TEM Sample Thickness Measurement via Diffraction Slope Analysis

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Solution Overview

Problem

The challenge in semiconductor manufacturing lies in accurately determining the endpoint for sample thinning in transmission electron microscopy (TEM) sample preparation, which is crucial for achieving precise and reproducible results, especially as feature sizes shrink, and current methods are labor-intensive and lack automation, making process control impractical.

Innovation Solution

A method is developed to determine the thickness of TEM samples by analyzing the slope of diffraction pattern images, using a relationship between image value slope and sample thickness, allowing for in-situ monitoring and automation of the thinning process, enabling precise endpoint detection and increased throughput.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Extent of automation

If manual methods are used for endpoint determination in sample thinning, then operator experience and training can compensate for lack of automation, but the process becomes labor-intensive, time-consuming, and impractical for manufacturing process control

Engineering Contradiction:

Improveautomation of endpoint determinationVSAvoidtime required for sample preparation

Core Design Contradiction:

Extent of automationVSLoss of time

Solution Approach 1:

The patent implements in-situ monitoring of diffraction patterns during the sample thinning process. The system continuously captures diffraction pattern images, calculates image value slopes, and compares them against reference data to provide real-time feedback on sample thickness. This automated feedback loop enables precise endpoint detection without manual intervention, resolving the contradiction between automation and time consumption.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces manual visual inspection and operator judgment with an automated computational system. The system uses algorithms to calculate image value slopes from diffraction patterns and automatically determines endpoint based on predetermined criteria, substituting the mechanical/manual process with an automated electronic measurement and decision-making system.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If traditional diffraction pattern analysis is used without slope calculation, then the method is simpler, but measurement precision and reproducibility are insufficient for small feature sizes

Engineering Contradiction:

Improveprecision of thickness measurementVSAvoidcomplexity of analysis method

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent transforms the diffraction pattern analysis by changing the parameter being measured from raw image values to the slope of image values. This parameter transformation enhances the sensitivity and precision of thickness measurements. The system calculates the slope of image values across the diffraction pattern, which provides a more precise indicator of sample thickness, particularly for small feature sizes, while maintaining manageable computational complexity.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If sample thickness is not accurately controlled, then the thinning process is faster, but the quality and reproducibility of TEM samples deteriorate

Engineering Contradiction:

Improvethickness control of sampleVSAvoidthroughput of sample preparation

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent establishes predetermined reference diffraction patterns and slope criteria before the thinning process begins. These reference standards are prepared in advance based on known thickness values, allowing the system to quickly compare actual measurements against established benchmarks during production. This preliminary preparation enables both precise thickness control and maintained productivity during the actual thinning process.

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 approach allows for accurate and reproducible TEM sample preparation, enhancing the precision and efficiency of sample thinning, facilitating the integration of TEM analysis into manufacturing process control and improving the quality of lamella samples.

Implementation Method 1

In a TEM, a broad beam impacts the sample and electrons that are transmitted through the sample are focused to form an image of the sample

Methodology Applied

Scientific EffectElectron transmission: Electron Beam

Implementation Method 2

obtaining a diffraction pattern image of a sample of a first material, said diffraction pattern image comprising at least image values representative for the diffraction pattern obtained for said sample

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentUS10978272B2Measurement and endpointing of sample thickness

Publication Date: 2021.04.13 FEI CO

AI summary

The invention relates to a method of determining the thickness of a sample. According to this method, a diffraction pattern image of a sample of a first material is obtained. Said diffraction pattern image comprises at least image values representative for the diffraction pattern obtained for said sample. A slope of said image values is then determined. The slope is compared to a relation between the thickness of said first material and the slope of image value of a corresponding diffraction pattern image of said first material. The determined slope and said relation are used to determine the thickness of said sample.