Multi-wavelength DIC Inspection for Metal Defect Classification

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Solution Overview

Problem

Current defect inspection systems in semiconductor fabrication are inadequate for classifying defects based on composition, relying on separate tools like EDX, which have long measurement times and expose samples to further contaminants, reducing throughput.

Innovation Solution

A multi-wavelength differential interference contrast (DIC) inspection system that uses sheared illumination beams to generate images of a sample, allowing for the classification of defects as metal or non-metal by comparing defect-induced phase shifts at different wavelengths, thereby eliminating the need for separate composition analysis tools.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If separate composition analysis tools like EDX are used to classify defects, then measurement precision is improved, but productivity deteriorates due to long measurement times and sample transfer requirements

Engineering Contradiction:

Improvedefect composition classification accuracyVSAvoidinspection throughput

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent merges defect detection and composition analysis functions into a single inspection system. The optical inspection system now performs both defect detection and compositional classification using multi-wavelength interferometry, eliminating the need to transfer samples to separate EDX tools and thereby maintaining high throughput while achieving accurate composition analysis.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The inspection system is designed with multi-functionality to perform both defect detection and composition analysis. By equipping the system with multi-wavelength interferometry capability, it can classify defects by composition (metal vs. non-metal) in addition to detecting their presence, making the system universal and eliminating the need for specialized separate tools.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If separate composition analysis tools are used, then measurement precision is improved, but loss of time increases due to sample transfer and repositioning

Engineering Contradiction:

Improvedefect composition classification accuracyVSAvoidsample transfer and repositioning time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent combines defect detection and composition analysis into a single inspection process. The multi-wavelength interferometry system performs both functions without requiring sample transfer to separate tools, thereby eliminating the time loss associated with moving and repositioning samples between different instruments.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The system performs composition analysis in the same inspection pass as defect detection, rather than requiring a subsequent separate analysis step. By conducting both measurements simultaneously on the same sample in the same position, the system eliminates the time required for preliminary sample preparation and transfer operations.

Inventive Principle:

Principle #10Preliminary action

3Measurement precision

If separate composition analysis tools are used, then measurement precision is improved, but object-affected harmful factors increase due to sample exposure to contaminants

Engineering Contradiction:

Improvedefect composition classification accuracyVSAvoidsample contamination during transfer

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent merges defect detection and composition analysis into a single controlled inspection environment. By performing both functions within the same optical inspection system, the sample remains in a controlled atmosphere throughout the process and is not exposed to potential contaminants that would be present during transfer to and from separate EDX tools.

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

Enables efficient and accurate classification of defects by comparing phase shifts across multiple wavelengths, improving throughput and reducing contamination risks, while providing insight into the root cause of defects without the need for additional equipment.

Implementation Method 1

differential interference contrast imaging tool configured to generate one or more images of a sample based on illumination with two sheared illumination beams

Methodology Applied

Scientific EffectInterference: Interference

Implementation Method 2

induced phase difference between the two sheared illumination beams are selectable for any particular image of the sample

Methodology Applied

Scientific EffectPhase difference:

Data Source

PatentUS11017520B2Multi-wavelength interferometry for defect classification

Publication Date: 2021.05.25 KLA CORP

AI summary

An inspection system may include a controller coupled to a differential interference contrast imaging tool for generating images of a sample based on illumination with two sheared illumination beams. The controller may determine a first defect-induced phase shift based on a first set of images of a defect on the sample with a first selected illumination spectrum and two or more selected induced phase differences between the two sheared illumination beams, determine a second defect-induced phase shift based a second set of images of the defect with a second selected illumination spectrum and two or more selected induced phase differences between the two sheared illumination beams, and classify the defect as a metal or a non-metal based on a comparison of the first phase shift to the second phase shift.