Automated Sample Orientation for Focused Ion Beam Alignment
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Solution Overview
Problem
Current methods for preparing samples for transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) are site-specific and time-consuming, often requiring sectioning of the original sample, which can be destructive and lack efficient alignment capabilities, especially for non-crystallographic materials.
Innovation Solution
A method involving the selection of two or three points on the sample area of interest to create a calibrated image line or plane, allowing for precise alignment perpendicular to the charged particle beam, independent of crystalline orientation, using autofocusing techniques and sample stage adjustments in the X-Y-Z axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional sample preparation methods (cleaving, chemical polishing, mechanical polishing, ion milling) are used, then samples can be prepared for TEM viewing, but the process is time-consuming (180-360 seconds alignment time) and not site-specific
Solution Approach 1:
The patent performs preliminary actions by selecting reference points and creating calibrated image lines or planes before the actual alignment process. This preparation enables rapid automated alignment by providing a reference framework, reducing alignment time from 180-360 seconds to 45 seconds while maintaining precision.
Solution Approach 2:
The patent replaces manual mechanical alignment operations with an automated image-processing-based system. By using software to select points, create calibrated lines, and determine sample orientation, the system eliminates time-consuming manual mechanical adjustment while achieving superior alignment precision.
2Reliability
If traditional sample preparation methods are used, then samples can be prepared, but the process is destructive and requires sectioning the original sample
Solution Approach 1:
The patent replaces destructive mechanical preparation methods (cleaving, polishing, ion milling) with a non-destructive image-processing approach. By using calibrated lines and planes derived from imaging data, the system determines sample orientation without physically altering or sectioning the sample, preserving sample integrity while simplifying preparation.
Solution Approach 2:
The patent creates a digital copy or representation of the sample's geometric features through calibrated image lines and planes. This virtual model enables alignment determination without physical manipulation of the actual sample, avoiding destruction while maintaining preparation simplicity.
3Measurement precision
If traditional alignment routines are used for crystallographic structures, then alignment can be achieved, but the process is extensively time-consuming and requires multiple focusing routines
Solution Approach 1:
The patent performs preliminary actions by pre-selecting reference points and creating calibrated image lines that encode orientation information. This preparation eliminates the need for multiple iterative focusing routines during alignment, enabling single-step automated alignment that maintains crystallographic precision while dramatically improving throughput.
Solution Approach 2:
The patent extracts essential alignment information (sample orientation) from a small number of selected reference points and calibrated lines. By isolating and utilizing only the critical geometric features needed for alignment, the system eliminates time-consuming multiple focusing routines while maintaining precise crystallographic alignment capability.
4Productivity
If feature sizes are reduced to increase device density, then higher device density is achieved, but the features become too small for ordinary SEM resolution
Solution Approach 1:
The patent introduces calibrated image lines and planes as intermediary reference structures that enable precise measurement of sub-SEM-resolution features. These calibrated references provide a measurement framework that allows accurate characterization of features smaller than the SEM resolution limit by comparing feature positions relative to the known calibrated geometry.
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 enables rapid, robust, and repeatable sample alignment, significantly reducing alignment time from traditional methods (45 seconds vs. 180-360 seconds), enhancing throughput and allowing for precise crystallographic and material stack alignment without damaging the sample.
Implementation Method 1
In a scanning transmission electron microscope (STEM), a primary electron beam is focused to a fine spot, and the spot is scanned across the sample surface. Electrons that are transmitted through the work piece are collected by an electron detector on the far side of the sample
Implementation Method 2
Electrons that are transmitted through the sample are focused to form an image of the sample
Implementation Method 3
adjustments in the X-Y-Z axes
Data Source
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AI summary
A method for aligning a sample that is placed in the vacuum chamber so that the sample is oriented normal to the focused ion beam is disclosed. The locations of different spots on the sample surface are determined using a focusing routine. The locations of the different spots are used to create an image line or an image plane that determines the proper calibrations that are needed. The image line or image plane is then used to calibrate the sample stage so that the sample is aligned substantially normal to the focused ion beam.