Objective Lens Array Assembly with Control Lens for Electron Beam Focusing

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Solution Overview

Problem

Current charged-particle assessment tools face challenges in improving throughput and efficiency during the inspection of semiconductor IC chip manufacturing, where pattern defects can significantly reduce yield and require high-speed detection of micro and nano-scale defects.

Innovation Solution

The implementation of an objective lens array assembly with a control lens array positioned up-beam of the objective lens array, which pre-focuses sub-beams before projecting them onto the sample, along with a beam-limiting aperture array to optimize beam focusing and energy control, enhancing the focusing capabilities of electron-optical systems.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a single objective lens is used to focus the electron beam, then the device complexity is low, but the throughput and inspection speed are insufficient for high-speed defect detection

Engineering Contradiction:

ImprovethroughputVSAvoiddevice complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent divides the single objective lens into multiple objective lenses arranged in an array. Each objective lens focuses a corresponding sub-beam onto the sample, enabling parallel inspection of multiple regions. This segmentation increases throughput while keeping each individual lens relatively simple in structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent combines multiple objective lenses and their corresponding control lenses into a single integrated assembly. The control lens array is positioned upstream of the objective lens array, with each control lens paired with an objective lens to form a focusing unit. This merging enables coordinated operation of multiple lenses to achieve high-speed parallel inspection.

Inventive Principle:

Principle #5Merging (Combining)

2Productivity

If multiple objective lenses are used to increase throughput, then the inspection speed improves, but the focusing accuracy and beam control become more difficult

Engineering Contradiction:

Improveinspection speedVSAvoidfocusing accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent introduces control lenses as intermediary elements positioned upstream of the objective lenses. Each control lens pre-focuses and conditions its corresponding sub-beam before it reaches the objective lens. This intermediary stage enables independent adjustment and optimization of each beam path, maintaining focusing accuracy despite the presence of multiple lenses.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent applies local quality by allowing each control lens-objective lens pair to be independently optimized for its specific sub-beam. Each lens can be adjusted to account for local variations in beam characteristics, ensuring that focusing accuracy is maintained across all channels rather than requiring uniform performance from all lenses.

Inventive Principle:

Principle #3Local quality

3Measurement precision

If the electron beam is focused directly onto the sample without pre-focusing, then the optical path is short and simple, but the resolution and focus control are insufficient for high-precision inspection

Engineering Contradiction:

ImproveresolutionVSAvoidoptical path length

Core Design Contradiction:

Measurement precisionVSLength of stationary object

Solution Approach 1:

The patent implements preliminary action by using control lenses to pre-focus and condition the electron beams upstream of the objective lenses. This pre-focusing stage prepares the beams in advance, allowing the objective lenses to perform final precise focusing on the sample. The preliminary action enables better resolution and focus control without requiring an excessively long optical path.

Inventive Principle:

Principle #10Preliminary action

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 improves the focusing accuracy and throughput of charged-particle assessment tools, allowing for higher resolution and reduced aberrations, thereby enhancing the detection of micro and nano-scale defects and maintaining high yield in IC chip manufacturing.

Implementation Method 1

a control lens array associated with the objective lens array and positioned up-beam of the objective lens array, the control lenses being configured to pre-focus the sub-beams

Methodology Applied

Scientific EffectElectrostatic lens focusing: Electrostatic Lens

Implementation Method 2

an objective lens array, each objective lens being configured to project a respective sub-beam of the multi-beam onto the sample

Methodology Applied

Scientific EffectElectrostatic lens focusing: Electrostatic Lens

Data Source

PatentUS20230245849A1Objective lens array assembly, electron-optical system, electron-optical system array, method of focusing, objective lens arrangement

Publication Date: 2023.08.03 ASML NETHERLANDS BV

AI summary

Arrangements involving objective lens array assemblies for charged-particle assessment tools are disclosed. In one arrangement, the assembly comprises an objective lens array and a control lens array. Each objective lens projects a respective sub-beam of a multi-beam onto a sample. The control lens array is associated with the objective lens array and positioned up-beam of the objective lens array. The control lenses pre-focus the sub-beams.