Overlay Mark Measurement Using Moiré Absolute Position Detection

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Solution Overview

Problem

Existing overlay mark measurement methods struggle to meet the increasing demands for smaller mark sizes, faster measurement speeds, and improved accuracy in semiconductor manufacturing, particularly in determining the overlay accuracy between multilayer circuit patterns.

Innovation Solution

An absolute position measurement method for overlay marks is developed, which involves acquiring images of overlay marks formed by patterns with different pitches, extracting luminance signals, and determining the absolute positions of the patterns using formulas based on moire image positions and luminance signals, allowing for precise calculation of relative positional deviations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional relative position measurement methods are used, then measurement accuracy can be maintained, but measurement speed is slow and mark size cannot be reduced further

Engineering Contradiction:

Improvemeasurement speedVSAvoidoverlay measurement accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent inverts the conventional measurement approach by measuring absolute positions of patterns in each layer separately rather than measuring relative positions directly. This inversion enables faster measurement through absolute position detection while maintaining accuracy through the mathematical relationship between absolute positions and relative overlay deviation

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the measurement parameter from relative position deviation to absolute position. By determining absolute positions of patterns in different layers and calculating overlay deviation from these absolute positions, the system achieves both high measurement speed and high accuracy, resolving the contradiction between productivity and precision

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If overlay mark size is reduced to meet finer pattern demands, then manufacturing precision improves, but measurement accuracy deteriorates due to limited resolution

Engineering Contradiction:

Improveoverlay accuracyVSAvoidmark measurement accuracy

Core Design Contradiction:

Manufacturing precisionVSMeasurement precision

Solution Approach 1:

The patent introduces moire patterns as an intermediary element that bridges the gap between fine pattern structures and measurement capabilities. The moire patterns generated by overlaying patterns with different pitches provide measurable features that maintain accuracy even when the original patterns are too fine to be directly resolved

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent transitions from direct spatial measurement of fine patterns to measurement in a different dimensional space through moire pattern formation. By converting the fine pattern overlay information into moire pattern positions, the system achieves accurate measurement without being limited by the direct resolution of the fine patterns themselves

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Productivity

If absolute position measurement method is implemented, then measurement speed increases, but device complexity increases due to additional processing steps

Engineering Contradiction:

Improvemeasurement speedVSAvoidmeasurement system complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical alignment and relative position measurement mechanisms with an optical measurement system that captures absolute positions. By using optical imaging and mathematical calculation rather than complex mechanical linkage, the system achieves high speed while keeping the physical device relatively simple

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

This method enhances measurement speed and accuracy by enabling the determination of absolute positions of patterns, facilitating faster and more precise overlay error detection and correction, thereby improving semiconductor manufacturing quality.

Implementation Method 1

an imaging unit that receives light from the overlay mark and acquires an image of the overlay mark

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Implementation Method 2

a fringe based overlay mark (hereinafter, referred to as 'FBO mark') in which a moire pattern formed by overlaying is detected to determine the deviation of the two layers

Methodology Applied

Scientific EffectMoiré Effect: Moiré Effect

Data Source

PatentUS20250355369A1Mark measurement method, measurement device, lithography device, calculator, and storage medium

Publication Date: 2025.11.20 NIKON CORP

AI summary

A measurement method including: acquiring an image of an overlay mark formed by overlaying a first pattern in which a line-and-space is repeatedly formed at a first pitch P1 in a predetermined direction in a layer on a substrate and a second pattern in which a line-and-space is repeatedly formed at a second pitch P2 different from the first pitch P1 in the predetermined direction in another layer different from the layer; extracting a luminance signal of the overlay mark in the predetermined direction from the acquired image of the overlay mark; and determining an absolute position of at least one of the first pattern and the second pattern in the predetermined direction from the extracted luminance signal.