Voltage-Contrast Metrology Marks for Sub-10 nm Overlay Measurement

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Solution Overview

Problem

As semiconductor manufacturing advances, the resolution limitations of optical scatterometers become inadequate for measuring sub-100 or sub-10 nanometer IC components due to discrepancies between optical resolution and device dimensions, requiring complex manual calibration or offset estimation for accurate overlay error and critical dimension measurements.

Innovation Solution

The implementation of voltage-contrast metrology marks, comprising test structures in consecutive layers on a substrate, which utilize a charged-particle beam tool to generate voltage-contrast images, allowing for the determination of overlay values and critical dimensions with improved accuracy and throughput.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If optical scatterometer is used for measurement, then measurement throughput is maintained, but measurement precision deteriorates due to resolution limitations at sub-100 nanometer scale

Engineering Contradiction:

Improveoverlay error measurement precisionVSAvoidcalibration complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent introduces an intermediary voltage-contrast imaging method that bridges the gap between optical scatterometer capabilities and electron beam tool precision. The voltage-contrast image serves as a mediator that can be obtained with lower-resolution tools while still providing accurate overlay and CD measurements, eliminating the need for complex calibration procedures.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the measurement parameter from optical intensity (in scatterometry) to voltage contrast in electron beam images. By utilizing the voltage-contrast effect where connected structures appear bright and disconnected structures appear dark, the method achieves higher measurement precision without requiring complex optical calibration systems.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If electron beam tool with high resolution is used, then measurement precision improves, but productivity deteriorates due to slow scanning speed

Engineering Contradiction:

Improvecritical dimension measurement precisionVSAvoidmeasurement throughput

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent applies partial action by using only the voltage-contrast information (bright/dark appearance) rather than full high-resolution imaging. This allows lower-resolution, faster electron beam tools to achieve the necessary measurement precision for overlay and CD determination without requiring the slow scanning speeds of high-resolution instruments.

Inventive Principle:

Principle #16Partial or excessive action

3Productivity

If optical scatterometer is used, then productivity is maintained, but measurement precision deteriorates due to wavelength limitations

Engineering Contradiction:

Improvemeasurement throughputVSAvoidsub-10 nanometer measurement accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent substitutes the optical measurement system with an electron beam-based voltage-contrast imaging system. This replacement enables sub-10 nanometer measurement precision while maintaining productivity, as the voltage-contrast method can be implemented with faster, lower-resolution electron beam tools rather than requiring high-resolution optical scatterometers with wavelength limitations.

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 approach enables precise measurement of overlay errors and critical dimensions at the nanometer scale, enhancing the accuracy and efficiency of semiconductor fabrication by leveraging the voltage-contrast imaging method, even with low-resolution electron beam tools, thus improving the packing density and alignment of IC components.

Implementation Method 1

a measurement mark is provided. The measurement mark includes a set of first test structures developed in a first layer on a substrate, each of the set of first test structures comprising a plurality of first features made of first conducting material. The measurement mark also includes a set of second test structures developed in a second layer adjacent to the first layer, each of the set of second test structures comprising a plurality of second features made of second conducting material. The measurement mark is configured to indicate connectivity between the set of first test structures and associated second test structures in the set of second test structures when imaged using a voltage-contrast imaging method.

Methodology Applied

Scientific EffectVoltage-contrast imaging: Electron Beam

Data Source

PatentUS12169366B2Voltage contrast metrology mark

Publication Date: 2024.12.17 ASML NETHERLANDS BV

AI summary

A measurement mark is disclosed. According to certain embodiments, the measurement mark includes a set of first test structures developed in a first layer on a substrate, each of the set of first test structures comprising a plurality of first features made of first conducting material. The measurement mark also includes a set of second test structures developed in a second layer adjacent to the first layer, each of the set of second test structures comprising a plurality of second features made of second conducting material. The measurement mark is configured to indicate connectivity between the set of first test structures and associated second test structures in the set of second test structures when imaged using a voltage-contrast imaging method.