Pattern Measurement Apparatus Using Design Data Alignment

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Solution Overview

Problem

Conventional pattern measurement methods for OPC masks struggle to achieve precise line width measurements due to the inclusion of stepped portions and corners in the measurement region, leading to inaccuracies in secondary electron images.

Innovation Solution

A pattern measurement apparatus and method that define a measurement region based on design data, using characteristic portions to align and position the measurement region in the secondary electron image, excluding stepped portions and corners to ensure precise line width measurement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the measurement region is defined based only on the secondary electron image to include a straight-line portion, then the measurement process is simplified, but the measurement precision deteriorates due to undetected stepped portions

Engineering Contradiction:

Improvemeasurement process simplicityVSAvoidline width measurement accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent merges the secondary electron image with the design data to define the measurement region. By combining information from both the actual image and the original design patterns, the system can identify stepped portions that are invisible in the secondary electron image alone, thereby maintaining measurement simplicity while improving accuracy.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent introduces a new dimension of information by utilizing design data alongside the secondary electron image. This additional dimensional information allows the measurement region definition unit to detect stepped portions through pattern recognition in the design data, resolving the contradiction between operational simplicity and measurement precision.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Area of stationary object

If the measurement region includes corners of the pattern, then the measurement coverage is increased, but the measurement precision deteriorates due to edge effects

Engineering Contradiction:

Improvemeasurement region coverageVSAvoidline width measurement accuracy

Core Design Contradiction:

Area of stationary objectVSMeasurement precision

Solution Approach 1:

The patent applies local quality by differentiating the treatment of different regions within the measurement area. The measurement region definition unit selectively excludes corners and stepped portions based on the design data, allowing the measurement region to include most of the pattern area while maintaining high precision in the measured line width by avoiding problematic local regions.

Inventive Principle:

Principle #3Local quality

3Measurement precision

If the measurement region is defined to exclude stepped portions using design data, then the measurement precision is improved, but the device complexity increases

Engineering Contradiction:

Improveline width measurement accuracyVSAvoidmeasurement system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The measurement region definition unit performs multiple functions: it defines the measurement region, detects stepped portions, and identifies appropriate measurement locations all in one process. By making this unit multi-functional and integrating it into the existing measurement system, the patent improves measurement precision without proportionally increasing device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 allows for precise measurement of line widths by accurately positioning the measurement region, excluding curved or stepped portions, thereby improving measurement accuracy and reliability.

Implementation Method 1

an electron beam irradiation unit (3a, 430) configured to irradiate a surface of a sample with an electron beam; a detector (9, 422) configured to detect secondary electrons generated on the surface of the sample

Methodology Applied

Scientific EffectSecondary electron emission: Electron Impact Desorption

Data Source

PatentUS8507858B2Pattern measurement apparatus and pattern measurement method

Publication Date: 2013.08.13 ADVANTEST CORP

AI summary

Referring to design data for a sample, a measurement region is defined at a portion in the design data which has no step in an edge of a pattern. In addition, an edge as a characteristic portion is detected from the design data, and an edge as a characteristic portion corresponding to the characteristic portion of the design data is detected from a secondary electron image. Then, the measurement region is positioned and located in a secondary electron image based on a positional relationship between the edge of the design data and the edge of the secondary electron image. A width of the pattern is measured on the basis of a distance between the two edges included in the measurement region thus located.