Objective Lens Electrodes for Longer Working Distance in Particle Microscopy

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Solution Overview

Problem

Existing charged particle microscope systems face challenges in positioning probes with nanometer-scale precision due to the limitations in focusing charged particle beams, particularly in maintaining a sufficient focal working distance while controlling the landing energy and beam focus properties.

Innovation Solution

The use of an objective lens with a shielding electrode and a steering electrode, which adjusts the location of the main objective plane to increase the focal working distance, while the shielding electrode partially shields the test region from the lens electrostatic field, thereby controlling the landing energy and beam focus.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the focal working distance of the objective lens is increased, then the positioning precision of probes is improved, but the landing energy control and beam focus properties deteriorate

Engineering Contradiction:

Improvepositioning precision of probesVSAvoidlanding energy control and beam focus properties

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The objective lens is segmented into multiple functional electrodes: a main lens electrode for primary focusing, a steering electrode for beam direction control, and a shielding electrode for electrostatic field management. This segmentation allows independent optimization of working distance and beam control without compromising either function.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The shielding electrode acts as an intermediary element between the main lens electrode and the test region. It shields the test region from the lens electrostatic field while allowing the focused charged particle beam to pass through, thereby maintaining both increased working distance and proper beam focus properties.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If the shielding electrode is positioned closer to the test region, then the protection from lens electrostatic field is improved, but the focal working distance decreases

Engineering Contradiction:

Improveprotection from lens electrostatic fieldVSAvoidfocal working distance

Core Design Contradiction:

Object-affected harmful factorsVSLength of moving object

Solution Approach 1:

The shielding electrode is designed with specific local properties: it is positioned at an optimized distance from the test region to provide adequate electrostatic shielding while maintaining sufficient focal working distance. The electrode's geometry and potential distribution are tailored to create a localized shielded zone without compromising the overall focusing capability.

Inventive Principle:

Principle #3Local quality

3Adaptability or versatility

If the steering electrode voltage is increased, then the main objective plane location adjustment is improved, but the device complexity increases

Engineering Contradiction:

Improvemain objective plane location adjustmentVSAvoidelectrode voltage control system

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The steering electrode voltage is made dynamically adjustable to shift the main objective plane location as needed. This dynamic control allows the system to adapt to different positioning requirements while maintaining a relatively simple electrode structure, avoiding the need for complex mechanical adjustment mechanisms.

Inventive Principle:

Principle #15Dynamics

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 allows for increased focal working distance, controlled landing energy, and improved beam focus properties, enabling precise positioning of probes and protecting samples from adverse effects of charged particles.

Implementation Method 1

The shielding electrode is configured to at least partially shield a test region downstream of the objective lens from a lens electrostatic field generated within the objective lens

Methodology Applied

Scientific EffectElectrostatic shielding: Electrostatic Induction

Implementation Method 2

The objective lens is configured such that varying a steering electrode voltage that is applied to the steering electrode adjusts a location of a main objective plane of the objective lens in a downstream direction to increase a focal working distance of the objective lens

Methodology Applied

Scientific EffectElectrostatic lens effect: Electrostatic Lens

Implementation Method 3

The objective lens is configured to generate a lens electrostatic field to at least partially direct a charged particle beam along an optical axis to a focus location with a landing energy

Methodology Applied

Scientific EffectElectrostatic focusing: Electrostatic Lens

Data Source

PatentUS20250191873A1Objective lenses, charged particle microscopes including the same, and associated methods

Publication Date: 2025.06.12 FEI CO

AI summary

Objective lenses, charged particle microscopes including the same, and associated methods are disclosed herein. An objective lens can include a lens body, a shielding electrode, and a steering electrode. The objective lens is configured such that varying a steering electrode voltage adjusts a location of a main objective plane of the objective lens to vary a focal working distance of the objective lens. A method can include positioning a sample relative to an objective lens and operating the objective lens to focus a charged particle beam to a focus location.