Mirror-Mode Electron Microscopy for Electrical Defect Detection

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Solution Overview

Problem

Conventional electrical process monitoring techniques in semiconductor manufacturing, such as electrical probing and voltage contrast electron beam imaging, are inadequate for detecting defects in smaller device structures due to low voltage-contrast sensitivity and resistance discrimination, requiring special test structures and being slow and typically performed late in the process flow.

Innovation Solution

The method involves mirror-mode electron-beam imaging at multiple voltage differences between an electron source and a substrate, with image data analysis to calculate variations in features, allowing for rapid in-line detection of electrical defects with improved voltage-contrast sensitivity and resistance discrimination without the need for special test structures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If voltage contrast electron beam imaging is used, then inspection speed is improved and in-line monitoring is enabled, but voltage-contrast sensitivity and resistance discrimination are insufficient

Engineering Contradiction:

Improveinspection speedVSAvoidvoltage-contrast sensitivity

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent changes the imaging mode from conventional voltage contrast to mirror-mode electron microscopy, and varies the acceleration voltage to optimize the detection of voltage contrast. This parameter change enables both high inspection speed and improved voltage-contrast sensitivity simultaneously

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system dynamically adjusts the acceleration voltage during mirror-mode imaging to enhance voltage-contrast sensitivity. By making the imaging parameters dynamic and adaptive, the system achieves both high speed and high precision measurement

Inventive Principle:

Principle #15Dynamics

2Ease of manufacture

If conventional voltage contrast methods are used, then inspection can be performed in-line during fabrication, but voltage resolution is only 5 to 10 volts which is inadequate for precise measurements

Engineering Contradiction:

Improvein-line inspection capabilityVSAvoidvoltage resolution

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent implements mirror-mode electron microscopy with optimized acceleration voltage parameters, achieving voltage resolution in the tens of milli-volts range while maintaining in-line inspection capability during fabrication

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the conventional voltage contrast imaging mechanism with mirror-mode electron microscopy, substituting a more sensitive detection mechanism that achieves superior voltage resolution while maintaining manufacturing integration

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If device design rules are shrunk to increase device density, then productivity is improved, but detection of defects in smaller structures with higher aspect ratios becomes more challenging

Engineering Contradiction:

Improvedevice densityVSAvoiddefect detection capability

Core Design Contradiction:

ProductivityVSDifficulty of detecting and measuring

Solution Approach 1:

The patent uses mirror-mode electron microscopy with optimized electron beam parameters and acceleration voltage to enhance the detection capability for smaller device structures with higher aspect ratios, enabling defect detection in scaled-down devices

Inventive Principle:

Principle #35Parameter changes

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 accurate and rapid determination of process-related electrical parameters with voltage contrast sensitivity in the tens of milli-volts, significantly improving defect detection capabilities compared to traditional scanning electron microscopes, allowing for more precise measurements and process control.

Implementation Method 1

mirror-mode electron-beam imaging is performed on a region of the substrate at multiple voltage differences between an electron source and a substrate

Methodology Applied

Scientific EffectElectron scattering: Scattering

Implementation Method 2

The electron beam instrument is configured for mirror-mode electron-beam imaging of a region of the substrate

Methodology Applied

Scientific EffectElectron beam interaction: Electron Beam

Data Source

PatentUS7514681B1Electrical process monitoring using mirror-mode electron microscopy

Publication Date: 2009.04.07 KLA TENCOR TECHNOLOGY CORP

AI summary

One embodiment relates to a method of inspecting a substrate using electrons. Mirror-mode electron-beam imaging is performed on a region of the substrate at multiple voltage differences between an electron source and a substrate, and image data is stored corresponding to the multiple voltage differences. A calculation is made of a measure of variation of an imaged aspect of a feature in the region with respect to the voltage difference between the electron source and the substrate. Other embodiments and features are also disclosed.