Asymmetric Metrology Targets for Overlay and CD Correction

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The increasing demand for accuracy in overlay and critical dimension (CD) in semiconductor manufacturing, due to reduced feature sizes, leads to errors in patterning processes, such as imaging errors from optical aberration and substrate heating, which can cause device failure.

Innovation Solution

A method and apparatus that utilize a metrology target with intentionally asymmetric optical characteristics to measure changes in physical configurations, allowing for the setup, monitoring, or correction of patterning process parameters through a hardware computer system, using a plurality of design of experiment (DoE) target areas with geometric symmetry.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If feature sizes are reduced to increase device functionality, then device performance is improved, but measurement precision and manufacturing precision deteriorate due to increased errors in overlay and critical dimension

Engineering Contradiction:

Improvedevice functionalityVSAvoidoverlay and critical dimension accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The metrology target is divided into multiple design of experiment (DoE) target areas, each with specific asymmetric structures. This segmentation allows independent measurement of different process parameters while maintaining overall measurement precision despite reduced feature sizes

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces intentionally asymmetric optical characteristics in the metrology target structures. This asymmetry creates measurable differences in radiation patterns that enable precise determination of patterning process parameters, directly addressing the precision loss from feature size reduction

Inventive Principle:

Principle #4Asymmetry

2Adaptability or versatility

If feature sizes are reduced to increase device functionality, then device performance is improved, but manufacturing precision deteriorates due to imaging errors from optical aberration and substrate heating

Engineering Contradiction:

Improvedevice functionalityVSAvoidpatterning process accuracy

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The metrology target with asymmetric structures is prepared in advance on the substrate before final patterning. This preliminary structure allows measurement and correction of process parameters like optical aberration and heating effects before they affect the actual device features, maintaining manufacturing precision

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The asymmetric metrology target provides measurable feedback on patterning process parameters. By analyzing the radiation patterns from the asymmetric structures, the system can detect and correct for imaging errors, creating a feedback loop that maintains precision despite reduced feature sizes

Inventive Principle:

Principle #23Feedback

3Ease of manufacture

If conventional symmetric metrology targets are used, then device manufacturing is simplified, but the ability to characterize and correct patterning errors is insufficient

Engineering Contradiction:

Improvemetrology target fabricationVSAvoiderror characterization capability

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent deliberately introduces asymmetric optical characteristics into the metrology target structures. This asymmetry creates distinct radiation patterns that are highly sensitive to patterning process variations, enabling precise error characterization while maintaining relatively simple fabrication through standard lithographic processes

Inventive Principle:

Principle #4Asymmetry

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

Enhances the ability to characterize and minimize errors in overlay and CD, improving the functioning of semiconductor devices by accurately determining and adjusting patterning process parameters.

Implementation Method 1

obtaining a detected representation of radiation redirected by each of a plurality of structures from a substrate... each structure has an intentional different physical configuration... causes an asymmetric optical characteristic distribution

Methodology Applied

Scientific EffectOptical diffraction: Diffraction

Data Source

PatentUS12468235B2Method and apparatus to determine a patterning process parameter

Publication Date: 2025.11.11 ASML NETHERLANDS BV

AI summary

A method including: obtaining a detected representation of radiation redirected by each of a plurality of structures from a substrate additionally having a device pattern thereon, wherein each structure has an intentional different physical configuration of the respective structure than the respective nominal physical configuration of the respective structure, wherein each structure has geometric symmetry at the respective nominal physical configuration, wherein the intentional different physical configuration of the structure causes an asymmetric optical characteristic distribution and wherein a patterning process parameter measures change in the physical configuration; and determining a value, based on the detected representations and based on the intentional different physical configurations, to setup, monitor or correct a measurement recipe for determining the patterning process parameter.