Multi-Beam Microscope Focus Setting for Image Plane Tilt Correction

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Solution Overview

Problem

Existing multi-beam electron microscopes face challenges in achieving high throughput and precise measurements of semiconductor features with resolutions below 5 nm, due to limitations in setting the optimal focal plane and maintaining constant particle optical parameters.

Innovation Solution

A multiple particle beam system and method that precisely sets the optimal focal plane for a multi-beam microscope by determining deviations in beam directions, aligning the displacement stage, and using a compensator to maintain telecentricity and correct for image plane tilt and curved image surface errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a multi-beam electron microscope uses a large number of primary beams to increase throughput, then productivity is improved, but maintaining uniform resolution below 5 nm across all beams becomes difficult due to image plane tilt and curved image surface errors

Engineering Contradiction:

ImprovethroughputVSAvoidresolution uniformity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent performs preliminary determination of the optimal focal plane for each primary beam before actual imaging. By pre-calculating and storing the optimal focal position for each beam in a lookup table, the system eliminates the need for time-consuming real-time focus adjustments during imaging, thereby maintaining both high throughput and uniform resolution across all beams.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements a feedback mechanism where the optimal focal plane for each primary beam is determined based on measured image plane tilt and curved image surface errors. This feedback information is used to adjust the focal plane settings, ensuring that all beams achieve uniform sub-5nm resolution while maintaining high productivity.

Inventive Principle:

Principle #23Feedback

2Measurement precision

If the focal plane is adjusted to achieve optimal resolution for one region, then measurement precision is improved, but other regions with different optimal focal planes suffer from reduced resolution

Engineering Contradiction:

ImproveresolutionVSAvoidfocus plane adaptation

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent divides the image field into multiple regions, each corresponding to a specific primary beam. For each beam, the system independently determines and stores the optimal focal plane in a lookup table. This segmentation allows each beam to be optimized independently, ensuring that all regions maintain uniform sub-5nm resolution simultaneously.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system changes the focal plane parameter for each primary beam based on predetermined information about image plane tilt and curved image surface errors. By adjusting the focal plane position for each beam individually, the system achieves optimal resolution across the entire image field while maintaining adaptability to different imaging conditions.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If traditional focus setting methods are used without considering image plane tilt, then device complexity is reduced, but measurement precision deteriorates due to non-perpendicular beam incidence

Engineering Contradiction:

Improvefocus setting complexityVSAvoidresolution

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent performs preliminary determination and storage of optimal focal plane information for each primary beam, including corrections for image plane tilt and curved image surface errors. This pre-computed lookup table eliminates the need for complex real-time calculations during imaging, maintaining simple device operation while achieving uniform sub-5nm resolution through perpendicular beam incidence.

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

The system achieves high-resolution imaging with a large image field, ensuring a uniform resolution of below 5 nm for a large number of primary beams, thereby enhancing throughput and precision in semiconductor wafer inspection.

Implementation Method 1

The plurality of J charged individual particle beams (primary beams) are focused on the surface of a sample to be examined by way of a common objective lens

Methodology Applied

Scientific EffectFocusing: Focusing

Implementation Method 2

positioning a surface of an object in a first setting plane with a first z-position z(1)=z1

Methodology Applied

Scientific EffectMechanical displacement: Displacement

Data Source

PatentUS12283457B2Multiple particle beam microscope and associated method with an improved focus setting taking into account an image plane tilt

Publication Date: 2025.04.22 CARL ZEISS MULTISEM GMBH

AI summary

A multiple particle beam microscope and an associated method set a desired focal plane with an optical resolution and set a telecentric irradiation with the plurality of the primary beams. A method determines an optimal setting plane, into which an object surface is brought. Further, a system provides an improved resolution and telecentric irradiation for a large number of primary beams. Targeted selection and targeted individual influencing of individual primary beams and/or a mechanism means for influencing the plurality of primary beams in collective fashion can be implemented.