Ion Beam Sample Preparation for TEM Artifact Reduction

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current methods for preparing ultra-thin TEM samples suffer from issues such as bending and curtaining, which affect the structural integrity and quality of the samples, especially at thicknesses below 60 nm, and are not suitable for automated processes.

Innovation Solution

The method involves depositing material onto the sample face during the preparation process to reinforce structural integrity and reduce or prevent bending and curtaining, using a deposition gas while milling to fill irregularities and voids, and removing the deposited material before imaging to ensure a smooth and artifact-free surface.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If ion beam milling is used to prepare ultra-thin TEM samples, then sample thickness is reduced to enable TEM imaging, but bending and curtaining artifacts occur that degrade sample quality

Engineering Contradiction:

Improvesample thicknessVSAvoidsample quality

Core Design Contradiction:

Volume of moving objectVSManufacturing precision

Solution Approach 1:

A protective layer is deposited on the sample surface before ion beam milling begins. This preliminary deposition prevents bending and curtaining artifacts from occurring during the thinning process by providing structural support to the sample as material is removed.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The deposited material acts as an intermediary between the ion beam and the sample. It is continuously deposited during milling to compensate for material removal, smoothing out irregularities and preventing the formation of bending and curtaining artifacts while enabling ultra-thin sample preparation.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If material is deposited during ion beam milling to prevent bending and curtaining, then sample quality is improved, but process complexity increases

Engineering Contradiction:

Improvesample qualityVSAvoidprocess complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The deposition and milling operations are merged into a single simultaneous process. Both operations occur in the same vacuum chamber using the same ion beam, eliminating the need for separate deposition and milling steps and reducing overall process complexity despite the added functionality.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The ion beam serves multiple functions: it mills the sample to reduce thickness, it activates deposition of protective material, and it smooths the surface. This multi-functionality reduces the need for separate specialized equipment and processes.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Strength

If a protective layer is deposited before milling, then structural integrity is reinforced, but additional material removal time is required

Engineering Contradiction:

Improvestructural integrityVSAvoidpreparation time

Core Design Contradiction:

StrengthVSLoss of time

Solution Approach 1:

The deposition and milling operations proceed simultaneously and continuously throughout the sample preparation process. Material is deposited at the same rate it is removed by milling, maintaining constant structural reinforcement without requiring separate sequential steps, thus eliminating additional time overhead.

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The beam parameters (current, voltage, focus) are dynamically adjusted during the process to balance the rates of deposition and removal. This optimization ensures the protective layer is maintained at the optimal thickness throughout milling, preventing artifacts while minimizing total processing time.

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 approach effectively reduces or eliminates bending and curtaining, enabling the production of high-quality ultra-thin TEM samples suitable for automated processing and improving the accuracy of structural characterization.

Implementation Method 1

directing an ion beam toward a work piece to remove material and expose a surface

Methodology Applied

Scientific EffectIon beam sputtering: Sputtering

Implementation Method 2

a deposition gas is activated by the ion beam to deposit material on the exposed surface

Methodology Applied

Scientific EffectIon beam-induced deposition: Physical Vapour Deposition

Implementation Method 3

the deposited material smoothing the irregularities

Methodology Applied

Scientific EffectMaterial deposition: Deposition (physical)

Data Source

PatentUS8822921B2Method for preparing samples for imaging

Publication Date: 2014.09.02 FEI CO

AI summary

A method and apparatus is provided for preparing samples for observation in a charged particle beam system in a manner that reduces or prevents artifacts. Material is deposited onto the sample using charged particle beam deposition just before or during the final milling, which results in an artifact-free surface. Embodiments are useful for preparing cross sections for SEM observation of samples having layers of materials of different hardnesses. Embodiments are useful for preparation of thin TEM samples.