Multi-Function Overlay Marks for Noise-Robust Overlay and Focus Metrology

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Solution Overview

Problem

Conventional overlay marks in the semiconductor industry face challenges in accurately measuring overlay alignment due to noise interference from pattern density variations and inability to extract focus and critical dimension information.

Innovation Solution

The development of innovative overlay marks that incorporate specific configurations of gratings and sub-patterns, allowing for reduced noise interference and the ability to measure both overlay alignment and focus, as well as critical dimension information, through diffraction light intensity analysis.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional overlay marks are used to measure overlay alignment, then overlay measurement can be performed, but measurement accuracy is affected by noise from pattern density variations

Engineering Contradiction:

Improveoverlay measurement accuracyVSAvoidnoise from pattern density variations

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The overlay mark is divided into multiple components including a first grating structure and a second grating structure with different orientations. Each grating component responds differently to pattern density variations, allowing the system to segment the measurement function and identify the noise component separately from the true overlay signal.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs grating structures with asymmetric orientations (e.g., 0 degrees and 45 degrees) where the different orientations create asymmetric responses to pattern density noise. By analyzing the differential signals from these asymmetrically oriented gratings, the system can isolate and eliminate the symmetric noise component while preserving the asymmetric overlay information.

Inventive Principle:

Principle #4Asymmetry

2Adaptability or versatility

If conventional overlay marks are used, then overlay measurement is possible, but focus and critical dimension information cannot be determined

Engineering Contradiction:

Improvemeasurement capabilityVSAvoidfocus and critical dimension information

Core Design Contradiction:

Adaptability or versatilityVSLoss of information

Solution Approach 1:

The overlay mark structure is designed to perform multiple functions simultaneously: it measures overlay alignment through grating asymmetry, determines focus through diffraction intensity analysis, and extracts critical dimension information through pitch measurements. This multi-functional design eliminates the need for separate measurement targets for each parameter.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent extends the measurement capability from a single overlay dimension to multiple dimensions by incorporating gratings with different orientations and analyzing diffraction patterns in multiple orders. This dimensional expansion allows extraction of focus and critical dimension information alongside overlay measurements from the same mark structure.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Productivity

If overlay marks are placed in different locations on the IC, then coverage is improved, but measurement accuracy varies due to pattern density differences

Engineering Contradiction:

Improvemeasurement coverageVSAvoidmeasurement accuracy consistency

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The overlay mark design incorporates local quality variations through gratings with different orientations at different locations within the same mark. The 0-degree gratings and 45-degree gratings are strategically positioned to optimize their response to local pattern density conditions, allowing each grating component to be tailored to its local environment while contributing to the overall measurement.

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

These overlay marks provide improved measurement accuracy and the capability to determine optimal focus and critical dimension, enhancing semiconductor fabrication processes by minimizing noise effects and extracting relevant data effectively.

Implementation Method 1

allowing for reduced noise interference and the ability to measure both overlay alignment and focus, as well as critical dimension information, through diffraction light intensity analysis

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentUS12055860B2Multi-function overlay marks for reducing noise and extracting focus and critical dimension information

Publication Date: 2024.08.06 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

An overlay mark includes a first, a second, a third, and a fourth component. The first component is located in a first region of the first overlay mark and includes a plurality of gratings that extend in a first direction. The second component is located in a second region of the first overlay mark and includes a plurality of gratings that extend in the first direction. The third component is located in a third region of the first overlay mark and includes a plurality of gratings that extend in a second direction different from the first direction. The fourth component is located in a fourth region of the first overlay mark and includes a plurality of gratings that extend in the second direction. The first region is aligned with the second region. The third region is aligned with the fourth region.