Semiconductor Layer-by-Layer SEM X-Ray Imaging for 3D Resolution
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Solution Overview
Problem
Current methods for investigating semiconductor samples using focused ion beam etching and X-ray detection face limitations in achieving high volumetric spatial resolution and elemental information, particularly in distinguishing between adjacent structures, due to the size of the interaction volume and trade-offs between resolution and acquisition times.
Innovation Solution
The method involves layer-by-layer investigation of semiconductor samples using focused ion beam etching and X-ray detection, with post-processing techniques that include optimization algorithms and wavelength-dependent X-ray detection, allowing for enhanced volumetric spatial resolution and elemental information by deconvoluting detection signals and modeling the interaction volume's spatial mixing behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the interaction volume is reduced to improve spatial resolution, then volumetric spatial resolution improves, but acquisition time increases
Solution Approach 1:
The investigation volume is divided into multiple layers along the beam direction, with each layer being investigated separately by adjusting the electron beam energy to correspond to the thickness of individual layers. This segmentation allows for high spatial resolution in the depth direction while maintaining reasonable acquisition times by focusing measurements on specific depth ranges rather than the entire volume simultaneously.
Solution Approach 2:
The electron beam energy is dynamically adjusted to match the thickness of the layer being investigated. By varying the beam energy according to the specific layer depth, the interaction volume is optimized for each measurement, achieving high spatial resolution without requiring excessively long acquisition times for the entire sample volume.
2Measurement precision
If the interaction volume is reduced to improve spatial resolution, then volumetric spatial resolution improves, but elemental information completeness deteriorates
Solution Approach 1:
The sample is investigated in multiple layers, with each layer providing elemental information for its specific depth range. By combining the elemental data from all layers, complete elemental information for the entire investigation volume is obtained while maintaining high spatial resolution within each layer.
Solution Approach 2:
The investigation process continuously progresses through multiple layers from shallow to deep depths. Each layer measurement contributes elemental information that complements the previous layers, ensuring that the complete elemental composition of the entire volume is captured without gaps, while each individual measurement maintains high spatial resolution.
3Ease of operation
If FIB etching is used to prepare layers, then layer-by-layer investigation is enabled, but contamination and debris are introduced
Solution Approach 1:
The harmful effects of FIB etching (contamination and debris) are extracted and separated from the measurement process. The FIB is used only for initial layer preparation and removal, while the subsequent investigation is performed with the electron beam and X-ray detection, avoiding further contamination during the actual measurement phase.
Solution Approach 2:
The electron beam serves as an intermediary that enables layer-by-layer investigation without direct physical contact or material removal. By using electron beam energy adjustment to control the interaction volume depth, the method achieves layer-specific investigation without introducing the contamination and debris associated with physical etching methods.
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 achieves improved volumetric spatial resolution better than 10 nm and enhanced elemental information, enabling detailed analysis of chip structures such as semiconductor memory and 3D-NAND structures, while minimizing contamination and debris from FIB etching.
Implementation Method 1
preparing a layer to be investigated of the semiconductor sample by etching an initial sample surface with a FIB
Implementation Method 2
detecting X-rays emanating from the aligned region of interest volume
Data Source
AI summary
A method includes preparing an initial layer of a semiconductor sample., and aligning a surface area of a region of interest volume of the prepared layer with an object field of an SEM. An electron energy of an electron beam of the SEM is adjusted. The region of interest volume is probed with the SEM within the object field. X-rays emanating from the aligned region of interest volume are detected. A detection signal is post-processed to deconvolute the detection signal into structured data attributed to the sample structure within the region of interest volume. A next layer to be investigated is prepared by FIB etching and the steps “preparing” to “post-processing” are repeated until the layer by layer investigation of a superimposed volume of interest of the sample is completed.