Optical Scatterometry for Edge Placement Error Measurement

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current methods for measuring edge placement error in lithographic processes are either destructive or indirect, making them time-consuming and limiting the ability to adjust processing conditions in real-time, and they often use targets with different dimensions and pitches than the actual product features, reducing measurement accuracy.

Innovation Solution

A method and apparatus for directly and non-invasively measuring edge placement error by using a substrate with layers of electrically conducting and non-electrically conducting materials, where the edge placement error is determined by analyzing the reflectivity of the substrate when illuminated with optical radiation, allowing for precise correlation with the actual product structure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If destructive measurement techniques are used to measure edge placement error, then measurement accuracy is improved, but the substrate is damaged and measurement time increases

Engineering Contradiction:

Improveedge placement error measurement accuracyVSAvoidmeasurement time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent replaces destructive mechanical cross-sectioning methods with optical scattering measurement. The scatterometer directs radiation at the substrate and analyzes scattered light patterns to determine edge placement error, eliminating the need for physical sectioning while maintaining measurement accuracy and enabling rapid non-contact measurement.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a scatterometer as an intermediary measurement device that uses optical radiation to indirectly probe the edge placement error. Instead of directly observing or sectioning the structure, the scatterometer measures scattering characteristics that correlate with edge placement, providing a non-destructive measurement pathway.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If indirect measurement methods are used to determine edge placement error, then measurement speed is improved, but measurement accuracy deteriorates due to reliance on separate overlay and critical dimension measurements

Engineering Contradiction:

Improvemeasurement speedVSAvoidedge placement error measurement accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent replaces the indirect multi-step measurement approach (separate overlay and critical dimension measurements) with a direct optical scattering measurement that specifically targets edge placement error. The scatterometer configuration and analysis method are designed to directly extract edge placement information from scattering patterns, providing both speed and accuracy.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of operation

If conventional scatterometry is used with large grating targets, then measurement simplicity is improved, but measurement relevance to actual product features deteriorates due to dimension and pitch differences

Engineering Contradiction:

Improvemeasurement simplicityVSAvoidmeasurement correlation with product features

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent applies local quality by designing the scatterometer to measure specific local features (edge placement error) rather than averaging over large grating areas. The measurement target and analysis are optimized to focus on the critical edge regions, ensuring the measurement reflects actual product feature characteristics rather than bulk grating properties.

Inventive Principle:

Principle #3Local quality

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 rapid and accurate measurement of edge placement error, allowing for immediate adjustments to processing conditions and improving the correlation between measurement targets and actual product features, thereby enhancing the precision and efficiency of the lithographic process.

Implementation Method 1

detecting scattered radiation while illuminating the first structure with optical radiation to obtain a first signal

Methodology Applied

Scientific EffectScattering: Scattering

Data Source

PatentUS10156797B2Method of determining edge placement error, inspection apparatus, patterning device, substrate and device manufacturing method

Publication Date: 2018.12.18 ASML NETHERLANDS BV

AI summary

A method of determining edge placement error within a structure produced using a lithographic process, the method including: receiving a substrate having a first structure produced using the lithographic process, the first structure having first and second layers, each of the layers having first areas of electrically conducting material and second areas of non-electrically conducting material; receiving a target signal indicative of a first target relative position which is indicative of target position of edges between the first areas and the second areas of the first layer relative to edges between the first areas and second areas of the second layer in the first structure during the lithographic process; detecting scattered radiation while illuminating the first structure with optical radiation to obtain a first signal; and ascertaining an edge placement error parameter on the basis of first signal and the first target relative position.