Multi-function overlay marks for noise reduction and focus extraction

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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 advanced overlay marks that incorporate specific configurations of gratings and sub-patterns, allowing for reduced noise interference and the ability to measure overlay, focus, and 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 interference from pattern density

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The overlay mark is divided into multiple isolated target portions (e.g., four separate targets) instead of a single continuous pattern. Each target portion is spatially separated and surrounded by isolation structures, which segment the measurement function into independent units that are less sensitive to surrounding pattern density variations, thereby reducing noise interference.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Isolation structures (such as isolation lines or patterns) are introduced as intermediary elements between the target portions and the surrounding IC patterns. These intermediary structures act as buffers that prevent noise from the high-density IC patterns from directly affecting the overlay measurement, thus reducing harmful noise interference.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 capability (overlay, focus, CD)VSAvoidfocus and critical dimension information

Core Design Contradiction:

Adaptability or versatilityVSLoss of information

Solution Approach 1:

The overlay mark structure is designed to perform multiple measurement functions simultaneously. By incorporating specific target portion configurations (such as alternating light and dark regions with defined geometries), the same mark structure enables extraction of overlay, focus, and critical dimension information through diffraction light intensity analysis, making the measurement system universal rather than specialized for a single parameter.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The measurement capability is extended from a single dimension (overlay) to multiple dimensions (overlay, focus, and critical dimension) by utilizing the spatial and optical characteristics of the target portions. The diffraction pattern analysis leverages additional optical dimensions (intensity, angle, order) to extract multiple process parameters from the same physical structure.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Area of stationary object

If overlay marks are placed in high pattern density regions, then space utilization is improved, but measurement accuracy deteriorates due to noise

Engineering Contradiction:

Improvespace utilization of overlay markVSAvoidoverlay measurement accuracy

Core Design Contradiction:

Area of stationary objectVSMeasurement precision

Solution Approach 1:

Isolation structures are introduced as intermediary elements between the target portions and the surrounding IC patterns. These intermediary structures act as buffers that prevent noise from the high-density IC patterns from directly affecting the overlay measurement, thus reducing harmful noise interference.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

Inventive Principle:

Principle #1Segmentation

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 marks provide improved overlay measurement accuracy and the capability to determine optimal focus and critical dimension information, enhancing semiconductor fabrication processes.

Implementation Method 1

diffraction light intensity analysis

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentUS11448975B2Multi-function overlay marks for reducing noise and extracting focus and critical dimension information

Publication Date: 2022.09.20 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.