Foil Grid Lens Aberration Correction Electron Beam

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing electron beam apparatuses face challenges in reliably detecting signal electron beams, particularly backscattered electrons with a wide angular spread, due to aberrations caused by electron lenses, which also affect the primary electron beam.

Innovation Solution

The use of a foil or grid lens with a central opening for the primary electron beam and a surrounding foil or grid that is substantially transparent to electrons allows for the correction of aberrations in the signal electron beam while maintaining the primary beam unaffected.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If an electron lens is used to focus or collimate the signal electron beam, then the spatial resolution and detection efficiency are improved, but chromatic and spherical aberrations occur and the primary electron beam is negatively influenced

Engineering Contradiction:

Improvespatial resolutionVSAvoidchromatic and spherical aberrations

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The system separates the optical paths for the primary electron beam and the signal electron beam by using different regions of the same foil or grid lens. The central opening (with diameter of 100 μm or more) is dedicated to the primary beam, while the surrounding annular region handles the signal electron beam, allowing independent optimization of each path without mutual interference.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the foil or grid lens are designed with different functional properties. The central opening provides a clear path for the primary beam with minimal interaction, while the surrounding foil or grid structure with controlled transparency (allowing 10-90% of electrons to pass) provides the necessary focusing or collimating effect for the signal beam. This local differentiation enables each region to optimize its specific function.

Inventive Principle:

Principle #3Local quality

2Reliability

If a foil or grid lens is used to correct aberrations of the signal electron beam, then the detection reliability is improved, but the primary electron beam may be affected

Engineering Contradiction:

Improvedetection reliabilityVSAvoidinfluence on primary electron beam

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The foil or grid lens is divided into two functional zones: a central opening with diameter of 100 μm or more that allows the primary electron beam to pass through with minimal interaction, and a surrounding annular foil or grid structure that interacts with the signal electron beam to provide aberration correction. This spatial segmentation ensures that the primary beam remains largely unaffected while the signal beam receives the necessary correction.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The transparency of the foil or grid is carefully controlled to allow between 10-90% of electrons to pass through, creating a gradient effect that provides the necessary optical power for aberration correction while minimizing scattering and other harmful effects on the signal beam, while the central opening maintains high transparency for the primary beam.

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 configuration enables reliable detection of signal electron beams by correcting spherical and chromatic aberrations, resulting in a collimated signal electron beam that can be efficiently directed to detectors, without affecting the primary electron beam.

Implementation Method 1

The foil or grid lens is configured to influence off-axial electrons of the signal electron beam propagating through the foil or grid lens in an opposite direction as compared to the primary electron beam

Methodology Applied

Scientific EffectElectrostatic field effect: Electric Field

Implementation Method 2

an objective lens configured to focus the primary electron beam on the sample for causing an emission of a signal electron beam

Methodology Applied

Scientific EffectElectromagnetic focusing: Electromagnet

Data Source

PatentUS20250087442A1Electron beam apparatus, foil or grid lens, and method of operating an electron beam apparatus

Publication Date: 2025.03.13 ICT INTEGRATED CIRCUIT TESTING GESELLSCHAFT FUER HALBLEITERPRUEFTECHNIK GMBH

AI summary

An electron beam apparatus (100) is described, including an electron source (105) configured to generate a primary electron beam propagating along an optical axis (A), a sample stage (108) configured to support a sample, an objective lens (120) configured to focus the primary electron beam on the sample for causing an emission of a signal electron beam and a foil or grid lens (300, 400) for influencing the signal electron beam. The foil or grid lens includes an electrode (340) that surrounds the optical axis; and a first foil or grid (320) adjacent to the electrode and perpendicular to the optical axis, the first foil or grid being substantially transparent to electrons, wherein a central opening (325) configured to allow the primary electron beam to pass through the central opening is provided in the first foil or grid.