SEM Length Measurement via Beam Blanker Charge Control

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Solution Overview

Problem

Scanning electron microscopes face challenges in accurately measuring the dimensions of semiconductor patterns due to charge-up phenomena caused by electron beam irradiation, leading to unstable detected electron amounts and dimension measurement errors, especially in patterns with varying widths and material distributions.

Innovation Solution

A scanning electron microscope with a length measurement function that includes an electron gun, a measurement target region setting unit, a beam blanker unit, and a control unit, which designates and irradiates the electron beam only on specific measurement regions with equal areas to minimize surface potential variations, using an electrostatic electrode and beam control plate to control electron beam irradiation and deflection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If electron beam is irradiated onto the sample to perform observation and measurement, then image display and pattern measurement are enabled, but charge-up phenomenon occurs causing dimension measurement errors

Engineering Contradiction:

Improvedimension measurement accuracyVSAvoidcharge-up phenomenon

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by setting different irradiation states for different regions of the sample. The measurement region receives electron beam irradiation for imaging, while non-measurement regions are excluded from irradiation. This localized approach ensures that only the necessary area is charged, minimizing overall charge-up effects and preventing dimension measurement errors while maintaining measurement precision in the target region.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent segments the sample area into measurement regions and non-measurement regions. By dividing the sample into these distinct zones and controlling electron beam irradiation separately for each zone, the system enables precise dimension measurement in the measurement region while preventing charge-up in other areas, thus resolving the contradiction between measurement capability and charge-up prevention.

Inventive Principle:

Principle #1Segmentation

2Area of stationary object

If electron beam is irradiated on larger pattern intervals or wider line widths, then measurement coverage is improved, but surface potential variation increases causing dimension error

Engineering Contradiction:

Improvemeasurement region areaVSAvoiddimension measurement accuracy

Core Design Contradiction:

Area of stationary objectVSMeasurement precision

Solution Approach 1:

The patent implements local quality by controlling electron beam irradiation to be confined strictly to the measurement region. By setting the irradiation area equal to the measurement region area and excluding all other areas, the system maintains consistent surface potential within the measurement region regardless of the overall pattern size or interval, thereby preventing dimension errors while ensuring adequate measurement coverage.

Inventive Principle:

Principle #3Local quality

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 high-accuracy length measurements by maintaining consistent electron beam irradiation, reducing measurement errors attributed to pattern shape and material variations, and optimizing measurement time through raster or vector scans.

Implementation Method 1

an electron beam is irradiated onto a portion of the sample

Methodology Applied

Scientific EffectElectron beam: Electron Beam

Implementation Method 2

an amount of electrons such as secondary electrons are converted into luminance

Methodology Applied

Scientific EffectSecondary electron emission: Electron Impact Desorption

Implementation Method 3

a beam blanker unit for controlling an irradiation of the electron beam depending on the measurement region

Methodology Applied

Scientific EffectElectrostatic deflection: Electrostatic Induction

Implementation Method 4

using an electrostatic electrode and beam control plate to control electron beam irradiation and deflection

Methodology Applied

Scientific EffectElectrostatic force: Electrostatics

Data Source

PatentUS7791022B2Scanning electron microscope with length measurement function and dimension length measurement method

Publication Date: 2010.09.07 ADVANTEST CORP

AI summary

A scanning electron microscope with a length measurement function includes an electron gun for emitting an electron beam, a measurement target region setting unit for setting a measurement region for a pattern formed on a sample, a storing unit for storing the designated measurement region, a beam blanker unit for controlling an irradiation of the electron beam depending on the measurement region, and a control unit for extracting the designated measurement region from the storing unit, interrupting the electron beam with the beam blanker unit in a region other than the measurement region, irradiating the electron beam onto the sample in the measurement region, capturing an image of the measurement region, and measuring the pattern. The measurement region may be a pair of regions having the same areas as each other.