Scanning Electron Microscope Parameter Verification via Edge Sharpness Ratios

Solution Overview

Problem

Conventional scanning electron microscopes fail to accurately verify the adjustment of operation parameters such as focus and astigmatism correction parameters, leading to potential misalignment and suboptimal image quality due to the inability to compare actual pattern shapes with image patterns.

Innovation Solution

A method involving the calculation of edge sharpness ratios in multiple directions and comparison with design data edge length ratios, along with a corner-rounding process, to determine if operation parameters are correctly adjusted, emitting an alarm if discrepancies are found.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Extent of automation

If automatic focusing and astigmatism adjustment are achieved by acquiring multiple images and calculating edge sharpness, then image quality evaluation is automated, but the system cannot recognize actual pattern shapes leading to incorrect parameter determination

Engineering Contradiction:

Improveautomatic focusing and astigmatism adjustmentVSAvoidoperation parameter determination accuracy

Core Design Contradiction:

Extent of automationVSMeasurement precision

Solution Approach 1:

The patent creates a virtual model (copy) of the actual pattern shape from design data, which represents the true geometry of the pattern. This virtual model is then compared with the imaged pattern to evaluate whether operation parameters are correctly adjusted, eliminating the need for the system to recognize actual pattern shapes directly.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent changes the evaluation parameter from direct pattern shape recognition to comparing edge sharpness characteristics. By evaluating edge sharpness in multiple directions and comparing it with the virtual model, the system can determine operation parameter accuracy without needing to recognize actual pattern shapes.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If edge sharpness is calculated in multiple directions to account for astigmatism, then measurement comprehensiveness is improved, but the system still cannot distinguish between astigmatic and non-astigmatic images

Engineering Contradiction:

Improveimage quality evaluation reliabilityVSAvoidpattern shape information

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The patent creates a virtual model (copy) of the actual pattern shape from design data, which represents the true geometry of the pattern. This virtual model is then compared with the imaged pattern to evaluate whether operation parameters are correctly adjusted, eliminating the need for the system to recognize actual pattern shapes directly.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent changes the evaluation parameter from direct pattern shape recognition to comparing edge sharpness characteristics. By evaluating edge sharpness in multiple directions and comparing it with the virtual model, the system can determine operation parameter accuracy without needing to recognize actual pattern shapes.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If the system compares image patterns with recognized actual shapes, then parameter verification accuracy would be improved, but the system lacks the capability to recognize actual pattern shapes

Engineering Contradiction:

Improveparameter verification accuracyVSAvoidpattern recognition capability

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent creates a virtual model (copy) of the actual pattern shape from design data, which represents the true geometry of the pattern. This virtual model is then compared with the imaged pattern to evaluate whether operation parameters are correctly adjusted, eliminating the need for the system to recognize actual pattern shapes directly.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent introduces a virtual model as an intermediary between the design data and the imaged pattern. This virtual model serves as a reference that bridges the gap, allowing comparison without requiring direct pattern recognition capability in the imaging system.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS10446365B2Method of verifying operation parameter of scanning electron microscope

Publication Date: 2019.10.15 TASMIT INC

AI summary

A method capable of verifying whether operation parameters, such as a focus parameter and an astigmatism correction parameter, of a scanning electron microscope are correctly adjusted. This method includes: determining a ratio of a length of an edge in a first direction to a length of the edge in a second direction perpendicular to the first direction, the edge being an edge of a pattern selected from design data; generating images of the pattern while changing an operation parameter of a scanning electron microscope; calculating an edge sharpness in the first direction of each of the images and calculating an edge sharpness in the second direction of each of the images; determining a ratio of a peak value of the edge sharpness in the first direction to a peak value of the edge sharpness in the second direction; and emitting an alarm if the ratio of the peak values does not coincide with the ratio of the lengths of the edge.