due to systematic errors from different recipe types

Engineering Contradiction:

Improvemeasurement coverageVSAvoidoverlay measurement precision

Core Design Contradiction:

Quantity of substanceVSMeasurement precision

Solution Approach 1:

The patent segments the measurement results into contributions from different independent sources (true overlay value, systematic errors, random errors) using independent component analysis. This allows separation of the true value from systematic errors introduced by different measurement recipes, enabling accurate determination of true overlay despite using multiple recipe types.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces independent component analysis as an intermediary computational method that processes the combined measurement results from multiple recipes. This intermediary analysis separates the contributions from different sources, allowing the true overlay value to be extracted without being contaminated by systematic errors from specific recipe types.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If different types of substrate measurement recipes are used, then measurement versatility is improved, but reliability of individual recipe accuracy deteriorates

Engineering Contradiction:

Improvemeasurement recipe versatilityVSAvoidrecipe accuracy reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent segments the measurement results into contributions from different independent sources (true overlay value, systematic errors, random errors) using independent component analysis. This allows separation of the true value from systematic errors introduced by different measurement recipes, enabling accurate determination of true overlay despite using multiple recipe types.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses the measurement results from multiple recipes to provide feedback about the systematic errors of each recipe type. By analyzing the variations in results across different recipes, the system can identify and quantify systematic errors, then use this feedback to determine the true overlay value and assess each recipe's accuracy.

Inventive Principle:

Principle #23Feedback

3Device complexity

If systematic errors are present in substrate measurements, then measurement complexity is reduced, but measurement precision deteriorates

Engineering Contradiction:

Improvemeasurement system complexityVSAvoidoverlay measurement precision

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent introduces independent component analysis as an intermediary computational method that processes the combined measurement results from multiple recipes. This intermediary analysis separates the contributions from different sources, allowing the true overlay value to be extracted without being contaminated by systematic errors from specific recipe types.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces physical measurement system modifications with a computational approach. Instead of modifying the measurement hardware to eliminate systematic errors, the patent uses independent component analysis to mathematically separate and remove the effects of systematic errors from the measurement results.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS11016397B2Source separation from metrology data

Publication Date: 2021.05.25 ASML NETHERLANDS BV

AI summary

A method and a computer program product that relates to lithographic apparatuses and, processes, and more particularly to a method and computer program to inspect substrates produced by the lithographic apparatuses and processes. The method and/or computer program product includes determining contributions from independent sources from results measured from a lithography process or a substrate processed by the lithography process, wherein the results are measured using a plurality of different substrate measurement recipes.