Variable-Tilt Specimen Holder for FIB Milling Monitoring
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Solution Overview
Problem
Current methods for preparing specimens for transmission electron microscopy (TEM) face challenges in accurately monitoring the milling progress of fragile, thin specimens within focused ion-beam (FIB) microscopes, which can lead to specimen destruction and require venting the vacuum chamber, disrupting the FIB process.
Innovation Solution
A variable tilt TEM grid holder system integrated with a single-channel optical processing system and light detector allows for precise monitoring of specimen thickness during milling, enabling automated adjustment of specimen orientation and light detection within the FIB chamber without venting, using components like the Omniprobe Optoprobe and AutoProbe systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional monitoring methods are used during FIB milling, then the milling process can proceed, but the specimen may be destroyed due to inaccurate monitoring and the vacuum chamber must be vented
Solution Approach 1:
The patent implements real-time optical feedback monitoring during FIB milling. A light source illuminates the specimen from below through the TEM grid, and a light detector measures the transmitted light intensity. As the ion beam mills the specimen, changes in light transmission provide continuous feedback on specimen thickness and milling progress, enabling precise control while maintaining vacuum conditions and preventing specimen destruction.
Solution Approach 2:
The patent introduces light as an intermediary medium to monitor specimen thickness during milling. Instead of direct visual inspection or post-milling analysis, optical radiation passes through the specimen to provide indirect but continuous measurement of specimen integrity and milling progress, allowing non-invasive monitoring within the vacuum chamber.
2Difficulty of detecting and measuring
If the vacuum chamber is vented to monitor specimen milling, then direct observation is possible, but the FIB process is disrupted and chamber performance degrades
Solution Approach 1:
The patent replaces mechanical/physical intervention (venting the chamber for observation) with an optical monitoring system. Light transmission measurement through the TEM grid enables specimen observation and milling monitoring without breaking vacuum, eliminating the need to vent and re-pump the chamber, thus maintaining continuous FIB operation and preventing performance degradation.
Solution Approach 2:
The patent maintains the vacuum environment as an inert atmosphere throughout the monitoring process. By using optical detection that is compatible with vacuum conditions, the system allows specimen observation and milling control without introducing air or disrupting the vacuum, thereby preserving FIB process efficiency and chamber performance.
3Ease of operation
If manual specimen handling is used for TEM preparation, then specimens can be transferred, but the process is time-consuming and requires venting the chamber
Solution Approach 1:
The patent merges the FIB milling chamber with TEM specimen holder capability. The TEM grid holder with integrated optical monitoring is positioned within the FIB chamber, allowing specimens to be milled, monitored, and prepared for TEM analysis in a single continuous vacuum environment. This eliminates separate transfer steps and chamber venting cycles, significantly reducing preparation time.
Solution Approach 2:
The patent enables continuous specimen preparation without interruption. Specimens are milled by the ion beam, monitored in real-time via light transmission, and held on the TEM grid throughout the entire process within the vacuum chamber. This continuous operation eliminates time losses associated with venting, transferring, and re-pumping the chamber between FIB and TEM operations.
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 faster, more accurate monitoring of milling progress, ensuring the production of high-quality, thin TEM specimens while maintaining the vacuum integrity of the FIB chamber, thus preventing specimen destruction and enhancing the efficiency of the FIB process.
Implementation Method 1
directing a beam of light to the TEM specimen at a first location within the vacuum chamber and directing a beam of light from the light source through the TEM specimen to the light detector
Implementation Method 2
The process involves directing an ion beam at the TEM specimen to mill and thin the specimen for TEM analysis
Data Source
AI summary
An apparatus for monitoring sample milling in a charged-particle instrument has a variable-tilt specimen holder attached to the instrument tilt stage. The variable-tilt specimen holder includes a first pivoting plate having a slot for holding a specimen rotatably supported in the specimen holder. The first pivoting plate has a range of rotation sufficient to move the axis of thinning of the specimen from a first position where the tilt stage is placed at its maximum range of tilt and the angle between the preferred axis of thinning of the specimen and the axis of the ion beam column of the instrument is greater than zero, to a second position where the axis for thinning of the specimen is substantially parallel to the axis of the ion-beam column. A light detector intercepts light passing through the specimen as it is thinned to determine an endpoint for milling of the specimen.