Multi-Function Overlay Marks for Low-Noise Focus and CD 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 and inability to extract focus and critical dimension information effectively.

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 interference and location-dependent pattern density

Engineering Contradiction:

Improveoverlay measurement accuracyVSAvoidnoise interference

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The overlay mark is divided into multiple components: a first grating structure and a second grating structure with different orientations. Each grating structure processes specific spatial frequency information independently, allowing noise reduction through selective signal combination while maintaining measurement accuracy

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the overlay mark have specialized functions: the first grating structure is optimized for measuring overlay in one direction while the second grating structure measures overlay in a perpendicular direction. This local specialization allows each region to contribute optimally to the overall measurement while reducing location-dependent noise

Inventive Principle:

Principle #3Local quality

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 CD information

Core Design Contradiction:

Adaptability or versatilityVSLoss of information

Solution Approach 1:

The overlay mark structure is designed to perform multiple measurement functions simultaneously: overlay measurement through grating asymmetry analysis, focus determination through diffraction intensity ratios, and critical dimension extraction through pitch calibration. This multi-functional design eliminates the need for separate measurement targets for each parameter

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Measurement precision

If overlay marks with multiple components are used to reduce noise and enable multi-parameter measurement, then measurement accuracy and versatility improve, but device complexity increases

Engineering Contradiction:

Improvemeasurement accuracyVSAvoidoverlay mark structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Multiple measurement functions (overlay, focus, critical dimension) are merged into a single integrated overlay mark structure. The first and second grating structures are combined in one target, allowing all measurements to be performed simultaneously on the same physical object, reducing the need for multiple separate measurement targets

Inventive Principle:

Principle #5Merging (Combining)

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 dimensions, enhancing semiconductor fabrication processes.

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

PatentUS11835864B2Multi-function overlay marks for reducing noise and extracting focus and critical dimension information

Publication Date: 2023.12.05 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.