SEM Entropy Detection for Focused Ion Beam Delayer End Points
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing end point detection techniques for delayering processes in electronic structures are insufficient in certain situations, making it challenging to reliably detect the transition between different layers during the delayering of samples.
Innovation Solution
The proposed solution involves taking SEM images at multiple intervals during the delayering process and analyzing the second derivative of the brightness entropy to identify the transition from one layer to another.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing end point detection techniques (secondary electron yield, secondary ion flux) are used, then layer transition detection is possible in many scenarios, but detection reliability is insufficient in certain situations
Solution Approach 1:
The patent replaces physical signal-based detection (secondary electron yield, secondary ion flux) with image processing-based detection. By capturing SEM images and analyzing brightness entropy, the system substitutes mechanical/physical measurement methods with optical/image analysis methods, achieving more reliable layer transition detection in challenging scenarios where traditional signals fail.
Solution Approach 2:
The patent transforms the detection approach by changing from monitoring physical signals (electron yield, ion flux) to analyzing image brightness entropy parameters. This parameter transformation allows detection of layer transitions through statistical properties of image data, improving reliability when traditional signal-based methods are insufficient.
2Measurement precision
If SEM images are captured and entropy analysis is performed, then layer transition detection accuracy is improved, but processing time and computational complexity increase
Solution Approach 1:
The patent extracts only the essential feature (brightness entropy) from complete SEM images for analysis. Instead of processing full image data or multiple complex features, the method isolates and analyzes the entropy parameter, which captures the critical information needed for layer transition detection while minimizing computational overhead and processing time.
3Measurement precision
If multiple gray scale images are acquired at multiple intervals during delayering, then layer transition detection accuracy is improved, but the complexity of the detection system increases
Solution Approach 1:
The patent uses the existing SEM imaging system for dual purposes: both for standard sample imaging and for layer transition detection. By acquiring gray scale images that serve both conventional imaging needs and entropy-based detection, the system achieves multi-functionality without adding dedicated detection hardware, thereby improving accuracy while limiting complexity increase.
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 provides improved end point detection results, enabling accurate identification of layer transitions and effectively stopping the delayering process when the desired layer is reached.
Implementation Method 1
a sample such as a silicon wafer that includes one or more electronic structures formed thereon can be milled and analyzed with a focused ion beam (FIB)
Implementation Method 2
some end point detection techniques evaluate one or more signals that are dependent on the material being milled, such as secondary electron yield, secondary ion flux
Data Source
AI summary
A method of delayering a sample that includes a second layer formed under a first layer, where the first and second layers are different materials or different texture, the method including: acquiring a plurality of gray scale images of the region of interest in an iterative process by alternating a sequence of delayering the region of interest with a first charged particle beam and imaging a surface of the region of interest with a second charged particle beam; after each iteration of acquiring a gray scale image, calculating an entropy of the acquired gray scale image and calculating a second derivative of the entropy; determining whether a transition from the first layer to the second layer occurred based on the second derivative of the entropy; and if it is determined that a transition from the first layer to the second layer did not occur, proceeding with a next iteration of acquiring a plurality of gray scale images, and if it is determined that a transition from the first layer to the second layer did occurred, end pointing the delayering process.